NON-INVASIVE DEVICE FOR SYNCHRONIZING CHEST
COMPRESSION AND VENTILATION PARAMETERS TO RESIDUAL
MYOCARDIAL ACTIVITY DURING CARDIOPULMONARY
RESUSCITATION
BACKGROUND OF THE INVENTION
[000 1] This invention relates generally to the field of cardiovascular
medicine, and in particular to the treatment of patients suffering from a
spectrum of cardiac states, ranging from shock to pulseless electrical
activity, in which the patient appears to be lifeless and in cardiac arrest
yet retains some mechanical activity in the myocardial wall motion.
[0002] One common technique for treating persons suffering from
cardiac arrest is the use of cardiopulmonary resuscitation (CPR). In this
procedure, the patient's chest is repeatedly compressed, often in
combination with periodic ventilations. Administration of electrical
countershock and drugs intended to assist in restoration of
cardiopulmonary function to chest compression and ventilation,
constitutes advanced life support. For a variety of reasons, the
effectiveness of CPR has been limited. Hence, devices or techniques
which can improve the effectiveness of CPR are greatly needed.
[0003] In additional to sudden cardiac arrest, refractory-shock
(which is referred to herein as "shock") is often fatal. For example, if not
properly stabilized, a person suffering from shock can progress into
cardiac arrest, which, because it is not sudden in nature, is usually fatal.
Emergency medicine and critical care practitioners approach the
treatment of shock principally by attempting to alleviate the cause
because there are no non-invasive techniques that may beneficial in
assisting circulation. Hence, devices and techniques are also needed to
1
1910457treat those suffering from refractory shock and shock that is progressing
toward cardiac arrest.
[0004] There is no general consensus as to when it is the
appropriate to start administering CPR as the patient's blood pressure
progressively decreases. This relates to a lack of demonstrated efficacy
and concern that chest compression may interfere with residual cardiac
function, even though CPR may at some point be beneficial in shock
patients as they progress to cardiac arrest. Hence there a need for a
device or technique to prevent CPR from interfering with residual
cardiac function.
[0005] Unlike cardiac arrest caused by ventricular fibrillation,
pulseless electrical activity (PEA) is a heterogeneous entity with respect
to cardiac function and hemodynamics. PEA is a clinical condition
characterized by unresponsiveness and lack of palpable pulse in the
presence of organized cardiac electrical activity. Pulseless electrical
activity has previously been referred to as electromechanical
dissociation (EMD). During PEA, electrical activity of the heart may or
may not be indicative of cardiac mechanical movements and particularly
cardiac output.
[0006] Pulseless electrical activity is not necessarily a condition of
complete mechanical quiescence in the heart. In PEA, the heart may
have a regular organized electrical rhythm such as supraventricular or
ventricular rhythms. These cardiac rhythms may not be associated with
mechanical activity of the heart in PEA.
[0007] As an example of cardiac mechanical patterns during PEA,
patients may have weak ventricular contractions and detectable aortic
2
1910457pressure - which is a condition referred as pseudo-PEA. Various
studies have documented that between 40-88% of patients with PEA
had residual cardiac mechanical activity (pseudo-PEA). In pseudo-PEA,
the patient may appear lifeless and without a pulse, despite some
degree of residual left ventricle function and hemodynamics. The
outcome of patients suffering PEA has tended to be worse than those in
ventricular fibrillation, possibly reflecting the potential of CPR chest
compressions and residual myocardial mechanical activity to interfere
with each other's efficacy. Hence there is a need for a device or
technique to enhance the efficacy of CPR in PEA.
BRIEF DESCRIPTION OF THE INVENTION
[0008] Disclosed herein are techniques and systems for treating
those suffering from a variety of myocardial pathophysiologic states
ranging in hemodynamics from awake patients in refractory shock to
those who appear to be lifeless, yet who still retain some degree of
residual myocardial mechanical function. It has been observed when
performing open chest cardiac massage, that coordinating compression
and relaxation with the heart's residual mechanical activity often
improves recovery of cardiac function. Extrapolating from this, if
mechanical myocardial function is present but inadequate, as in PEA,
external chest compressions should likely be directed toward assisting
cardiac ejection-that is compressing the chest during its intrinsic
contractions-and then releasing the chest so as not to interfere with
ventricular filling. CPR that is not synchronized with the heart's residual
mechanical function may result in application of the compression phase
when the left ventricle is trying to fill, resulting in significantly decreased
cardiac output on the next ejection secondary to the Frank-Starling Law.
Interference with ventricular filling by compression of the chest can be
3
1910457so deleterious that it can, in and of itself, cause complete loss of
residual myocardial function resulting in true cardiac arrest.
[0009] A system is disclosed here that detects residual myocardial
activity in an apparently lifeless patient and outputs signals to trigger
chest compressions by mechanical chest compression devices; to
audibly indicate when to initiate such chest compressions, or to other
interventions that benefit from synchronization with residual myocardial
activity. These other interventions may include but are not limited to:
abdominal counter-pulsation, ventilation, phasic limb-compression,
myocardial electrical stimulation, intravascular fluid shifting,
intravascular balloon inflation-deflation, intra-esophageal or intra-
pericardial balloon inflation, application of transthoracic electromagnetic
irradiation, and the like.
[00 10] A method is disclosed here for improving the cardiac output
of patients suffering from a range of pathophysiologic states such as
pulseless electrical activity or shock, which having some residual
myocardial wall mechanical activity. According to the method, residual
myocardial activity is sensed to determine the presence of residual
ventricular phasic movement, with or without residual left or right
ventricular pump function, but having an apparent ejection phase and a
relaxation phase. A compressive force is repeatedly applied based on
the sensed myocardial activity such that, for example, the compressive
force is applied during at least some of the ejection phases and is
ceased during at least some of the relaxation phases to permit cardiac
filling, thereby creating or enhancing cardiac output and organ
perfusion. The synchronization with the sensed myocardial activity may
also be used when the patient's chest is actively lifted during
4
1910457decompression. In this way, the chances for improving the outcome of
patients suffering from shock or cardiac arrest are improved.
[00 ] The compressive force may be applied over a variable range
of time intervals. For example, the compressive force may be applied
for only a certain portion of the contraction or ejection phase, such as at
the beginning, middle or end. As another example, the compressive
force may be applied during each and every sensed contraction or
ejection phase, or only during certain contraction or ejection phases.
[00 12] The start of the chest compression and the duration of the
compression can be adjusted to improve patient outcomes. For
example, the adjustments to the start time or duration may be adjusted
to optimize the chest compressions or other phasic therapy, where the
adjustment is based on feedback of a patient condition or physiologic
parameter during one or more prior chest compressions. The feedback
signal may, for example, indicate a rate or amount of cardiac ejection or
filling, cardiac output or other indicator of mechanical activity of the
heart or arterial blood flow. The feedback signal is coupled to the
therapy by logic circuits so as to vary the synchronized phasic
therapies, e.g., chest compressions, and vary the application of the
therapies. By varying the therapies and their application and
subsequently re-measuring the feedback signals, the logic circuits can
determine which synchronized therapy, or therapies, and pattern of
synchronized therapy is optimal and most effective to improve cardiac
ejection, cardiac output or otherwise improve the condition of the
patient. For example, the logic circuit may vary each of the
synchronized therapies and combinations of therapies to determine
which pattern of therapy or therapies when synchronized with residual
5
1910457myocardial synchronization results in the greatest measured cardiac
output or results in some other measurable condition that indicates that
the phasic therapy(ies) are being applied optimally .
[00 13] Electrical stimulation of the heart may be applied in
conjunction with or in addition to chest compressions. The electrical
stimulations may be synchronized with electrical signals (ECG/EKG) of
the inherent heartbeat, which may be slow and weak, or if there are no
regular electrical heart signals, with pulsatile flow or myocardial
movements. For example, the electrical stimulation may be
synchronized with arterial pulses, such as aortic pressure (AoP), based
on detected pulsatile pressure, blood flow, or myocardial movements.
[00 14] Ventilations are another phasic therapy that may be applied
to the patient based on the sensed myocardial activity or
hemodynamics. The patient may be ventilated manually or by a
mechanical ventilator. The ventilation may be synchronized with chest
compressions or other resuscitative therapies in conditions such as
shock or pseudo-PEA.
[00 15] The compressive force may be applied using a variety of
devices or equipment. Some examples include mechanical chest
compression devices, inflatable vests, nerve stimulators, abdominal
compression devices, chest or abdominal active decompression
devices, limb phasic compression devices, and the like. Further, the
compressive force may be applied at different locations on the chest,
abdomen, limbs, or back, such as the left lateral chest, cardiac point of
maximal impulse and the like.
6
1910457[00 16] The myocardial activity may be sensed using a variety of
sensing systems. Such systems may include electrocardiography,
Doppler ultrasonography, plethysmography, phonocardiography,
echocardiography, transthoracic impedance and the like. These may be
incorporated into a probe that is coupled to the chest, abdomen, back,
extremities, or a combination of these, or placed within the body, such
as within the esophagus, trachea, or stomach. These various types of
sensors may detect myocardial activity by detecting, for example,
cardiac electrical activity, contractions, other movements of the heart,
palpable pulses of arteries. These measurements may be made from
standard locations such as the precordium, but also from the
esophagus, trachea, or abdomen. Variations in the skin indicative of
pulsating blood flow, and the rhythm and chemical content of the breath,
may also be utilized.
[00 17] The sensors and algorithms optimally suited to sense
myocardial activity may depend on characteristics of a particular patient.
Further, the sensors optimally suited to sense myocardial activity may
change during the course of treating. To determine the optimal sensor
or sensors that best indicate myocardial activity, the system may
include algorithms to validate the sensor(s) and to correlate sensor
output data to a desired patient response, such as improved cardiac
output. To validate the sensors, the system may apply or prompt the
application of therapies such as chest compressions at a predetermined
rate, force or vector and compare the outputs of the sensors to
expected sensor outputs or otherwise determine which sensor(s)
generate signals that most accurately indicate the response of the
patient to the predetermined chest compressions. The validation of
sensors results in an identification of sensors and arrangements of
7
1910457sensors that generate signals that most accurately measure or predict
the response of the patient. The sensors may be validated at the
initiation of therapy and may be revalidated periodically during treatment
of the patient, such as at regular intervals or when a substantial change,
e.g., beyond a threshold amount, occurs in the response of the patient
to treatment.
[00 18] The validated sensors or validated arrangement of sensors
are those sensors that have been determined to most accurately
measure or predict a predetermined response(s) of the patient. Once
the sensors have been validated, signals generated only by the
sensors, or pattern of sensors, identified in the validation process are
used to provide feedback to the algorithms that determine the
application of phasic therapies such a chest compressions and
ventilation. Using these signals, the algorithms may generate and
adjust a regimen for chest compressions and ventilations of the
patients. The regimen may dictate the force to be applied by the chest
compressions, the frequency of the chest compressions, the shape and
duration of the force applied by the chest compressions, the
synchronization and phasing of the chest compressions with sensed
myocardial activity, the location on the chest or other body location,
e.g., legs, of compressions, and a vector of the chest or other
compressions. The algorithms may vary the regimen to optimize a
condition of the patient, such as to increase sensed cardiac output.
[0019] In some cases, chest compressions may be performed
manually, such as using traditional CPR techniques. In such cases, an
audio or visual signal may be produced to indicate when the ejection
phase is sensed. The generated signals may indicate to a rescuer when
8
1910457to apply the chest compressions, whether to apply more or less force
during the compressions, or whether to apply the compressions to a
different location on the chest. In this way, the rescuer will be prompted
as to when, how and where to apply the compressive force to the
patient. The tone, volume, or other parameter, of the synchronizing
prompt may be varied so as to assist the rescuer in providing optimal
CPR. In some cases, the chest, abdomen, or extremities may also be
actively or passively compressed or decompressed in an alternating
manner with chest compressions, and in synchronization with either
cardiac ejection or filling.
[0020] A system is disclosed here for improving the cardiac output
and prognosis of a patient who is suffering from impaired myocardial
mechanical states such as pulseless electrical activity or shock but
having residual myocardial wall motion. The system comprises a
myocardial activity sensor that is adapted to sense movement of the
myocardial wall and or myocardial valvular motion to determine the
presence of residual ventricular contract and relaxation, and/or pump
function having an ejection phase and a filling phase. The system may
also include a compression device that is configured to repeatedly apply
a compressive force to the heart, either through the chest wall,
intrathoracically through the pericardium, or directly to the myocardium
through an endoscope and pericardial window. Further, a controller is
employed to receive signals from the myocardial activity sensor and to
control operation of the compression device such that the compression
device repeatedly applies a compressive force to the heart such that the
compressive force is applied during at least some of the ejection phases
and is ceased during at least some of the relaxation phases to permit
9
1910457residual cardiac filling, thereby enhancing cardiac output and organ
perfusion.
[002 1] As an option to using a mechanical compression device or
as an initial treatment applied before the compression device is setup
on a patient, chest compressions may be performed manually. In such
cases, the system may include a cadence device that is configured to
produce audio and/or visual signals indicative of when compressive
forces are to be applied and ceased. This same cadence system may
be utilized to synchronization other therapies phasic therapies such as
ventilation or abdominal counterpulsation.
[0022] The myocardial activity sensors that may be used include
electrocardiography sensors, Doppler ultrasonography sensors,
plethysmography sensors, phonocardiography sensors,
echocardiography sensors, transthoracic impedance sensors, magnetic
resonance imaging, and radiographic fluoroscopy. These sensors may
be placed on the patient's chest, abdomen, back or extremities, within
body cavities such as the esophagus, or some distance from the patient
in the case of technologies like radiography or magnetic resonance
imaging. If the patient has an arterial pressure catheter in place, the
controller may also utilize that signal for synchronization. Further, the
controller may be configured to apply the compressive force during
each sensed ejection phase or during only at certain ejection phases.
As another option, the controller may be configured to apply the
compressive force for only a certain duration of the ejection phase.
[0023] The system may further include a ventilator device that is
configured to provide ventilation to the patient based on the sensed
10
0457residual myocardial mechanical activity. The controller may also vary
the pattern of individual ventilations so as to optimize synchronization.
[0024] A sensor may detect the expansion and relaxation of the
chest due to ventilation or chest compressions. The sensor may be a
plastic adhesive strip applied to the chest that stretches and contracts
with the movement of the chest due. The stretch and contraction of the
adhesive strip may be detected as a change in an electrical property,
e.g., resistance, of the strip, optically due to a change in transmissivity
or reflection of the strip or by other means. The stretch and contraction
of the adhesive strip causes the adhesive strip sensor to generate
signals indicative of the expansion and relaxation of the chest. These
signals may be used by the algorithms to predict when blood is being
drawn into the heart as the chest relaxes (expands) or when blood is
being forced from the heart as the chest is compressed.
[0025] The phasic device may be a mechanical compression
device, an inflatable vest, a nerve stimulator, or the like. Further, the
system may include a lifting device that is configured to actively
decompress the chest during the relaxation phase, or compress the
abdomen during chest decompression.
[0026] In another embodiment, a logic circuit may be used to vary
the phasic therapeutic device or devices such that the optimal pattern
and combination can be determined and applied. This pattern may be
variable over time and the invention will monitor for the possibility by
occasionally varying the pattern of therapies and adjusting according to
an indicator of hemodynamics or predictor of outcome.
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1910457[0027] During resuscitation of patients suffering cardiac arrest, the
presence and degree of residual left ventricular mechanical (physical)
activity may vary over time. The system may be configured to detect
transient periods of left ventricular mechanical activity and to
synchronize therapies only during these periods to assist residual
cardiac mechanical activity and achieve a greater cardiac output.
[0028] The sensor functions may be utilized to determine the vector
of left ventricular ejection and to optimize the force vector of chest
compression spatially. This might be done utilizing an array of Doppler
probes placed over the chest to detect the velocity of residual
myocardial motion from multiple locations and calculate the vector of
that motion.
[0029] The vector of left ventricular blood flow ejection is generally
from the point of maximal impulse in the left lateral chest between 4th
and 6th intercostal spaces near the lateral clavicular line toward the
medial cephalad direction. The system disclosed here can determine
the vector and align the force of chest compression with the vector to
assist ejection of blood and minimize interference with ventricular filling.
[0030] Utilizing an indicator of cardiac output, such as exhaled end-
tidal carbon dioxide or vital organ oxymetry, the controller circuit could
apply synchronized therapies during progressive shock and determine if
they benefit the patient through increased blood flow.
[003 1] A system is disclosed here to treat a patient having a heart
and a chest, the system comprising: a least one sensor monitoring
cardiac activity in the patient by detecting at least one of myocardial
pump activity, myocardial mechanical activity, hemodynamics and
12
1910457organ perfusion; a logic controller receiving signals from the at least one
sensor and generating control commands for controlling one or more
phasic therapies and synchronizing the one or more phasic therapies
with the monitored cardiac activity in the patient; and wherein the logic
controller executes an algorithm stored in memory associated with the
logic controller, wherein the algorithm causes the logic controller to
generate commands to vary patterns of the application of the one or
more phasic therapies, and thereafter detect changes in at least one of
the sensed myocardial pump activity, myocardial mechanical activity,
hemodynamics and organ perfusion due to variations in the patterns,
and determine one of the patterns of phasic therapies corresponding to
a desired level of at least one of sensed myocardial pump activity,
myocardial mechanical activity, hemodynamics and organ perfusion
hemodynamics and organ perfusion.
[0032] A method is disclosed here to treat a patient in shock
comprising: sensing myocardial motion or pulsatile blood flow in the
patient; repeatedly applying a phasic therapy to the patient
synchronized to the sensed actual myocardial motion or pulsatile blood
flow, wherein the phasic therapy includes repeatedly applying a
compressive force to the chest or an electrical shock to the heart of the
patient, and adjusting the compressive force or electrical shock
depending on whether the force or shock coincides with a heart beat as
indicated by sensed myocardial motion or pulsatile blood flow.
[0033] A system is disclosed here to treat a patient having a heart
and a chest, the system comprising: a least one sensor monitoring
cardiac activity in the patient by detecting at least one of myocardial
pump activity, myocardial mechanical activity, hemodynamics and
13
1910457organ perfusion; a logic controller receiving signals from the at least one
sensor and generating control commands for controlling one or more
phasic therapies and synchronizing the one or more phasic therapies
with the monitored cardiac activity in the patient; and wherein the logic
controller executes an algorithm stored in memory associated with the
logic controller, wherein the algorithm causes the logic controller to
generate commands to vary patterns of one or more phasic therapies,
and thereafter detect changes in at least one of the sensed parameters
due to variation in the pattern of phasic therapies. The logic circuit
would then determine which one of the patterns of phasic therapies
corresponding to a desired level of at least one of sensed myocardial
pump activity, myocardial mechanical activity, hemodynamics and
organ perfusion hemodynamics and organ perfusion.
[0034] A method is disclosed here to treat a patient comprising:
sensing a natural rate of myocardial activity of the heart of the patient,
and repeatedly applying a phasic therapy to the patient synchronized to
the sensed myocardial activity, wherein the phasic therapy includes
repeated myocardial electrical stimulation applied at a rate faster than
the sensed natural rate of myocardial activity. The method may further
comprise a sensing system comparing at least one of the sensed
myocardial pump activity, myocardial mechanical activity,
hemodynamics and organ perfusion hemodynamics and organ
perfusion with and without application of the phasic therapies to
determine which of the phasic therapies optimally augments
hemodynamics or perfusion.
[003 5] A method is disclosed here to treat a patient having a heart
and a chest, the system comprising: monitoring cardiac activity in the
14
1910457patient by detecting with at least one sensor at least one of myocardial
pump activity, myocardial mechanical activity, hemodynamics and
organ perfusion; receiving the signals from the at least one sensor and,
based on the signals, synchronizing one or more phasic therapies
applied to the patient to the monitored cardiac activity in the patient;
varying the one or more phasic therapies; detect changes in at least
one of the sensed myocardial pump activity, myocardial mechanical
activity, hemodynamics and organ perfusion due to the variations in the
one or more phasic therapies; determine one of the variations of the
phasic therapies corresponding to a desired level of at least one of
sensed myocardial pump activity, myocardial mechanical activity,
hemodynamics and organ perfusion hemodynamics and organ
perfusion.
[0036] The method may further comprise comparing at least one of
the sensed myocardial pump activity, myocardial mechanical activity,
hemodynamics and organ perfusion with and without application of the
phasic therapies to determine which of the phasic therapies optimally
augments hemodynamics or perfusion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] FIGURE 1 is a schematic view of a system that may be used
to improve the cardiac output of a patient according to the invention.
[0038] FIGURE 2 is a schematic diagram of a controller that may be
used to actuate a compression device based on signals from a
myocardial activity sensor according to the invention.
15
1910457[0039] FIGURE 3 is a graph illustrating exemplary times for
applying compressive forces according to the invention.
[0040] FIGURE 4 is a flow chart illustrating one method for
improving the cardiac output of a patient according to the invention.
[004 1] FIGURE 5 is a flow chart illustrating a method to validate
sensors used to detect myocardial motion and other patient parameters.
[0042] FIGURES 6A and 6B are a flow chart of an exemplary
algorithm to determine when to initiate chest compressions and
optimize a chest compression regimen that may be combined with
ventilation of the patient and electrical stimulation of the heart.
[0043] FIGURE 7A is a chart illustrating chest compressions of
varying force applied in synchronization with a slow heart beat.
[0044] FIGURE 7B is a chart illustrating a method to correct a
synchronization error between chest compressions and a heart beat.
[0045] FIGURE 8 is a chart illustrating a method to synchronize a
chest compression to a heart beat.
[0046] FIGURE 9 is a chart illustrating a method to synchronize
electrical cardiac stimulation to pulsatile flow or mechanical myocardial
activity.
DETAILED DESCRIPTION
[0047] The invention relates to techniques and devices that may be
used to increase cardiac output for patients suffering from a wide variety
16
1910457of ailments ranging from shock to pulseless electrical activity (PEA)
where the patient appears to be lifeless yet has some residual
mechanical heart activity. One exemplary technique of the invention is
to sense when the heart is beating and then synchronize chest
compressions, or other resuscitative techniques, with movement of the
myocardial wall. In this way, various techniques may be used to
optimally synchronize chest compressions (or other elements of CPR)
with residual left ventricular function to improve the outcome of such
patients. Hence, the invention may be used to synchronize the
compression force of external devices, on or around the chest, with the
ejection phase of the residual left ventricular function, and the relaxation
phase with residual cardiac filling. In another aspect, the system and
method disclosed herein provides various techniques and devices for
sensing residual mechanical function, and then turn this information into
a useful data stream that may be used to operate the various
components of resuscitative technology, including adjuncts to blood
flow, ventilation, and cardiac stimulating technology.
[0048] Such techniques may be used with patients suffering from a
wide range of ailments. One exemplary use is for patients who are
believed to be in cardiac arrest with pulseless electrical activity (PEA)
and non-detectable blood pressures, but who still have residual left
ventricular function to some degree. However, it will be appreciated that
the invention is not intended to be limited to only such a use, but to a
wide range of conditions where there is some organized electrical (but
impaired) mechanical cardiac activity.
[0049] For example, at one end of such a spectrum is normal
spontaneous circulation, where the cardiac outputs are normal and left
17
1910457ventricular mechanical and pumping function are normal. Below that
level is hypotension then compensated shock. In such cases, the blood
pressure and the patient's pulse are still palpable and there may be
good cardiac output. However, for various reasons, the cardiac output is
unable to meet the metabolic demands of the body and homeostasis is
at risk. This is evident by parameters such as decreasing urine output
and increasing serum lactate, which are markers of inadequate organ
function.
[0050] Below compensated shock is the state of uncompensated
shock. This is a state in which the myocardium and the cardiovascular
system are no longer able to provide adequate amounts of blood flow,
oxygen and nutrients to meet the needs of vital organs, and the function
of those organs is affected to the extent that they are beginning to
become damaged. Blood pressures in this state might be, for example,
70/30 mm Hg. systolic over diastolic. Also, urine output may cease, and
the patient may become confused because of inadequate cerebral
function. Importantly, as shock progresses, the pathways to multi-organ
system failure are initiated.
[005 1] Below classical uncompensated shock is what might be
called "extreme shock" which borders on cardiac arrest. In this case, the
patient exhibits some residual myocardial function including some left
ventricular ejection, but cardiac output is wholly inadequate to meet the
needs of vital organs. For example, cardiac output might be less than 1
liter per minute, blood pressure might be 50/20, urine output may be
minimal or absent, and the patient may be stuporous or comatose.
Further, the patient may appear to be near death with significantly
impaired cerebral function and stupor bordering on coma. If untreated.
18
1910457extreme shock will result in true cardiac arrest in a timeframe of
minutes. Generally, it is not possible to palpate arterial pulses manually
in this range, and such patients may be classified as PEA by clinical
personnel even thought their heart continues to beat.
[0052] Below the state of extreme shock is pulseless electrical
activity (PEA) cardiac arrest, which importantly also has a spectrum of
conditions and a range of hemodynamics. For example, at its upper
end, PEA has both left ventricular mechanical function and cardiac
output, but not sufficient enough to be detected as a peripheral radial or
femoral pulse. If an intra-arterial catheter is placed into the patient, the
blood pressure might be only 45/25, with blood pressure measurable
only in major arteries of the chest, neck or groin. A Doppler probe
placed over the neck or groin may detect forward blood flow. Blood flow
is so profoundly inadequate that the patient will generally appear lifeless
and their pupils may dilate and become fixed. Further, they appear to be
in cardiac arrest despite the presence of residual pump function and
forward flow. The high end of PEA dynamics overlaps the low end of
"extreme shock." In such cases, the clinical personnel may not be able
to distinguish the differences. The electrocardiogram, while showing
organized electrical activity, is variable in its pathology and may be
relatively normal in its QRS configuration. The inventor has termed
electromechanical dissociation (EMD) with residual myocardial
mechanical activity "pseudo-EMD."
[0053] Below the "high end" stage of PEA is electromechanical
dissociation with almost absent left ventricular function. The blood
pressure measured by intravascular catheters just above the aortic
valve will show aortic pulsations but the blood pressures measured are
19
1910457on the order of 25/15 mm HG, and there will be almost no associated
forward blood flow. Without application of CPR, oxygen delivered to the
vital organs will be essentially absent and irreparable injury to organs
such as the brain occurs within minutes. The electrocardiogram rarely
has a normal appearing QRS configuration, and the overall pattern of
the ECG may be slurred out and irregular.
[0054] The final stage of PEA is an organized electrical rhythm but
no left ventricular mechanical function. This is true cardiac arrest. A
catheter measuring pressures above the aortic valve will detect no
pressure pulse and echocardiography will show no cardiac movement.
Further, the cardiac output is 0 and the patient is in complete global
ischemia and cardiac arrest. Without application of CPR, oxygen
delivered to the vital organs will be 0 , and irreparable injury to organs
such as the brain occurs within minutes. The overall pattern of the ECG
is invariably slurred out and irregular.
[0055] Along the spectrum described above, the invention may be
used in all cases where there is some myocardial mechanical activity
and synchronized resuscitative therapies may improve cardiac output.
In such cases, the invention may be used to detect residual mechanical
activity and to synchronize such activity of the heart with resuscitation
techniques, such as those used in CPR (including chest
compressions/decompressions and/or ventilation). Hence, the invention
may be utilized in any pathophysiologic state from true cardiac arrest, to
pseudo-EMD PEA, through the various stages of shock, or in any
hemodynamics state in which residual myocardial mechanical function
with and without cardiac output exists. By synchronizing chest
compressions and/or decompressions, among other potentially cyclical
2 0
10457therapies, both ejection and filling phases of the cardiac cycle may be
augmented. In so doing, cardiac output and organ profusion may be
increased, thereby improving the outcome of patients with impaired
hemodynamics.
[0056] As one particularly important example, one clinical situation
that often occurs and is challenging for physicians, is when patients
progress from shock to apparent PEA cardiac arrest. In the earlier
stages of this process, physicians tend to treat such patients with
intravenous medications and possibly controlled ventilation. While drugs
such as antibiotics may be administered to patients in states such as
septic shock, pressor drugs such as dopamine continue to be a
mainstay of treatment. Pressors, however, have generally not been
shown to improve the outcome of such patients despite raising the
blood pressure. This may be because they improve biood pressure but
also raise vital organ oxygen utilization, such that the overall balance
between oxygen supply and demand is not improved. Pressor drugs
also have significant direct vital organ toxicity.
[0057] If, however, these parenteral therapies do not stabilize the
patient, their shock may progress inexorably towards more and more
extreme states and eventually become cardiac arrest. Many
practitioners in emergency medicine and critical care continue to be
unsure-and the medical literature remains unclear--as to which point a
patient whose blood pressure is dropping should begin to receive chest
compressions. Indeed, physicians generally do not apply techniques
such as external chest compress before subjective loss of vital signs.
This is because CPR, and in particular chest compressions, can
interfere with cardiac function and in particular cardiac filling if applied in
2 1
1910457an unsynchronized manner. For instance, a patient whose blood
pressure is 60/40 who begins to receive chest compressions out of
synchronization with heart function could rapidly progress into full
cardiac arrest. More specifically, in performing CPR without
synchronization, application of the compression phase when the left
ventricle is trying to fill may significantly decrease cardiac output on the
next ejection secondary to the Frank Starling Law of the heart. Hence,
by detecting myocardial mechanical function, chest compressions can
be synchronized with the ejection phase so that patients in shock may
be treated without exacerbating their condition and possibly moving
them toward cardiac arrest.
[0058] Hence, the issue as to when chest compressions should
begin when a patient is progressing through the stages of shock may be
addressed by synchronizing chest compressions, and possibly other
mechanical adjuncts, with the ejection and relaxation phases, so that
the clinician may be more confident that chest compressions are
assisting and not interfering with residual circulatory function. In this
way, the clinician does not need to be as concerned with the question
as to when to begin chest compressions. In this manner, the invention
may act to allow use of external mechanical adjuncts in the treatment of
any form of shock in a manner similar to the methods by which intra-
aortic balloon counterpulsation has been applied in cardiogenic shock.
The invention may thus allow application of such adjuncts in the pre¬
hospital, and Emergency Department environments.
[0059] Another advantage of using synchronization is that it may be
performed as an adjunct to therapies directed at the cause of the shock,
such as antibiotics or thrombolysis, enhancing vital organ perfusion
2 2
1910457while these therapies are being administered. Indeed, improved
hemodynamics may not only stave off organ injury, it may improve the
efficacy of parenteral therapies. Further, synchronized chest
compressions are unlikely to have significant organ toxicity, unlike
pressor drugs.
[0060] As described above, one particular application of the
invention is in connection with those suffering from pulseless electrical
activity (PEA). PEA is one of the three broad-types of cardiac arrest, the
other two being ventricular fibrillation and asystole. PEA is also referred
to as electromechanical disassociation (EMD). PEA has been described
as "the presence of organized electrical activity on the
electrocardiogram but without palpable pulses." Rosen P, Baker F J ,
Barkin R M, Braen G R, Dailey R H, Levy R C. Emergency Medicine
Concepts and Clinical Practice. 2nd ed. St Louis: CV Mosby, 1988.
Unlike ventricular fibrillation, which can be specifically reversed with
electrical countershock, PEA does not have a specific countermeasure.
This may explain the traditionally worse outcome of patients in PEA
compared to ventricular fibrillation. Unfortunately, the incidence of PEA
is increasing, possible because early risk modification is changing the
natural history of cardiovascular disease. It is now reported by some
authorities that the majority of patients in cardiac arrest are in PEA at
the time of EMS arrival. Additionally, a significant fraction of patients
that are shocked out of ventricular fibrillation, or resuscitated from
asystole, will experience PEA at some point during their resuscitation.
The combination of these circumstances mean that a large majority of
patients receiving advanced life support for treatment of cardiac arrest
will have PEA at some time during resuscitation. Hence, now or in the
2 3
1 10 457near future PEA may supersede classical ventricular fibrillation in
importance. It may already have done so.
[006 1] Many patients with PEA have residual cardiac mechanical
activity, and many have detectable blood pressures. This condition may
be referred to as pseudo-EMD PEA. In such cases, the patient may
appear lifeless and without a pulse. However, there often remains some
degree of residual left ventricular function. Hence, one important feature
of the invention is to sense when the patient still has some myocardial
function and then to synchronize phasic .
resuscitation therapies,
especially compression of the chest, with the heart's residual
mechanical function. In this way, the compression phase of CPR may
occur during the ejection phase, and the relaxation phase can allow
elastic recoil of the chest-with associated decreases in intrathoracic
pressure when the left ventricle is trying to fill. In this way, synchronizing
phasic resuscitative therapies with residual ventricular ejection and
filling, may improve hemodynamics, the rate of a return to spontaneous
circulation (ROSC), and long term survival.
[0062] The invention may incorporate various non-invasive sensing
technologies (represented by sensor 12 in Fig. 1) to acquire real-time
data describing the pattern of myocardial wall and or valve motion so as
to allow synchronization of chest compressions and other therapies. If,
however, invasive indicators of hemodynamics, such as intra-arterial
pressure or flow monitors, are present, then the invention may act as an
interface between those inputs and phasic resuscitative therapies as
exemplifies by external chest compression. To apply proper
synchronization between the forces of external devices, on or around
the chest or body, and the ejection and filling phases of residual left
24
1910457ventricular function, a variety of devices may be used. The decision that
residual myocardial activity exists may be made from a logic circuit with
inputs from multiple sensing modalities. The invention may utilize
sensing technology to collect the data on myocardial wall function,
myocardial valve motion, blood flow in vascular structures, vital organ
oxygen or energy status, or exhaled pulmonary gas, and this data may
be passed through logic circuits and a controlling output signal passed
to the devices that deliver therapies. Because the pattern of mechanical
residual wall function may be variable over time, the invention may be
designed to promptly identify residual function and to vary therapeutics
based on feed back to a logic circuit. Also, the synchronizing of external
chest compressions may be used with other techniques, such as with
abdominal counter pulsations, phasic limb compression, ventilation, and
electrical stimulation, among others, to augment cardiac ejection and
filling. In this way, the patient may be stabilized to allow sufficient time
for primary therapies, such as thrombolysis, to be effective.
[0063] A wide variety of equipment and device may be used to
provide chest compressions. For example, various types of automated
compression systems may be use to compress the chest. These include
systems, such as the AutoPulse Resuscitation System, by ZOLL
Circulation, Inc. of Sunnyvale, Calif., the Thumper manufactured by
Michigan Instruments or the LUCAS device, and the like. Further, the
invention is not limited to automated compression systems, but may be
used with manual techniques as well. For example, the invention may
be used to provide an audio and/or visual signal to indicate to a rescuer
as to when to manually apply chest compressions. Further, in some
cases a suction device may be adhered to the chest so that the chest
may be actively lifted intermittently with chest compressions.
2 5
1910457[0064] Using either manual or automated equipment, the invention
may be configured to synchronize external chest compressions with any
residual mechanical activity of the myocardium such that when the
myocardium enters pumping or systole phase, CPR is in the chest
compression phase. Further, when the heart enters its refilling or
diastole phase, chest compressions enter the relaxation phase.
Sensory data may be passed through a logic circuit and outputs of that
circuit used to control when during cardiac ejection or filling of
synchronization occurs. These relationships may be varied over time to
optimize the efficacy.
[0065] In addition to synchronizing chest compressions with
residual heart function, the invention may also be use to synchronize
ventilations with residual heart function. For example, inspiration and
expiration may be synchronized with residual myocardial function so as
to increase cardiac output. For instance, inspiration may be
synchronized to systole and expiration with diastole. To apply
ventilations, the invention may use a traditional ventilator or ventilations
may be provided manually, such as by using a ventilatory bag. In the
latter case, an audio and/or visual signal may be provided to the rescuer
as to when to apply proper ventilations.
[0066] With both chest compressions and ventilations, the timing,
frequency and/or duration may be varied depending on the particular
treatment. For example, chest compressions may occur during the
entire systole phase, or only during a portion of it. Further, chest
compressions may occur every systole phase or during only certain
systole phases. A similar scenario may occur with ventilations. The
controller may use one or more sensory inputs, and a logic circuit
2 6
19J0457utilizing and indicator or indicators of efficacy, to optimize the effect of
synchronization on hemodynamics.
[0067] The system disclosed herein may be utilized with any
therapy that may benefit from synchronization with residual myocardial
mechanical function in apparently lifeless patients. Chest compression
and decompression, abdominal counter-pulsation, ventilation, phasic
limb-compression, myocardial electrical stimulation, intravascular fluid
shifting, intravascular or intra-pericardial balloon inflation-deflation,
application of transthoracic electromagnetic irradiation, among others.
The controller logic circuit may vary the pattern of synchronization
among multiple therapies so as to determine the optimal pattern with
respect to increasing hemodynamics.
[0068] Myocardial electrical stimulation is, for example, external
electrical shocks delivered through metal paddles or electrodes applied
to the chest, or electrical signals applied directly to the heart from a
internal pacemaker modified to synchronize myocardial electrical
stimulations to, for example, myocardial wall function or detected
pulsatile blood flow.
[0069] To sense myocardial wall function, a variety of noninvasive
devices and technologies may be used. For example, one technology
that may be used is electrocardiography (ECG). ECG may be an
attractive detection method because it is already used in most clinical
situations during resuscitation. However, because myocardial activity is
not always present with ECG during PEA, it may need to be used in
combination with other sensing techniques as described below. Another
example of a sensing technique that may be used is Doppler
ultrasonography (DOP). Doppler ultrasound uses the Doppler shift of
2 7
1910457ultrasonic wave to quantify the blood flow in peripheral vessels. This
may be applied with a transducer on the neck for carotid flow, the groin
for femoral flow, or a transthoracic or intraesophageal transducer for
aortic flow. A Doppler probe may also be placed at the cardiac point of
maximum impulse to detect movement of blood within the myocardium.
An array of Doppler probes may be used to determine the vector of
residual myocardial mechanical function and align chest compression
and relation with that vector.
[0070] A dynamic pressure sensor detects pulsatile flow by sensing
the oxygen content in a peripheral vein. The oxygen content sensed by
the ROSS sensors as blood pulses through the peripheral vein.
Similarly a pulse oximetry sensor may also be used to detect the
oxygen content in a blood vessel in, for example, the toes, fingers or ear
lobes. The oxygen content of the blood may be used to determine when
to initiate and terminate CPR and mechanical or electrical cardiac
stimulation. For example, if the ROSS sensor or pulse oximetry sensor
detects pulsatile flow and an oxygen content above a threshold, the
system may reduce the force of chest compressions or terminate chest
compressions. Similarly, i f the ROSS or oximetry sensor detects no
pulsatile flow or an oxygen level falling below a threshold, the system
may initiate manual chest compressor or electrical cardiac stimulation.
The system may adjust various parameters of phasic therapies based
on trends in the sensed oxygen status.
[007 1] The data regarding pulses in peripheral blood vessels may
be utilized to estimate residual myocardial mechanical function, such as
the cardiac ejection phase, based on stored information regarding the
2 8
1910457delay between the myocardial mechanical function and pulse pressure
or pulsatile flow in the peripheral blood vessel.
[0072] A further sensing technique that may be used is
plethysmography (PLETH). Plethysmography may be applied by
measuring changes in the transthoracic AC electrical impedance with
heart motion. A further technique that may be used is
phonocardiography (PHONO). Phonocardiography records the
acoustical energy detected by a stethoscope over the heart. Still a
further technique that may be used is echocardiography (ECHO). With
echocardiography or ultrasound imaging of the heart, left ventricular
ejection can be quantified. In some cases, echocardiograph detection of
heart function may be combined with ECG. Also, sensitivity may be
improved through the use of intravenously injected microbubbles or
other ultrasound enhancing technologies.
[0073] It may be optimal to combine a number of these detection
systems so as to increase the sensitivity and specificity of detecting
residual myocardial mechanical function. Additionally, it may be optimal
to incorporate a logic circuit which compares combinations of sensing
technologies to an indicator of actual cardiac output, such as end-tidal
carbon dioxide or aortic flow. In this manner, the invention could
determine which combination of sensing technologies are most
predictive of improvements derived from synchronization.
[0074] Additionally, the logic circuit of the invention might be
capable of varying the synchronized therapeutics against indicators of
actual cardiac output so as to determine which pattern of synchronized
therapy is most effective. It may vary synchronization within one
2 9
1910457therapeutic device or multiple therapeutic devices so as to identify the
optimal pattern.
[0075] Referring now to FIG. 1, a system 10 for improving cardiac
output will be described. System 10 includes a sensor, or sensors, 12
that may be used to detect residual myocardial mechanical function. In
one embodiment, sensor 12 may comprise a surface probe that rests on
the patient's chest. Sensor 12 may be placed at a variety of locations on
the chest. For example, one location may be the anterior chest in one of
the intercostal spaces. Another location may be the sub-xiphoid location
in the epigastrium. Sensor 12 may sense myocardial wall motion using
any of the technologies described herein, including ultrasound, Doppler
technology, echocardiography, plethysmography and the like. As an
alternative to placing sensor 12 on the patient's chest, it will be
appreciated that other locations may be used as well, such as a probe
that is placed on the neck over the carotids, or into the patient's
esophagus. It will also be appreciated that sensor 12 may be an array of
sensors.
[0076] The sensor 12 may be a sensor or sensors for a variety of
sensing systems such as electrocardiography, Doppler
ultrasonography, plethysmography, phonocardiography,
echocardiography, transthoracic impedance and the like. The sensor 12
may be incorporated into a probe that is coupled to the chest, abdomen,
back, extremities, or a combination of these, or placed within the body,
such as within the esophagus, trachea, or stomach. These various
types of sensors detect myocardial activity by detecting, for example,
cardiac electrical activity; physical contractions and other movements of
the heart, palpable pulses of arteries in, for example, the esophagus,
3 0
1910457trachea, or stomach; variations in the skin indicative of pulsating blood
flow and the rhythm and chemical content of the breath.
[0077] The data collected by sensor 12 is transmitted to a controller
4 having signal processing and logic capabilities. A further description
of controller 14 will be described hereinafter with reference to FIG. 2 .
Controller 14 is also electronically coupled to a compression device 16
that may be used to apply external chest compression to the patient. In
some embodiments, it will be appreciated that controller 14 could be
incorporated into compression device 16 or into any of the sensors. For
ease of use, both the sensor 12 and the controller 14 may be
incorporated into the therapy device 16. Further, controller 14 could be
wirelessly connected to the sensing and/or compression devices. In the
example illustrated in FIG. 1, chest compression device 16 includes an
interface member 18 that is coupled to a piston 20 which moves
interface member 8 against the chest in a repeating manner. In this
way, chest compression device 16 may apply repeating chest
compressions to the patient. In some cases, interface member 18 may
be configured to adhere to the patient's chest so that as piston 20 lifts
interface member 18, the patients' chest will also be lifted. In this way,
chest compression device 16 may apply alternating chest compressions
and decompressions. Although described in the context of chest
compression device 16, it will be appreciated that a wide variety of
equipment may be used to apply chest, abdomen or extremity
compressions and/or decompressions in an automated manner as
described herein, and that the invention is not intended to be limited to
only the specific embodiment of chest compression device 16. For
instance, examples of existing CPR equipment that may be modified to
function in connection with controller 14 include the AutoPulse
31
1910457Resuscitation System by Revivant of Sunnyvale, Calif., or the Thumper
manufactured by Michigan Instruments. As another option, an inflatable
vest 2 1 may be coupled to controller 14 and be configured to be inflated
and deflated to perform proper synchronization.
[0078] As an alternative to applying automated chest compressions,
the invention may also be used with manual techniques. In such cases,
controller 14 may include a speaker 22 and/or a light 24 that provide
information to a rescuer as to when to apply chest compressions and/or
decompressions. For example, speaker 22 may be configured as a
metronome to apply a repeating signal, or could give instructions in a
human understandable voice. Light 24 may be configured to repeatedly
flash to indicate when to apply chest compressions and/or
decompressions. It will also be appreciated that a force transducer may
be placed between the hands of the person providing manual chest
compression and the patients such that the force, timing and vector of
chest compression can be sensed so that the accuracy of
synchronization is evaluated.
[0079] Chest compressions may be applied at a variety of locations.
Examples include the sternal area, parasternal areas, circumferentially,
the back, and the like. The abdomen may be compressed or
counterpulsed broadly or with specific emphasis on the areas of the
abdominal aorta or inferior vena cava. The extremities may be
compressed rhythmically. The pattern of ventilation may be varied.
[0080] Controller 14 configured to receive data from sensor 12 and
then process the signals in order to operate chest compression device
16 , speaker 22 or light 24. More specifically, controller 14 is configured
to synchronize external chest compressions and/or decompressions
3 2
1910457with any residual mechanical activity of the myocardium sensed by
sensor 12. In this way, when the myocardium enters the pumping or
systole phase, chest compression device 16 is configured to force
interface member 18 against the chest to apply a chest compression.
When the heart enters its refilling or diastole phase, controller 14 is
configured to lift interface member 18 so that no compressive forces are
being applied to the chest. It is understood that the therapeutic impulses
may be restricted to a portion of each phase.
[008 1] The vest 2 1 may include separately inflatable chambers 23
wherein each chamber is coupled via a conduit 25 to an air pump 27.
Valves 29 in the conduits are actuated by the controller 14 to cause the
inflation and deflation of the chamber associated with the valve. By
selectively inflating and deflating the chambers, specific locations on the
chest and back of the patient that are compressed can be to enhance
the chest compressions and increase the cardiac output. As an
alternative to a vest with chambers, the chest compression device may
include a force interface member 18 that is segmented into a plurality of
separately actuated pads 18a, 18b applied to compress the chest.
Depending on which of the pads 18a, 18b are actuated to compress the
chest and the sequence in with one or more of the pads are actuated
the position on the chest of the chest compressions and the vector of
the force applied by the chest compression can be varied to enhance,
for example, cardiac output.
[0082] System 10 further includes a ventilation system 26 that is
coupled to controller 14. For example, ventilation system 26 may
comprise a ventilator that is in fluid communication with a mask 28.
Controller 14 may be configured to synchronize inspiration and
3 3
19 0457expiration to residual myocardial function as detected by sensor 12. For
example, ventilation system 26 may be configured to provide positive
pressure ventilations during systole and allow for expiration during
diastole, or vice versa. Controller 14 may also be configured to
coordinate operation of ventilation system 26 with chest compression
device 16. As an option to using a mechanical ventilator, the invention
may also utilize other techniques, such as a ventilatory bag that may be
mechanically squeezed by the patient. In such cases, speaker 22 or
light 24 may be actuated to indicate to the rescuer as to when to apply
proper ventilations.
[0083] Referring now to FIG. 2, one aspect of controller 14 will be
described in greater detail. As previously described, controller 14
receives signals from sensor 12 regarding residual myocardial wall
function. Typically, signals from sensor 12 will be in analog form. As
such, controller 14 may include an amplifier and filter 30 which amplify
and filter the analog signal. Controller 14 also includes a peak or slope
detector 32 which is circuitry that detects either peaks or slopes of the
analog signal that are indicative of myocardial wall motion. Detector 32
may be configured to trigger on rapid increases in signal amplitude. The
triggered signal from detector 32 will pass through a variable time delay
circuitry which is fed to a pulse generator 36 that converts the analog
trigger into a digital pulse of fixed amplitude and duration. The variable
time delay 32 may be added to this pulse to allow for fine adjustment of
synchronization in timing. The delayed pulse is then processed as an
output to chest compression device 16 in digital format.
[0084] The controller may combine inputs from a number of sensing
systems so as to increase the sensitivity and specificity of detecting
3 4
1910457residual myocardial mechanical function. Additionally, it may be optimal
to incorporate a logic circuit, possibly within a microprocessor, which
compares combinations of sensing technologies to an indicator of actual
cardiac output, such as end-tidal carbon dioxide or aortic flow. In this
manner, the invention could determine which combination of sensing
technologies are most predictive of improvements derived from
synchronization. Additionally, the logic circuit of the invention might be
capable of varying the synchronized therapeutics and comparing the
combinations to amount of residual myocardial synchronization and
measured cardiac output so as to determine which pattern of
synchronized therapy is most effective.
[0085] As previously mentioned, chest or abdominal compressions
and/or ventilations may be applied during different times of the cardiac
cycle and may be varied over the cycles themselves. The arterial blood
pressure shown in FIG. 3 represents the pulsatile flow as indicated by
the increase in arterial blood pressure for each pulse 300. The dotted
lines in FIG. 3 refer to an initial increase or predetermined change to an
upward slope 302 in arterial blood pressure, a peak pressure 304 and
an end of the pressure pulse, such as represented by a predetermined
change to a downward slope of the pressure. For example, as
illustrated in FIG. 3 , a chest compression may be applied each time the
sensor detects the ejection phase, and this compression may occur
throughout the entire ejection phase as shown in A - Full Cycle portion
of FIG. 3 . Alternatively, the chest compression could be applied only
during the first half of the ejection cycle as shown in B - 1st
Half Cycle.
As another option, the chest compression could be applied during the
second half of the ejection cycle as shown in C - 2nd Half Cycle. As a
further alternative, chest compressions could be applied during each
3 5
0457ejection cycle, or only during certain ejection cycles, such as every
second, third, or fourth ejection cycle. Also, the magnitude of chest
compressions may be evaluated to determine if they should be
increased or decreased throughout the procedure. A similar scenario
may be used for chest decompressions, abdominal compression
decompression or counterpulsations, limb compressions, and the
phases of ventilations.
[0086] In summary, by utilizing a sensor, or combination of sensors,
an apparently lifeless patient's residual myocardial wall function may be
detected and the application of phasic resuscitative therapies, including
chest compressions and/or decompressions as well as abdominal
counterpulsations, and ventilations may be precisely controlled so that
the application of CPR components enhances, and does not interfere
with the existing mechanical activity of the heart. The device may also
potentially be used in patients suffering severe shock with residual signs
of life.
[0087] Referring to FIG. 4 , one exemplary method for treating a
patient suffering from ailments ranging from shock to PEA will be
described. Initially, the patient is evaluated to determine if there is any
myocardial activity as illustrated in step 40. If myocardial activity is not
present, the rescuer may wish to consider other treatments as
illustrated in step 42. For example, such treatments could include the
use of a defibrillating shock as is known in the art. If some myocardial
wall activity is detected, the process proceeds to step 44 where the
timing of the ejection phase and filling phase is determined. As
previously described, this may be determined by the use of a sensor
that is used to sense myocardial wall activity. Also determined may be
36
1910457the vector and baseline oxygen or energy state of vital organs.
Depending on the amount of activity exhibited by the heart, a
compressive force may be applied to the heart during one or more of
the ejection phases as illustrated in step 46. This may be accomplished
by using automated equipment or by using manual techniques. In either
event, the applied compressive forces may be synchronized with the
ejection phase so that the compressive forces do not interfere with the
refilling phase. Optionally, as illustrated in step 48, the manner of
compressions may be varied. This may include the time, duration,
amount, frequency, vector, and the like. These variables may be initially
set after measuring the amount of myocardial wall activity and may be
changed or varied throughout the procedure depending on the patient's
physiological condition.
[0088] As illustrated in step 50, the patient may periodically be
provided with ventilations. The phases of ventilations may also be
synchronized with the sensed ejection phases and refilling phases as
measured in step 44. Further, the ventilations may be coordinated with
the application of the chest compressions.
[0089] In some cases, the patient's chest may be actively lifted in
an alternating manner with chest compressions as illustrated in step 52.
In such cases, the chest may be lifted during the filling phase as
measured in step 44.
[0090] As another optional step 54, the patient may periodically be
provided with medications as part of the treatment. Examples of
medications that may be applied include epinephrine, vasopressin,
amiodarone, and the like. Alternative phasic therapies may also be
synchronized with residual myocardial activity. These may include,
3 7
1910457among others: abdominal counterpulsation, ventilation, phasic limb-
compression, myocardial electrical stimulation, intravascular fluid
shifting, intravascular balloon inflation-deflation, application of
transthoracic electromagnetic irradiation.
[009 1] Throughout the procedure, the patient's heart may be
continually monitored to determine myocardial activity as well as other
physiological conditions. For example, after each of the treatments in
steps 46, 48, 50, 52 and 54, the condition and response of the patient is
monitored. Depending on the sensed response and condition, the
selection and application of these treatments may be adjusted to
achieve a desired response and condition of the patient. Depending on
the patient's condition, any of the items discussed in steps 44-54 may
be varied or stopped over time. At step 56, the process ends.
[0092] FIGURE 5 is a flow chart illustrating an exemplary process
executed by the controller 14 to validate the sensors 12 shown in Figure
1. The sensor validation process 500 may be embodied in an algorithm
stored as software or firmware in electronic memory of the controller 14
and executed by a processor of the controller. The sensor validation
process 500 may include applying a predetermined regimen 502 chest
compression regimen, such as a regimen of one or more chest
compressions of predetermined force(s), vector(s), frequency and
location(s) on the chest. Each of the sensors generate and output
signals to the controller that indicate a condition of the patient being
sensed by each of the sensors.
[0093] The controller analyzes 504 the output signals to determine
which of the output signals or group of signals best indicate the a
condition of the patient, such as cardiac output. The algorithm 500 may
3 8
1910457compare the actual output signals to expected sensor output signals
506 stored in the memory of the controller. Based on the comparison,
the controller identifies 508 the sensor(s) generating signal(s) that
accurately and clearly report the condition of the patient in response to
the regimen of chest compression(s).
[0094] The sensors identified in step 5 10 are deemed to be best
suited to sense myocardial activity may depend on the particular patient
and the circumstances of the PEA condition. The sensor validation
procedure 500 may be performed at the initiation of chest compressions
and periodically thereafter, especially if myocardial output does not
improve in an expected manner.
[0095] Once the sensors have been validated, signals generated by
the sensors identified in the validation process are used to provide
feedback to the algorithms, such as shown in Figure 4 and 6 , that
determine the chest compressions and optionally synchronized
ventilation and synchronized electrical stimulation of the heart. Using
these signals, the algorithms may generate and adjust a regimen for
chest compressions and ventilations of the patients. The regimen may
dictate the force to be applied by the chest compressions, the frequency
of the chest compressions, the shape and duration of the force applied
by the chest compressions, the synchronization and phasing of the
chest compressions with sensed myocardial activity, the location on the
chest or other body location, e.g., legs, of compressions, and a vector of
the chest or other compressions. The algorithms may vary the regimen
to optimize a condition of the patient, such as to increase sensed actual
cardiac output or actual hemodynamics, e.g., pulsatile blood flow.
3 9
1910457[0096] FIGURES 6A and 6B are a flow chart of an exemplary
algorithm 600 to determine when to initiated chest compressions,
synchronize the chest compressions to cardiac activity and optimize the
chest compression regimen which may be combined with ventilation of
the patient and external electrical stimulation of the heart. In step 602,
sensors applied to a patient suffering from shock or other cardiac
aliment are monitored to detect cardiac electrical activity, e.g.,
electrocardiography (ECG/EKG), and to detect directly myocardial
motion or pulsatile blood flow.
[0097] The sensor signals from step 602 provide the controller and
the health care provider with information from which to determine
whether to initiate chest compressions. For example, if the ECG signals
indicate a steady, regular heart beat, the controller may determine that
chest compressions are not needed, in steps 604 and 606. The signals
from step 602 may be analyzed in step 604 to determine whether, for
example, the ECG signals do not indicate a regular or sufficiently
frequent heart beat. If the ECG signals indicate an irregular or
infrequent heart beat, the controller may determine (604) that chest
compressions are needed (606) to augment the remaining natural
cardiac activity.
[0098] In addition, signals from the sensors detecting pulsatile
blood flow and actual myocardial motion may be compared to the
signals of cardiac electrical activity to confirm that the cardiac electrical
activity is synchronized with actual cardiac output. I f the there is no
detectable cardiac electrical activity or if the cardiac electrical activity is
disassociated with pulsatile or actual ejection of blood from the heart,
the controller may rely on sensors detecting actual myocardial
40
1910457movement or pulsatile blood flow to monitor cardiac movement and
output. The controller may perform a sensor validation algorithm (Fig.
5) to identify the sensors generating signals that accurately and clearly
indicate cardiac movement and output.
[0099] After chest compressions have been initiated (step 606), the
controller executes algorithms (Fig. 4) to synchronize (step 608) the
chest compressions to the sensed myocardial motion, e.g., to an
EKG/ECG signal or to sensor signals indicative of pulsatile or actual
myocardial motion. While the chest compressions are applied, the
controller relies on the validated sensors to provide feedback
information regarding the contraction or ejection phase of the heart and
the cardiac output of the heart.
[00 100] In step 6 0 , the controller executes algorithms (see Fig. 4) to
optimize the chest compression regimen to enhance cardiac output.
The chest compression regimen may be optimized using the signals
generated by the validated sensors that provide information regarding
cardiac output or another condition of the patient. The chest
compression regimen may be optimized by varying the parameters of
the chest compressions, such as varying the force and frequency of the
compressions, the location of the compressions on the chest or other
location on the patient and the phase of the synchronization between
the compressions and the contraction/ejection of the heart. To optimize,
the controller may vary one or more of the parameters of the chest
compressions and analyze the response to the varied parameter(s)
generated by the validated sensors.
[00 101] Examples of parameters of the chest compression that may
be varied and optimized include: the depth of the compressions made
4 1
1910457into the chest; the during of each compression, the velocity of each
compression, the force applied to the chest during each compression,
the rate of the chest compression, the shape of the compression (such
as the duration at the depth of the compression), the location of the
compression on the chest, and the phase of synchronization between
the chest compression and the sensed cardiac activity. While varying
one or more of these parameters, the response of the patient to the
chest compression is monitor and a determination is made at to which
combination of parameter setting yields the most advantageous
response, such as strongest arterial pulse flow.
[00 102] In step 612, the controller synchronizes ventilation of the
patient and electrical stimulation of the heart to the chest compressions
or to contraction/ejection of the heart. The electrical stimulation may be
repeated and coordinated with the chest compressions. In step 614,
the sensors, e.g., validated sensors, detect or measure the response of
the patient to one or more of the compressions, ventilation and electrical
stimulations. In step 616, a determination is made that the detected or
measured response is achieving a desired result or outcome in the
patient. If a desired result or outcome is not being achieved, the
controller may adjust the compressions, ventilation or electrical
stimulations until the desired result or outcome is achieved.
[00 103] FIGURE 7A is a chart 700 illustrating chest compressions
applied in synchronization with a slow heart beat. Patients suffering a
cardiac arrhythmia may have a slow heartbeat 702, e.g., a heartbeat
below 55 to 60 beats per minute. The controller detects the heart beat
from sensor signals indicating pulsatile flow and determines that the
heart beat is slow and sensors detecting aortic pressure that provide
4 2
1910457signals indicating a weak heartbeat. To compensate for a slow or weak
heartbeat, the controller generates commands 706, 708 to actuate a
chest compression device or audible and visible commands to notify
when chest compressions are to be applied and, optionally, to indicate a
force to be applied by the chest compressions.
[00 104] The audible commands may include computer generated
voice commands such as, during the chest compressions, "press
softer", "press harder", "press deeper", "press shallower", "press faster
(or slower)" and "press lower (or higher) on the abdomen". Similarly,
visible commands may be computer generated display images
corresponding to these voice commands. The audible and visible
commands may be the result of computer analysis of feedback signals
generated from sensors monitoring the pulsatile flow, myocardial
activity, breathing or other condition of the patient.
[00 105] The force of the chest compressions to be applied is
indicated by the length of the dotted line 706, 708 shown in Figure 7 .
The chest compressions 708 that coincide with each heartbeat 704 may
be synchronized with the ejection phase of the heartbeat. Chest
compressions may not be applied during the ejection phase and during
the period during which the heart is susceptible to comodio cordius.
Additional chest compressions 706 are applied during periods between
the natural heart beat. The force of these chest compressions 706 may
be sufficient to result in a cardiac output which approximates the
desired cardiac output 7 10 . The level of force of the chest
compressions that is commanded by the controller may be varied based
on feedback signals from sensors detecting the cardiac output. Further
the chest compressions 708 that coincide with the heartbeat may be
4 3
04 57applied at a substantially lower force than the chest compressions 706
that are out-of-phase with the natural heartbeat. The lower force of the
chest compressions 706 are intended to augment the natural
contraction of the heart to ejection blood at a sufficient force to achieve
a desired level of cardiac output. The controller estimates the lower
level of force to be applied by the chest compressions 708 (as
indicated by the short dotted lines associated with 708 on Fig. 8) and
issues commands to the chest compression device to apply a certain
level of chest compressions. The controller may also issue an alert to a
health care provider to not apply a force to the chest during a period
712 coinciding with the heartbeat to avoid having chest compressions
applied which counter act the natural heartbeat 704.
[00 106] FIGURE 7B is a time line chart including a line 802 indicating
a slow heart beat, a line 804 indicating chest compressions occurring
more frequently than the heart beat, a line 806 indicating a timer
triggering the chest compression, and a line 808 indicating an error
correction counter. As indicated by line 802, the heartbeat is naturally
occurring once every three (3) seconds, in this example. This slow
heart beat may be detected by its ECG electrical signal. Because the
heartbeat is slow, chest compressions (see line 804) are applied more
frequently, e.g., every second, than the heart beat. The higher
frequency of the chest compressions may be a harmonic of the
frequency of the heart beat. A harmonic frequency should maintain
synchronization between the chest compressions and the natural heart
beat.
[001 07] The chest compressions are synchronized with the heart
beat. In this example, every third chest compression 8 10 coincides with
44
1910457the heart beat. It is desirable that the chest compression be
synchronized with the ejection phase of the heartbeat. For example, the
start of the chest compression should coincide with the QRS electrical
signals 8 12 that precedes the ejection phase of the cardiac cycle.
[00 108] A timer in the system that controls or triggers the chest
compressions generates a timing signal 806 that triggers the start 814
and end 8 6 of each chest compression. The timing signal 806 triggers
chest compressions at regular intervals, such as about every second.
The regular intervals of the chest compressions may, over time,
become unsynchronized with the heart beat 802.
[00 109] To maintain synchronization between the chest
compressions and the heart beat, a timer or counter generates an error
signal 808. The timer is in the system that controls or triggers the chest
compressions. The error signal is used to measure the period between
the QRS signal 812 and the chest compression 8 10 , e.g., the initiation
of the chest compression, nearest the QRS signal. If the QRS signal
812 and the chest compression are synchronized, an error period 818
may be instantaneous or brief as shown by the error signal 808. A
longer error signal 820 results i f the initiation of the chest compression
does not occur at about the same time as the QRS signal. As an
alternative to the QRS signal, the error period 818, 820 may be
determined based on sensed pulsatile flow or sensed mechanical
myocardial activity.
[00 110] The error period is triggered by the chest compression timing
signal 806 and particularly by the signal 814 initiating the chest
compression. The error period 820 may be a positive period if the chest
compression starts 814 before the QRS period. A positive error period
4 5
1910457is applied by the system to delay the next chest compression by the
duration of the period. The delay should cause the chest compression
that coincides with the next heart beat to by synchronized with that
heart beat. Similarly, the error period 820 may be a negative period if
the QRS signal precedes the chest compression signal. A negative
error period 820 may be applied to advance the occurrence of the next
chest compression by the duration of the negative error period. The
advance should cause the chest compression that coincides with the
next heart beat to be synchronized with the heart beat.
[OOl l l ] The determination of the error period is similar to a phase
lock loop control technique conventionally used in control systems. The
delay or advance due to an error period 820 to the chest compression
signal 814 may occur entirely in a period between two chest
compressions, or may be distributed evenly between two or more
periods depending on the length of the delay or advance. Similarly, the
error period 820 may not result in a delay or advance if the period is
shorter than a threshold duration, e.g., 0 milliseconds.
[00 112] FIGURE 8 is a chart illustrating a method to synchronize
chest compressions 902 to a heart beat shown by line 904. The
electrical signals of a heart beat conventionally include a P-wave, the
QRS waves, and the T wave. It is well known that the P-wave indicates
atrial electrical activation (depolarization), the QRS wave complex
indicates a rapid depolarization of the ventricles and the start of the
cardiac ejection phase, and the T wave indicates the recovery
(repolarization) of the ventricles. The chest compression 902 optimally
occurs during the ejection phase immediately following the QRS wave.
4 6
1910457[001 13] The chest compression is terminated 906 before a safety
period 908 before the T wave. The period may be a short duration such
as 10 to 200 milliseconds. The safety period 908 is applied to ensure
that the chest compression does not continue to the T wave particularly
during the portion 910 of the T wave during which the heart is
vulnerable to commotio cordis, which is a disruption of the heart rhythm
due to a blow to the heart during the T wave.
[00 114] FIGURE 9 is a chart illustrating a method to synchronize
electrical cardiac stimulation 1002 to aortic pressure (AoP) pulses 1004
due to myocardial mechanical activity. The aortic pressure (AoP) pulses
may be detected based on ECG signals, pulsatile flow and myocardial
activity. I f the heart is producing ECG signals that are synchronized
with the myocardial mechanical activity, the QRS signal 1006 of the
ECG may be applied to trigger each electrical cardiac stimulation pulse
008. Alternatively, the electrical stimulation pulses 1008 may be trigger
based on pulsatile flow or sensed myocardial mechanical activity.
[001 5] The electrical stimulation pulses 1008 may be applied at a
frequency greater than the natural heat beat, such as in the manner
shown and described in connection with Figure 7B. Further, the
frequency and timing of the electrical stimulation pulses may be
adjusted in the manner shown and described in connection with Figure
8.
[001 16] The electrical pulse signals 1008 may be applied to the
chest of the patient or directly to the heart for each heart beat. The
electrical signal is applied for each heart beat to assist the heart in
restoring natural electrical stimulation, to resynchronize the natural
electrical stimulation to the myocardial mechanical activity or to
4 7
1910457supplement the natural electrical stimulation to increase the ejection
force from the myocardial mechanical activity.
[001 17] The electrical pulse signals may be a "pacer pulse" such as
that delivered by a conventional pacemaker and having a value of less
than 500 milliamps (mA). Alternatively, the electrical pulse signals may
shock the heart by delivering a pulse of between 500mA to 5A, which is
similar to a low energy defibrillator pulse.
[00 118] The application of the electrical pulse signals for each heart
beat is in contrast to a conventional pacemaker device that does not
issue an electrical stimulation for each heart beat. A conventional
pacemaker issues an electrical stimulation one if and when a timer
expires without the occurrence of a natural heart beat. A conventional
pacemaker issues an electrical signal when a natural heartbeat does
not occur in a prescribed period and does not issue an electrical signal
that is synchronized with a naturally heartbeat.
[00 119] The invention has now been described in detail for purposes
of clarity and understanding. However, it will be appreciated that certain
changes and modifications may be practiced within the scope of the
appended claims.
4 8
1910457WHAT IS CLAIMED IS:
1. A method to treat a patient in shock comprising:
sensing myocardial motion or pulsatile blood flow in the patient;
repeatedly applying a phasic therapy to the patient synchronized
to the sensed actual myocardial motion or pulsatile blood flow, wherein
the phasic therapy includes repeatedly applying a compressive force to
the chest or an electrical shock to the heart of the patient, and
adjusting the compressive force or electrical shock depending on
whether the force or shock coincides with a heart beat as indicated by
sensed myocardial motion or pulsatile blood flow.
2 . A method as in claim 1 wherein the repeated application of
the phasic therapy augments cardiac ejection of blood and the
cessation of the application of the compressive force and the electrical
shock avoids interfering with filling of the heart.
3. A method as in claim 1 or 2 wherein the phasic therapy
includes a second phasic therapy selected from a group consisting of
active chest decompression, abdominal compression, ventilation, phasic
limb-compression, myocardial electrical stimulation, intravascular fluid
shifting, intravascular or internal visceral balloon inflation-deflation, and
application of transthoracic electromagnetic irradiation.
4 9
19104574 . A method as in any of claims 1 to 3 wherein the compressive
force is applied to at least one of a sternal, a parasternal or an
intercostal area of the chest.
5 . A method as in any of claims 1 to 4 wherein the compressive
force or electrical shock is applied during each ejection phase of the
heart in which the phasic therapy is applied.
6 . A method as in any of claims 1 to 5 wherein the compressive
force or electrical shock is applied during less than all of the ejection
phase of the heart during a period in which the phasic therapy is
applied.
7 . A method as in any of claims 1 to 6 wherein the compressive
force or electrical shock is applied during a predetermined portion of the
ejection phase and the cessation occurs during another portion of the
ejection phase.
8 . A method as in any of claims 1 to 7 wherein the phasic therapy
comprises actively lifting or actively decompressing of the chest during
the relaxation phase and during the cessation of the compressive force.
9 . A method as in claim 8 wherein the lifting or decompression is
applied during an entirety of the relaxation phase.
10 . A method of claim 8 or 9 wherein the lifting or decompression
is applied during a predetermined portion of the relaxation phase and is
not applied during another portion of the relaxation phase.
5 0
1910457. A method as in any of claims 1 to 0 further comprising
applying or altering ventilations, gas flow or airway pressure of the
patient based on the sensed myocardial motion or pulsatile blood flow.
12. A method as in any of claims 1 to 11 wherein the
compressive force is applied using equipment selected from a group
consisting of mechanical compression devices; inflatable vests, nerve or
muscle stimulators; and a suction based compression-decompression
device.
13 . A method as in any of claims 1 to 12 wherein a sensing
system directly senses the actual myocardial motion or pulsatile blood
flow.
14. A method as in claim 13 wherein the sensing system
comprises one or more sensors in a group consisting sensors of
echocardiography, Doppler ultrasonography, plethysmography and
phonocardiography.
15 . A method as in claim 13 or 14 wherein the sensing system
comprises an array of sensors applied to the patient.
16. A method as in any of claims 1 to 5 further comprising
displaying or broadcasting information indicating the sensed actual
myocardial motion or pulsatile blood flow.
51
19 1045717. A method as in claim 16 wherein the repeated application of
the phasic therapy is applied manually in synchronization with the
displayed or broadcasted information.
18. A method as in any of claims 1 to 17 further comprising
delaying initial application to the heart of the phasic therapy until a
sensed natural heartbeat has a rate below a predetermined threshold
rate.
19 . A method to treat a patient as in claim 18 further comprising
applying the chest compressions or the electric shocks at a rate faster
than the sensed natural heartbeat.
20. A method to treat a patient comprising:
sensing a natural rate of myocardial activity of the heart of the
patient, and
repeatedly applying a phasic therapy to the patient synchronized
to the sensed myocardial activity, wherein the phasic therapy includes
repeated myocardial electrical stimulation applied at a rate faster than
the sensed natural rate of myocardial activity.
2 1. A method as in claim 20 wherein the myocardial electrical
stimulation is applied during at least a portion of an ejection phase of
the heart.
52
191045722. A method as in claim 20 or 2 1 wherein the myocardial
electrical stimulation is not applied during a relaxation phase of the
heart.
23. A method to treat a patient as in any of claims 20 to 22
further comprising determining the patient is in shock before the
repeated application of the phasic therapy.
24. A method to treat a patient as in any of claims 20 to 23
further comprising determining the patient is suffering pulseless
electrical activity (PEA) before applying the phasic therapy.
25. A method to treat a patient as in any of claims 20 to 24
further comprising determining the patient is suffering cardiac arrest
before the repeated application of the phasic therapy.
26. A method as in any of claims 20 to 25 wherein the repeated
application of the phasic therapy augments cardiac ejection of blood
and the cessation of the application of the compressive force avoids
interfering with filling of the heart.
27. A method as in any of claims 20 to 26 wherein the phasic
therapy includes a second phasic therapy selected from a group
consisting of active chest decompression, abdominal compression,
ventilation, phasic limb-compression, myocardial electrical stimulation,
intravascular fluid shifting, intravascular or internal visceral balloon
53
10457inflation-deflation, and application of transthoracic electromagnetic
irradiation.
28. A method as in any of claims 20 to 27 wherein the
compressive force is applied to at least one of a sternal, a parasternal or
an intercostal area of the chest.
29. A method as in any of claims 20 to 28 wherein the
compressive force is applied during each ejection phase of the heart in
which the phasic therapy is applied.
30. A method as in any of claims 20 to 29 wherein the
compressive force is applied during less than all of the ejection phase of
the heart during a period in which the phasic therapy is applied.
3 1. A method as in any of claims 20 to 30 wherein the
compressive force is applied during a predetermined portion of the
ejection phase and the cessation occurs during another portion of the
ejection phase.
32. A method as in any of claims 20 to 3 1 wherein the phasic
therapy comprises actively lifting or actively decompressing of the chest
during the relaxation phase and during the cessation of the compressive
force.
33. A method as in any of claims 20 to 32 wherein the lifting or
decompression is applied during an entirety of the relaxation phase.
54
191045734. A method as in any of claims 20 to 33 wherein the lifting or
decompression is applied during a predetermined portion of the
relaxation phase and is not applied during another portion of the
relaxation phase.
35. A method as in any of claims 20 to 34 further comprising
applying or altering ventilations, gas flow or airway pressure of the
patient based on the sensed actual myocardial motion or pulsatile blood
flow.
36. A method as in any of claims 20 to 35 wherein the
compressive force is applied using equipment selected from a group
consisting of mechanical compression devices; inflatable vests, nerve or
muscle stimulators; and a suction based compression-decompression
device.
37. A method as in any of claims 20 to 36 wherein a sensing
system senses the actual myocardial motion or pulsatile blood flow.
38. A method as in claim 37 wherein the sensing system
comprises one or more sensors in a group consisting sensors of
echocardiography, Doppler ultrasonography, plethysmography and
phonocardiography.
39. A method as in any of claims 20 to 38 further comprising
displaying or broadcasting information indicating the sensed actual
myocardial motion or pulsatile blood flow.
55
191045740. A method as in claim 39 wherein the repeated application of
the phasic therapy is applied manually in synchronization with the
displayed or broadcasted information.
4 . A system to treat a patient having a heart and a chest, the
system comprising:
a least one sensor monitoring cardiac activity in the patient by
detecting at least one of myocardial pump activity, myocardial
mechanical activity, hemodynamics and organ perfusion;
a logic controller receiving signals from the at least one sensor
and generating control commands for controlling one or more phasic
therapies and synchronizing the one or more phasic therapies with the
monitored cardiac activity in the patient; and
wherein the logic controller executes an algorithm stored in
memory associated with the logic controller, wherein the algorithm
causes the logic controller to generate commands to vary patterns of
the application of the one or more phasic therapies, and thereafter
detect changes in at least one of the sensed myocardial pump activity,
myocardial mechanical activity, hemodynamics and organ perfusion due
to variations in the patterns, and determine one of the patterns of phasic
therapies corresponding to a desired level of at least one of sensed
myocardial pump activity, myocardial mechanical activity,
5
1910457hemodynamics and organ perfusion hemodynamics and organ
perfusion.
42. The system of claim 4 1 further comprising a sensing
system comparing at least one of the sensed myocardial pump activity,
myocardial mechanical activity, hemodynamics and organ perfusion
hemodynamics and organ perfusion with and without application of the
phasic therapies to determine which of the phasic therapies optimally
augments hemodynamics or perfusion.
43. A method to treat a patient having a heart and a chest, the
system comprising:
monitoring cardiac activity in the patient by detecting with at least
one sensor at least one of myocardial pump activity, myocardial
mechanical activity, hemodynamics and organ perfusion;
receiving the signals from the at least one sensor and, based on
the signals, synchronizing one or more phasic therapies applied to the
patient to the monitored cardiac activity in the patient;
varying the one or more phasic therapies;
detect changes in at least one of the sensed myocardial pump
activity, myocardial mechanical activity, hemodynamics and organ
perfusion due to the variations in the one or more phasic therapies;
determining at least one of the variations of the phasic therapies
corresponding to a desired level of at least one of sensed myocardial
5 7
1910457pump activity, myocardial mechanical activity, hemodynamics and organ
perfusion hemodynamics and organ perfusion.
44. The method of claim 43 further comprise comparing at least
one of the sensed myocardial pump activity, myocardial mechanical
activity, hemodynamics and organ perfusion hemodynamics and organ
perfusion with and without application of the phasic therapies to
determine which of the phasic therapies optimally augments
hemodynamics or perfusion.
45. A method to treat a patient comprising:
sensing a natural rate of myocardial activity of the heart of the
patient;
repeatedly applying a phasic therapy to the patient synchronized
to the sensed myocardial activity, wherein the repeated phasic therapy
is applied at a higher frequency than the frequency of the natural rate;
determining an error period between an event in the myocardial
activity and the phasic therapy applied at time proximate to the
myocardial activity, and
advancing or delaying one of the applications of the phasic
therapy by a period determined using the error period.
46. The method to treat a patient as in claim 45 wherein the
higher frequency of the phasic therapy is a harmonic of the frequency of
the natural rate.
58
191045747. The method to treat a patient as in claim 45 or 46 wherein
the myocardial activity is a QRS signal.
48. The method to treat a patient as in any of claims 45 to 47
further comprising terminating the phasic therapy before a vulnerable
period in a T wave of the myocardial activity.
49. The method to treat a patient as in any of claims 45 to 48
further comprising terminating the phasic therapy a safety period before
a T wave of the myocardial activity.