F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN INVASIVE BLOOD PRESSURE MONITOR WITH IMPROVED PERFORMANCE

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED

(b) NATIONALITY : An Indian Company

(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India and also having a place of business named as "Medical Equipments & Systems" at Gate No. 5, Mysore Campus, KIADB Industrial Area, Hebbal, Mysore- 570018 Karnataka, India

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to intra-arterial blood pressure monitoring to gain a beat-to -beat record of a patient’s blood pressure. More particularly, the present invention relates to an invasive blood pressure analyzer/system for physiological monitoring of patients with improved performance with transducer establishing zero level.

BACKGROUND AND PRIOR ART OF THE INVENTION
Invasive (intra-arterial) blood pressure (IBP) monitoring is a commonly used technique of physiological monitoring in the Intensive Care Unit (ICU) and is also often used in the operating theatre. The technique involves the insertion of a catheter with pressure sensing transducer into a suitable artery and then displaying the measured pressure wave on a monitor.
The most common reason for using intra-arterial blood pressure monitoring is to gain a ‘beat-to-beat’ or real time record of a patient’s blood pressure.
Monitoring direct arterial pulse pressure provides valuable information in terms of pressure value or measurement, but it also provides valuable information in terms of its shape and contour. The arterial pulse wave can exhibit changes that are related to specific underlying pathology.
Indications for the use of direct arterial blood pressure monitoring include shock, critical illness, peripheral vasoconstriction, and intra-operative and post-operative monitoring of high-risk patients. In addition, arterial catheters allow for frequent blood sampling and monitoring of blood gas measurement
By way of an example the location on the human body for Catheterization are as below
• Arterial : - Radial, femoral, dorsalis pedis
• CVP :- Internal Jugular, Subclavian, Brachial , femoral
By way of an example the values for the blood pressure are as below.
Type Arterial CVP
Systolic 120 mmHg 10 mmHg
Diastolic 80 mmHg 17.4 mmHg
Mean 96 mmHg 6.10 mmHg

The components of an intra-arterial monitoring system can be considered in three main parts
1. the measuring apparatus
2. the transducer
3. the monitor

The measuring apparatus consists of an arterial cannula connected to plastic tubing containing a continuous column of saline, which conducts the pressure wave to the transducer.
The arterial line is also connected to a flushing system consisting of a 500ml bag of saline pressurized to 300mmHg via a flushing device. The flush system provides a slow but continual flushing of the system at a rate of approximately 4-5ml per hour. A rapid flush can be delivered by manually opening the flush valve. There is also usually a 3-way tap to allow for arterial blood In the case of intra-arterial monitoring.
The transducer consists of a flexible silicone rubber diaphragm at front end and a semiconductor, which changes its properties linearly with applied pressure at the back end. The gap between the two is filled with gel, which linearly transmits the pressure to strain gauge semiconductor.

As pressure is applied to the diaphragm it stretches and its resistance changes, altering the electrical output from the system. The transducers used are differential pressure transducers and so must be calibrated relative to atmospheric pressure before use.
Strain gauge transducers are sensitive to temperature changes (typically 0.1 mm Hg/1° C) and require occasional checking of the zero-pressure baseline for drift. The room in which they are being used should be maintained at a fairly constant temperature. Solutions flushed through the transducers in to the body of patient can also cause temperature variance and baseline drifts to occur.
The most common major mistakes in pressure monitoring involve failure to establish zero, failure to recheck the zero value for transducer drift, and failure to re-level the transducer appropriately when changes in patient position
US 5937950 patent teach us a cable system includes a plurality of device cables having distal ends adapted to be electrically connected to medical sensing devices that, in turn, are attached to a patient. A main cable has a first end electrically connected to proximal ends of the plurality of device cables and the second end is adapted to be connected to a monitor.
This invention does not tell anything about calibration and zeroing of transducers and the monitoring apparatus. Also the cables at patient side are still cluttered.
The inventor to calibrate or zero the transducer has provided no foolproof switch. There is need for a cable with better management and accessibility.
US patent number 3894535 discloses a blood pressure monitor system with pushbutton zero-offset compensation. Here the system includes a manual control which when operated, automatically provides a feedback signal to compensate for zero-offset of the pressure transducer when zero pressure is applied to the transducer. In the prior art untrained nurses manually vary a potentiometer, using hunt and seek method and used to nullify the offset voltage.
This invention is not sufficiently automated and requires manual judgment to decide the offset.
Also the digitizing pressure waveform display and displaying and storing the noise free filtered waveform are not done.

OBJECTS OF THE INVENTION
Overall object of the present invention is to overcome the disadvantages / drawbacks of the prior art.
A basic object of the present invention is to provide an invasive blood pressure analyzer/system with improved performance with transducer establishing zero level.
Another object of the present invention is to provide an invasive blood pressure analyzer/system that rechecks the zero value for transducer drift.
Yet another object of the invention is easy accessibility of the highly used features.
In the dual channel IBP interface cable (for individual pressure channels) a switch is provided for directly zeroing the pressure channel without accessing the monitor. Two pressure channels are merged for better cable management and accessibility.
Yet another object of the invention is method of improvement in Pressure Measurement accuracy and method to accurately measuring pressure even with transducers having large offset errors without compromising the pressure measurement range. The error is measured in the ADC by applying the fixed voltage at using DAC with pressure input. After error measurement the same error will be compensated with correction in DAC. Same resolution and accuracy specification is used in both DAC and ADC to achieve the better accuracy in the error removal.
Yet another object of the invention is method for improving the representation of pressure waveform for better interpretation and diagnosis. Pressure waveform is displayed in such a way that the maximum resolution is achieved in the display for proper pressure morphology interpretation.
These and other advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

According to one of the aspect of the present invention the system is provided an integrated apparatus for physiological blood pressure monitoring of patients, said system comprising:
an enclosure means;
a display means displays information through a graphical user interface;
a capacitive touch keyboard having a push button on/off switch to turn on/off said apparatus;
a power supply assembly comprises a battery charger and controller , a lithium-ion battery pack adapted to convert ac to dc power supply;
analog signal acquisition modules;
at least one transducers connected to the patient at proximal end , said transducer comprises
a junction box ;
a connector connected with said junction box at the distal end electrically and mechanically connected through a interfacing cable with said apparatus ;
a push button switch for adjustment of zeroing ;
a micro-controller operatively connected with said transducers , said controller comprises : an 8 channel ADC for the Pressure signal and transducer offset error measurement and 8 channel DAC for biasing the Circuit and transducer offset error removal;
an instrumentation amplifier operatively connected with said junction box for amplifying the pressure signal and transducer offset error ,
a low pass filter for noise removal;
an High gain amplifier for the lower pressure measurement;
an Low gain amplifier for the Full scale pressure measurement.
such that said microcontroller adapted to measure the Offset error at one of the ADC channel and Corrected using the DAC, such that a fixed DC voltage is applied through from DAC and measured from the ADC without feeding any pressure signal,
such that any difference in the measured value at ADC and the DAC will be the offset error; and
an audio and visual indication/alarm devices operatively connected with said microcontroller such that when the zeroing and calibration is achieved so that the caregiver can concentrate only on leveling, zeroing and calibrating the transducer rather than rushing towards the monitor multiple times for pressing the switch.

DETAILED DESTRIPTION OF THE INVENTION
The present invention relates to an invasive blood pressure analyzer/system for physiological monitoring of patients with improved performance with transducer establishing zero level.
According to the first embodiment of the present invention there is provided an integrated apparatus for physiological blood pressure monitoring of patients. The system comprising an enclosure means; a display means displays information through a graphical user interface; a capacitive touch keyboard having a push button on/off switch to turn on/off the apparatus; a power supply assembly comprises a battery charger and controller, a lithium-ion battery pack adapted to convert ac to dc power supply; analog signal acquisition modules; at least one transducers connected to the patient at proximal end; a micro-controller operatively connected with the transducers, the controller comprises : an 8 channel ADC for the Pressure signal and transducer offset error measurement and 8 channel DAC for biasing the Circuit and transducer offset error removal; an instrumentation amplifier operatively connected with the junction box for amplifying the pressure signal and transducer offset error, a low pass filter for noise removal; an High gain amplifier for the lower pressure measurement; an Low gain amplifier for the Full scale pressure measurement; an audio and visual indication/alarm devices operatively connected with the microcontroller such that when the zeroing and calibration is achieved so that the caregiver can concentrate only on leveling, zeroing and calibrating the transducer rather than rushing towards the monitor multiple times for pressing the switch.

The transducer comprises a junction box; a connector connected with the junction box at the distal end electrically and mechanically connected through a interfacing cable with the apparatus; a push button switch for adjustment of zeroing
The microcontroller adapted to measure the Offset error at one of the ADC channel and Corrected using the DAC, such that a fixed DC voltage is applied through from DAC and measured from the ADC without feeding any pressure signal,
such that any difference in the measured value at ADC and the DAC will be the offset error.

The enclosure comprises master batch resins, which are bio-compatible plastics and composites.

The enclosure means adapted to enclose the apparatus in various sized plastic Enclosure / cabinet so that it is hand carried and transportable from one location to another accompanying the patient.
The micro controller adapted to measure/analyze zeroing.
The micro controller adapted to detect the press of the push button switch such that If the pressure channel is not zeroed a message “Not Zeroed” will be displayed in the display means and during the switch Off condition micro-controller input signal GPIO1 will be High and when ever this switch is pressed the GPIO1 will become low. The resistor 220 is used to bias / pull-up the signal GPIO to avoid false triggering.
The micro-controller gets indication for First High to low transition for initiating the pressure zeroing and thereafter a messages “ Press again for zeroing” will be displayed in the display means, a second press at zero switch will zero the pressure channel and a message “Zeroed” will be displayed at display means.
The apparatus provides high level of accuracy as the same resolution ADC and DAC is used in the removal of transducer-offset error.
The high level of accuracy as the same DC accuracy specification is used for providing the High level of accuracy in the removal of transducer-offset error.

The apparatus further provides indication for changing the pressure transducer by posting a message “ Change Transducer” in the TFT display when the pressure transducer offset error crosses the limit or it can saturate the pressure measurement channel thus detecting the incompatible transducer or permanent transducer damage also.
The apparatus provides the way to measure the multiple gain channels without using external multiplexer and ADC measurement channel switches as per the pressure value monitored.
The display means having the two view modes normal view mode and enhanced view mode for representing the pressure waveform optimally.
The microcontroller provides manual scaling options where user selects low pressure scale (Baseline) and high pressure scale (saturation line) as per the measured pressure values (Systolic and Diastolic).
The microcontroller provides auto-scaling option where the apparatus automatically selects low-pressure scale (Baseline) and high-pressure scale (saturation line) as per the measured pressure values (Systolic and Diastolic).

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawing:
Figure 1 illustrates invasive blood pressure monitor with improved performance (over all view)
Figure 2 illustrates the block diagram – Analog front end and digital section, MCU, display, automatic Offset Error correction using feedback compensation technique.
Figure 3 illustrates Flow chart for ‘Zeroing logic flow’ and permanent transducer damage detection.
Figure 4 illustrates Pressure waveform measurement, base line and saturation line selection when auto scale selected.
Figure 5 illustrates Pressure waveform measurement from high gain and low gain channels when manual scale selected.
Figure 6 illustrates logic flow for Pressure waveform measurement while switching between high gain and low gain channels to avoid waveform saturation/clipping or otherwise waveform with too small amplitude.
Figure 7 illustrates Multi-Channel transducer cable with push switch-overall view.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the system and method has been discussed below to describe the way it operates. However, such description should not be considered as any limitation of scope of the present system. The structure thus conceived is susceptible of numerous modifications and variations; all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
The working of this invention can be easily understood by referring to Fig 1, Fig 2, Fig 3, Fig 4, Fig 5, Fig 6 & Fig 7.
Fig 1 gives overall view of the invasive blood pressure analyzer / monitor with improved performance.
Part 102 is an enclosure or cabinet for this novel invasive arterial blood pressure patient monitor with automatic Offset Error correction using feedback compensation technique.
This enclosure is injection molded from master batch resins which are biocompatible plastics and composites. This enclosure is rectangular in shape. Although for the reason of clarity in drawings, only one type of enclosure with arterial IBP sensor cables are explained, It is understood that other shapes of enclosures with the physiological sensor cables not described in this invention can also be used without deviating from the sprit and scope of the invention. All such modifications and improvements still fall within the scope of this invention.

The other vital sensors that can be used with IBP are Electrocardiography, Pulse oxymeter, respiration gas analysis, Capnography, human body temperature, EEG monitoring, thermo-dilution cardiac output, Cerebral pressure monitoring, Anesthesia gas monitoring.

The enclosure 102 contains an AC to DC power supply. This AC/DC power supply will convert the energy into regulated DC. This d.c. is electrically connected to DC/DC voltage converter which in turn consists of a PCB and several power converting circuits with various DC outputs.
This highly regulated and noise /ripple free power is fed to various electronic circuits assembled inside the enclosure 102. Since these are standard components, they are not shown to simplify the drawings.
Part 140 is saline filled bag placed at a height of two to three meters above the hospital floor level using a pole or wall mounted stand. This bag is inserted in to a pressure cuff 138 which is inflated to above the worst maximum pressure of the patient. This pressure will keep the blood from coming out in the catheter at needle 118. The pressure bag is used when one measures pressures in arteries or vessels carrying blood at high pressure. The bag 140 is pierced with piercing device attached with the drip chamber 136 & arterial IV line/ peripheral artery catheter 142. The saline is allowed to drip and fill the entire line up to transducer 128. The 128 contain a deformable diaphragm connected to a Wheat-stone bridge, which converts the mechanical energy of the pressure waves into electric signals. The signals are then amplified, displayed, or recorded. The part 134 is a saline flow-controlling device.
The patient end line with needle 118 is inserted inside the radial artery so that blood, under pressure fills the line 122. The hydrostatic pressure from 142 will prevent the blood from traveling further upwards but the transducer 128 senses the dynamic changes in pulse pressure due to the pumping heart.
The transducer 128 is electrically connected to cable 124, which in turn connected to the junction box 112.
The transducer 128 with parts 142,126,122,136 can be designed and manufactured specially for this invention or can be incorporated as a ready-made component from the market.
The transducers measuring pressure from other part of the body are also connected to this junction box. By way of an example transducer with needle end 116 and cable 114 are shown. There can be three or four transducers connected to this junction box 112. The junction box 112 is connected to the connector 132 by a trunk cable and this is plugged in to the monitor and connector 130.
The PMS is switched on by pressing the ON/OFF switch on the keyboard 110. The motherboard 208/ Fig 2 will boot and initialize the pressure monitoring software. The number of IBP cables and transducers connected are automatically detected and the display 106 will show the graphical and numerical screens accordingly.
The screen 106 will be divided equally so that all the pressure channels corresponding to the catheters 118, 116 are shown.
Prior to initiating patient monitoring, the pressure transducer must be zeroed, calibrated, and leveled to the appropriate position on the patient.
The “zeroing stopcock valve” 126 has three positions a) Open to air , close to patient , b) close to air and patient , c) Open to patient close to air.
Open the three way zeroing valve 126 close to patient but open to air. At this stage the “ IBP ZERO” on the keyboard 110 or the touch screen placed over 106 to be pressed two times to confirm that keys are intentionally pressed and not by accident. The monitor will measure the value from 128 and display the “zero”.
The transducer is zeroed. The cock 126 is to be closed now to air and open to patient to monitor the IBP pressure.
The transducer now has a reference-ambient atmospheric pressure against which all intra-vascular pressures are measured. This process underscores the fact that all pressures displayed on the monitor are referenced to atmospheric pressure, outside the body. To be precise, it is this air-fluid interface at the level of the stopcock that is the zero pressure locus. This point must be aligned with a specific position on the patient like heart level to ensure the correct transducer measurement.
Zeroing also refers to adjustment of the Wheat-stone bridge in the transducer 128 so that zero current flows to the detector at zero pressure.
The pressure transducer must be set at the appropriate level in relation to the patient in order to measure blood pressure correctly. This is usually taken to be level with the patient’s heart, at the 4th intercostal space, in the mid-auxiliary line. Failure to do this results in an error due to hydrostatic pressure (the pressure exerted by a column of fluid – in this case, blood) being measured in addition to blood pressure. The leveling is also changed when patient position is altered due to adjusting the height of the operating room table or intensive care bed.
This can be significant – every 10cm error in leveling will result in a 7.4mmHg error in the pressure measured; a transducer too low over reads, a transducer too high under reads.
The three components or characteristics of intra-vascular pressures measured through a fluid- filled catheter are:
• Residual or static pressure inside the fluid-filled vessel
• Dynamic pressure, which is caused by the imparted kinetic energy of the moving fluid (similar to the encountered in arterial pressures when the catheter tip is directly facing the flow of fluid).
• Hydrostatic pressure, which results from the difference between the ends of the fluid-filled tubes) the tip of the catheter and the air-reference port of the transducer).
Figure 2 illustrates the block diagram – Analog front end and digital section, MCU, display, automatic Offset Error correction using feedback compensation technique.
The part 208 is main /mother board will contain a MCU or embedded micro-controller, RAM, Flash Disk, Micro-disk, RS232 to TTL communication circuit to accept analog OEM modules, USB / LAN , inter connecting circuits and so on.
Block 202 represents entire invasive blood pressure transducer cable of which transducer 128 is a part. Block 204 represents 124,114,120,112,132.
The push button switch 120 will send a zero to one transition signal. This switch is again shown near the 208 for the sake of clarity. Actually this switch will be part of block 204.
The 208 is connected to graphics controller 216 to which a TFT – flat panel LCD display 106 that has also a touch screen panel on the outer surface facing the user of the equipment.
The TFT display 106 will display the information through Graphical user Interface so that the necessary information in text /graphic / waveform is displayed and can be understandable by human beings.
The inputs to the motherboard 208 are entered through capacitive touch activated keyboard 110 provided with system ON/OFF switch and few other menu keys.
The part 108 is technically known as “optical encoder” which is having a push button – vertical movement switch and position coded horizontal and circular photo switches. Together this will act like a navigation key and mimic the functions of mouse and joysticks found in computers known in the prior art.
The main board with MCU part 208 contains an 8 channel ADC for the Pressure signal and transducer offset error measurement, an 8 channel DAC for biasing the Circuit and transducer offset error removal.
During zeroing the available pressure is measured at 214/Fig.2- analog low pass filter. The ADC channel is inside MCU 208. If the measured pressure Y is not equal to the fixed value X mmHg then
Offset error shall be calculated by
Z = (X – Y) mmHg.
Where X = Target Pressure value during zeroing
Y = Measured Pressure value during zeroing
Z = Offset Error during zeroing
After calculation of the Offset Error, in the feedback inverted offset error value (-Z) is applied to compensate this error. Again the new pressure reading is measured in the same channel and zeroed. Due to this feedback system, the Transducer Offset error and Atmospheric pressure change gets compensated. This helps in maintaining the specified pressure measurement range.
If the measured pressure is out of range even after several steps (i.e. –300 mmHg and +300 mmHg) then the logic inside MCU 208 assumes that there is mechanical or electrical damage to the transducer 128. A message will be flashed on the TFT display 106 announcing “ transducer offset error- Please replace the transducer with new one’.
Fig 3 explains the flow chart for ‘zeroing logic flow’, removing the transducer offset error improvement of the performance of the pressure measurement and detection logic for permanent transducer damage hitherto unavailable in the prior art.
At every power ON and whenever the transducer is get connected system will display a message “Not Zeroed” that indicates to the user pressure channel zeroing is required. This is step 302 in Fig 3.
For Zeroing the pressure channel, The “zeroing stopcock valve” 126 to be kept open to air and zero switch 120 to be pressed once that displays a message “Press Zero Switch again for Zeroing” in TFT 106. Next switch 120 press initiates zeroing. This is step 303.
From DAC of 208 initial DC bias voltage DAC0 applied at the ref pin of the instrumentation amplifier. This is step 304. The output is measured at the ADC input of micro-controller 208. This is step 305. The Offset Error is calculated on basis of the difference of the ADC and DAC values. If there is an Offset Error in the transducer will get reflected at the ADC input. This is step 306.

In the step 307, If Offset Error from step 306 is > ±C mmHg then a message “ Transducer Offset Error” 309 is displayed at TFT display 106 that indicates the bad or incompatible transducer is connected. If the step 307, Offset Error Z is <= ±C mmHg , the New DAC value in step 308 to be calculated after removing the observed offset error at step 306.
At this stage a condition ‘if Offset Error is > ±1 mmHg, is checked at step 310. At step 312, new DAC value DAC0 is applied at the ref pin of the instrumentation amplifier at Step 304 for providing the new DC bias. If this error is continued again then a message “ Not Zeroed” at step 313 is displayed at TFT display 106. This indicates again pressure channel zeroing is required.
If Offset Error Z is <= ±1 mmHg at step 310,then Pressure values is measured in both gain channel G1- 210 and G2- 212. This is step 311.
After the pressure measurement in both gain channel 210 and 212 , one more stage of the software zeroing at step 314 is performed to remove the errors due the component tolerances and temperature variation. After completion of the software zeroing a message “Zeroed” at step 315 is indicated at TFT display 106 to indicate the channel is ready to monitor the true pressure values.

The flow chart in Fig 3 and the block diagram 200-Fig 2, shows that the following novel improvement with respect to the existing system is possible with this invention.
Due to the usage of novel Offset Error correction using feedback compensation technique there will not be any change in the measurement range due to Transducer offset Error.
The same analog voltage at 214 filter is monitored simultaneously and continuously in both low gain 210 and High gain 212 channel.
Pressure value measured and calculated with the low gain channel to remove the ADC saturation at MCU 208 with the specified measurement range.
Because both gain channels 210 and 212 in Fig2. are measured continuously for pressure waveform and pressure value always calculated from the low gain channels. The following are few outcomes those improves the performances.
There is Improvement in the stability of the pressure measurement and representation during the switching of different hardware gains. Since hysterics is used for the pressure waveform switching during auto scale, there shall not be any problem in the pressure waveform display on 106.
Separate Hardware channel 210 and 212 for the pressure measurement to compensate the ADC saturation instead of single waveform channel in the prior art. Pressure values are calculated from the low gain channel and this channel gain is selected by considering the full-scale measurement range (-30 to 300mmHg) with +-20 mmHg margin. Because in any condition (with in the specified measurement range) low gain channel of ADC cannot go in saturation and pressure waveform switching can be done without any obstruction and time delay.
The Transducer calibration is the next step following the zeroing procedure In this a known pressure is given to the transducer 128 typically 300 mmHg. The transducer reads this and displays the reading in 106. Sometime a resistor placed parallel to the transducer 128 is switched and transducer is bypassed. The resistor value is such that it will generate a precise voltage drop equal to 300mmHg.
The calibration of the transducer and associated IBP hardware is done as below.
• Soft calibration to remove the hardware de-rating due to temperature variation in different place and drift due to continuous use.
Measurement module will have the option to calibrate the hardware channel to remove the error due to the components de-rating because of the temperature environment and continuous use.
This software calibration will be performed by service personnel to remove the hardware inaccuracy. The steps required to perform this calibrations are:
1. Connect the Calibration module to the system in place of the pressure Transducer 128 at connector 130. This can also be done by pulling out the connector-cables 114 or 702 and connecting the calibration module.
2. Select pressure as 0mmhg in the calibration module,(this calibration is different from open to air – transducer calibration ) then perform zeroing to complete the low pressure calibration (0mmHg Cal) .
3. Select pressure as 300mmhg in the calibration module, then perform High Cal to complete the High pressure calibration (300mmHg Cal)
This helps in improving and maintaining the performance of the system in the full service life.+
Further method for improving the representation of pressure waveform for better interpretation and diagnosis is as disclosed below.
The novel System will be having the option to display the pressure waveform in different modes on the TFT display 106.
1. Normal view Mode
2. Enhanced view mode
In case of the normal view mode, it is very difficult to diagnosis the pressure waveforms (i.e. Diacrotic notch) when the pressure is high and the variation between the systolic and diastolic is very low.
But In case of the enhanced view mode, the DC(direct current) part of the waveform is suppressed and AC (alternating current) part is amplified and displayed in the TFT display 106, where user will be able to identify, study and diagnose pressure waveform very accurately. This will eliminate the shifting of the waveform towards baseline and saturation line. This is clearly shown in Part 146.
The visual plotting in the system in different view modes is as shown in Fig 1. Part 144 and 146.
The waveform 144 is normal view mode. The waveform 146 is enhanced view mode.
1) Normal view mode: This is the view mode that is normally used to display the pressure waveform in the medical system. In normal view mode the base line is fixed to the 0 mmHg, the saturation line will be selected as per the maximum pressure reading required to be displayed in the TFT display. In some of the cases where negative pressure reading required to be monitored, the baseline will be in the minimum negative pressure value. Normal view mode will be having the two scaling mode form scaling the pressure waveforms.
a. Manual scaling: In case of the manual scaling user required to select different scale options as per the pressure values. In this mode the base line is fixed to the 0 mmHg, the saturation line will be selected as per the maximum pressure reading required to be displayed in the TFT display. In some of the cases where negative pressure reading required to be monitored the baseline will be in the minimum negative pressure value.
b. Auto scaling: In case of the Auto scaling, system automatically selects any one scale out of available scale options as per the measured pressure diastolic pressure value. In this mode the base line is fixed to the 0 mmHg, the saturation line will be selected as per the maximum pressure reading (Diastolic) required to be displayed in the TFT display.
2) Enhanced view mode: This view mode is the novel feature. In enhanced view mode the base line to be selected as per the minimum pressure (systolic) read from the acquired waveform at connector 132, the saturation line will be selected as per the maximum pressure (Diastolic) read from the acquired analog waveform at connector 132 required to be displayed in the TFT display. Enhanced view mode will also be having the two types of scaling selection to display the pressure waveforms as below.

Figure 4 illustrates Pressure waveform measurement from high gain 212 and low gain 210 channels when manual scale selected.
a. Manual scaling: In case of the manual scaling user required to select manually different scale options by selecting the pop up menus on 106 as per the pressure values. Using input devices such as 110 and108 can do this. In this mode the base line to be selected as per the minimum pressure (systolic) reading instead of default 0 mmHg, the saturation line will be selected as per the maximum pressure (Diastolic) reading required to be displayed in the TFT display.

Once manual scale is selected as shown in Fig 5 the pressure is measured from low gain channel 210 first. If the scale selected is less than 60 mmHg on 106 then high gain channel 212 will take over else low gain channel will continue to measure the pressure.
Figure 5 illustrates Pressure waveform measurement in enhanced view mode, base line and saturation line selection when auto scale selected.
b. Auto scaling: In case of the Auto scaling, system automatically selects two scale out of available scale options as per the measured pressure systolic pressure value (base line) and as per the measured pressure diastolic pressure value (Saturation line). In this mode the base line and saturation line will be selected by system to display the amplified pressure waveform in the TFT display 106.
In case of the auto scaling, Pressure waveform scale is selected as per the measured systolic and diastolic values at connector 132 rather than predetermined values.
As per the measured systolic pressure values the next Higher available scale option is selected and as per the measured diastolic pressure values the next lower available scale option is selected as shown in flow chart of Fig 5
The flow of logic in Fig 5 is as follows.
Step 502 is the start of measurement. At step 504 pressure channel zeroing will be done. At step 506 the peak systolic and peak diastolic pressure will be measured. This is shown in waveform 146. Let us assume that systolic pressure is A and diastolic pressure is B mmHg. The saturation line at 146 will be little higher than the peak of the waveform so that the magnified waveform is not clipped. At step 508 the waveform saturation line level is calculated as L=B-b1. Where b1 is the gap between the peak of the waveform and the saturation line.
Again the system will measure the Systolic pressure A mmHg and Diastolic pressure B mmHg.
At step 512, A is checked for whether it is greater than H, which means the peak of the waveform is touching the saturation line. If yes then at step 518 the saturation line is further shifted up to accommodate the waveform. If no then at the step 516 , 514and 520 the value is checked for whether it is same or decreased.
Similar way the baseline pressure value selection is done for 146. The step 522 is start of measurement. At step 524 pressure channel is zeroed. The peak systolic and diastolic pressures are measured as A and B at 526.
The waveform baseline is set at L=B-b1 at step 528. After sometime the pressure A and B is measured again at step 530.
At step 532, comparison is done to check whether the diastolic peak is touching the base line. At step 536,534,538,540 either the base line is lowered further, kept at same level or shifted up to accommodate the waveform.
Figure 6 illustrates logic flow for Pressure waveform measurement with auto scale while switching between high gain and low gain channels to avoid waveform saturation/clipping or otherwise waveform with too small amplitude.
This is continues loop. When auto scale is selected the analogue pressure value at connector 132 is measured. To start with the low gain channel G1, which is part 210 is selected so that the entire waveform appears on the screen, which is part 144. Then the pressure value is checked for whether it is say less than 60 mmHg. If yes then the waveform visible on the screen 144 will be small in amplitude and difficult to see the waveform segment for any abnormalities. Then the high gain amplifier G2, which is part 212, is switched. The waveform amplitude displayed on 106 is now increased and it will occupy the entire space between base line and saturation line. While this enhanced waveform is being displayed the pressure is also monitoring to see that it does not cross the upper limit say 80 mmHg. When this happens the low gain channel G1 –Part 210 starts the measurement as long as the pressure range is < 60 mmHg.
The two waveforms 144 and 146 are shown together on the screen 106 just for the easy understanding of the reader. In reality only of them will be displayed depending upon the logic explained in Fig. 6.
Figure 7 illustrates Multi-Channel transducer cable with push switch-overall view
The connector 132, yoke 112, recessed push-switch 120, Extension cable 114, transducer connector 702 together consists of a novel sensor cable disclosed in this invention. The detailed information of the novel interface cable designed for this invasive blood pressure analyzer is shown in Fig 7. Part 132 is a 12-pin circular color-coded connector at patient monitor end. Part 112 is a yoke having hollow place with printed circuit board and components soldered inside. The enhanced inside view is shown inside the dotted circle.
The push button switches for zeroing and calibration are mounted on this yoke. The push button 120 is mounted such a way that the height is lower than the top surface of the yoke 112. Since the top surface of 112 is recessed around the switch 120 the chances of accidental operation of the switch is lesser when the yoke 112 is continuously pressed against any surface.
Part 114 is branching cable for channel one or two IBP. The transducers are attached to this 114 and the other end consisting of needle 118 is inserted inside the patient’s artery.
There can be more than two branches like 114 in case there is a need to monitor the invasive blood pressure from multiple sites. The novel feature of the cable is implementation of multiple push button switches for calibration and zeroing of pressure, which can be done at very near place of the patient unlike prior art where the push buttons on the monitor has to be pressed.
In addition the monitor 102 described in Fig 1 can give audio and visual alarms when the zeroing and calibration is achieved so that the caregiver can concentrate only on leveling, zeroing and calibrating the transducer rather than rushing towards the monitor multiple times for pressing the switch. Part 104 in Fig 100 is visual alarm with various colors like RED, BLUE and YELLOW. There will be also audio alarm inside 102 which is shown as block 218 , Fig 2. These audio & visual alarms can also be shifted & located inside the yoke 120. The necessary wiring can be routed through 132 connector & the trunk cable. Since the level of transducer 128 can change with the heart level during the usage, the system 102 can be programmed to display a warning message ‘Check transducer level with the heart’ on 106. The duration for this timer can be fixed like 5 minutes, 10 minutes.

WE CLAIM:

1. An integrated apparatus for invasive blood pressure monitoring of patients at multiple locations on the human body, said system comprising :
an enclosure means;
a display means displays information through a graphical user interface;
a capacitive touch keyboard having a push button on/off switch to turn on/off said apparatus;
a power supply assembly comprises a battery charger and controller , a lithium-ion battery pack adapted to convert ac to dc power supply;
analog signal acquisition modules;
at least one transducers connected to the patient at proximal end , said transducer comprises
a junction box ;
a connector connected with said junction box at the distal end electrically and mechanically connected through a interfacing cable with said apparatus ;
a push button switch for adjustment of zeroing ;
a micro-controller operatively connected with said transducers, said controller comprises: an 8 channel ADC for the Pressure signal and transducer offset error measurement and 8 channel DAC for biasing the Circuit and transducer offset error removal;
an instrumentation amplifier operatively connected with said junction box for amplifying the pressure signal and transducer offset error ,
a low pass filter for noise removal;
an High gain amplifier for the lower pressure measurement;
an Low gain amplifier for the Full scale pressure measurement;
such that said microcontroller adapted to measure the Offset error at one of the ADC channel and Corrected using the DAC, such that a fixed DC voltage is applied from DAC and measured from the ADC without feeding any pressure signal,
such that any difference in the measured value at ADC and the DAC will be the offset error; and an audio and visual indication/alarm devices operatively connected with said micro-controller such that when the zeroing and calibration is achieved so that the caregiver can concentrate only on leveling, zeroing and calibrating the transducer rather than rushing towards the monitor multiple times for pressing the switch.
2. Apparatus as claimed in claim 1 wherein said enclosure means adapted to enclose the said apparatus in various sized plastic Enclosure / cabinet so that it is hand carried and transportable from one location to another accompanying the patient.

3. Apparatus as claimed in claim 1 wherein said micro controller adapted to measure/analyze zeroing.

4. Apparatus as claimed in claim 1 wherein said micro controller adapted o detect the press of said push button switch such that If the pressure channel is not zeroed a message “Not Zeroed” will be displayed in said display means and during the switch-Off condition micro-controller GPIO1 will be High and when ever this switch is pressed the GPIO1 will become low.
5. Apparatus as claimed in claim 5 wherein said microcontroller gets indication for First High to low transition for initiating the pressure zeroing and thereafter a messages “ Press again for zeroing” will be displayed in the display means, a second press at zero switch will zero the pressure channel and a message “Zeroed” will be displayed at display means.
6. Apparatus as claimed in claim 1 provides the high level of accuracy as the same resolution ADC and DAC is used in the removal of transducer-offset error.

7. Apparatus as claimed in claim 1 provides the high level of accuracy as the same DC accuracy specification is used for providing the high level of accuracy in the removal of transducer-offset error.

8. Apparatus as claimed in claim 1 provides indication for changing the pressure transducer by posting a message “ Change Transducer” in the TFT display when the pressure transducer offset error crosses the limit or it can saturate the pressure measurement channel thus detecting the incompatible transducer or permanent transducer damage also.

9. Apparatus as claimed in claim 1 provides the way to measure the multiple gain channel without using external multiplexer and ADC measurement channel switches as per the pressure value monitored.

10. Apparatus as claimed in claim 1 wherein said display means having the two view modes normal view mode and enhanced view mode for representing the pressure waveform optimally.

11. Apparatus as claimed in claim 1 wherein said microcontroller provides manual scaling options where user selects low pressure scale (Baseline) and high pressure scale (saturation line) as per the measured pressure values (Systolic and Diastolic).

12. Apparatus as claimed in claim 1 wherein said microcontroller provides auto scaling option where said apparatus automatically selects low pressure scale (Baseline) and high pressure scale (saturation line) as per the measured pressure values (Systolic and Diastolic).

13. Apparatus as claimed in claim 1 further comprising multi-channel transducer adaptor cable with 12 pin circular connector at monitor end and removable adaptor cable for operatively connecting transducer cable on the patient side.

14. Apparatus as claimed in claim 13 wherein said multi-channel cable comprising a yoke in the middle having recessed push button switches so that the top surface of the push button switch is lower than the top surface of the yoke by which the accidental activation of the switches are avoided.

15. Apparatus as claimed in claim 14 wherein said switches comprising providing calibration, zeroing and to acknowledge the patient related and hardware related alarms.

16. Apparatus as claimed in claim 14 wherein said yoke comprising audio and visual alarm components like micro speaker, LED lamps in various colors to provide the information to the caregiver without the need to look in to the monitor.

17. Apparatus as claimed in claim 14 said yoke comprising color-coded, keyed connectors to operatively connected with “removable adaptor cables with invasive blood pressure transducer”

18. An integrated apparatus for invasive blood pressure monitoring of patients at multiple locations on the human body as herein substantially described and illustrated with the accompanying drawings.