EP0185084A4

EP0185084A4 - A technique for generating an arterial curve associated with an individual's blood pressure

Info

Publication number: EP0185084A4
Application number: EP85903487A
Authority: EP
Inventors: William Trevor Link
Original assignee: American Hospital Supply Corp
Current assignee: American Hospital Supply Corp
Priority date: 1984-06-19
Filing date: 1985-06-17
Publication date: 1988-01-28
Also published as: JPS61502726A; EP0185084A1; WO1986000208A1

Abstract

A technique for generating certain arterial blood pressure related curves V/P and dV/dP (42, 43) of a given individual using cuff pressure peak to peak values (curve 40). This is accomplished using only these latter values and the individuals diastolic and systolic blood pressures.

Description

A TECHNIQUE FOR GENERATING AN ARTERIAL CURVE ASSOCIATED WITH AN INDIVIDUAL'S BLOOD PRESSURE

The present invention relates generally to blood pres- sure evaluation procedures and more particularly to non-invasive technique for generating an arterial curve associated with an individual's blood pressure.

The most reliable ways presently known for obtaining information relating to an individual's blood pressure require invasive procedures. Such procedures are not carried out routinely but only under extreme circum¬ stances, for example during heart surgery. Under less critical conditions, blood pressure information including specifically an individual's systolic (maximum) and diastolic (minimum) blood pressures is obtained non-invasively. There are two well known non-invasive techniques presently being used today, one is commonly referred to as auscultation and the other is based on oscillometry. Both of these non-invasive techniques use the standard arm cuff which most people are familiar with. However, in the auscultatory method, the systolic and diastolic pressures are determined by listening to certain sounds (Korotkoff sounds) which occur as a result of the cuff first being pressurized and then depressurized whereas oscillometry actually measures changes in pressure in the cuff as a result of changes in blood pressure as the cuff is first pressurized and then depressurized. As will be seen hereinafter, the various embodiments of the present invention are based on oscillometry. In order to more fully appreciate these embodiments, reference is made to applicant's own United States Patent 3,903,872 (the Link patent) for obtaining blood pressure information non-invasively. This patent which is incorporated herein by reference describes, among other things, a way of obtaining the diastolic pressure of an individual in accordance with a technique which will be discussed in more detail hereinafter. In United States Patents 4,009,709 and 4,074,711 (Link et al) which are also incorporated herein by reference, non-invasive techniques using oscillometry are disclosed for obtaining the systolic pressure of an individual. These techniques will also be discussed hereinafter.

While the various procedures described in the Link and Link et al patents just recited and other patents held by applicant are satisfactory for their intended purposes, it is an object of the present invention to provide additional uncomplicated and yet reliable techniques for obtaining different types of informa¬ tion relating to an individual's blood pressure.

A more specific object of the present invention is to provide a new, uncomplicated and yet reliable technique for generating blood pressure related curves corresponding to those described in United States Patent 3,903,872 and the Link article.

As will be described in more detail hereinafter, the objects just recited are achieved by means of oscillometry. In accordance with this technique, a suitably sized cuff, for example one which is 20 inches long and 5 inches wide, is positioned around the upper arm of an individual, a human being specifically or a mammal in general (hereinafter referred to as the patient) and initially pressurized to a level which is believed to be clearly greater than the patient's systolic pressure, for example 180 Torr. It is assumed that this pressure will also cause the patient's artery within the sleeve to completely collapse. Thereafter, cuff pressure is gradually reduced toward zero during which time the cuff continuously changes in pressure in an oscillating fashion due to the combination of (1) the internal blood pressure changes in the patient's artery and (2) changes in cuff pressure. The latter at any given time in the procedure is known and oscillatory changes in cuff pressure can be readily measured, for example with an oscilloscope. By using these two parameters in conjunction with information which may be made. available from methods disclosed in the above-recited United States patents it is possible to achieve the foregoing objectives in an uncomplicated and reliable way utilizing the techniques of the present invention to be described hereinafter.

In this regard, it should be noted at the outset that the typically 5" wide pressure cuff entirely surrounds a corresponding 5" length of artery. The tissue of the arm is for the most part incompressible, and therefore any change in the volume of the artery, caused for example by pulsations of blood, results in a corresponding change in the volume of air in the air bladder which is within the cuff and therefore adjacent to the arm. This change in air volume produces a small but accurately measurable pressure change in the air. This equivalence of pressure pulsations in the cuff bladder to volume pulsations of the artery is the essence of oscillometry. In order to more fully appreciate the various tech¬ niques of the present invention, the following more detailed background information is provided in con¬ junction with Figures 1-5 of the drawings where:

FIGURE 1 (corresponding to Figure 6 in United States Patent 3,903,872) diagrammatically illustrates the shapes of successive cuff pressure versus time pulses (cuff pulses) as the measured cuff pressure changes from 90 Torr to 80 Torr to 70 Torr, assuming the patient has a diastolic pressure of 80 Torr;

FIGURE 1A diagrammatically illustrates a full series of cuff pulses corresponding to those in Figure 1 from a cuff pressure of 160 Torr to a cuff pressure of zero;

FIGURE 2 diagrammatically illustrates a curve corre¬ sponding to arterial or cuff volume (V), that is, the volume of the patient's artery within the cuff (as measured by cuff volume) versus wall pressure (P ) across the artery wall within the cuff and, super- imposed on this curve, a curve which is intended to correspond to the actual blood pressure waveform of a patient, the two curves being provided together in order to illustrate the principles of oscillometry, as relied upon in the above-recited patents;

FIGURES 3 and 4 diagrammatically illustrate the cuff curve of Figure 1 in ways which display techniques for obtaining a given patient's systolic and diastolic blood pressures in accordance with the Link and Link et al patents recited above; and

FIGURE 5 diagrammatically illustrates a compliance curve for the patient's artery, that is, a curve which displays the ratio ΔV/ΔP against the arterial wall pressure P , where ΔV is the incremental change in the arterial volume corresponding to a preselected constant change in blood pressure ΔP. This curve being initially determined in order to provide the cuff or arterial volume curve (V/P) of Figure 2 bv means of integration, as will be seen.

Turning first to Figure 1, this figure diagrammatical¬ ly illustrates three successive waveforms lOh, lOi and 10j which correspond to the change in volume in a pressurized cuff, as described above, at three differ¬ ent cuff pressures, specifically cuff pressures of 90 Torr, 80 Torr and 70 Torr. In actual practice, a greater number of waveforms (hereinafter referred to as cuff pulses) are generated starting at a cuff pressure of 160 Torr and ending at a cuff pressure of zero, as will be seen in Figure 1A. By generating these waveforms at known cuff pressures, both the diastolic and systolic pressures of a patient can be determined in accordance with the above-recited patents. While this will be explained in more detail below, it is important to note initially that each waveform has what may be referred to as a systolic rise S at one end of the waveform, a diastolic decline D, at the opposite end and a maximum amplitude A.

While the systolic rise S is fairly consistent and distinctive from one cuff pulse 10 to another, both the diastolic decline D, and amplitude A vary from pulse to pulse for reasons to be explained hereinafter. It is because of these variations that ^"the techniques dis¬ closed in the Link and Link et al patents recited above are able to determine the diastolic and systolic pressures. Specifically, as will be seen, when the diastolic pressure of a patient is equal to the cuff pressure, the cuff pulse generated has a diastolic decline which is greater in slope than the diastolic decline of any of the other cuff pulses. Thus, assuming that the diastolic decline has a maximum slope at the cuff pulse lOi illustrated in Figure 1, the patient providing these waveforms would have a diastolic pressure of 80 Torr. At the same time, this patient's systolic pressure can be de¬ termined by first finding which of the cuff pulses displays a maximum amplitude A and then, moving up in cuff pressure, finding the cuff pulse having half that amplitude. The cuff pressure responsible for producing this half-amplitude pulse will equal the patient's systolic blood pressure. In order to more fully understand these capabilities, reference is made to Figures 2-5 in conjunction with the above-recited Link and Link et al patents.

Turning now to Figure 2, attention is directed to the curves illustrated there in order to explain why the cuff pulses of Figure 1 result from changes in cuff pressure. The generally S-shaped curve 12 illustrated is shown within a horizontal/vertical coordinate system where the horizontal axis represents the wall pressure P across the artery wall of a given patient, within the confines of the applied cuff, and the vertical axis represents arterial volume V of the artery within the cuff, as measured by the internal volume of the cuff itself. In order to fully understand this V/P curve

(hereinafter merely referred to as an arterial or a cuff curve) , it is important to keep in mind the definition of Pw. The wall pressure Pw of the arterv of the patient at any given time is equal to the blood pressure P. of the patient within the artery at that time less the applied pressure of the cuff P . Thus:

Vw = P.b - Pc ...U) For purposes of the present discussion, it will be assumed that pressure is measured in Torr (mmHg) and that the section of the horizontal axis to the right of the vertical axis represents positive wall pres- sures while the section of the axis to the left of the vertical axis represents negative wall pressures. As a result, when no pressure is applied to the cuff (e.g. P =0) , P at any given point in time is equal to the blood pressure of the patient at that time. As the cuff is p^fressurized,' Pw decreases (moves to the left along the horizontal axis) . When the cuff pressure P is equal to the blood pressure P. at any given point in time, P at that time is equal to zero (e.g. at the vertical axis) . As the cuff pressure is increased beyond the blood pressure at any point in time, P at that time becomes more negative (moves further to the left on the horizontal axis) .

With the definitions of the vertical axis V and the horizontal axis Pw in mind, attention is now directed to an interpretation of the generally S-shaped cuff curve 12 within this coordinate system. For the moment, it is being assumed that this curve is charac¬ teristic of the particular patient being evaluated. That is, it is being assumed that the patient's artery within the cuff and therefore the cuff itself will change in volume along the S-shaped curve and only along the curve with changes in P . Hereinafter, with regard to Figure 3, it will be shown that the arterial curve 12 of a given patient can be generated from his cuff pulses 10 and corresponding cuff pressures P . Thus, for the time being, it will^" be assumed that the arterial curve illustrated in Figure 2 corresponds to that of the given patient.

With the foregoing in mind, the arterial curve of Figure 2 will now be examined. Let it first be assumed that no pressure is applied to the patient's cuff so that Pc equals zero. As a result, Pw equals the blood pressure P. of the patient. In this regard, it is important to note that P. varies with time between the patient's diastolic blood pressure P_b( ) and his systolic blood pressure P. (S). For purposes of this discussion, let it be assumed that these values are known and that specifically the patient's diastolic blood pressure is 80 Torr and his systolic blood pressure is 120 Torr. Thus, with no pressure in the cuff, Pw oscillates back and forth with time between

P. (D) and P. (S) , that is, between 80 Torr and 120 Torr. This 40 Torr measuring band is illustrated by dotted lines in Figure 2 at 14 and actually represents the patient's pulse pressure ΔP which is equal to 40 Torr in this case.

The patient's actual blood pressure waveform 15 is superimposed on the V/P coordinate system in Figure 2 within the pulse pressure band 14. As seen there, this waveform is made up of a series of actual blood pressure pulses 16, each of which corresponds to a single beat of the patient's heart. Note that each pulse starts at a minimum pressure (the diastolic pressure of the patient) and sharply increases along its leading edge which is the systolic rise_, S until it reaches a maximum (the patient's systolic^' blood pres¬ sure) , at which time it drops back down along a trailing edge which includes a dichrotic notch and a diastolic decline D, to the minimum pressure again. At those points in time when the patient's blood pressure is at a minimum (that is, at the diastolic ends of pulses 16), the volume of the patient's artery and therefore the volume of the cuff is fixed by the arterial curve at the value indicated at V.l . On the other hand, whenever the patient's blood pressure is maximum (at the systolic end of each blood pressure pulse 16) , the arterial curve fixes arterial and therefore cuff volume at the slightly higher value indicated at Therefore, it should be apparent that for each heart beat, assuming a cuff pressure P of zero, the volume V (the cuff volume) moves between the values V.. and V«, thereby generating a series of cuff pulses lOq corresponding to those illustrated in Figure 1 but at a cuff pressure P =0, as shown in Figure 1A. Thus, as the patient's blood pressure rises from a minimum to a maximum, the volume of the artery rises from V., to ^~7m in a generally corresponding manner and as the patient's blood pressure drops back down to a minimum, the arterial volume falls from V_ to V.. in a generally corre- sponding manner. Thus, each of the arterial pulses 10 in Figure 2 has a systolic rise S and a diastolic decline D, corresponding to the systolic rise and diastolic decline of each blood pressure pulse 16.

Having shown how the cuff pulses lOq are dependent upon the volume curve at a cuff pressure of zero, we will now describe how the arterial curve causes these arterial pulses to change with applied cuff pressure.

Let us assume now a cuff pressure of 50 Torr. Under these conditions, Pw oscillates back and forth between 30 Torr and 70 Torr. The 30 Torr value is determined by subtracting the cuff pressure P of 50 Torr from the diastolic blood pressure •P-_hf-D) of 80 Torr and the 70 Torr value is determined by subtracting the same P of 50 Torr from the systolic blood pressure P_h(D) of 120 Torr. Thus, the entire 40 Torr band has merely been shifted to the left an amount equal to 50 Torr as indicated by the band 14*. Under these circumstances, P oscillates back and forth along a steeper segment of the arterial curve so as to cause the volume of the patient's artery and therefore the volume of the cuff to oscillate between the values V 3, and V4.. This results in the production of arterial pulses 101 at a P of 50 Torr. Note that the amplitude of each cuff pulse 101 is greater than the amplitude of each cuff pulse lOq. This is because the 40 Torr band 14' at a cuff pressure of 50 Torr is on a steeper part of the volume slope than the band 14 at a cuff pressure of zero. Indeed, as we increase the cuff pressure P (which decreases P ) and therefore move the pressure band to the left on the horizontal axis, we first continue to move along steeper sections of the arterial curve and thereafter less steep sections. Therefore, the amplitude A (see Figures 1 and 1A) of the corresponding cuff pulses lOq, 101 and so on will first increase to a maximum and then decrease again. At a cuff pressure P of 100, the entire 40 Torr pressure band is shifted to the left so as to uniformly straddle opposite sides of the vertical axis, as indicated at 14". This results in a corresponding cuff pulse lOg having approximately a maximum ampli- tude (ΔV ax in Figure 2) .

Moving still further to the left, at for example, a cuff pressure P of 160 Torr, the entire 40 Torr band is moved a substantial distance to the left of the vertical axis, as indicated at 14''' such that the resultant change in volume (amplitude of the corre¬ sponding cuff pulse 10a) is quite small. By increasing the cuff pressure to even a greater amount, the band is moved still further to the left, eventually producing very small changes in volume V. From a physical standpoint, this represents a collapsed artery. In other words, sufficient cuff pressure is being applied over and above the internal blood pressure P. to cause the wall of the artery to collapse. At the other extreme, that is, when the cuff pressure P is zero, there are no external constraints placed on the artery and the latter is free to fluctuate back and forth based on its internal pressure P. only, Between these extremes, the amplitude A of cuff pulse 10 (e.g. ΔV) will increase to a maximum and then decrease again, as stated. It is this characteristic of the volume curve which is used to determine the patient's systolic pressure in accordance with the previously recited Link et al patents, as will be described with regard to Figures 3 and 4.

As previously mentioned, it should be noted that a blood pressure increase causes an arterial volume increase. This arterial volume increase causes a cuff bladder air volume decrease which in turn causes a cuff bladder air-pressure increase. Therefore a blood pressure increase results in a cuff air pressure increase. This is emphasized as follows:

blood ->^■ arterial cuff air cuff air pressure volume volume pressure increase increase decrease increase

Thus: blood ^■*^■ cuff air pressure pressure increase increase

Referring to Figure 3, the same arterial curve 12 illustrated in Figure 2 is again shown ^' but with a single superimposed pressure band 14'''' at a cuff pressure P of 120 Torr. Assume again that the diastolic pressure of the patient is 80 Torr and his systolic pressure is 120 which means that P __ is equal to the patient's systolic pressure. Under these circumstances, P oscillates back and forth within band 14'''' between wall pressures of -40 Torr and zero, as shown. This results in a change in arterial volume ΔV (e.g., the amplitude A of a corresponding cuff pulse) which is approximately equal to one-half of the maximum change in arterial volume (e.g., max cuff pulse amplitude) . It may be recalled that a maximum change in volume ΔV max (and therefore a maximum cuff pulse amplitude Amax) results from a cuff pressure P __*• of about 100 Torr (e.g. the pressure band

14" in Figure 2) . Thus, when the cuff pressure P is equal to the patient's systolic blood pressure P. (S) , the amplitude A of the resultant cuff pulse 10 is about one-half of the amplitude of the cuff pulse having a maximum amplitude. Therefore, a patient's systolic blood pressure can be determined by first generating a series of cuff pulses across the cuff pressure spectrum, as in Figure 1A. From these pulses, the one having maximum amplitude Amax is determined and then the cuff pulse having half that amplitude (at a greater cuff pressure) is found. The cuff pressure P used to generate that pulse corresponds to the patient's systolic pressure. In other words, by evaluating the amplitudes of the various cuff pulses, the one corre¬ sponding to the band 14'''' illustrated in Figure 3 can be found. Once that pulse is found, its associated cuff pressure is assumed to be equal to the patient's systolic pressure. This is discussed in more detail in Link et al United States Patents 4,009,709 and 4,074,711 and means are provided in these latter patents for electronically making these evaluations.

Returning to Figure 2, it should be noted that the actual blood pressure waveform 15 is shown having a uniform repetition rate, for example 60 pulses/minute, and that each blood pressure pulse 16 making up this waveform is identical to the next one. Both of these aspects of the waveform are^' assumed for purposes herein. Moreover, each pulse has its own systolic rise Sr and diastolic decline Dd,, as mentioned hereto- fore. It should also be noted that the arterial curve 12 dictates the relationship between V and P at each and every point on the waveform 15 of individual blood pressure pulse 16, not merely at the extreme diastolic and systolic end points of each pulse. Thus, one could measure the change in volume ΔV at two different cuff pressures along the diastolic decline only. In this case, the measuring band (e.g. the pressure difference between the two measuring points) is substantially narrower than band 14. As best illustrated in Figure 4, ΔV. ' is determined for a cuff pressure P of zero using the pressure band 18 which encompasses a small part of the diastolic decline of each blood pressure pulse 16. ^~7m ^% is determined for a cuff pressure of P of 50 Torr by shifting the band to 18' and, ΔV,' is determined for a cuff pressure Pc of 80 Torr (e.g ^J. the patient's diastolic blood pressure) by shifting the band to 18". Note that ΔV is maximum when the cuff pressure P __*- is equal to the patient's diastolic blood pressure. Therefore, by determining the change in volume ΔV at the end of the diastolic slope of the patient's actual blood pressure waveform for each and every cuff pressure, the one cuff pressure producing a maximum change will correspond to the patient's diastolic blood pressure. The lowest pressure part of the diastolic decline D. forming part of each pulse 16 is particularly suitable for this purpose since it can be readily located during each cycle of the^' waveform. This is because it immediately precedes the systolic rise S which is readily distinguishable each time it appears. This procedure is described in more detail in the previously recited Link Patent 3,903,872 along with means for carrying out this procedure electronically. The foregoing discussions for obtaining a given pa¬ tient's systolic and diastolic blood pressures have assumed that the patient's arterial curve corresponded to the one illustrated in Figures 2, 3 and 4. While this assumption is reasonably valid, it is possible to determine the patient's own volume curve using the principles associated with Figure 4. Specifically, using the narrower bands 18, 18' and so on as measuring bands, the change in volume ΔV (e.g., the change in cuff volume) resulting from different cuff pressures P is plotted, as shown in Figure 5. Thus at a cuff pressure P of zero, there is a relatively small change in volume ΔV, as evidenced by the small ΔV. ' in Figure 4. As the cuff pressure P increases, the change in volume ΔV continues to increase to a maximum (ΔV_' in Figure 4) and then decreases. In mathematical terms, this curve represents incremental changes in volume with incremental changes in pressure or dV/dP (Figure 5) . By integrating this curve we obtain the cuff curve or the V/P curve of Figures 2-4.

Having discussed Figures 1-5 in regards to the prior art techniques for obtaining diastolic and systolic blood pressures for a given patient in accordance with the techniques described in the above-recited Link and Link et al patents, attention is now directed to the present invention, as discussed briefly above, in conjunction with remaining Figures 6-9 where:

FIGURE 6 graphically displays the peak to peak ampli¬ tude A of various cuff pulses of Figure 1A against cuff pressure;

FIGURE 7 graphically illustrates an arterial curve corresponding to the one illustrated in Figure 2 but generated from the information in Figures 1A and 6 only; FIGURE 8 illustrates the same curve as Figure 7 normalized to zero volume at negative wall pressures and having superimposed thereon its differentiated curve; and

FIGURE 9 schematically illustrates an arrangement for electronically generating the curves of Figure 8;

Turning now to Figures 6-9 in conjunction with Figure 1A, attention is directed to a technique for generating arterial or cuff curve for a given individual in accordance with the present invention. As stated previously. Figure 1A illustrates a particular pa¬ tient's cuff pulses 10a, 10b and so on, as read out on an oscilloscope, for varying cuff pressures (P __) starting with a cuff pressure of 160 Torr (Pulse 10a) and ending with a cuff pressure of zero (pulse lOq) . Note that the peak to peak amplitude (A) of each cuff pulse has been measured and so indicated in Figure 1A. As will be seen below, by using only this information and the patient's diastolic and systolic pressures which may be determined in any suitable manner, for example in accordance with the previously recited Link and Link et al patents, the particular patient's own arterial or cuff (V/P) curve and his arterial compli¬ ance (dV/dP) curve can be generated in a way which is different than has been done heretofore.

Referring to Figure 6, the^" peak to peak amplitude values (A) measured from Figure 1A have been graphically plotted against cuff pressure and a resultant curve 40 drawn. Using information taken from this curve and the patient's diastolic and systolic blood pressures, the S-shaped arterial (V/P) curve 42 of Figure 7 may be plotted. In order to more fully understand how this is accomplished, it must be kept in mind that the patient's diastolic and systolic pressures together provide a pulse pressure band (e.g. a measuring band) corresponding to the band 14 illustrated in Figure 2. Assuming the patient's diastolic blood pressure is 85 Torr and his systolic blood pressure is 125 Torr, this band is precisely

40 Torr wide. It must also be kept in mind that the arterial curve 42 is plotted in an x-y coordinate system in which the x-axis corresponds to P (the wall pressure of the patient's artery) and the y-axis represents relative arterial volume, as previously described with respect to Figure 2. As a reminder,

Pwal.l. = P.bl.ood, - Pcuf mfm or Pw = Pb. - Pc. Thus, ^' with a cuff pressure P of zero, the measuring band is between 85 Torr and 125 Torr and the peak to peak amplitude of the cuff pulse is 0.1 Torr which corresponds (is in direct proportion) to the change in arterial volume (ΔV) resulting from this cuff pressure. In other words, as the patient's blood pressure rises and falls within the measuring band of 85 Torr and 125 Torr, ΔV changes .an amount directly proportionate to 0.1 Torr. This point can be plotted in Figure 7 as point 1.

At a cuff pressure of 40 Torr, the wall pressure P oscillates back and forth within the 40 Torr measuring band between 85 Torr and 45 Torr. As seen in Figures 1A, 6 and 7, this results in a peak to peak amplitude of 0.50 Torr and a directly proportionate change in ΔV. This may be plotted as point 2. ^' Additional points 3, 4 and 5 have been plotted in Figure 7 corresponding to cuff pressures of 80, 120 and 160. While only five points were plotted, it should be understood that points corresponding to all of the cuff pressures actually measured in Figure 1A and even those interpolated from the curve of Figure 6 could have been plotted. From these points, the arterial (V/P) curve 42 illustrated in Figure 7 can be readily drawn. This curve is reproduced in Figure 8 with the axis corresponding to P moved downward, as shown. Once the arterial curve is generated, the patient's compliance curve dV/dP, 43, (V/P curve) can be generated by differentiating the arterial curve or it can be provided directly from the peak to peak (A) data from Figure 6. It is noted that the oscillometric cuff pulse amplitudes A shown in Figure la often do not become zero for even very large values of the cuff pressure but approach a small and fairly constant value for large cuff pressure. This small value may be subtracted from each of the other amplitude values A in the table of Figure la and graphed in Figure 6. The resulting slightly reduced values A could then be utilized to provide a somewhat improved V/P curve by using the method described above. Figure 9 illustrates means 44 for receiving the various cuff pulses corre¬ sponding to those in Figure 1A from a given individual through a cuff (not shown) applied to the individuals arm and a transducer forming part of means 44. Means 44 then extracts the peak to peak information and upon receiving the patient's diastolic and systolic blood pressures from suitable inputs shown in Figure 9 is able to act on this information so as to generate either or both the arterial V/P curve and dV/dP curves 42 and 43, respectively, which can be permanently recorded or placed on an oscilloscope, as generally indicated at 46. The electronics necessary to make means 44 function in this manner can be readily provided in view of the teachings herein.

Claims

WHAT IS CLAIMED IS:

1. A method of providing an arterial curve charac¬ teristic of a particular mammal, comprising the steps of: (a) placing a blood pressure cuff around a particular artery of said mammal;

(b) using means cooperating with said cuff, pressurizing the latter at a number of different pres¬ sure levels from zero pressure to a pressure at least equal to the mammal's systolic pressure and generating cuff pulses having peak to peak amplitude values corre¬ sponding to and dependent on said different pressure levels;

(c) determining the diastolic and systolic pres- sures of said mammal; and

(d) graphically generating said arterial curve in a way which requires the use of said peak to peak values and said diastolic and systolic pressures.

2. A method according to Claim 1 wherein only said peak to peak amplitude values and said diastolic and systolic pressures are used to graphically generate said arterial curve.

3. An apparatus for providing an arterial curve characteristic of a particular mammal, comprising: (a) a blood pressure cuff for placement around a particular artery of said mammal;

(b) means cooperating with said cuff for pres¬ surizing the latter at a number of different pressure levels from zero pressure to a pressure at least equal to the mammal's systolic pressure and for generating cuff pulses having peak to peak amplitude values corre¬ sponding to and dependent on said different pressure levels; (c) means for determining the diastolic and systolic pressures of said mammal; and

(d) means for graphically generating said arte¬ rial curve in a way which requires the use of said peak to peak values and said diastolic and systolic pressures.

4. An apparatus according to Claim 3 wherein only said peak to peak amplitude values and said diastolic and systolic pressures are used to graphically gener- ate said arterial curve.

5. A method of providing an arterial curve charac¬ teristic of a particular mammal, comprising the steps of:

(a) placing cuff means adjacent a particular artery of said mammal;

(b) using means cooperating with said cuff means, pressurizing the latter at a number of different pressure levels from zero pressure to a pressure at least equal to the mammal's systolic pressure and generating cuff pulses having peak to peak amplitude values corresponding to and dependent on said different pressure levels;

(c) determining the diastolic and systolic pressure of said mammal; and (d) generating said arterial curve ill a way which requires the use of said peak to peak values and said diastolic and systolic pressures.

6. A method according to Claim 1 wherein only said peak to peak amplitude values and said diastolic and systolic pressures are used to generate said arterial curve.

7. An apparatus for providing an arterial curve characteristic of a particular mammal, comprising: (a) blood pressure cuff means for placement adjacent a particular artery of said mammal;

(b) means cooperating with said cuff means for pressurizing the latter at a number of different pressure levels from zero pressure to a pressure at least equal to the mammal's systolic pressure and for generating cuff pulses having peak to peak amplitude values corresponding to and dependent on said different pressure levels; (c) means for determining the diastolic and systolic pressures of said mammal; and

(d) means for generating said arterial curve in a way which requires the use of said peak to peak values and said diastolic and systolic pressures.

8. An apparatus according to Claim 7 wherein only said peak to peak amplitude values and said diastolic and systolic pressures are used to generate said arterial curve.