Noninvasive blood pressure measuring method and apparatus

• US 6,932,772 B2
• Filed: 10/16/2001
• Issued: 08/23/2005
• Est. Priority Date: 04/21/1999
• Status: Expired due to Term

• Current Assignee: Xi'An Libang Medical Electronics Co., Ltd.
• Original Assignee: Jie Kan
• Inventors: Kan, Jie
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US09/978,345
• Publication Number:
  US 20020026121A1
• Time in Patent Office: 1,407 Days
• Field of Search: 600485-507, 602 5- 12, 602 20- 22
• US Class Current: 600/490
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/043 in a linear array
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/6824 Arm or wrist

Abstract

A method and a device for non-invasive blood pressure measurement wherein the angle between the hand and the wrist, and the turning angle of the wrist relative to the middle part of the forearm, are kept to the most suitable degree for measuring the blood pressure of the radial artery. At least one pressure bladder and one arterial pulse transducer array are placed on the skin over the radial artery of the wrist to apply the external pressure to the artery and to detect the change of the arterial pulse signals. This method and device can correctly measure the intermittent or continuous blood pressure of the radial artery or the ulnar artery based on the principles of oscillation method and volume compensation method, and effectively eliminate the influence on the measurement due to body movement and the influence on blood circulation and neural function of the hand caused by long-term blood pressure measurement.

Claims

1. A method for non-invasively measuring arterial blood pressure at a wrist of a patient, said method comprising the steps of:

a) keeping a wrist of a patient at a posture which lowers a position of at least one tendon of the wrist near to a radial artery to be measured, and causes the radial artery to be close to a radius of the wrist;

b) applying a changing external pressure to the skin above a point where the radial artery crosses a most protuberant spot on a volar aspect of the radius of the wrist;

c) detecting a pulse wave signal of the radial artery along with a change in said external pressure on the skin above said point;

d) measuring blood pressure of the radial artery by measuring said external pressure applied to the radial artery when said pulse wave signal changes.

2. The method as defined in claim 1, wherein said step of keeping the wrist at said posture comprises forming a flexing angle of between approximately 100 and 170 degrees between a dorsal side of the wrist and a dorsal side of the hand attached to the wrist.

3. The method as defined in claim 1, wherein said step of keeping the wrist at said posture comprises forming a flexing angle of between approximately 100 and 170 degrees between a dorsal side of the wrist and a dorsal side of the hand attached to the wrist, and synchronously forming a turning angle of the wrist relative to the forearm attached to the wrist of between approximately 30 and 100 degrees towards a medial side of the patient'"'"'s body.

4. The method as defined in claim 1, wherein said step of keeping the wrist at said posture comprises forming a flexing angle of between approximately 100 and 170 degrees between a dorsal side of the wrist and a dorsal side of the hand attached to the wrist, and synchronously forming a deflecting angle from a central line of the palm of the hand relative to a central line of a volar side of the wrist at between approximately 10 and 40 degrees towards the little finger of the hand.

5. The method as defined in claim 1, wherein said step of keeping the wrist at said posture comprises forming a flexing angle of between approximately 100 and 170 degrees between a dorsal side of the wrist and a dorsal side of the hand attached to the wrist, and synchronously forming a turning angle of the wrist relative to the forearm attached to the wrist of between approximately 30 and 100 degrees towards a medial side of the patient'"'"'s body and a deflecting angle from a central line of the palm of the hand relative to a central line of a volar side of the wrist at between approximately 10 and 40 degrees towards the little finger of the hand.

6. The method as defined in claim 1, wherein said step of detecting a pulse wave signal of the radial artery includes measuring an oscillation in said external pressure caused by a pulsation of the radial artery.

7. The method as defined in claim 1, wherein said step of detecting a pulse wave signal of the radial artery includes measuring an oscillation in volume of the radial artery at a site which is on the skin above the radial artery and within a compressing area of said external pressure.

8. The method as defined in claim 1, wherein said step of detecting a pulse wave signal of the radial artery includes measuring an oscillation in volume of the radial artery at a plurality of sites which are on the skin above the radial artery and within a compressing area of said external pressure, and selecting one optimal measuring site, and then outputting the volume oscillation measured at said optimal measuring site as an optimal pulse wave signal, said plurality of sites including at least two columns and two lines of measuring sites along directions that are parallel and perpendicular to the radial artery respectively.

9. The method as defined in claim 8, wherein said step of selecting one optimal measuring site comprising the steps of:

a) selecting a column of measuring sites from all columns of measuring sites, said selected column of measuring sites having a feature that the pulse wave signals detected at said selected column of measuring sites all possess maximum amplitude points when said external pressure is close to the mean blood pressure of the patient, and amplitude values of the maximum amplitude points of the pulse wave signals detected at said selected column of measuring sites being larger than those detected at other columns of measuring sites;

b) selecting one optimal site from the selected column of measuring sites, said optimal site having a feature that the pulse wave signal detected at said selected site possesses a point close to disappearance when said external pressure is close to the systolic blood pressure of the patient;

wherein the value of the external pressure, when the amplitude of the pulse wave signals detected at said optimal site is close to maximum, and the value of the external pressure, when the amplitude of the pulse wave signal detected at said optimal site is close to disappearance, are lower than said values of external pressures detected at other sites of the selected column of measuring sites.

10. The method as defined in claim 8, further comprising displaying a position of said optimal measuring site within the compressing area of said external pressure, so that an operator can adjust a position of said external pressure according to said displaying step to cause a center of said external pressure to correspond to said optimal measuring site.

11. The method as defined in claim 8, further comprising the step of automatically checking whether the center of said external pressure corresponds to said optimal measuring site, and giving a warning signal when the center of said external pressure does not correspond to said optimal measuring site, so as to prompt an operator to readjust the position of said external pressure.

12. The method as defined in claim 1, wherein said step of measuring the blood pressure of the radial artery includes intermittently measuring the blood pressure of the radial artery according to an oscillometric method.

13. The method as defined in claim 1, wherein said step of measuring the blood pressure of the radial artery includes continuously measuring the blood pressure of the radial artery according to vascular unloading method.

14. The method as defined in claim 1, wherein said step of measuring the blood pressure of the radial artery includes at least one of intermittently measuring the blood pressure of the radial artery according to oscillometric method and continuously measuring the blood pressure of the radial artery according to vascular unloading method.

15. The method as defined in claim 1, wherein said step of applying changing external pressure to the radial artery, and detecting the pulse wave signal of the radial artery so as to measure the blood pressure of the radial artery can be switched to become applying changing external pressure to an ulnar artery of the wrist, and detecting the pulse wave signal of the ulnar artery so as to measure a blood pressure of the ulnar artery.

16. The method as defined in claim 15, further comprising the step of calibrating the measured ulnar artery blood pressure according to the measured radial artery blood pressure.

17. An apparatus for non-invasively measuring arterial blood pressure at a wrist of a patient comprising:

a) a wrist holding device including a support board, wherein said support board is shaped to adapt to a flexing angle of between approximately 100 and 170 degrees between a dorsal side of the wrist and a dorsal side of a hand attached to the wrist and a turning angle of between approximately 30 and 100 degrees of the wrist relative to the forearm attached to the wrist towards a medial side of the patient'"'"'s body;

b) a pressure bladder for applying an external pressure to the radial artery, wherein said pressure bladder comprises a compressing wall adapted to face the skin above the radial artery of the wrist;

c) a pressure bladder holding device for stably positioning said pressure bladder on the skin above a point where the radial artery crosses a most protuberant spot on a volar aspect of the radius of the wrist;

d) a pulse transducer for detecting a pulse wave signal of the radial artery; and

e) a pressure feeding-measuring system connected to said pressure bladder and said pulse transducer;

said pressure feeding-measuring system including a pressure feeding device for feeding pressure to said pressure bladder, and a signal processing device for processing the detected pulse wave signal of the radial artery and controlling said pressure feeding device, so as to measure blood pressure of the radial artery by measuring said external pressure applied to the radial artery when the detected pulse wave signal of the radial artery changes.

18. The apparatus as defined in claim 17, wherein said support board is made of a rigid material and possesses a shape adapted to cover at least a portion of the dorsal side of the hand, the flexing wrist joint, and the forearm attached to the wrist, and has several straps fixed onto the support board by several non-extensible devices respectively for stably holding the forearm, wrist and hand of the patient to the support board.

19. The apparatus as defined in claim 17, wherein said support board is shaped to further adapt to a deflecting angle from a control line of the palm of the hand relative to a central line of the volar side of the wrist at between approximately 10 and 40 degrees towards the little finger of the hand.

20. The apparatus as defined in claim 18, wherein said support board comprises an inner surface adapted to face the skin of the wrist and an outer surface opposite to said inner surface, said inner surface is shaped to adept to at least the shape of the irregular surface of the dorsal side of the flexing wrist joint, and a potion of said outer surface is adapted to cover at least the dorsal side of the flexing joint and is shaped to regular column surface.

21. The apparatus as defined in claim 17, wherein said pressure bladder and said bladder holding device are integrated into a whole, to form a strap embedded with said pressure bladder, said compressing wall of said pressure bladder is made of a resilient membrane shaped to upheave towards the wrist, said strap is made of at least a semi-rigid material with slight elasticity and shaped into a ring with an elliptic cross section similar to that of the wrist, and two ends of an opening of said strap are connected by non-extensible means.

22. The apparatus as defined in claim 17, wherein said pulse transducer is a pressure transducer having a pressure sensing surface connected to said pressure bladder by at least one of air and liquid.

23. The apparatus as defined in claim 17, wherein said pulse transducer is a volume transducer;

said volume transducer is preferably a reflective photoelectric transducer that consists of at least one light emitting device and at least one photoelectric device, said light emitting device and said photoelectric device are arranged vertical to the radial artery, wherein a midpoint between said at least one light emitting device and said at least one photoelectric device corresponds to an area center of said compressing wall of said pressure bladder, and said at least one light emitting device and said at least one photoelectric device are fixed on an inner surface of said compressing wall of said pressure bladder.

24. The apparatus as defined in claim 17, wherein said pulse transducer is a volume transducer array including a reflective photoelectric transducer array having a plurality of light emitting devices and a plurality of photoelectric devices which output independent pulse signals respectively;

said photoelectric devices are arranged to form a rectangular array having at least two photoelectric devices in each of a line and a column of the array;

said light emitting devices are arranged around said photoelectric device array;

a center of said photoelectric device array corresponds to an area center of said compressing wall of said pressure bladder;

said light emitting devices and photoelectric devices are fixed on an inner surface of said compressing wall of said pressure bladder;

each output of the photoelectric devices of said photoelectric device array are respectively connected to corresponding input of an optimal transducer selector to select an optimal transducer.

25. The apparatus as defined in claim 24, wherein said optimal transducer selector selects the optimal transducer according to the steps of:

a) selecting one column of transducers from all columns of transducers, said selected column of transducers having a feature that the pulse wave signals detected by said selected column of transducers all possess maximum amplitude points when said bladder pressure is close to mean blood pressure of the patient, and amplitude values of the maximum amplitude points of the pulse wave signals detected by said selected column of transducers being larger than those detected by other columns of transducers;

b) selecting one optimal transducer from said selected column of transducers, said optimal transducer having a feature that the pulse wave signals detected by said optimal transducer possesses a point close to disappearance when said bladder pressure is close to systolic blood pressure of the patient, when the values of the bladder pressures when the amplitude of the pulse wave signals detected by said optimal transducer are respectively close to maximum and disappearance are respectively lower than the values of the bladder pressures when the amplitudes of the pulse wave signals detected synchronously by other transducers of said selected column of transducers are respectively close to maximum and disappearance.

26. The apparatus as defined in claim 24, further comprising a device for displaying transducer position to indicate a detailed position of the optimal transducer in said photoelectric device array.

27. The apparatus as defined in claim 24, further comprising a warning device of transducer position to issue a warning signal when a position of said optimal transducer does not correspond to the center of said photoelectric device array.

28. The apparatus as defined in claim 17, wherein said pressure feeding-measuring system is capable of intermittently measuring the blood pressure of the radial artery according to oscillometric method.

29. The apparatus as defined in claim 17, wherein said pressure feeding-measuring system is capable of continuously measuring the blood pressure of the radial artery according to vascular unloading method.

30. The apparatus as defined in claim 17, wherein said pressure feeding-measuring system is capable of both intermittently measuring the blood pressure of the radial artery according to oscillometric method and continuously measuring the blood pressure of the radial artery according to vascular unloading method;

said apparatus further comprising a switching device for controlling said pressure feeding-measuring system to intermittently measure the radial artery blood pressure according to the oscillometric method and to continuously measure the radial artery blood pressure according to the vascular unloading method.

31. The apparatus as defined in claim 17, further comprising;

a pressure bladder adapted to be positioned on the skin above an ulnar artery of the patient for applying external pressure to the ulnar artery,

a pulse transducer for detecting the pulse wave signal of the ulnar artery, and

a switching device for switching the two pressure bladders and pulse transducers to measure either radial arterial blood pressure or ulnar arterial blood pressure.

32. The apparatus as defined in claim 31, further comprising a calibrating device for calibrating a measured ulnar artery blood pressure value according to the measured radial artery blood pressure value.