Apparatus and process for determining systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate, pulse wave

We claim:

1. An automatic blood pressure measuring system for measuring a blood pressure in a blood vessel of a living body comprising:

proximal cuff means, inflated to include a first fixed mass of air, for exerting a pressure at a first location on the blood vessel;

proximal sensing means, coupled to said proximal cuff means, for sensing a pressure of said first fixed mass of air of said proximal cuff means and producing a proximal sensing means output signal indicative thereof;

proximal lifting means for pressing said proximal cuff means against the blood vessel at said first location;

distal cuff means, inflated to include a second fixed mass of air, for exerting a pressure on the blood vessel at a second location farther from the heart than said first location;

distal sensing means, coupled to said distal cuff means, for sensing a pressure of said second fixed mass of air of said distal cuff means and producing a distal sensing means output signal indicative thereof;

distal lifting means for pressing said distal cuff means against the blood vessel at said second location; and

processing means for:

controlling said proximal lifting means and said distal lifting means to press said proximal cuff means and said distal cuff means against the blood vessel when a blood pressure reading is desired;

monitoring said proximal sensing means output signal and said distal sensing means output signal; and

determining the blood pressure based on said proximal sensing means output signal and said distal sensing means output signal.

2. Apparatus of claim 1 further comprising:

a proximal valve for introducing air into and releasing air from said proximal cuff means;

a distal valve for introducing air into and releasing air from said distal cuff means; and

a high pressure air source for inflating said proximal cuff means and said distal cuff means to said first and second fixed mass of air, respectively, through said proximal valve and said distal valve respectively.

3. Apparatus of claim 2 wherein said processing means is also for:

controlling said proximal valve, said distal valve, and said high pressure air source, before measuring the blood pressure, such that said proximal cuff means and said distal cuff means are inflated with high pressure air from said high pressure air source until said proximal cuff means is filled with said first fixed mass of air and said distal cuff means is filled with said second fixed mass of air; and

controlling said proximal valve and said distal valve after measuring the blood pressure has taken place such that said high pressure air is released from said proximal cuff means and said distal cuff means.

4. Apparatus of claim 1 wherein said processing means is also for:

filtering said proximal sensing means output signal such that said pressure of said first mass of air is separated into a proximal static pressure and a proximal dynamic pressure;

filtering said distal sensing means output signal such that said pressure of said second mass of air is separated into a distal static pressure and a distal dynamic pressure; and

determining the blood pressure based on said proximal static pressure, said proximal dynamic pressure, said distal static pressure, and said distal dynamic pressure.

5. Apparatus of claim 4 wherein said processing means is also for:

controlling said distal lifting means such that said distal dynamic pressure increases to a maximum and then decreases;

monitoring said distal dynamic pressure and said distal static pressure to determine said maximum;

fixing said distal lifting means such that said distal dynamic pressure remains substantially at said maximum;

subsequent to said fixing step, controlling said proximal lifting means such that said proximal static pressure increases to a first diastolic pressure where said distal dynamic pressure decreases from said maximum;

monitoring said distal dynamic pressure and said proximal static pressure to determine said first diastolic pressure;

controlling said proximal lifting means such that said proximal static pressure increases to a mean arterial pressure where said proximal dynamic pressure increases to a maximum and then decreases;

monitoring said proximal dynamic pressure and said proximal static pressure to determine said mean arterial pressure;

controlling said proximal lifting means such that said proximal static pressure increases to a systolic pressure where said distal dynamic pressure decreases to a minimum; and

monitoring said distal dynamic pressure and said proximal static pressure to determine said systolic pressure.

6. Apparatus of claim 5 wherein said processing means is also for:

recording said distal sensing means output signal to reveal pressure pulses of individual heart beats;

calculating a first K value according to the following formula where S is the lowest recorded value of said distal sensing means output signal, D is the highest recorded value of said distal sensing means output signal, and MAP is the average of the recorded distal sensing means output signal over a heart beat:

K=(MAP-D)/(S-D);

calculating a second K value according to the following formula where S is said systolic pressure, D is said diastolic pressure, and MAP is said mean arterial pressure;

K=(MAP-D)/(S-D); and

comparing said first K value and said second K value to determine a reliability factor for the blood pressure measurement.

7. Apparatus of claim 4 wherein said processing means is also for:

controlling said distal lifting means such that said distal dynamic pressure increases to a maximum and then decreases;

monitoring said distal dynamic pressure and said distal static pressure to determine said maximum;

fixing said distal lifting means such that said distal static pressure remains at a fixed value above said distal static pressure corresponding to said maximum;

subsequent to said fixing step, controlling said proximal lifting means such that said proximal static pressure increases to a diastolic pressure where said distal dynamic pressure decreases from said fixed value;

monitoring said distal dynamic pressure and said proximal static pressure to determine said diastolic pressure;

controlling said proximal lifting means such that said proximal static pressure increases to a mean arterial pressure where said proximal dynamic pressure increases to a maximum and then decreases;

monitoring said proximal dynamic pressure and said proximal static pressure to determine said mean arterial pressure;

controlling said proximal lifting means such that said proximal static pressure increases to a systolic pressure where said distal dynamic pressure decreases to a minimum; and

monitoring said distal dynamic pressure and said proximal static pressure to determine said systolic pressure.

8. Apparatus of claim 7 wherein said processing means is also for:

recording said distal sensing means output signal to reveal pressure pulses of individual heart beats;

calculating a first K value according to the following formula where S is the lowest recorded value of said distal sensing means output signal, D is the highest recorded value of said distal sensing means output signal, and MAP is the average of the recorded distal sensing means output signal over a heart beat:

K=(MAP-D)/(S-D);

calculating a second K value according to the following formula where S is said systolic pressure, D is said diastolic pressure, and MAP is said mean arterial pressure:

K=(MAP-D)/(S-D); and

comparing said first K value and said second K value to determine a reliability factor for the blood pressure measurement.

9. Apparatus of claim 4 wherein said processing means is also for:

controlling said distal lifting means such that said distal dynamic pressure increases to a maximum and the decreases;

monitoring said distal dynamic pressure and said distal static pressure to determine said maximum;

fixing said distal lifting means such that said distal static pressure remains at a fixed value below said distal static pressure corresponding to said maximum;

subsequent to said fixing step, controlling said proximal lifting means such that said proximal static pressure increases to a diastolic pressure where said distal dynamic pressure increases from said fixed value;

monitoring said distal dynamic pressure and said proximal static pressure to determine said diastolic pressure;

controlling said proximal lifting means such that said proximal static pressure increases to a mean arterial pressure where said proximal dynamic pressure increases to a maximum and then decreases;

monitoring said proximal dynamic pressure and said proximal static pressure to determine said mean arterial pressure;

controlling said proximal lifting means such that said proximal static pressure increases to a systolic pressure where said distal dynamic pressure decreases to a minimum; and

monitoring said distal dynamic pressure and said proximal static pressure to determine said systolic pressure.

10. Apparatus of claim 9 wherein said processing means is also for:

controlling said proximal lifting means such that said proximal static pressure increases to another mean arterial pressure where said distal dynamic pressure increases to said maximum;

monitoring said distal dynamic pressure and said proximal static pressure to determine said another mean arterial pressure.

11. Apparatus of claim 9 wherein said processing means is also for:

recording said distal sensing means output signal to reveal pressure pulses of individual heart beats;

calculating a first K value according to the following formula where S is the lowest recorded value of said distal sensing means output signal, D is the highest recorded value of said distal sensing means output signal, and MAP is the average of the recorded distal sensing means output signal over a heart beat:

K=(MAP-D)/(S-D);

calculating a second K value according to the following formula where S is said systolic pressure, D is said diastolic pressure, and MAP is said mean arterial pressure:

K=(MAP-D)/(S-D); and

comparing said first K value and said second K value to determine a reliability factor for the blood pressure measurement.

12. Apparatus of claim 4 wherein said processing means is also for:

monitoring the amplitude envelope of said distal dynamic pressure to reveal periodic oscillations due to respiration; and

timing the period of said periodic oscillations of said amplitude envelope to determine a respiratory rate.

13. Apparatus of claim 4 wherein said processing means is also for:

monitoring the amplitude of said distal dynamic pressure to reveal pressure pulses of individual heart beats; and

timing the period of said pressure pulses to determine a pulse rate.

14. An apparatus for measuring a blood pressure in a blood vessel of a limb of a body comprising:

a cuff;

inflating means for inflating said cuff to a fixed mass of air before a measurement interval, and for sealing said fixed mass of air into said cuff throughout said measurement interval;

pressing means for pressing said cuff, after said sealing and during said measurement interval, to generate a pressure on the blood vessel;

sensing means coupled to said cuff, for sensing a pressure of said fixed mass of air of said cuff and for producing an output signal indicative thereof; and

calculating means for calculating a blood pressure based on said sensed pressure.

15. Apparatus of claim 14 wherein:

said cuff contacts less than the entire limb.

16. Apparatus of claim 14 wherein:

said cuff has a small volume compared with the volume of the blood vessel.

17. Apparatus of claim 14 further comprising:

limb stopping means, disposed on an opposite side of the limb from said cuff for forming a surface against which said pressure means presses the limb.

18. Apparatus of claim 17 further comprising:

a proximity sensor, coupled to said limb stopping means, for detecting when the limb is pressed against said limb stopping means.

19. An apparatus for measuring a blood pressure in a blood vessel of a limb of a body comprising:

cuff;

inflating means for inflating said cuff to a fixed mass of air;

pressing means for pressing said cuff, inflated to said fixed mass of air, to exert a pressure on the blood vessel;

sensing means, coupled to said cuff, for sensing a pressure of said fixed means of air of said cuff and for producing an output signal indicative thereof; and

calculating means for calculating a blood pressure on said sensed pressure, wherein said inflating means comprises:

a high pressure air source for producing high pressure air with minimal pressure variations; and

a buffer tank for receiving said high pressure air from said high pressure air source and muffling said variations in said air pressure.

20. An apparatus for measuring a blood pressure in a blood vessel of a limb of a body comprising:

cuff means;

inflating means for inflating said cuff means to a fixed mass of air, the inflating means comprising:

a high pressure air source for producing high pressure air with minimal pressure variations; and

a buffer tank for receiving said high pressure air from said high pressure air source and muffling said variations in said air pressure;

pressing means for pressing said cuff means, inflated to said fixed mass of air, to exert a pressure on the blood vessel, the pressing means including:

a lifter bladder for receiving said muffled high pressure air from said buffer tank and for expanding when said muffled high pressure air from said buffer tank is introduced thereinto;

a base plate, coupled to said lifter bladder, against which said lifter bladder presses to expand; and

a lifter for moving away from said base plate, the lifter being coupled to said lifter bladder on the side opposite said base plate such that expansion of said lifter bladder between said base plate and said lifter moves the lifter away from said base plate;

sensing means, coupled to said cuff means, for sensing a pressure of said fixed mass of air of said cuff means and for producing an output signal indicative thereof; and

calculating means for calculating a blood pressure on said sensed pressure.

21. A method of measuring blood pressure in a blood vessel, comprising the steps of:

applying a distal pressure to the blood vessel at a first location such that the blood vessel opens and closes the maximum amount possible with each beat of the heart;

subsequent to applying said distal pressure, applying a proximal pressure to the blood vessel at a second location on the blood vessel closer to the heart;

recording a diastolic pressure as a lowest value of said proximal pressure where said blood vessel at said first location opens and closes less than said maximum amount possible; and

recording a systolic pressure as a lowest value of said proximal pressure where said blood vessel at said first location remains closed during each beat of the heart.

22. The method of claim 21 further including the step of:

recording a mean arterial pressure as said distal pressure applied to the blood vessel at a first location where the blood vessel opens and closes the maximum amount possible on each beat of the heart.

23. A method of measuring blood pressure in a blood vessel comprising the steps of:

applying a distal pressure to the blood vessel at a first location such that the blood vessel opens and closes less than a maximum amount possible on each beat of the heart;

subsequent to applying said distal pressure, applying a proximal pressure to the blood vessel at a second location on the blood vessel closer to the heart;

recording diastolic pressure as the lowest value of said proximal pressure where the amount said blood vessel at said first location opens and closes changes;

recording systolic pressure as said the lowest value of said proximal pressure where said blood vessel at said first location remains closed during each beat of the heart;

24. The method of claim 23 further including the step of:

recording mean arterial pressure as said distal pressure applied to the blood vessel at a first location where the blood vessel opens and closes the maximum amount possible on each beat of the heart.

25. The method of claim 24 further including the step of:

recording mean arterial pressure as the proximal pressure where said blood vessel at said first location opens and closes the maximum amount possible on each beat of the heart.

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FIELD OF THE INVENTION

This invention relates to the automatic, non-invasive measurement of blood pressure and vital signs through the use of an oscillometric method. Specifically, it relates to a monitor capable of measuring blood pressure, pulse, and respiration rate through the finger.

BACKGROUND OF THE INVENTION

The measurement of blood pressure is an important tool for the medical professional. The term "blood pressure" is a relative term whose precise meaning depends very much on the method used. Blood pressure is the force exerted by the blood against the inner walls of the blood vessels. It is determined by the flow of blood and the resistance to that flow.

Blood pressure is comprised of three parts: the systolic, diastolic, and mean blood pressure. Systolic pressure is the maximum arterial pressure. Diastolic is the minimum arterial pressure. Mean blood pressure is the static pressure that is equivalent to an average pressure. It is found by dividing the area under a single pulse wave by the width of the pulse.

The aortic pressure pulse rises abruptly with aortic ejection and then falls smoothly to the point of the dicrotic notch. The dicrotic notch is attributed to a reflected wave from the recoil of the blood column against the closed aortic valve.

There are several factors that influence arterial blood pressure. They are cardiac output, elastic recoil of the aorta and large arteries, peripheral resistance, volume of blood in the arterial system and viscosity of the blood. Changes in any of the five factors alter either systolic pressure, diastolic pressure, or both pressures.

Devices to measure blood pressure are classified as either direct or indirect. Devices utilizing direct methods all include introducing a pressure sensing element into the blood stream. Because direct methods are invasive, devices utilizing direct methods of measuring blood pressure are impractical for routine clinical examination. Unfortunately, such devices also require a high level of technical skill for the operator. Accordingly, a number of devices utilizing non-invasive indirect methods have been developed. Even though these devices only provide approximate values for intravascular pressure, they are used extensively because physicians need to make routine measurements of blood pressure.

Sphygmomanometry is perhaps the most common type of indirect blood pressure measurement. Sphygmomanometry involves the arrest of flow down an axial artery by the application of a pneumatic cuff. The pressure inside the cuff is manometrically registered. The cuff should meet basic design requirements. Good friction contact is maintained between the cuff and the skin to aid in the constraint of longitudinal tissue motion. The cuff is wide enough to transmit pressure to the artery and the cuff bladder completely encircles the arm.

With sphygmomanometry there must be a means for detecting cessation and onset of blood flow past the cuff as it is inflated or deflated. Monitoring the distal pulse with the finger is one such means. This is, however, insensitive and subjective. Accordingly, more sensitive and objective methods including microphone-amplifier recording, visible capillary refilling or pulsation, plethysmographic pulsation detection, and mercury-in-rubber pulsation detection have been tested. Most notably, auscultation, transcutaneous ultrasonic detection of blood flow, transcutaneous ultrasonic detection of arterial wall movement, and oscillometric pulsation detection are used.

There are two principal ultrasonic methods used in measuring blood pressure. Both methods, however, use a cuff which encircles the limb. In one method, motion of the arterial wall is sensed. In the other, the flow of the blood itself is measured using a Doppler blood flow meter.

Because the walls of the artery beneath an occluding cuff experience a characteristic motion during deflation, it is possible to identify these movements with the first method of ultrasound detection. Two small piezoelectric elements are used. One emits ultrasound and the other detects the ultrasonic echo reflected from the underlying artery. As cuff pressure passes systolic and diastolic pressure, characteristic transitions in the ultrasonic signal are detected.

With the other ultrasonic method, a Doppler blood-flow transducer is placed on the skin over an artery distal to the cuff. When the artery is open, the pulsatile Doppler flow signal is heard or recorded graphically. When the artery is occluded by the cuff, the flow signal disappears. Systolic pressure is read on the first appearance of flow when cuff pressure is decreased During cuff deflation.

The flush method uses an elastic bandage and a limb-encircling cuff. Starting from the tip of the extremity and proceeding to the trunk, a limb is wrapped with a tight elastic bandage such that all the blood is squeezed from the limb. A cuff is then applied just above the trunk end of the bandage and inflated to a high pressure. The bandage is then removed. The opposite undrained limb is then placed beside the blanched member and both are examined in a bright light. Cuff pressure is reduced slowly, and as it passes systolic pressure, blood enters the member and it flushes red. At that particular instant, cuff pressure is read as systolic. There is no indication when cuff pressure is at diastolic pressure or at mean pressure.

Auscultation is listening to sounds that occur within the body. These sounds are known as the Korotkoff sounds in honor of the Russian physician who first proposed the method in 1905. To obtain systolic and diastolic pressure with the auscultatory method, the brachial artery is located and the receiver of a stethoscope placed over it. Cuff pressure is then quickly raised to a point well above systolic pressure. Cuff pressure is then reduced slowly while the observer listens to the arterial sounds. As cuff pressure falls below systolic pressure, a spurt of blood passes under the cuff and a sound is heard in the stethoscope. The cuff pressure at which this sound occurs indicates the systolic pressure. As cuff pressure continues to fall, the sounds become louder, then softer, then very loud, then they become muffled and disappear. Most physicians read the point where the sound disappears as diastolic pressure. However, if the sounds continue to an abnormally low point, physicians use the point where the sound becomes muffled.

In the oscillometric method, variations in amplitude of the blood pressure oscillations are used to identify systolic and mean pressures. There are two components to pressure in a cuff, a static pressure component and a dynamic component. The static component is due to the pressure exerted by the cuff on the limb of body. The dynamic component is due to the pulsation of blood pushing on the cuff. When utilizing the oscillometric method, it is necessary to employ some form of amplification to monitor the small changes in the amplitude of the dynamic component.

In the oscillometric method, cuff pressure is first raised quickly to a point well above systolic pressure where the cuff completely occludes the underlying artery throughout the cardiac cycle. Even though the artery is completely occluded, blood pulsates against the upper edge of the cuff which nevertheless results in small amplitude oscillations on a cuff pressure indicator.

Cuff pressure is then reduced slowly. When cuff pressure falls below systolic pressure, a spurt of blood flows in the artery and the cuff pressure oscillations become larger. As the cuff pressure is further reduced, the oscillations reach a maximum. This maximum corresponds to the maximum change in artery wall dimensions when the heart opens the artery and when the cuff forces the artery closed again on each heart stroke. A further decrease in cuff pressure, therefore, results in a more continuously open artery and the amplitude of the dynamic cuff pressure decreases. The point where amplitude oscillations begin to increase is the point at which systolic pressure is read. The point of maximum oscillation is the mean arterial pressure.

There is, however, no obvious change in cuff pressure oscillation when cuff pressure passes diastolic pressure. Because of this, some physicians have selected diastolic pressure to be the cuff pressure when the oscillations attain a preselected ratio of the maximum amplitude. The ratio is usually chosen to be around 0.8. It has also been assumed that diastolic blood pressure can be obtained from cuff pressure at the point of medium cuff-pressure perturbation.

The methods described above are all manual. These methods all require someone listening and watching to detect the blood pressure. Accordingly, automatic devices capable of reading blood pressure have been developed. The advantages of automatic monitors include ease of use, lower skill level needed by operator, and the elimination of human error in listening for sounds. Automatic, non-invasive blood pressure monitors of this type work either by auscultation or oscillotonometry.

Monitors using auscultation have been available for a number of years.

The first automatic oscillotonometer, on the other hand, was described by Yelderman and Ream in 1977. It consisted of a limb cuff inflated above systolic pressure. Transducers then sensed changes in cuff pressure as the cuff slowly deflated. The first pressure impulse was recorded as systolic pressure; the lowest cuff pressure at which oscillations were maximum was recorded as mean pressure; and the last recorded beat was taken as diastolic pressure. A microprocessor controlled the frequency of recordings and displayed the measurements. The device also included circuits capable of rejecting artifacts produced by patient movement or extraneous pressure on the cuff. Monitors of this type are commercially available.

U.S. Pat. No. 3,903,872 issued to Link in 1975 discloses a single arm cuff for detecting systolic and diastolic blood pressure. The method operates on the principle that pressure applied adjacent to a blood vessel can be plotted against a time derivative of the observed cuff pressure.

U.S. Pat. No. 4,009,709 issued to Link et al. in 1977 discloses a method for detecting systolic pressure. The method uses a conventional arm cuff and an appropriate sensing device to determine the maximum peak pulse amplitude. The systolic pressure is read when the pressure on the cuff is increased until the peak pulse amplitude reading is one half the maximum value.

U.S. Pat. No. 4,651,747 and U.S. Pat. No. 4,664,126 issued to Link in 1987 disclose using a waveform to determine systolic and diastolic pressure. The systolic pressure is determined using the pressure where one-half the maximum pulse amplitude occurs. The diastolic pressure is determined using the slope of the diastolic portion of the pulse curve. Link further shows a method to calculate the area under the curve to obtain the mean arterial pressure.

U.S. Pat. No. 4,729,382 issued to Schaffer et al in 1988 discloses using a two cuff method. The device includes a pressure differential sensor on each cuff and a third sensor to read the static pressure on the proximal cuff. The cuffs are inflated above the point where the second cuff (proximal cuff) occludes blood flow. The sensor in the first cuff (distal cuff) senses no arterially induced pressure pulsation amplitudes. Then deflation begins in both cuffs. When the first cuff detects a pulse, the static pressure sensor connected to the second cuff (proximal cuff) is read to record the systolic pressure. The diastolic pressure is read when the signal on the second cuff (proximal cuff) reaches a steady state.

SUMMARY OF THE INVENTION

The invention comprises an apparatus and process for automatically measuring physiological conditions such as systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, pulse rate, pulse wave shape, respiratory pattern, and respiratory rate. One embodiment of the invention uses two cuffs for affecting blood flow in a limb of the body to be monitored. One of the cuffs, the proximal cuff, is located on the limb of the body at a location proximate to the heart. The other cuff, the distal cuff, is located on the same limb at a location more distant from the heart.

Each cuff also incorporates a pressure sensor and a valve. The pressure sensor detects both the static component of the blood pressure and the dynamic component of the blood pressure by detecting the pressure the cuff exerts on the limb. The valve lets air in and out of the cuff. The pressure with which a cuff presses on the limb is further increased by inflating a bladder beneath the cuff. The inflating bladder presses a lifter against the cuff and the cuff in turn presses against the limb of the body. A microcomputer controls inflating the bladders and monitoring the sensors.

When blood pressure is to be monitored, each cuff is inflated with a given mass of air. The pressure with which the distal cuff presses against the limb is then increased by inflating distal bladder until the maximum dynamic change in cuff pressure is sensed.

When the static distal cuff pressure approximates the cuff pressure for maximum dynamic signal amplitude, several blood pressure pulse wave shapes are stored. The microcomputer then uses this data to determine mean arterial blood pressure, the pulse rate, and the respiratory rate.

The pressure with which the proximal cuff presses against the limb is then increased. Diastolic pressure is sensed when the amplitude of the dynamic distal cuff pressure amplitude decreases.

As the static pressure of the proximal cuff increases further, a maximum dynamic proximal cuff pressure amplitude is detected. The static proximal cuff pressure at which this occurs is recorded as the mean arterial blood pressure.

The pressure of the proximal cuff then continues to increase. Systolic blood pressure is sensed when the distal dynamic cuff pressure amplitude falls to a minimum steady state value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of one of the two bladder-lifter-sensor-cuff-stop assemblies of the present invention.

FIG. 1A represents an alternative embodiment of cuff support to that shown in FIG. 1.

FIG. 1B represents internal anatomic relationships in a cross-section of a finger.

FIG. 2 is functional block diagram of the present invention.

FIG. 2a is a general flowchart of a blood pressure measurement cycle.

FIG. 2b is a flowchart of the Inflate Cuffs Process of the general flowchart of FIG. 2a.

FIG. 2c is a flowchart of the Set Distal Dynamic Amplitude Process of the general flowchart of FIG. 2a.

FIG. 2d is a flowchart of the Detect Diastolic Pressure Process of the general flowchart of FIG. 2a.

FIG. 2e is a flowchart of the Detect Mean Arterial Pressure Process of the general flowchart of FIG. 2a as used in methods one and two.

FIG. 2f is a flowchart of the Detect Mean Arterial Pressure Process of the general flowchart of FIG. 2a as used in method three.

FIG. 2g is a flowchart of the Detect Systolic Pressure Process of the general flowchart of FIG. 2a.

FIG. 3 is a diagram which depicts blood flow in an artery being affected by the proximal and the distal bladder-lifter-sensor-cuff-stop assembly.

FIGS. 4-a through 4-f depict the changes in artery wall dimensions due to increasing cuff pressures being applied to the artery.

FIG. 4-a depicts the artery wall not changing dimensions at and below diastolic pressure being applied by the cuff.

FIG. 4-b depicts a slight change in the dimensions of the artery wall when a pressure slightly above diastolic pressure is being applied by the cuff.

FIG. 4-c depicts a larger change in the dimensions of the artery wall when the cuff exerts a pressure greater than the pressure exerted by the cuff in FIG. 4-b.

FIG. 4-d depicts the maximum change in the dimensions of the artery wall when the cuff exerts a pressure on the artery equal to the means arterial pressure.

FIG. 4-e depicts a change in artery dimensions smaller than that in FIG. 4-d when the pressure exerted on the artery by the cuff is increased above mean arterial pressure.

FIG. 4-f depicts no change in artery dimensions because the pressure exerted on the artery by the cuff is so great that the heart cannot force the artery open at any point in its pumping cycle.

FIG. 5-a is a plot of three blood pressure pulse wave shapes for three beats of the heart.

FIG. 5-b is a plot of the amplitude of the dynamic component of the distal cuff pressure versus the magnitude of the static component of the distal cuff pressure.

FIG. 5-c is table of variables and their definitions.

FIG. 6-a is a plot showing the decline of the amplitude of the dynamic component of distal cuff pressure versus the increase in static proximal cuff pressure (when static distal cuff pressure is held constant near the mean arterial pressure).

FIG. 6-b is a plot showing rise and the subsequent decline of the amplitude of the dynamic component of distal cuff pressure versus the increase in static proximal cuff pressure (when static distal pressure is held constant below the mean arterial pressure).

FIG. 7 is a plot of the static proximal and distal cuff pressures throughout the monitoring process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A first embodiment will now be described. The embodiment uses two lifter assemblies (FIG. 1). The one