FR2498440A1 - METHOD AND APPARATUS FOR MEASURING PRESSURE - Google Patents

Abstract

A.PROCEDE AND APPARATUS FOR MEASURING SYSTOLIC BLOOD PRESSURE WITHOUT PENETRATION IN THE BODY. B. PROCEDURE AND APPARATUS CHARACTERIZED IN THAT THEY ALLOW TO APPLY BY AN INFLATABLE BRACELET 101 A VARIABLE PRESSURE TO A PATIENT LIMB, TO MEASURE THE OSCILLATIONS PRODUCED BY THE BLOOD PULSATIONS WHEN THE PRESSURE OF THE BRACELET REDUCES BY SUPERIOR STEPS AT THE EXPECTED SYSTOLIC PRESSURE AND A PRESSURE LOWER THAN THE DIASTOLIC PRESSURE, MEASURE THE AVERAGE ARTERIAL PRESSURE WHEN THE PRESSURE OSCILLATIONS ARE AT THE MAXIMUM, AND DETERMINE THE SYSTOLIC PRESSURE BY EQUALING A FIRST LINEAR APPROXIMATION MORE THAN THE MEASURED OF THE MEASURED FROM THE EXPECTED SYSTOLIC PRESSURE TO A SECOND LINEAR APPROXIMATION CORRESPONDING TO SEVERAL MEASUREMENTS ABOVE THE EXPECTED SYSTOLIC PRESSURE, THE DIASTOLIC PRESSURE BEING DETERMINED FOR AN AMPLITUDE OF OSCILLATIONS EQUIVALENT TO THAT OF THE SYSTOLIC PRESSURE. C. THE INVENTION APPLIES IN THE FIELD OF MEDICAL DIAGNOSIS.

Description

The invention relates to a method and an apparatus

  measuring blood pressure, and more specifically a dis-

  positive to measure the arterial blood pressure by oscillometry, that is to say by observation of the pressure oscillations produced by the arterial pulsations of the blood

  in a pressurized air bracelet.

  Variations in blood pressure in different

  The different physiological states of a patient are of great interest for modern diagnostic procedures. The traditional method of characterizing blood pressure consists of

  to determine the values of the systolic pressure and the pressure

  diastolic discharge. It was also found that the mean arterial pressure (P A M) was a very useful measurement parameter for indicating blood pressure. Mean arterial blood pressure is defined as the time average of the instantaneous blood pressure, or as the weighted average of the systolic and diastolic pressures. In particular, if one represents the blood pressure as a function of time, the P A M

  is at a level chosen so that the area

  the systolic part of the curve and the level of P A M is equal to the area between the level of P A M and the

  diastolic part of the curve. The level of the P A M may be

  grossly from systolic and diastolic values

  by the following formula t P A M = Diastolic + 1/3 (systolic diastolic) The value determined by this equation can be

  suffer from inaccuracies due to possible shocks, condi-

  environmental conditions of the room or certain

  to variations in the waveform of the blood pulse.

  There are currently several methods of

  wise current to measure the different values of pressure

  blood pressure. The most accurate method is to measure

  blood pressure directly using an arterial cannula

  rial. However, penetration techniques are often poorly adapted and may be very painful for

the patient.

  As a result, a number of non-penetration techniques have been developed. One of the most common techniques of current use is to obstruct the vessels

  of a patient's limb by an inflatable

  2.- Turning this member. We let it go down slowly

  gas pressure (typically the air pressure) in the bracelet.

  When the decreasing pressure becomes equal to the pressior. ar-

  In this case, characteristic noises, commonly known as Korotkoff sounds, may be heard by shortening the blood flow. When the decreasing pressure of the bracelet reaches the diastolic blood pressure, Korotkoff sounds

  also modify typically.

  These phenomena can be used easily to measure systolic and diastolic blood pressures

  by observing the pressure of the bracelet by means of a sphygmoman-

  Mercury meter or conventional anole, while shortening to the

  the flow of blood in the arteries. This technique was also automated by detecting Korotkoff sounds in the inflatable bracelet by means of microphoners or ultrasonic transducers. One of the problems with this process is that

  can not be used to measure arterial pressure directly

  mean value to be calculated by the formula above, from the systolic and diastolic values. This formula may, on the other hand, be imprecise as a result of various factors such as

  as shocks or possible troubles.

  A technique discovered more recently is the oscillometric method for the detection and quantitative measurement of blood pressure values. This technique uses an inflatable air strap obstructing the blood vessels as

  in the case of Korotkoff's technique, but detects

  re different blood pressure values. More precise-

  When the air pressure in the inflatable air strap drops below the systolic blood pressure, small pressure oscillations can be seen superimposed on the

  basic pressure of the bracelet. These small oscillations of

  affect the air pressure of the surrounding wristband

  the patient's limb as a result of dilation and contrac-

  arteries produced by the pulsed flow of blood.

  Pressure oscillations increase by

  and reach a maximum value when the pressure of the

  bracelet becomes equal to the mean arterial blood pressure-

  born. Oscillations then decrease in amplitude until

  appear completely below a threshold value of applied wrist pressure. We can then easily measure 3.-

  mean arterial pressure by detecting the pressure of

  air ring for which we obtain the maximum amplitude of the pressure oscillations in the air bracelet. This technique

  can easily be automatized and is particularly

  practical in blood pressure measuring devices.

  guine controlled by microprocessors.

  However, a problem that remains with the blood pressure measuring devices according to the prior art, using the oscillometric method, is that although the mean arterial pressure can be easily measured, there is

  still no precise method for measuring the system pressure

tolic or diastolic pressure.

  As a result, most devices according to the prior art are based on extrapolation of systolic and diastolic pressures from the measurement of mean arterial pressure. For example, it has been observed that the pressures

  systolic and diastolic appear at points where the

  pressure cillations in the air bracelet reach a

  amplitude of the order of half that of the oscillations cor-

  responding to the average arterial pressure. This method allows

  makes it easy to calculate systolic and diastolic

  from mean arterial pressure, but poses

  for a number of additional problems. Artifacts introduced by the patient's movements or by external disturbances can lead to

  wrong results if they occur when measuring the pres-

  the bracelet in the vicinity of the diastolic pressures and

  tolique. Next, the half-amplitude relationship between the

  medium pressure and system pressure oscillations.

  tolic / diastolic is not exactly correct. As a result, the systolic and diastolic pressures calculated by this

  are only approximations of the true values.

  The invention aims to overcome these drawbacks.

  by creating a more accurate method of determining systolic and diastolic blood pressures using a

  measuring blood pressure operating in oscillometric mode

cudgel.

  The invention thus makes it possible to obtain

  accurate systolic and diastolic blood pressures in the presence of noise or other external disturbances, and 4.- in the case of shocks, harsh environments or various disorders. The invention further allows for better removal of artifacts in the readings of systolic and diastolic blood pressures. For this purpose, the invention relates to a method for measuring systolic blood pressure without penetration into the body, characterized in that it comprises the various steps of obstructing blood flow in the body.

  limb by applying to that limb a different external pressure

  and measurable, to vary this pressure by several successive steps between an amplitude for which the blood flow is practically obstructed and not amplitude for which

  the blood flow is practically free; to watch, in every

  the stages, the amplitude of the pressure oscillations pro-

  induced by the pulses of the blood flow in the limb in question, to deduce a first relation between the amplitude of oscillation and the corresponding pressure, this relation

  being obtained from a number of bone amplitudes

  cations and corresponding pressure values for pressures above the expected systolic pressure; to deduce a relationship between the oscillation aoplit-ilude and the corresponding pressure, c-shooting a certain no-b

  amplitudes of oscillations and pressure of

  for pressures below the systolic pressure; and to unearth the pressure washer

  common area satisfying the two re-ions corresponding to a

  their esteem of the 'pres..ro sr.gine: vstoliqueo ebtiente thus z -ire terlmination more precise

  systolic and diastolic pressures and better elimination of

  nation of artifacts, n computing ie; Eystolic and diastolic attendants from a series of _szu-es effecte on the

  air bracelet in the area of the ystolic and / or dias-

  tolic, rather than from a seriousness of the

  mean or mean blood pressure. unique

  killed in the vicinity of syets pressures .: Or diastolic and more precise. this is the case. when

  the air pressure in the wristband obtr.unt the blood vessels

  When the blood pressure decreases from a value greater than the systolic blood pressure, the amplitude of the oscillations of the wrist air pressure decreases slowly and progressively at a first approximately constant rate. However, when

  the air pressure of the bracelet reaches the vicinity of the pres-

  systolic pressure, the rate of increase in

  cillations accelerates abruptly, The amplitude of the oscillations

  then continue to grow in a second, approximate

  constant when the air pressure of the wristband decreases,

  in order to reach a maximum value for the arterial pressure

  average. The amplitude of the oscillations then decreases

  at the same rate as in the second case until

reaches the diastolic pressure.

  At this point, the decay rate of

  the amplitude of the oscillations goes to a second, more pro-

  gressive until we reach a wrist pressure for which oscillations disappear. The invention allows

  to determine the systolic pressure from the pressure of

  celet for which there is a variation in the speed of increase

  the amplitude of the oseillations, when the pressure of the

  bracelet goes through the value corresponding to the systolic pressure

  lic. The diastolic pressure is then determined by measuring

  the wrist pressure for an amplitude of oscillation corres-

  to that of the measured systolic pressure.

  More specifically, in a preferred embodiment of the invention, a series of "locks" are made when the wrist pressure decreases.Each reading consists of reading the peak oscillation amplitude and the corresponding base pressure of the wristband. select a number

  amplitude readings corresponding to brace-

  let exceed the expected systolic pressure. On the other hand,

  a number of corresponding amplitude readings are selected

  at bracelet pressures below the system pressure

  expected tolic. From each set of readings, one

  deduced, by well-known methods, two relations representing

  respectively the peak amplitude variations of each set of readings, depending on the pressure variations of the bracelet. These relationships, which may for example be linear equations, are treated in such a way as to determine the values of bracelet pressures and corresponding oscillation amplitudes which satisfy the two above relationships. At 6, - mathematical sense we pose that these two relations are equal

  in order to solve them according to the systolic pressure.

  In the graphic sense, the two functions are represented by curves (illustrated by lines connecting the peak values of each set), the extensions of these curves intersecting each other.

  for a wrist pressure equal to the systolic pressure.

  The diastolic pressure is then determined by detecting the amplitude of the wristband pressure that sleeps an oscillation amplitude equal to that of the calculated systolic pressure. We will notice that we can reverse these operations by

  starting with determining the diastolic pressure to de-

  then draw the systolic pressure.

  The invention will be described in detail by means of the accompanying drawings in which:

  FIG. 1 is a block diagram of a FIG.

  2 represents a typical set of readings obtained by means of the apparatus of FIG. 1; FIG. 3 is a cursive diagram of the operating mode of the circuit of the FIG. 1, to obtain the readings of FIG.

  FIG. 4 is a cursory diagram of the program

  used to calculate systolic and diastolic

  than. In Figure 1, an air strap 101 is placed around a patient's limb, preferably around the

  arm or thigh so as to obstruct in a controlled manner

  blood vessels of this limb to prepare the measure

  arterial blood pressure. The bracelet 101 is a disc

  well known positive including an air bladder connected to two

  flexible tubes 102 and 103. It is possible to inflate or deflate the ves-

  the strap 101 by means of a flexible tube 103 connected to a valve 104. The valve 104 is controlled, via the wire 105, by a control circuit 150 described hereinafter, and

  allows to inflate the bracelet 101 by compressed air from

  from a source of compressed air (not shown) connected by a tube 106. The valve 104 can also operate under

  the control of the circuit 150, to deflate in steps

  the wristband 101. The air bladder of wristband 101 is also

  equipped with a second flexible link 102 connected to a block

transducer 107.

  7.- This second connection makes it possible to measure the air pressure of the bracelet without disturbing the flow of air in the tube 103. The transducer block 107 responds to the air pressure

  of the bracelet, in relation to atmospheric pressure, to give

  an electrical signal of amplitude proportional to the pressure prevailing in the strap 101. The output of the transducer 107

  is provided with amplification connection conductors 108 and 109

  respective loudspeakers 111 and 112. The amplifier 112 is an amplifier

  DC indicator giving its output 114 a signal

  representing the average base pressure in the bracelet 101.

  The amplifier 111 is an AC amplifier (shown schematically by an amplifier 110 connected in series with a capacitor 110), giving at its output 113 a signal corresponding to the pressure oscillations resulting from the blood pulsations in the blood vessels of the patient's limb . We can choose the output 113 of the amplifier

  111 or the output 114 of the amplifier 112, by means of a multiple

  Tiplexeur 115 controlled by the circuit 150 via the driver 120, and apply this output, by the driver 125, to the analog-digital converter 130. This converter converts the analog signals of the amplifiers 111

  and 112 in digital signals used by the processing circuit.

  information to calculate mean arterial blood pressure

  and systolic and diastolic blood pressures.

  As a result, the control circuit 150 allows in summary to control the multiplexer 115 and the converter

  analogue-digital signal 130 to obtain a digital signal

  sensing of the base pressure of the air strap 101 when passing through the amplifier 112, or the amplitude of the pressure oscillations produced by the patient's blood flow in the

  bracelet 101 when passing through the amplifier 111.

  As will be described in more detail below, the control circuit 150 implements a memory 140 and a calculating circuit 160 for selectively performing a series of readings, each reading representing a base pressure.

  and the corresponding oscillation amplitude. When these differences

  the readings are complete, the control circuit 150

  memory 140 to selectively transfer readings

  to the computing circuit 160, via the

  141. The circuit 150 then cooperates with the calculation circuit 8.- to calculate the mean blood pressure and the pressures

  systolic and diastolic blood products produced at exit 161.

  In the embodiment described here, the

  analog-digital converter 130, the memory 140, the circuit

  cooked control 150 and the calculation circuit 160 (all included in the enclosure dashed 170) can be grouped in

  a microprocessor unrique. These functions can also be

  by classical circuits described hereinafter.

  FIG. 2 represents a typical set of readings obtained by means of the circuit of FIG.

  2 represents a graph in which the horizontal tax represents

  the values, increasing to the right, of the pressure of the bracelet and the vertical axis, the values, increasing towards the naut, of the amplitude of the oscillations. the series of "dots" in this graph represent the readings each corresponding to a oscillation amplitude and to a base pressure of the bracelet read respectively on the vertical axis and on the horizontal axis,

  Figures 2, 3 and 4 will be used to describe the cycle of

  In particular, FIG. 3 shows the cursive circuit diagram of FIG. 1 during circuit. taking into account eG es Tmeós: resulting from the pressure signals produced by the burn! In section 301, the circuit circuit (50) is operable to auto-populate 104, to sweep the pressure-bearing braze 22 at a time. In the present case, 1:.: - aclet 101 is gorged

torr.

  Dance letce 302, e _ciuit de cormande 150

  stores in the memory 140 the output signal of the converts

  analog-to-digital server 130 representing the basic pressure

  of the bracelet. In the step 303N N the command is 150 ms.

  gasine in the memory 140 -n wh..n. -amplitude of oscilla-

  produced, in the form: nméric.te, by u co.nvisseur 430.

  Typically the oscillations of: -isior of air are -oroduire,

  in the bracelet 101, at the patient's fréquenoe - so-so

  typically killing between 60 and 8t Ha? 1z. However, the sampling operation is performed at a much higher rate, so that the amplitude variation of the oscillations during the sampling period is minimized. In step

  304 the sampled amplitude of the output signal of the converts

9.-

  130 is stored in the memory 140.

  In step 305 the amplitude of the oscillations

  is sampled again. This sampling operation

  ge is done at predetermined intervals. In step 306 the two previously obtained samples are compared. If the

  sample is less than the first step 307 is

  ted. If the second sample is greater than the first,

  step 310 which is executed. Assuming that the second sample

  is in the case of step 307, the control circuit takes an additional sample of the oscillation amplitude and compares it (in step 313) with the sample previously stored in the memory 140. If the present sample is smaller than the stored sample, indicating that the oscillation amplitude continues to decrease, the most recent sample is stored in place of the previously stored sample ( step 311) and a new sample is taken (step 307). This operation continues

  until the sample is greater than the sample

  stored, indicating that we have reached the minimum

  amplitude of oscillations. In this case, the control circuit

  of 150 executes step 315 and indicates that the stored sample

is minimum.

  The control circuit 150 then determines whether a maximum value of the amplitude of oscillations has been obtained in the step 321. If this is not the case, the steps are executed.

  310, 312, 314 and 316 in which additional samples

  are sampled and compared to a sample previously

  stored until the sample is less than the stored sample, indicating that it has reached

  maximum. When this occurs, the maximum is assigned to the

  As a minimum has already been found in step 320, the control circuit 150 proceeds to step 325 in which the minimum value is subtracted from the maximum value to obtain the peak-to-peak amplitude of the oscillations. This value is stored in step 330 and control circuit 150 then compares the current oscillation amplitude, stored in step

  3309 to those previously stored, to determine whether the

  amplitude of oscillation increases or decreases.

  Assuming that the amplitude of oscillation increases, thus indicating that the mean arterial pressure has not yet been reached, step 345 is performed in which a predetermined amount of air pressure is deflated. the bracelet 101. This quantity can for example be of the order

  from 10 to 20 Torr. A new set of readings is then taken

  and the operation continues in this way until

  that in step 335 it is determined that the oscillation amplitude

  present value is lower than the previous amplitude. In this case, the control circuit 150 executes step 340 and determines whether at least five of the six previously stored amplitudes are greater than the current amplitude. This condition, if satisfied, indicates that the base pressure of the bracelet is

  past the point of diastolic pressure and that one can stop

  the measure. If this condition is not satisfied, the

  continue until the basic pressure passes through

the diastolic point.

  When we have reached the end of the indi-

  on the cursive diagram 3, a series of readings

  measured pairs of points were stored in the memory of

  140. If they are shown on the graph these points appear

  in the form shown in Figure 2. Before proceeding

  to a specific description of the calculation of blood pressure

  systolic and diastolic, we will discuss the specific characteristics of the readings shown in Figure 2. These readings are in the form of a curve "bell". As is well known in the art, the base pressure of the bracelet corresponding to the maximum of the curve (point B) is equivalent to the mean arterial blood pressure. The systolic and diastolic pressure points correspond to a

  amplitude decrease to about half of the ampli-

  maximum study. In these points, such as, for example, points A

  and C, the slope of the curve shows a sharp inflection (ex-

  managed in the figure to make the description clearer).

  According to the invention, the calculation of the point of in-

  bending 203 of the curve is done using additional data points near the systolic pressure

  expected, to obtain an accurate calculation of this system pressure.

  tolique. More precisely, we choose as point of reading

  starting point, a point for which the amplitude of oscillation

  about half of the peak amplitude. This corresponds

  in two sets of three reading points are recorded around point 203, and correspond to three readings for which the base pressure of the bracelet is greater than the pressure at point 203,

  and three readings for which the base pressure of the brace-

  let is less than the pressure in point 203. In the embodiments illustrated here, the groups 201 and 202 are respectively selected. By using the three points of the group 201, an approximation is made.

  curve (indicated in 205) by mathematical methods.

  classical subjects. In the same way, the same linear approximation (206) is carried out on the three points of the group 202. the pressure corresponding to the intersection of the two straight lines (point D), ie the strap pressure E of the figure

  2, is the calculated systolic pressure. To calculate the pressure

At the diastolic side of the curve, a diastolic ratio is chosen for which the amplitude of the oscillations of the

  line 210 is equivalent to that calculated for the system pressure

  tolique. The corresponding base pressure of the bracelet (point

  A) is the calculated diastolic pressure.

  As can be seen, these measures can

  can be done by hand using the graph obtained from

  taking measurements from the device, to plot figure 2, and constructing lines 205 and 206 on the graph. Figure 4 shows the operations performed by the circuit of the

  Figure 1 to calculate the mean pressure and system pressures

tolic and diastolic.

  After obtaining and storing the readings corresponding to the basic pressures of the bracelet in a range

  including systolic and diastolic pressures, as

  written above, the control circuit 150 selects two readings corresponding to the highest wristband base pressure (respective readings 215 and 220 of FIG. 2). The amplitude of the oscillations of the two readings is compared in the step 403. If the last amplitude read is greater than the amplitude

  immediately preceding, step 402 is repeated and an amplification

  additional is read and compared to the immediate amplitude

  previously. This process is repeated until the amplifier

  current study is less than that of the previous reading.

  This occurs in point B of Figure 2 corresponding to the

mean blood pressure.

  12.- To choose a starting point for calculating the systolic pressure, the value of the amplitude of the oscillations at the mean arterial pressure point is halved in step 404. In step 405 the corresponing wrist pressure is determined. This would correspond to point 20C and to the pressure on the fúigare 2. Loreau we have determined the starting point of the decontrol of the systolic pressure,

  the control circuit 150 lil alrrt in the memory 140 the v-

  their amplitude of osiliation and basic pressure of a certain number of lect-res, prcidemuent carried out in 'eét.a pe 203. In the structure of realization illustrated here, one chooses

  three readings corresponding to the points 202 of FIG.

  the values are read in the calculation circuit 160. Under the control of the circuit 150, the calibration circuit 160 provides a mathematical relation adapted to the various points read.

  in the memory 140, this relation being for example a

tion.

  the determination of such a linear equation

  can be done by means of a number of mathematical techniques

  well known topics. As an example, we can assume that

  one of the three reads ocThcide.w & 0 the mathematical averermnnes

  of the three lectutre, the zome of the er: ers is then reduced to miniiun and peramet obtnir: e drii whose slope is the average of the slopes of the two .... pasast by each lctres remaining, and a point s - .. t% r at the average of

  three readings. This program allows you to read from

  tures, an equation falling into the form D =; OP +: a in which O is ii; mplirtde ds --z atuons 0 the base pressure of the bracelet and M and B des.e ... ta: lees to the Denite of the right & t 'Làterse v ioa; n asulpposarnt. , as a matter of fact, the revisions are as follows:

  Coordinated 01% '-n r02X2 0:! ...... i ..

  e-î-deseru. Derret de lo Lt le- s -ev_:.: Z M and p nar e.ns cu-

following

i ci0 -

and B = 0- M 13.-

  where O and are the simple averages of the coordinates

  born of the points and are given by the following equations: = o, + 02 + 0

0 = 1 2 3

- c01 + 02 + C3 C =

  One can also use the technique of ap-

  classic "least squares" approximation. In the approximation

  Linear method performed by this last least squares method, the slope of the equation obtained is as follows:

  X (C 1 ') (O - + (C 2 -C) (O 2 -) + (C 3 -) (O -)

(C1 _0) 2 + (C2 _) 2 + (C3 _) 2

  expression in which ,, C and B are given by the preceding equations. By using one or other of these equations and the coordinates of the readings obtained for the points of the group 203, we obtain a linear approximation of the form s op = C'I M + Sp The index P indicates that the coefficients p and Bp correspond to readings preceding the systolic point

expected 203.

  After having determined the value of the coefficients M and B of the first set of points, during the step 408, the control circuit 150 then reads in the memory 140 the values of amplitude of oscillation and corresponding basic pressure, for the three readings after point 203 (corresponding to set 201 of FIG. 2). By using in step 410 the readings thus obtained, the

  control circuit 150 gives a second equation of the best

  their adaptation to readings. As indicated above, we obtain

holds an equation of the form s

0 = C8 M8 + B8

  where the index S indicates that the coefficients are de-

  completed for the set of readings after point 203.

  According to the invention, the systolic pressure cal-

  abutment appears in point D of Figure 2 where the two

  straight determined by the equations of best fit.

  This point is obviously obtained when the amplitudes of oscilla-

  14.- tions 0p AND S are equal. In addition, the two bracelet base pressures are equivalent at this point oh Cp = = Csystolic To determine this point, we equalize the two equations calculated to solve them in common bracelet base pressure. The calculated systolic blood pressure is given by the following equation: C _ BS -Bp Systolic M - S The calculated systolic pressure of Figure 2

  corresponds to point 3. In step 415 we store the pressure

  calculated systolic pressure. The determination of the system pressure

  by the method according to the invention, leads to a determination

  accurate nation of the systolic value. Even if one of the

  used to make the approximation is wrong by

  patient's movements, or any other external noise.

  However, we can still obtain a reasonable approximation

  sonable. The mode of operation contrasts with the processes

  according to the prior art using for example a differentiation.

  these methods being very sensitive to artefacts in the systolic pressure zone. In the presence of a very important noise,

  we can get a better elimination of noise and arte-

  by increasing the number of readings used to

kill the approximation.

  According to another characteristic of the invention

  diastolic pressure is determined in step 414,

  starting by determining the amplitude of the oscillations cor-

  corresponding to the calculated systolic pressure. This result can

  be easily obtained by substituting the system pressure value

  calculated in one or other of the derived equations giving the corresponding oscillation amplitude 0systolic in the form: 0systolic = Csystolic MS + BS In step 414 the control circuit 150 then searches the memory 140 for the readings of the diastolic portion of the curve representing the oscillation amplitude as a function of the wrist pressure, to find the wrist pressure corresponding to the oscillation amplitude calculated immediately above (point A of Figure 2). in the stage

  416 the calculated diastolic pressure is stored.

15.-

  Systolic and diastolic pressures

  may be displayed in any suitable manner.

  nable by means of digital or analogue

  experts in the field.

  In an alternative embodiment, it is possible

  example, start by calculating diastolic pressure by

  killing two linear approximations for the peak sets near the expected diastolic pressure, and setting the approximations exactly to equal values,

  as described above to calculate the system pressure

  tolique. This systolic pressure can then be obtained by determining the wrist pressure for which the amplitude

Oscillations are equivalent.

  We can still use other mathematical relations than linear equations, these relations being

  drawn from reading sets by approximation techniques.

well known.

16.-

Claims (23)

REVEND I C ATIO NS   1. A method for measuring systolic blood pressure without penetration into the body, characterized in that it comprises the various steps of obstructing the flow of blood in a limb by applying to it a variable and measurable external pressure (301 ); to vary   this pressure by several successive stages between an ampli-   a study for which blood flow is practically obstructed and an amplitude for which blood flow is practically free; to monitor (401) in each of the steps, the amplitude of the pressure oscillations produced by the pulses of the blood flow in the member in question; to deduce (407) a first relation between the amplitude of oscillation and the corresponding pressure, this relation being obtained from a certain number of amplitudes of oscillations and values   corresponding pressure levels for pressures   above the expected systolic pressure; to deduce a second relation (410) between the amplitude of oscillation and the pressure   corresponding, from a certain number of amplitudes of os-   cations and corresponding pressure values for pressures below the expected systolic pressure;   and determining (412) a satisfactory common pressure value   the two relations corresponding to a calculated value of symtolic blood pressure.   2. A process according to claim 1, characterized   in that it also includes the different steps   being able to determine (403) the maximum amplitude of oscilla-   and set (404) the value of the expected systolic   due to a level for which the amplitude of oscillation corres-   dante is at half the maximum oscillation amplitude.   3. Process according to any one of the claims   cations 1 and 2, characterized in that the first relationship between -   oscillation amplitudes and pressure values cor- correspondents is linear.   4. Process according to any one of the   1 to 3, characterized in that the second relationship between   oscillation amplitudes and pressure val- correspondents is linear.   5. Process according to any one of the   1 to 4, characterized in that it further comprises the 17.-   different stages of determining the amplitude of the oscillation   corresponding to the calculated value of the   (415) and to set an additional value of the pressure for which the corresponding oscillation amplitude is equal to the amplitude determined in the first step, thereby permitting   thus to calculate the diastolic pressure (416).   6. Apparatus for carrying out the process   according to any one of claims 1 to 5, characterized in   what it includes means (101) for applying to a   limb of the human body a variable external pressure and   surable to obstruct blood flow in this limb; means (104) for varying this pressure by a plurality of successive steps, between an amplitude for which the blood flow is substantially obstructed and an amplitude for which the blood flow is substantially free; means (107) responsive to the pressure value of each of the steps for providing an output signal representing the amplitude of the oscillations produced at that pressure by the pulses of the blood flow in the limb; means (130, 140, 150) responsive to   at a number of pressure values lying   above the expected systolic pressure and responding to the signal   output to derive a first relationship between the amplifiers   oscillation studies and the corresponding pressure values;   means (130, 140, 150) responsive to a number of   their pressure is below the systolic pressure.   than expected and responding to the output signal to derive a second relationship between oscillation amplitudes and   corresponding pressure values; and means (160) responsive   to the first and second relationships above to de-   terminate a common pressure value satisfying both   corresponding to the calculated value of the blood pressure not systolic.   7. Apparatus according to claim 6, characterized   in that it includes, in addition, means corresponding to the   output signal to determine the maximum value of the amplitudes   oscillations, and means (160) corresponding to the amplitude of os-   maxrimum cillation to deduce a pressure value corresponding to   laying down at an amplitude of oscillation equal to half of the maximum oscillation amplitude.   8. Apparatus according to any one of the   18.- dications 6 and 7, characterized in that the first relationship between the amplitudes of oscillations and the pressure values corresponding, is linear.   9. Apparatus according to any one of the   6 to 8, characterized in that the second relationship between   oscillation amplitudes and pressure values corresponding to is linear.   10. Apparatus according to any one of the   6 to 9, characterized in that it further comprises   means (160) corresponding to the calculated value of the   systolic guine and at the output signal, to determine the   oscillation study corresponding to the calculated value of the systolic pressure; and means responsive to the values of the pressure and the output signal for determining a value of   additional pressure whose amplitude of oscillation corres-   is equal to the output signal of these latter means,   which allows to calculate the diastolic pressure.   11.- Method for determining a blood pressure value corresponding to one or the other of the pressures   systolic or diastolic, using an apparatus for   blood pressure without penetration into the body, such   that of claims 6 to 10, comprising means (101)   allowing the application of external pressure to a blood vessel   change over time over a range of values   systolic and diastolic pressures and means (107) responsive to pressure oscillations obtained in a partially occluded blood vessel for detecting the peak-to-peak amplitude of the oscillations for predetermined values of the external pressure, characterized in that it comprises   the different stages of determining an expected value   due to blood pressure; to deduce (407) a first relation   oscillation amplitudes and the corresponding values.   of external pressure, from a certain number of   range of oscillations and pressure values corresponding to   eggs at an outside pressure level higher than the expected value; to deduce (410) a second relation between   oscillation amplitudes and pressure values corresponding to   from a number of oscillation amplitudes-   and corresponding pressure values at an outside pressure level lower than the expected value; 1 9.-   and to determine (412) a common value of satisfactory pressure.   the two relations corresponding to a calculated value of systolic blood pressure.   12. The process according to claim 11, characterized   in that it also includes the different steps   being able to determine (403) the maximum amplitude of oscilla-   and set (404) the systolic pressure at a value for which the corresponding oscillation amplitude is half of the maximum amplitude.   13. Process according to any one of the   11 and 12, characterized in that the first relationship between oscillation amplitudes and pressure values corresponding, is linear.   14.- Process according to any one of the   11 to 13, characterized in that the second relationship   the amplitudes of oscillations and the pressure values corresponding, is linear.   15.- Process according to any one of the   11 to 14, characterized in that it comprises the   the steps of determining the oscillation amplitude corresponding to the computed systolic pressure value (415);   and to determine an additional pressure value whose   corresponding amplitude of oscillation is equal to the amplitude   determined in the first step, thus allowing calculation of diastolic pressure (416).   16.- Process according to any one of the   11 to 15, characterized in that the first relationship is calculated on the basis of at least three sets of values   of pressure and amplitudes of corresponding oscillations.   17.- Process according to any one of the   11 to 16, characterized in that the second relationship is calculated on the basis of at least three sets of values   of pressure and amplitudes of corresponding oscillations.   18. A process according to any one of the   11 to 17, characterized in that the first and second relations are calculated on the basis of at least three sets   corresponding pressure values and amplitudes of oscillations   dantes following each other immediately in time.   19.- Method for the quantitative determination of one of the systolic or diastolic blood pressures, setting 20.-   a blood pressure measuring device without penetration   in the body as claimed in claims 6 to 10,   comprising means (101) for applying a pressure   outdoor variable to an artery and responding, oscillating mode   metric, to the pulsations occurring in a partially obstructed artery, characterized in that it comprises the   different stages of applying to the artery a pres-   time-varying outer extent over a range including the expected systolic and diastolic pressures; determining the peak amplitude of each pulse detected by the apparatus when the external pressure varies between an amplitude greater than the expected systolic pressure and smaller than the expected diastolic pressure; determining the respective fonetions on either side of one of the expected pressures in a range of external pressures comprising this expected pressure, these functions representing the speeds of variation   relative to the external pressure, the amplitudes   peaks on either side of the pressure   stretched; and determining the external pressure for which the two above pressures are equal, the expected pressure being   then equal to the external pressure.   20. The process according to claim 19, characterized   in that it also includes the different steps   to be determined in an area of the range of ex-   including the ume of diastolic or systolic   as expected, a first function representing the rate of variation, with respect to the external pressure, of the peak amplitudes of at least two pulsation waves occurring for external pressures close to or greater than the pressure in question; determining a second function representing the speed of variation, with respect to the external pressure, of   peak amplitudes of at least two pulse waves are presented   in the vicinity but below the pressure in question; and to quantitatively establish that this pressure is equal to the   external pressure for which the first and second tions are equal.   21.- Process according to any one of the   19 and 20, characterized in that the determination of the peak amplitude of the pulses takes place in a zone of external presumptions including the expected systolic pressure, and in that the method further comprises the various steps. determining a first function representing the rate of variation, with respect to the external pressure, of the peak amplitudes of at least two waves occurring for respective external pressures close to but less than   the expected systolic pressure; to determine a second function   representing the speed of variation, relative to the external pressure, of the peak amplitudes of at least two waves   occurring for respective external pressures   but superior to the expected systolic pressure; and to quantitatively establish that the systolic pressure is equal to the external pressure for which the first and second functions are equal.   22. A process according to any one of the claims   catlions 19 to 21, characterized in that it further comprises   the different stages of determining a first fono-   representing the rate of change, relative to the external pressure, of two or more successive and adjacent waves occurring at respective outside pressure levels greater than the expected pressure; to determine a   second function representing the speed of variation,   external pressure porting of peak amplitudes of two or more successive and adjacent waves occurring at respective external pressure levels below the expected pressure; and to establish quantitatively that the blood pressure is equal to the external pressure for which the   first and second functions are equal.   23.- Process according to any one of the   dioations 19 to 22, characterized in that it comprises the   your steps of applying varying external pressure   ble over a range of expected systolic blood pressure; to determine the peak amplitude of each pulse detected by the device when the external pressure   varies from an amplitude greater than the expected systolic   due to an amplitude lower than this systolic pressure   stretched; to determine a first function representing the   the variation of the peak amplitudes of three successive and adjacent waves with respect to the external pressure occurring at respective external pressure levels higher than the expected systolic pressure to determine a 22.   second function representing the speed of variation,   port to external pressure, peak amplitudes of three successive and adjacent waves presenting for levels   respective external pressure pressures below the system pressure   expected tolic and to establish quantitatively that the pressure   systolic blood is equal to the external pressure for   which first and second functions are equal.