GB1588954A

GB1588954A - Blood pressure measuring device

Info

Publication number: GB1588954A
Application number: GB21369/78A
Authority: GB
Original assignee: SACKS A
Current assignee: SACKS A
Priority date: 1977-10-11
Filing date: 1978-05-23
Publication date: 1981-05-07
Also published as: ES474092A2; BE867564R; IT7868486A0; JPS5458987A; FR2405694A2; DE2842337A1

Description

(54) BLOOD PRESSURE MEASURING DEVICE (71) I, ALVIN HOWARD SACKS, a citizen of the United States of America, of 12682 Roble Veneno Lane, Los Altos Hills, California, United States of America, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a device for determining blood pressure without the use of a stethoscope or transducer. More particularly, the invention relates to a cuff which may be placed around a finger, thumb, wrist or any other extremity of the body containing an artery and can be inflated to perform a function analogous to that of the standard cuff used in all sphygmomanometers. The cuff may be inflated by means of a cylinder having a plunger resembling a large syringe. Since the pressure in the cuff is related to the volume of the air expelled from the syringe, a pressure reading is obtainable.

It has been found that the average person can sense the onset and cessation of conditions which are ordinarily detected by auscultation, conventionally by the use of a stethoscope, to determine both systolic and diastolic readings of pressure.

By using a device of the aforesaid type and by eliminating the transducer or even a stethoscope, a simplified means whereby a person can determine his own blood pressure is provided.

In our Specifiction 22738/76 (Serial No.

1546197) wedesc and claim an invention based on a new concept which is that the subject can sense the phenomenon of his blood flow which is responsible for producing the Korotkoff sounds. Hence the need for a stethoscope or transducer is eliminated and the person merely measures the points in a range of pressures at which the localized sensations in the artery begin and subside as applied pressure is increased or decreased.

It is important to point out that the Korotkoff sounds are localized arterial sensations which must not be confused with other "throbbing" or "pulsing" sensations noted during pressurization of the subject's extremity. The localized sensations in the artery are associated with the Korotkoff sounds. The generalized throbbing sensations felt at pressures above systolic (usually above the cuff) are related to pumped blood being able to enter the vessels covered by the cuff.

In the method of the invention in Specification 22738/76 (Serial No. 1546197) and in the present invention, the sensations at systolic cuff pressure are within the cuff and, in the arm, are felt very locally in the brachial artery.

Additionally, a general rhythmic swelling sensation of the whole member or extremity may be felt during pressurization (particularly in the finger at cuff pressures below diastolic), which is again unrelated to the Korotkoff sensations and is not confined to the artery. The early researchers of digital blood pressure failed to recognize the close relationship between the specific Korotkoff sensations of the subject and blood pressures. They were able to take only erratic and unreliable diastolic digital pressure readings by cuff pressurization of digits. They failed to distinguish between the true Korotkoff sensations and the non-Korotkoff associated throbbing sensations just discussed, which failure leads to erroneous pressure readings.

Based on their results, they even stated that subjective "sensations" where not consistently reliable to determine blood pressures.

In the method which is based soley upon the Korotkoff phenomenon, a subject can easily detect, in the range of cuff pressures between systolic and diastolic, the distinctly localized arterial sensations felt inside the cuff, which are associated with this phenomenon, and thereby obtain consistent and reliable readings of both sytolic and diastolic blood pressures.

Another simplification accomplished by the invention in Specification 22738/76 (Serial No.

1546197) and in the present invention is the replacement of manometric pressure measurement with measurement of the volume change of gaseous fluid required to produce that pressure. This is accomplished by making use of the perfect gas law and observing that the change involved is an isothermal one (i.e., the temperature remains constant). The gas law states that the pressure varies inversely with the volume. Therefore, the measured volume change can be calibrated in terms of pressure change and thus used to determine the pressure.

According to the invention described in Specification No. 22738/76, (Serial No.

1546197), referred to herein as the parent invention, there is provided blood pressure measuring apparatus of the kind having a sleeve inflatable against a part of the human body wherein the apparatus has a casing for restraining outward expansion of the sleeve in use and a syringe in or adapted for gastight communication with the exterior of the sleeve within the casing, for inflating the sleeve, said syringe being provided with graduations for determing the volume of gas passed into or out of the sleeve. The parent invention further provides a method of measuring blood pressure which comprises applying a sleeve to a part of the human body, said sleeve being inflatable by means of a syringe against that part but restrained from outward expansion, and measuring the difference in the volume of gas in the syringe required to bring the sleeve into gripping contact with the part of the body and the volume of gas required to produce in that part of the body (a) the onset of a tingling or throbbing sensation and (b) the cessation of said tingling or throbbing sensation.

According to the present invention the parent invention is modified in that (a) the inflatable sleeve is replaced by an inflatable part-annular diaphragm contained within the casing; and/or (b) the casing is annular and has adjusting means for bring the part of the body into firm engagement with the diaphragm within the casing said diaphragm being part annular; or the parent invention is improved in that (c) the casing and sleeve or diaphragm are integrated into a rigid plenum chamber to form a unit, said plenum chamber communicating directly with the interior of said sleeve or diaphragm, and the syringe is integrated into said unit, the syringe communicating with the interior of the plenum chamber and the interior of the sleeve or diaphragm; and/or (d) the device further comprises pressure responsive leak detecting means.

The present invention extends to a method of measuring blood pressure as claimed in Specification No. 1546197 modified in that it comprises applying apparatus of the present invention.

The accompanying drawings, in which similar characters of reference represent corresponding parts in each of the several views, illustrate various embodiments of the devices of the parent invention and present invention.

In the drawings Figures 1 to 7 represent the parent invention while Figures 3A and 8 to 15 illustrate the present invention.

Figure 1 is an elevational view, partly broken away in section and to reduce size, showing a device in accordance with the parent invention as applied to the finger of the user.

Figure 2 is a sectional view through a portion of the structure of Figure 1.

Figure 3 is an end elevation of the structure of Figure 2.

Figure 3A is a view similar to Figure 3 and partly broken away in section showing the diaphragm separate from the cuff, illustrating an embodiment of the present invention.

Figure 4 is a fragmentary elevational view showing the pressure scale in one position and the plunger retracted, referring to the present invention.

Figure 5 is a view similar to Figure 4 showing the plunger partly retracted.

Figure 6 is a view similar to Figure 5 showing the scale adjusted for "zero".

Figure 7 is a fragmentary elevational view of the plenum chamber partly broken away in section.

Figure 8 is a view similar to Figure 3A of a further modification in the present invention.

Figure 9 is a section taken substantially along the line 9-9 of Figure 8.

Figure 10 is a view similar to Figure 3A of still another modification in the present invention.

Figure 11 is an end elevational view of a still further modification by the present invention of the structure of Figure 1 partly broken away in section.

Figure 12 is an end elevational view of still another modification by the present invention to Figure 1 partly broken away in section.

Figure 13 is a view similar to Figure 1 boken away in section of a still further modification by the present invention.

Figure 14 is a view similar to Figure 3A of a still further modification by the present invention.

Figure 15 is an end elevational view partly broken away in section to reveal internal construction showing a container in which portions of a device, in accordance with the present invention, are installed.

Figure 16 is a view similar to Figure 15 showing still another modification in which the entire device, in accordance with the present invention, is installed in a cabinet incorporating the container unit pf Figure 15.

The perfect gas law is aAlollows: pV = RT Logp+LogV=LogR+LogT dp + dv ~ dT pWT if dT = 0, then dp = ~ dv p V Hence a 1% reduction in the overall gas volume of the system by compressing the plunger would produce a cuff pressure of 1% of one atmosphere or 7.6 mm. Hg. at sea level. If the chamber is inelastic, then the overall change in volume is just the volume displaced by the plunger. Otherwise, the compliance of the various components affects V and may be accounted for by calibration of the system.

The foregoing principle is applied to the present invention for monitoring blood pressure. The resulting relationship between pressure and volume is not quite linear but is determined for the particular device either from the above equations or by a once for all calibration against a manometer or by a combination of both.

In Figures 1 and 2, a cuff 11 is provided dimensioned to fit over the finger 28, wrist, arm or other extremity of the body containing an artery. Cuff 11 has an inelastic casing 12, and in the interior thereof is a tubular diaphragm 13, the ends 14 of which are brought around the outside of casing 12 and secured thereto by cement, bands (not shown) or other means. The relaxed diaphragm 13 is sufficiently large to conveniently fit over the finger 28.

In Figure 1, which illustrates the use of a tubular member, such as cylinder 18, and plunger device (conventionally used in injections, but preferably of such volume and diameter to afford accurate volume determinations in accordance with the above equations) as the control means cooperable with the casing and diaphragm, an opening 16 is formed in casing 12 outside diaphragm 13 and connects by duct means 26 to an inelastic tube 17, which is frxed to the closed end of cylinder 18. The plunger 19 fits in fluid tight relation to the internal wall of cylinder 18.

In Figure 1, in order to make it possible to insert plunger 19 into the cylinder 18 without inflating the diaphragm, a small hole or vent 21 is formed in the wall of cylinder 18. At the end of the cylinder 10 adjacent to tube 17 is a "zero-indicating" device which consists of a small aperture closed by a valve-like member 22 formed of a flexible piece of material so that when pressure is applied inside cylinder 18 the member 22 bulges outwardly (compare Figure 5 with Figure 4) indicating that there is a slight pressure on the inside of diaphragm 13. This pressure may be determined by measuring once with a manometer or other conventional means.

Movable on the outside of cylinder 18 is a scale 23 formed with indicia 24 indicating pressure.

In Figure 7, a rigid plenum chamber 29 may be interposed between tube 17a of the cylinder 18 and tube 26a which communicates with the cuff. By including the volurne of the plenum chamber in the total volume of the system, greater sensitivity is achieved in accordance with the equations.

In the use of the device as shown, with the diaphragm relaxed, the cuff 11 is slipped over the finger as shown in Figure 1. If the plunger 19 has not previously been inserted in the cylinder 18, this is then done, air escaping through vent 21 until the end of the plunger closes off the vent 21.

As has previously been expressed, the size of finger 28 or other extremity varies with the user. It is important to the determination of "zero" pressure to be able to observe when inflated diaphragm 13 is in firm engagement with the skin of the finger but pressure has not been applied which affects the flow of the blood through the artery. For this purpose, the member 22 is observed. When the member first distends from the relaxed position of Figure 4 to the distended position of Figure 5, then the cuff is in firm engagement with finger 28. This point is noted and the sliding scale is adjusted in position so that the "zero" marking is opposite the then position of the inner end of the plunger 19. In this connection, it is to be understood that since the invention relies on the perfect gas law, any air leak from the chamber would alter the pressure-volume relationship and therefore result in erroneous pressure readings. Accordingly, a pressureresponsive means may be provided according to the present invention which will automatically alert the user to any such leak during the use of the device. This means can consist of a second valve-like member, in addition to that used for zeroing, which is activated at a higher predetermined pressure. In Figure 15, which shows a plenum chamber 67 integrated with a casing 1 2d and a diaphragm 13d, one valvelike member 69 is for "zero-indicating", while the second valve-like member 72 is for leak detection.

As an alternative means according to the present invention for adjusting the device to a base volume at which the diaphragm is in firm engagement with the finger or other extremity, it is possible to use the adjusting means illustrated in Figures 8, 10 and 14.

In the embodiment of the parent invention shown in Figures 1 and 4-6, after adjusting the scale to the "zero" position, the plunger 19 is then moved slowly farther into the cylinder 18 causing the diaphragm 13 to be pressurized and gradually cut off circulation through the digital artery leading to the top of finger 28. At some point during this increasing pressurizing of the diaphragm, the subject can feel the onset of a slight localized throbbing sensation in the artery inside the cuff 11 which corresponds to the diastolic blood pressure. The location of the end of the plunger 19 relative to the scale marking 24 is then noted. The plunger 19 is further depressed until the subject notes the point in the pressure range at which the localized arterial throbbing stops, which indicates the systolic pressure has been reached and again the marking 24 on the scale 23 with relation to the end of the plunger 19 is noted and this indicates the systolic blood pressure. Preliminary to use of the device, the markings 24 on scale 23 have been calibrated with a standard manometer or calculated with the equations so that direct readings of blood pressure on the indicia 24 are obtainable.

Turning now to the modification by the present invention of Figure 3A, the diaphragm 1 3a is a hollow semicircle i.e. part annular in cross section rather than being a hollow circle in cross section as in Figure 3 and is cemented, or otherwise attached, to rigid casing 12. The opening of the rigid tube 26 into the diaphragm 13a is designated by reference numeral 31 in this modification and a corresponding opening 32 for tube 31 is made in cuff 12. When the plunger (not shown) is depressed in its cylinder, fluid transmitted through the tube 26 creates pressure inside the diaphragm 1 3a and the finger or other member which has been thrust into the cuff 11 is forced against the rigid wall 12 opposite the diaphragm 13a. In other respects, the structure of Figure 3A is similar to that of Figures 2 and 3 and the same reference numerals are used to designate corresponding parts.

In the modification of Figures 8 and 9, the cuff 1 la comprises a band 36 similar to that used in a hose clamp. In other words, there is an overlap 37 of the band 36 and the overlap 37 is formed with slots 37a. An adjustment screw 30 engages the slots 37a and is held in place by a screw holder 39. When the screw 38 is turned, it causes the overlap 37 to move relative to the holder 39 so as either to tighten or loosen the cuff 1 la, depending upon the direction in which the screw 38 is turned, all as well understood in the hose clamp art.

Diaphragm 1 3a in this and other modifications may consist of a sheet of relatively flexible materials having turned-in edges 33 cemented or otherwise adhered to the inside of band 36. Thus, there is an air-tight area communicating with tube 26a.

In the modification of Figures 8 and 9, an aperture 40 may be formed in the band 36 and a patch 22a of flexible material is cemented or otherwise adhered to band 36 covering aperture 40 so that pressure inside the cuff causes patch 22a to distend out through the aperture 40 in the same manner as the valve-like member 22 of Figure 1 distends out through a hole in the cylinder 18. In other respects, the modification of Figures 8 and 9 resembles that of the preceding modifications and the same reference numerals followed by the subscript a are used to designate corresponding parts.

Figure 10 is similar in structure to Figures 8 and 9 but is simplified. There are two halfcasings 41,42 joined together at a hinge 42a.

Opposite hinge 42a each of the casing halves 41, 42 is formed with an outward extending ear 43, one of which is threaded. A screw 38 through the opposite ear is threaded into the aperture and is used to bring the casing halves 41, 42 toward or away from each other to cause pressure on the finger. Diaphragm 13b has its edges attached to casing half 42. In other respects, the modification of Figure 10 resembles that of Figures 8 and 9 and the same reference numerals followed by the subscript b are used to designate corresponding parts.

Directing attention now to the modification of Figure 14, the casing 12c is solid as in Figure 3A and diaphragm 13c is similar to that of Figure 8. On the side of the casing 1 2c opposite the diaphragm 13c a boss 46 or other means of providing internal threads is located and, threaded into the boss 46, is an adjustment screw 47. Preferably, a piece of soft material 48 is fixed to the inner end of the screw 47.

The thumb or other member of the user is inserted in the cuff 12c and by turning the screw 47, the end 48 bears there-against and causes it to exert pressure on the diaphragm 13c. When the valve member 22c (similar to that of Figure 8) expands through the aperture 40c, that indicates that the zero point has been reached by turning of the screw 47. A plunger and cylinder similar to that of Figure 1 is then used to pressurize the diaphragm 13c. In other respects, the modification of Figure 14 resembles that of the preceding modifications and the same reference numerals followed by the subscript c are used to designate corresponding parts.

Note, that in all of these embodiments, the zero-indicating popout member 22, 22a, 22b, 22c may be placed anywhere in the system, be it on the cylinder, as in Figure 1, or on the cuff, as in Figures 8, 10 and 14.

In Figure 11, the cuff 11 in principle resembles that of Figure 3. The lower end of the cylinder 1 8f opens into an enlarged diameter cylinder 51 which functions as a plenum chamber and is connected through opening 52 to the interior of the diaphragm 13f. An opening 53 is formed in the plenum chamber 51 and a valve-like member 22f may project through the opening 53 when the pressure in the diaphragm 13f causes the latter to fit firmly against the exterior of the finger or other member inserted in the cuff 1 lf.

Figure 12 differs somewhat from the preceding modifications in that the plunger 19 of Figure 1 is omitted. A free floating piston 56 slides up and down in the transparent cylinder 1 8g and its position is controlled by a squeeze bulb 57 attached to the upper end of cylinder 18g. The bulb 57 is squeezed until the valvelike member 22g expands outwardly, indicating that the diaphragm 1 3g is in contact with the skin of the user. The scale 23g is then zeroed on the position of the free floating piston. Further compression of the bulb 57 causes the piston 56 to move downwardly and the systolic and diastolic pressures are noted as in the preceding modifications.

In Figure 13, the hollow tapered cone 61 replaces the cylinder of the preceding modifications. Plunger 62 has a ring 63 on its lower edge which engages the inside wall of the cone 61. An annular diaphragm 64 is either fixed on its inner edge to the plunger 62 or slides in airtight contact therewith and on its outer edge is fixed to the inside wall of the cone 61. In other respects, the modifications of Figures 11, 12 and 13 resemble those of the proceding modifications, and the same reference numerals followed by the subscripts f, g, or h, respectively, are used to designate corresponding parts.

Turning now to Figure 15, a container, or casing 66 is provided having a separate plenum chamber 67 formed therein, here shown to be in the upper left hand corner. A cylinder and plunger (not shown) but similar to that of Figure 1 are connected through the inelastic tubing 17d to the chamber 67. Another tube 26d leads from the chamber 67 of the cuff 1 ld which may be similar to the cuffs of the other modifications. Formed in the casing 66, so as to be visible from the exterior, is a first opening 68 in which is a valve-like member 69 and a second opening 71 in which is a second valvelike member 72. In the use of the modification of Figure 15, the finger or other extremity of the user is inserted in the opening in the diaphragm 1 3d and the piston (not shown) depressed causing pressurization of the plenum chamber 67. When the valve member 69 pops out of the opening 68, the diaphragm 13d is in form contact with the member of the user and the scale on the cylinder (not shown) is zeroed. The second valve member 72 is of a stiffer material than that of member 69 or in some other way is treated so that it does not pop out at the pressure which activates the valve member 69. This, the member 72 is a leak detector. If it does not pop out when a certain pre-selected pressure indicated on the scale of the cylinder is achieved, then the user knows that there is a leak in the system.

A one time calibration against a mercury manometer or other pressure gauge is used to determine the pressure at which the member 72 distends. In other respects, the modification of Figure 15 resembles that of the preceding modifications and the same reference numerals followed by the subscript d are used to indicate corresponding parts.

Figure 16 shows another modification of the casing of Figure 15. In this modification, the cylinder 18e is enclosed inside the casing 76 and the plunger 19e is depressed vertically along one side of the casing 76. Scale 23e is formed on the plunger l9e. A movable hairline 77 having a flange sliding in vertical slot 78 in casing 76 is set opposite the zero of scale 24e when valve 69e pops out and then is used to read the systolic and diastolic pressures on sclae 24e. In this modification, the tube 1 7e leads to the plenum chamber 67e from cylinder 18e. Casing 66e may be fixed in or detachable from larger casing 76. In the former case, the casing would be positioned so that the members 69e and 72e can be seen from outside the casing 76 through suitable holes therein. In other respects, the modification of Figure 16 resembles that of the preceding modifications and the same reference numerals followed by the subscript e are used to designate corresponding parts.

It will be understood that a reverse procedure may be followed after "zeroing", namely the diaphragm is fully pressurized over a range of pressure by depressing plunger 19, the plunger is then slowly withdrawn until the point at which localized arterial throbbing first commences and a reading made of systolic pressure, then the plunger is further withdrawn until the point at which the localized throbbing sensation ends and a reading made of diastolic pressure.

The term "determination of zero" as used herein means determination of the position of the plunger corresponding to some known pressure, namely, that small pressure required to fully inflate or move to a precise position th "zero indicating" device. The magnitude of this pressure is determined by a one-time calibrated against a manometer or other means for the particular device or design.

WHAT I CLAIM IS: 1. Blood pressure measuring apparatus as claimed in any of Claims 1 and 4 to 11 of Specification No. 22738/76 (Serial No. 1546 197), modified in that the inflatable sleeve is replaced by an inflatable part-annular diaphragm contained within the casing.

2. Apparatus according to Claim 1, substantially as described and shown in the accompanying Figures 3A, 8, 9, 10 and 14.

3. Blood pressure measuring apparatus as claimed in any of Claims 1 and 4 to 11 of Specification No. 22738/76 (Serial No. 1546 197) or Claim 1 herein, modified in that the casing is annular and has adjusting means for bringing the part of the body into firm engagement with the diaphragm within the casing, said diaphragm being partMannular.

4. Apparatus according to Claim 3, substantially as described and shown in the accompanying Figures 8, 9, 10 and 14.

5. Blood pressure measuring apparatus as claimed in any of Claims 1 to 8 and 10 to 12 of Specification No. 22738/76 (Serial No.

1546197) or Claim 1 herein, in which the casing and sleeve or diaphragm are integrated into a rigid plenum chamber to form a unit, said plenum chamber communicating directly with the interior of said sleeve or diaphragm, and the syringe is integrated into said unit, the syringe communicating with the interior of the plenum chamber and the interior of the sleeve or diaphragm.

6. Apparatus according to Claim 5, substantially as described and shown in the accompanying Figure 11.

7. Blood pressure measuring apparatus as claimed in any of the Claims of Specification No. 22738/76 (Serial No. 1546197) or in any preceding claim herein, further comprising

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. its inner edge to the plunger 62 or slides in airtight contact therewith and on its outer edge is fixed to the inside wall of the cone 61. In other respects, the modifications of Figures 11, 12 and 13 resemble those of the proceding modifications, and the same reference numerals followed by the subscripts f, g, or h, respectively, are used to designate corresponding parts. Turning now to Figure 15, a container, or casing 66 is provided having a separate plenum chamber 67 formed therein, here shown to be in the upper left hand corner. A cylinder and plunger (not shown) but similar to that of Figure 1 are connected through the inelastic tubing 17d to the chamber 67. Another tube 26d leads from the chamber 67 of the cuff 1 ld which may be similar to the cuffs of the other modifications. Formed in the casing 66, so as to be visible from the exterior, is a first opening 68 in which is a valve-like member 69 and a second opening 71 in which is a second valvelike member 72. In the use of the modification of Figure 15, the finger or other extremity of the user is inserted in the opening in the diaphragm 1 3d and the piston (not shown) depressed causing pressurization of the plenum chamber 67. When the valve member 69 pops out of the opening 68, the diaphragm 13d is in form contact with the member of the user and the scale on the cylinder (not shown) is zeroed. The second valve member 72 is of a stiffer material than that of member 69 or in some other way is treated so that it does not pop out at the pressure which activates the valve member 69. This, the member 72 is a leak detector. If it does not pop out when a certain pre-selected pressure indicated on the scale of the cylinder is achieved, then the user knows that there is a leak in the system. A one time calibration against a mercury manometer or other pressure gauge is used to determine the pressure at which the member 72 distends. In other respects, the modification of Figure 15 resembles that of the preceding modifications and the same reference numerals followed by the subscript d are used to indicate corresponding parts. Figure 16 shows another modification of the casing of Figure 15. In this modification, the cylinder 18e is enclosed inside the casing 76 and the plunger 19e is depressed vertically along one side of the casing 76. Scale 23e is formed on the plunger l9e. A movable hairline 77 having a flange sliding in vertical slot 78 in casing 76 is set opposite the zero of scale 24e when valve 69e pops out and then is used to read the systolic and diastolic pressures on sclae 24e. In this modification, the tube 1 7e leads to the plenum chamber 67e from cylinder 18e. Casing 66e may be fixed in or detachable from larger casing 76. In the former case, the casing would be positioned so that the members 69e and 72e can be seen from outside the casing 76 through suitable holes therein. In other respects, the modification of Figure 16 resembles that of the preceding modifications and the same reference numerals followed by the subscript e are used to designate corresponding parts. It will be understood that a reverse procedure may be followed after "zeroing", namely the diaphragm is fully pressurized over a range of pressure by depressing plunger 19, the plunger is then slowly withdrawn until the point at which localized arterial throbbing first commences and a reading made of systolic pressure, then the plunger is further withdrawn until the point at which the localized throbbing sensation ends and a reading made of diastolic pressure. The term "determination of zero" as used herein means determination of the position of the plunger corresponding to some known pressure, namely, that small pressure required to fully inflate or move to a precise position th "zero indicating" device. The magnitude of this pressure is determined by a one-time calibrated against a manometer or other means for the particular device or design. WHAT I CLAIM IS:

1. Blood pressure measuring apparatus as claimed in any of Claims 1 and 4 to 11 of Specification No. 22738/76 (Serial No. 1546 197), modified in that the inflatable sleeve is replaced by an inflatable part-annular diaphragm contained within the casing.

pressure responsive leak detecting means.

8. Apparatus according to Claim 7, sub stantially as described and shown in Figure 15.

9. A method of measuring blood pressure as claimed in any of Claims 14, 16, 17 and 18 of Specification No. 22738/76 (Serial No. 1546 197) modified in that it comprises applying apparatus as claimed in any of Claims 1 to 8 herein.