A) TECHNICAL FIELD
[0001] The present invention generally relates to medical devices such as invasive blood pressure (IBP) monitors and more particularly relates to an automatic gain selection and correction system for processing blood pressure (BP) signal such as low BP signal acquired from the invasive blood pressure monitor using hardware circuit and software application.
B) BACK GROUND OF THE INVENTION
[0002] The Blood Pressure [(strictly speaking: vascular pressure) refers to the force exerted by circulating blood on the walls of blood vessels and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as the blood moves through Arteries, arterioles, capillaries and veins. The term blood pressure generally refers to arterial pressure, i.e., the pressure in the larger arteries, arteries being the blood vessels which take blood away from the heart. The Arterial pressure is most commonly measured via a sphygmomanometer, which uses the height of a column of mercury to reflect the circulating pressure. Although many modem vascular pressure devices no longer use mercury, vascular pressure values are still universally reported in millimeters of mercury ( mmHg).
[0003] The systolic arteriaL pressure is defined as the peak pressure in the arteries, which occurs near the beginning of the cardiac cycle. The diastolic arterial pressure is the lowest pressure (at the resting phase of the cardiac cycle). The average pressure

throughout the cardiac cycle is reported as mean arterial pressure. The pulse pressure reflects the difference between the maximum and minimum pressures measured.The Arterial pressures can be measured invasively by penetrating the skin and measuring inside the blood vessels) or non-invasively.
[0004] The non-invasive auscultatory and oscillometric measurements are simpler and quicker than invasive measurements. They require less expertise in fitting, have virtually no complications: and are less unpleasant and painful for the patient. However, non-invasive measures may yield somewhat lower accuracy and small systematic differences in numerical results. Non-invasive measurement methods are more commonly used for routine examinations and monitoring.
[0005] The auscultatory method uses a stethoscope and a sphygmomanometer. This comprises an inflatable cuff placed around the upper arm at roughly the same vertical height as the heart, attached to a mercury or aneroid manometer. The mercury manometer, considered to be the gold measurement for arterial pressure measurement, measures the height of a column of mercury, giving an absolute result without need for calibration, and consequently not subject to the errors and drift of calibration which affect other methods. The use of mercury manometers is often required in clinical trials and for the clinical measurement of hypertension in high risk patients, including pregnant women.

[0006] A cuff of appropriate size is fitted and inflated manually by repeatedly squeezing a rubber bulb until the artery is completely occluded. Listening with the stethoscope to the brachial artery at the elbow, the examiner slowly releases the pressure in the cuff. When blood just starts to flow in the artery, the turbulent flow creates a "whooshing" or pounding (first Korotkoff sound). The pressure at which this sound is first heard is the systolic blood pressure. The cuff pressure is further released until no sound can be heard; (fifth Korotkoff sound), at the diastolic arterial pressure. Sometimes, the pressure is palpated (felt by hand) to get an estimate before auscultation.
[0007] The Oscillometric methods are sometimes used in the long-term measurement and sometimes in general practice. The equipment is functionally similar to that of the auscultatory method, but with an electronic pressure sensor (transducer) fitted in to
detect the blood flow, insteacl of using the stethoscope and the expert's ear. In practice,
■f
I the pressure sensor is a calibrated electronic device with a numerical readout of blood
pressure. To maintain accuracy, calibration must be checked periodically, unlike the
inherently accurate mercury manometer. In most cases the cuff is inflated and
released by an electrically operated pump and valve, which may be fitted on the wrist
(elevated to heart height), Although the upper arm is preferred. They vary widely in
accuracy, and should be checked at specified intervals and if necessaiy recalibrated.
[0008] The Oscillometric [measurement requires. less skill than the auscultatory
I technique, and may be suitable for use by untrained staff and for automated patient
home monitoring. The OsGillometric monitors may produce inaccurate readings in

patients with heart and circulation problems that include arterial sclerosis, arrhythmia,
1
preeclampsia, pulsus altenians, and pulsus paradoxus. The term NIBP, for Non-
ii Invasive Blood Pressure,:; is often used to describe oscillometric monitoring
equipment.
[0009] The Arterial blood, pressure (BP) is most accurately measured invasively through an arterial line. The Invasive arterial pressure measurement with intravascular cannulae involves direct measurement of arterial pressure by placing a cannula needle in an artery (usually radial, femoral, dorsalis pedis or brachial. This is usually done by an anesthesiologist or surgeon in a hospital.
[0010] The cannula must be connected to a sterile, fluid-filled system, which is connected to an electronic pressure transducer. The advantage of this system is that pressure is constantly monitored beat-by-beat, and a waveform (a graph of pressure against time) can be displayed. This invasive technique is regularly employed in human and veterinary intensive care medicine, anesthiology and for research purposes.
[0011] The Carmulation for invasive vascular pressure monitoring is infrequently associated with complications such as thrombosis, infection and bleeding. The Patients with invasive arterial monitoring require very close supervision, as there is a danger of severe bleeding, when the line becomes disconnected. It is generally reserved for patients where rapid variations in arterial pressure are anticipated.

[0012] The Invasive vascular pressure monitors are pressure monitoring systems designed to acquire pressure information for display and processing. There are a variety of invasive vascular pressure monitors for trauma, critical care, and operating room applications. These include single pressure, dual pressure, and multi-parameter (i.e. pressure / temperature): The monitors can be used for measurement and follow-up of arterial, central venous, pulmonary arterial, left atrial, right atrial, femoral arterial, umbilical venous, umbilical arterial, and intracranial pressures.
[0013] The Vascular pressure parameters are derived in the monitor's microcomputer system. Usually, the systolic, diastolic and mean pressures are displayed simultaneously for pulsatile waveforms (i.e. arterial and pulmonary arterial). Some monitors also calculate and'display the CPP (cerebral perfusion pressure). Normally, a zero key on the front of the monitor makes pressure zeroing extremely fast and easy. The Alarm limits may be set to assist the medical professional responsible for
!F
I
observing the patient. The High and low alarms may be set on displayed temperature parameters.
[0014] The Blood pressure is one of the most important vital signs used in the assessment of a patient's cardiovascular health. In critical care, it is usually monitored continuously using an invasive fluid-filled monitoring line, also called an arterial line, in which a catheter is inserted into an artery and blood pressure from the artery is transmitted to a blood pressure transducer through fluid-filled tubing 12 to 84 inches long. The arterial pressure [as measured by the transducer is displayed on an invasive blood pressure (IBP) monitor.

[0015] The multiple Invasive Blood Pressure (IBP) module designs use single hardware gain while processing IBP signal. The different gain requirements are generally satisfied by implementing the software gain in the module. These designs work properly while processing normal IBP signal but do not read low BP signal. During the processing of the extremely low Blood pressure signal (CVP) pressure waveform, the morphological degradation is observed and which is not clinically acceptable.
[0016] Hence there is a need to develop a system and method for adjusting the gain of the amplifier during the processing of the extremely low BP signal automatically. Also there is a need to read the high and the low BP waveforms accurately.
C) OBJECT OF THE PRESENT INVENTION
[0017] The Primary object of the present invention is to develop an automatic gain adjustment system to estimate and adjust the gain of the measured BP waveforms automatically so that the high and the low IBP waveforms are read accurately by adjusting the hardware and Software gains.
[0018] Another object of the present invention is to develop an automatic gain adjustment system to select and adjust the gain of the amplifier optimally by adjusting the hardware and software gain to read the low IBP signals accurately.

[0019] Yet another object of the present invention is to develop an automatic gain adjustment system to reduce the morphological distortion of the waveform during the processing of the low IBP Waveform.
[0020] Yet another object of the present invention is to develop an automatic gain adjustment system to read the low IBP signals accurately.
[0021] Yet another object of the present invention is to develop an automatic gain adjustment and correction system to provide an auto scaling option to upscale or downscale the measured BP waveform to display the measured low IBP waveforms in a readable gain.
[0022] Yet another object of the present invention is to develop an automatic gain
adjustment and correction system to optimise the software and hardware gains to
achieve an optimal gain to read the measured IBP waveforms accurately.
[0023] Yet another object of the present invention is to develop an automatic gain
adjustment and correction system to provide optimal gain automatically to improvise
the IBP Waveform resolution during the processing of the low blood pressure
waveform.
[0024] These and other objects and advantages of the present invention will become
readily apparent from the following detailed description taken in conjunction with the
■I accompanying drawings.

waveforms correctly. The input low IBP signal is fed to a digital switch to estimate an optimal overall gain so that the measured low IBP signal is measured accurately and the morphological distortion of the read low IBP waveform is avoided. First a suitable hard ware gain of the amplifier is selected based on the estimated optimal overall effective gain of the ampHfier. Then the software gain is selected based on the chosen hardware gain and the estimated overall effective optimal gain of the amplifier so that
overall effective gain obtained by multiplying the selected hardware gain and the
I
selected software gain is equal to the estimated overall effective optimal gain of the amplifier. The selected gain of the amplifier is applied to the amplifier to amplify the measured low IBP signal ,to read the measured IBP signal easily, efficiently and accurately. The amplified signal is conditioned and converted into digital signal. The digital signal is displayed on the monitor.
[0029] Thus the system provides an AUTO scaling option to display the waveform in a readable gain, when the selected gain is too less for displaying the range of the parameter. This AUTO scaling is implemented to upscale or downscale the waveform. Thus the system provides unitary hardware gain and a suitable software gain to obtain to read the low IBP signal easily, efficiently and quickly. The system estimates the optimal gain by adjusting the hardware gain and the software gain to improve the IBP waveform resolution during the measurement of low BP using the invasive techniques. The system estimates the optimal gain to reduce the morphological distortion of IBP waveform. The system estimates the optimal gain by adjusting the hardware and the software gains optimally and automatically to improve the user friendliness of the device in measuring the low BP values.

[0030] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0032] FIGURE. 1 illustrates a block circuit diagram of an automatic gain correction system for IBP monitor according to one embodiment of the present invention.
[0033] FIGURE. 2 illustrates a functional block diagram of an automatic gain correction system for IBP monitor according to one embodiment of the present invention.
[0034] FIGURE- 3 illustrates a flowchart explaining the operation of the automatic gain correction system for IBP monitor according to one embodiment of the present
invention.
[0035] FIGURE. 4 illustrates an example of look up table used for calculating the overall optimal effective gain using hardware and software gain according to one embodiment of the present invention.

[0036] Although specific features of the present invention are shown in some drawings and not in others; This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0037] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a' limiting sense.
[0038] The various embodiments of the present invention provide a system and method to automatically adjust the gain of the amplifier by selecting the optimal hardware gain and the software gain to acquire an optimal overall effective gain to process the low IBP signals so that the low IBP signals may be read accurately.
[0039] According to one embodiment of the present invention, the system is provided with a gain adjustment block / circuit to adjust the hardware gain and the software gain to obtain an optimal overall effective gain to read the low IBP signal accurately, easily and efficiently. The system reads the low IBP signal to detect an optimal overall effective gain so tliat the low IBP signal may be read accurately. The

measured low IBP signal is input into a digital switch to select a scale for displaying the input low IBP automatically in the IBP monitor. A gain adjustment block / circuit is provided in the system to estimate an optimal overall effective gain for the amplifier using a software application. The hardware gain is adjusted in multiples of integer or in the integral niultiple values of a whole number based on the estimated overall optimal effective gain using an application software. Then the software gain is computed in the gain adjustment block based on the calculated hardware gain and the estimated overall optimal effective gain using an application software to obtain the desired overall optimal effective gain. The detected gain is applied to boost the low IBP signal so that the low IBP signal may be read accurately.
[0040] According to one embodiment of the present invention, an automatic gain correction system is provided with a digital switch to receive the input IBP signal from an IBP monitor. The digital switch selects a gain scale based on the input IBP signal. A gain adjustment block is used to select a hardware gain based on the selected gain scale so that the hardware gain is equal to an integer value. The hardware gain is modified in multiples of integers. Then a software gain is selected with respect to the estimated hardware gain based on the selected gain scale so that the product of the selected hardware gain and the selected software gain is equal to the estimated overall optimal gain of the amplifier. The estimated overall gain value is applied to amplify the input low HP signal so that the amplified BP signal value is read easily. The output of the amplifier is digitized and displayed on the monitor.

[0041] When an auto scale is selected for plotting the waveform, the system senses the Systolic Pressure value at hardware gain of 1. When the Systolic Pressure value is less than threshold value of the current scale, then the system uses the software multiplication factor and hardware gain factor of current scale to obtain the overall gain of the system. On the contrary, when the Systolic Pressure value is more than threshold value of the currently selected scale, then system compares the Systolic Pressure value with thresho'ld value of next higher scale. When the Systolic Pressure value is less than threshold value of the next scale, then system uses the software multiplication factor and hardware gain factor of next scale. The acquired waveform value is multiplied by the estimated overall gain of the amplifier to upscale or downscale the waveform. Tlie maximum gain is selected automatically and reduced gradually until the clipping of the waveform is detected. Thus an optimal gain for the required signal is estimated.
[0042] According to another embodiment of the present invention, an automatic gain adjustment method is provided to select and adjust the hardware gain and the software gain to obtain an optimal overall gain of the amplifier to read the low IBP waveforms correctly. The input low IBP signal is fed to a digital switch to estimate an optimal overall gain so that the measured low IBP signal is measured accurately and the morphological distortion of the read low IBP waveform is avoided. First a suitable hard ware gain of the amplifier is selected based on the estimated optimal overall gain of the amplifier. Then the software gain is selected based on the chosen hardware gain and the estimated overall gain of the amplifier so that optimal overall effective gain obtained by multiplying the selected hardware gain and the selected software gain is equal to the estimated overall optimal gain of the amplifier. The selected gain

of the amplifier is applied ^to the amplifier to boost the measured low IBP signal so that the measured IBP signal is read accurately, easily and efficiently. The amplified signal is conditioned using a level conditioning circuit. The level converted signal is transformed into a digital signal using an analogue to digital converter. The digital signal is displayed on the monitor of the IBP device.
[0043] Thus the system provides an AUTO scaling option to display the waveform in
a readable gain, when the selected gain is too less for displaying the range of the
■I parameter. This AUTO scaling is implemented to upscale or downscale the waveform.
Thus the system provides utiitary hardware gain and a suitable software gain to obtain
to read the low IBP signal deasily, efficiently and quickly. The system estimates the
optimal gain by adjusting the hardware gain and the software gain to improve the IBP
waveform resolution during the measurement of low BP using the invasive
techniques. The system estimates the optimal gain to reduce the morphological
distortion of IBP waveform. The system estimates the optimal gain by adjusting the
hardware and the software ■ gains optimally and automatically to improve the user
friendliness of the device inlmeasuring the low BP values.
[0044] The FIG. 1 illustrates a block circuit diagram of an automatic gain correction system for IBP monitor according to one embodiment of the present invention. According to one embodiment of the present invention, an automatic gain correction system is provided with a digital switch to receive the input IBP signal fi-om an IBP monitor. The digital switch selects a gain scale based on the input IBP signal. A gain adjustment block is used to select a hardware gain based on the selected gain scale so

that the hardware gain is equal to an integer value. The hardware gain is modified in multiples of integers. Then a software gain is selected with respect to the estimated hardware gain based on the selected gain scale so that the product of the selected hardware gain and the selected software gain is equal to the estimated overall optimal effective gain of the amplifier. The estimated overall effective gain value is applied to ampUfy the input low BP signal so that the amplified BP signal value is read easily and accurately The output of the amplifier is digitized and displayed on the monitor.
[0045] When an auto scale is selected for plotting the waveform, the system senses
the Systolic Pressure value at a hardware gain of 1. When the Systolic Pressure value
is less than threshold value of the currently selected scale, then the system uses the
software muhiplication factor and hardware gain factor of currently selected scale to
obtain the optimum overall effective gain of the system. On the contrary, when the
Systolic Pressure value is more than threshold value of the currently selected scale,
then system compares the Systolic Pressure value with threshold value of next higher
scale. When the Systolic Pressure value is less than threshold value of the next higher
scale, then system uses the respective software multiplication factor and hardware
I gain factor of the next higher scale. The acquired waveform value is multiplied by
the estimated optimum overall effective gain of the amplifier to upscale or downscale
the waveform. The maximum gain is selected automatically and reduced gradually
■i until the clipping of the waveform is detected. Thus an optimal gain for the required
signal is estimated.

[0046] The FIG. 2 illustrates a functional block diagram of an automatic gain correction system for IBP monitor according to one embodiment of the present invention. According to one embodiment of the present invention, an automatic gain correction system is provided with a digital switch to receive the input IBP signal from an IBP monitor. The digital switch selects a gain scale based on the input IBP signal. A gain adjustment block computes an effective overall optimum gain based on the selected gain scale using an application software. The gain adjustment block is used to calculate a hardware gain using an application software based on the selected gain scale and the computed optimum overall effective gain so that the hardware gain is equal to an integer value and the hard ware gain is in integral muhiples of a whole number. The hardware gain is modified in multiples of integers only. Then a software
gain is selected with respect to the estimated hardware gain based on the selected gain
■j
i! scale and the computed effective overall optimum gain so that the product of the
selected hardware gain and the selected software gain is equal to the estimated overall
effective optimal gain of the amplifier. The estimated optimum overall effective gain
value is applied to an operational amplifier to amplify the input low BP signal. The
amplified signal is passed through a level conditioning circuit to convert the signal
level of the amplified signal with in the range of ADC so that the amplified BP signal
value is read easily. The output of the amplifier is dighized by passing the amplified
signal through an analogue to digital converter. The digitized signal is then farther
processed for display on the monitor.
[0047] The FIG. 3 illustrates a flowchart explaining the operation of the automatic gain correction system for IBP monitor according to one embodiment of the present

invention. When auto scale is selected for plotting the waveform, the system senses the Systolic Pressure value at a hardware gain of 1. When the Systolic Pressure value is less than threshold value of the currently selected scale, then the system uses the software multiplication factor and hardware gain factor of cuirently selected scale to obtain the overall effective gain of the system. On the contrary, when the Systolic Pressure value is more than threshold value of the currently selected scale, then system compares the Systolic Pressure value with threshold value of the next higher scale. When the Systolic Pressure value is less than threshold value of the next higher scale, then system uses the respective software multiplication factor and hardware gain factor of the next higher scale. The acquired waveform value is multiplied by the
;l
estimated overall gain of thb amplifier to upscale or downscale the waveform. The maximum gain is selected automatically and reduced gradually until the clipping of the waveform is detected. Thus an optimal gain for the required signal is estimated.
[0048] The FIG. 4 illustrates an example of a look up table used for calculating the optimum overall effective gain using hardware gain and software gain according to one embodiment of the present invention. The digital switch selects an auto scale based on the input IBP signal. An effective overall gain requirement is calculated based on the selected scale.JA hardware gain is selected using a software application
!(
based on the selected auto kale and the estimated effective overall gain value. The hard ware gain is selected such that the selected hardware gain is in integral multiples of a whole number or in multiples of an integer. The hardware gain is also changed in multiples of integers only. Then a suitable software gain is selected with respect to the calculated overall gain and the selected auto scale based on the computed

hardware gain so that the product of the selected hardware gain and the software gain is equal to the estimated overall gain corresponding to the selected auto scale. The gain look up table lists the effective overall gain, the respective hardware gain and the software gain corresponding to each scale.
[0049] When an auto scale is selected for plotting the waveform, the system senses the Systolic Pressure value at a hardware gain of 1. When the Systolic Pressure value is less than threshold value of the currently selected scale, then the system uses the software multiplication factor and hardware gain factor of currently selected scale to obtain the overall effective gain of the system. On the contrary, when the Systolic Pressure value is more than threshold value of the currently selected scale, then system compares the Systolic Pressure value with threshold value of the next higher scale. When the Systolic Pressure value is less than threshold value of the next higher
scale, then system uses the respective software multiplication factor and the hardware
pi gain factor of the next higher scale to obtain the overall effective gain. The acquired
waveform value is multiplied by the estimated overall effective gain of the amplifier
to upscale or downscale the waveform. The maximum gain is selected automatically
and reduced gradually until the clipping of the waveform is detected. Thus an optimal
gain for the required signal is estimated.
[0050] Thus the automatic' gain adjustment system and method of the present invention calculates an effective overall optimum gain of amplifier by adjusting the hardware gain and the software gain to read the low IBP signals easily, efficiently, quickly and accurately.

G) ADVANTAGES OF THE PRESENT INVENTION
[0051] The various embodiments of the present invention provide a system and method for automatic optimal gain selection process using hardware and software gain for Invasive Blood Pressure signal processing during the processing of extremely
I
low Blood pressure signal (CVP). The present invention improvises IBP Waveform resolution during low blood pressure and reduces IBP Waveform morphological distortion.
[0052] Thus the system provides an AUTO scaling option to display the waveform in a readable gain, when the selected gain is too less- for displaying the range of the parameter. This AUTO scaling technique is implemented to upscale or downscale the waveform. Thus the system provides unitary hardware gain and a suitable software gain to obtain An optimum overall effective gain value to read the low IBP signal
I
accurately, easily, efficiently and quickly. TTie system estimates the optimum overall effective gain by adjusting the hardware gain and the software gain to improve the IBP waveform resolution during the measurement of low BP signals in an IBP monitor. The system estimates the optimal gain to reduce the morphological distortion of IBP waveform. The system estimates the optimal gain by adjusting the hardware and the software gains optimally and automatically to improve the user friendliness of the device in measuring the low BP values.

[0053] Although the invention is described with various specific embodiments, it will be obvious for a person skill'ed in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0054] It is also to be understood that the following claims are intended to cover all of
the generic and specific features of the present invention described herein and all the
f statements of the scope of the invention which as a matter of language might be said
to fall there between.

D) SUMMARY OF THE PRESENT INVENTION
[0025] The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
[0026] The various embodiments of the present invention provide a system and method to automatically adjust the gain of the amplifier by selecting the optimal hardware gain and the software gain to acquire an optimal overall effective gain to process the low IBP signals so that the low IBP signals may be read accurately.
[0027] According to one embodiment of the present invention, the system is provided with a gain adjustment block/circuit to adjust the hardw£u-e gain and the software gain to obtain an optimal overall gain to read the low IBP signal accurately and efficiently. The system reads the low IBP signal to detect an optimal gain so that the low IBP signal may be read accurately. The measured low IBP signal is input into a digital switch to estimate an optimal gain for the amplifier. The hardware gain is adjusted in multiples of integer and the software gain is adjusted using a gain adjustment block to obtain the desired overall gain. The detected gain is applied to boost the low IBP signal to read the low IBP signal accurately.
[0028] According to another embodiment of the present invention, an automatic gain adjustment method is provided to select and adjust the hardware gain and the software gain to obtain an optimal overall gain of the amplifier to read the low IBP

CLAIMS
WHAT IS CLAIMED IS:
1. An automatic gain adjustment system for IBP monitor, the system comprising:
A digital switch to receive an input BP signal from an IBP monitor to select an auto scale to display the BP signal waveform;
A gain adjustment blocli to calculate a suitable hardware gain based on the selected auto scale andj to compute a suitable software gain based on the calculated hardware gain;'
Wherein the gain adjustment block computes an optimum overall effective gain by multiplying the calculated hardware gain and the computed software gain to amplify the input IBP signal.
2, The system according ito claim 1, wherein the calculated effective overall gain
corresponds to the selected auto scale required for displaying the BP signal
I waveform on the IBP mohitor so that the input BP signal waveform is readable.
3. The system according to claim 1, wherein the hardware gain is calculated
corresponding to the selected auto scale based on the computed overall effective

gain using a software so that the hardware gain is in integral muhiples of a whole number and is changed in multiples of an integer only.
'■\ 4. The system according to claim 1, wherein the software gain is selected based on the calculated hardware gain and the effective overall gain that corresponds to the selected scale so that the product of the calculated hardware gain and the computed software gain is equal to the calculated effective overall gain.
5.. The system according to claim 1, ftirther comprising an amplifier whose gain is adjusted based on the calculated overall gain, to amplify the input low IBP signal to avoid the morphological degradation of the signal waveform and to improve the display resolution of the BP signal waveform.
6. The system according to claim 1, further comprising a signal conditioning
I
i( circuit to adjust the amplified signal to be within the display range of the monitor.
i'
7. An automatic gain adjustment method for IBP signal in an IBP monitor, the
method comprising:
inputting the measured BP signal received from the IBP monitor into a digital
r switch to select a suitable scale;
computing an effective overall gain corresponding to the selected scale using a software application in the gain adjustment circuit;

calculating a hardware gain based on the computed overall gain and the selected scale using a software application;
'F
estimating a software gain based on the calculated hardware gain and the selected scale;
wherein the product of the calculated hardware gain and the computed software gain is equal to the computed overall effective gain corresponds to the selected scale.
8. The method according to claim 7, wherein the calculated effective overall gain
I corresponds to the selected auto scale required for displaying the BP signal
waveform on the IBP monitor so that the input BP signal waveform is readable.
9. The method according to claim 7, wherein the hardware gain is calculated
corresponding to the selbcted auto scale based on the computed overall effective
gain using a software so that the hardware gain is in integral multiples of a whole
number and is changed in multiples of an integer only.
10. The method according to claim 7, wherein the software gain is selected based
on the calculated hardware gain and the effective overall gain that corresponds to
the selected scale so that the product of the calculated hardware gain and the
computed software gain is equal to the calculated effective overall gain.

11. The method according to claim 7, further adjusting the gain of an ampHfier
based on the calcuJated overall gain, to amplify the input low IBP signal to avoid
the morphological degradation of the signal waveform and to improve the display
resolution of the BP signal waveform.
12. The method according to claim 1, ftirther adjusting the amplified low IBP
signal using a signal conditioning circuit so that the level adjusted signal output
from the signal conditioning circuit is within the display range of the monitor.