Physiological sensing device

• US 6,491,647 B1
• Filed: 09/23/1999
• Issued: 12/10/2002
• Est. Priority Date: 09/23/1998
• Status: Expired due to Fees

• Current Assignee: Active Signal Technologies, Inc
• Original Assignee: Active Signal Technologies, Inc
• Inventors: Cooke, Arthur V., Bridger, Keith, Rubin, Gregg R., Lutian, Joseph J., Sewell, John M., Passaro, Edward J., Kuhn, Philip M., Waskey, Terence V.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): ASTORINO, MICHAEL C
• Application Number:
  US09/401,762
• Time in Patent Office: 1,174 Days
• Field of Search: 600/300, 600/500-508, 128/900
• US Class Current: 600/585
• CPC Class Codes: A61B 2562/02 Details of sensors specially adapted for in-vivo measurements
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/02444 Details of sensor A61B5/02427 takes precedence
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R
• CPC Class Codes: G01L 1/2231 the supports being disc- or ring-shaped, adapted for measuring a force along a single direction
• CPC Class Codes: Y10S 128/90 Blood pressure recorder

Abstract

The present invention relates to a non-invasive device for measuring physiological processes. More particularly, it concerns a device that can be applied externally to the body of an animal or human to detect and quantify displacement, force, motion, vibration and acoustic effects resulting from internal biological functions. Specifically, an inexpensive device is disclosed that is compact, light, portable and comfortable, and operates satisfactorily even with imprecise location on the body, ambient noise, motion and light.

Claims

1. A device for sensing physiological processes of a mammal, comprising:

(a) a housing;

(b) a sensing portion at least partially within the housing;

(c) a load transfer element in communication with the sensing portion; and

(d) an interface transition mechanism in communication with the load transfer element for interfacing with a portion of the mammal wherein at least a portion of the interface transition mechanism comprises a rigid stiffening member.

2. A device in accordance with claim 1, further comprising display means for displaying physiological process information determined from the sensing portion.

3. A device in accordance with claim 1, wherein the housing comprises side walls for contact with the mammal.

4. A device in accordance with claim 3, wherein the areas of the side walls for contact with the mammal and the area of the interface transition mechanism for interfacing with the mammal are substantially equal.

5. A device in accordance with claim 1, wherein the mass of the housing and the combined mass of the interface transition mechanism and load transfer element are substantially equal.

6. A device in accordance with claim 1, wherein the interface transition mechanism comprises an outer contact member, rigid stiffening member and at least one compliant return element that provides initial positioning of the rigid stiffening member with respect to the housing, the outer contact member being contoured on one surface for comfortable interface with the portion of the mammal and attached on its opposite surface to the rigid stiffening member.

7. A device in accordance with claim 1, wherein the interface transition mechanism is substantially rigid, incompressible and contoured on a surface for comfortable interface with the portion of the mammal, and another surface of the interface transition mechanism contacts the load transfer element at a point, along a line or across an area.

8. A device in accordance with claim 7, wherein the interface transition mechanism has substantially unconstrained rotational movement about the contact point, contact line or contact area with the load transfer element.

9. A device in accordance with claim 1, wherein the interface transition mechanism contacts the portion of the mammal over an area that is larger than an area on the mammal over which the physiological process is manifest.

10. A device in accordance with claim 1, wherein the load transfer element is essentially incompressible and rigid.

11. A device in accordance with claim 10, wherein the load transfer element is configured as a ball or rod.

12. A device in accordance with claim 1, wherein the load transfer element is constrained to move only along an axis between the physiological process and a most sensitive point on the sensing portion.

13. A device in accordance with claim 1, wherein the sensing portion comprises one or more pivot points, a displacement member and one or more sensing elements.

14. A device in accordance with claim 13, wherein the sensing elements are passive and generate signals without externally imposed signals or power.

15. A device in accordance with claim 14, wherein the sensing elements are piezoelectric, electrostrictive, magnetostrictive, or produce variable capacitance, eddy currents or inductance.

16. A device in accordance with claim 15, wherein the sensing elements comprise piezoelectric sensing elements which are monolithic polycrystals, multilayers of polycrystalline material, single crystals, or unimorphs comprising a layer of polycrystalline piezoceramic on a conductive substrate.

17. A device in accordance with claim 15, wherein said sensing elements comprise one or more strain gages, one or more photo-emitter and photo-detector pairs or a pressure sensor.

18. A device in accordance with claim 2, wherein the display updates continuously and is in the form of an alpha-numeric display, a graphical representation, dial, or color indicating the physiological process information.

19. A device in accordance with claim 1, wherein the physiological process is a propagation of a bolus of blood along a major artery in a wrist of the mammal.

20. A device in accordance with claim 1, wherein the physiological process is a heartbeat of the mammal.

21. A device in accordance with claim 1, wherein the physiological process is a breathing rate of the mammal.

22. A wrist mountable self-contained heart rate monitor comprising an automatic and continuous heart rate display generated by an assembly comprising a sensing portion, a load transfer element in communication with the sensing portion, and an interface transition mechanism in communication with the load transfer element for contacting the wrist, wherein at least a portion of the interface transition mechanism comprises a rigid stiffening member.

23. The heart rate monitor of claim 22, further comprising a time display.

24. The heart rate monitor of claim 23, wherein the heart rate display and time display are located on a watch face of the heart rate monitor, and the assembly is separately located on a wrist strap.

25. A device for sensing at least one physiological process of an animal, said device comprising:

(a) a sensing portion;

(b) a load transfer element in communication with the sensing portion;

(c) an interface transition mechanism in communication with the load transfer element wherein said interface transition mechanism interfaces with a portion of the animal and at least a portion of the interface transition mechanism comprises a rigid stiffening member.

26. The device in accordance with claim 25, wherein the sensing portion comprises one or more pivot points, a displacement member and one or more sensing elements.

27. The device in accordance with claim 26, wherein the sensing elements are passive and generate signals without externally imposed signals or power.

28. The device in accordance with claim 25, wherein the sensing portion comprises at least one sensing element which is piezoelectric, electrostrictive, or magnetostrictive, or which produces variable capacitance, eddy currents or inductance.

29. The device in accordance with claim 25, wherein the sensing portion comprises a sensing element which is a solid state or optical fiber pressure sensor.

30. The device in accordance with claim 25, wherein the sensing portion comprises a sensing element which is a proximity sensing device.

31. The device in accordance with claim 30, wherein the proximity sensing device includes a capacitance sensor.

32. The device in accordance with claim 31, wherein the capacitance sensor comprises a pair of conductive plates and a compressible dielectric material.

33. The device in accordance with claim 32, wherein the capacitance sensor further comprises at least one pivot point and a displacement member.

34. The device in accordance with claim 33, wherein the displacement member deflects in response to said load transfer element, which responds to said interface transition mechanism, which responds to the physiological process of said animal.

35. The device in accordance with claim 34, wherein the compressible dielectric material has a thickness;

and wherein the displacement member deflects by a distance which is less than said thickness of the compressible dielectric material.

36. The device in accordance with claim 34, wherein said pair of conductive plates includes a fixed plate and a movable plate which responds to the displacement member;

wherein said fixed plate, said movable plate and said compressible dielectric material have a capacitance; and

wherein said capacitance sensor further comprises means for measuring said capacitance.

37. The device in accordance with claim 30, wherein the proximity sensing device includes an eddy current sensor.

38. The device in accordance with claim 37, wherein the eddy current sensor comprises a stiffening member having a surface, a plurality of magnetic elements disposed on the surface of said stiffening member which opposes travel of said magnetic elements in a first direction, a plurality of edge flexures which oppose travel of said magnetic elements in a second direction which is opposite said first direction, and a plurality of eddy current detectors for sensing the proximity of said magnetic elements on the surface of said stiffening member.

39. The device in accordance with claim 30, wherein the proximity sensing device includes an optical sensor.

40. The device in accordance with claim 39, wherein the optical sensor comprises a displacement member having a surface, said displacement member is deflected in response to said load transfer element;

means for supporting said displacement member;

a plurality of light emitters on said surface;

a plurality of light detectors on said surface;

a light reflecting surface opposite said surface of said displacement member; and

means for measuring changes in light received by said light detectors from said light reflecting surface and from said light emitters when said displacement member deflects in response to said load transfer element.

41. The device in accordance with claim 30, wherein the proximity sensing device includes a magnetic sensor.

42. The device in accordance with claim 41, wherein the magnetic sensor comprises a magnetic core running in an electrical coil.

43. The device in accordance with claim 30, wherein the proximity sensing device includes an inductance sensor.

44. The device in accordance with claim 25, wherein the sensing portion comprises a sensing element which is a piezoelectric sensor.

45. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a displacement member having a surface and piezoelectric wafers bonded to said surface.

46. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a displacement member having a surface, and a piezoelectric crystal or a piezoelectric polymer bonded to said surface for detecting deflection of said displacement member in response to said load transfer element.

47. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a displacement member having a stiff surface, and a soft piezoelectric polymer sheet mounted to said stiff surface.

48. The device in accordance with claim 47, wherein the soft piezoelectric polymer sheet comprises polyvinylidene difluoride.

49. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a piezoelectric bimorph.

50. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a piezoelectric unimorph.

51. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a metallic central vein including an upper surface and a lower surface, with each of said surfaces having a piezoelectric ceramic layer thereon.

52. The device in accordance with claim 51, wherein said metallic central vein and said piezoelectric ceramic layers form a displacement member;

and wherein the piezoelectric sensor further comprises a pair of pivot points with said displacement member resting thereon.

53. The device in accordance with claim 52, wherein said displacement member is deflected in response to said load transfer elements;

and wherein the sensing element further includes a displacement-limiting stop to limit deflection of said displacement member.

54. The device in accordance with claim 44, wherein the piezoelectric sensor comprises a piezoelectric displacement member and a parallel piezoelectric canceling member.

55. The device in accordance with claim 54, wherein the piezoelectric sensor includes a center having a canceling mass.

56. The device in accordance with claim 55, wherein the piezoelectric sensor further includes a base and damping patches interposed between said base and said piezoelectric canceling member.

57. The device in accordance with claim 25, wherein the sensing portion comprises a sensing element which is an acoustic sensor.

58. The device in accordance with claim 57, wherein the acoustic sensor includes means for sensing sub-audible frequencies.

59. The device in accordance with claim 57, wherein the acoustic sensor includes means for sensing frequencies greater than 10 kHz.

60. The device in accordance with claim 57, wherein the acoustic sensor includes a flexible diaphragm.

61. The device in accordance with claim 25, wherein the sensing portion comprises a sensing element which includes a strain gauge.

62. The device in accordance with claim 61, wherein the strain gauge is a resistive strain gauge.

63. The device in accordance with claim 62, wherein the strain gauge is a semiconductor strain gauge.

64. The device in accordance with claim 61, wherein the load transfer element includes a spring element;

and wherein the strain gauge is attached to said spring element.

65. The device in accordance with claim 25, wherein the sensing portion comprises a sensing element which includes a fluid chamber, a flexible plate over said fluid chamber, and a pressure gage within said fluid chamber;

and wherein the load transfer element includes means for engaging said flexible plate.

66. The device in accordance with claim 25, wherein the sensing portion comprises at least one sensing element with an output.

67. The device in accordance with claim 66, wherein the processing portion comprises:

a filter at the output of said at least one sensing element;

a first amplifier having an input at the output of said sensor, an output, and a gain between said input and said output;

a second amplifier having an input at the output of said first amplifier and an output;

means for controlling the gain of said first amplifier; and

an analog to digital converter having an analog input at the output of said second amplifier and a digital output.

68. The device in accordance with claim 66, wherein said processing portion comprises means for processing the digital output of said analog to digital converter.

69. The device in accordance with claim 68, wherein said processing portion further comprises means for displaying physiological process information determined from the digital output of said analog to digital converter.

70. The device in accordance with claim 67, wherein said at least one sensing element further has a sensor signal and a capacitance at the output thereof;

and wherein said filter is a capacitive voltage divider at the output of said at least one sensing element and at the input of said first amplifier, said capacitive voltage divider has a capacitance which attenuates the sensor signal and reduces input impedance at the input of said first amplifier, thereby reducing power consumption of said first amplifier.

71. The device in accordance with claim 70, wherein said filter includes a resistor in parallel with a capacitor.

72. The device in accordance with claim 70, wherein said second amplifier includes a fixed gain between the input and the output thereof;

and wherein said means for controlling the gain of said first amplifier includes means for automatically adjusting said gain of said first amplifier as a function of said sensor signal.

73. The device in accordance with claim 72, wherein said means for automatically adjusting said gain includes means for adjusting said gain from one to greater than one hundred.

74. The device in accordance with claim 73, wherein said means for adjusting said gain includes a variable resistance.

75. The device in accordance with claim 74, wherein the input of said first amplifier is a positive input;

wherein said first amplifier also has a negative input; and

wherein said variable resistance is a field effect transistor which is electrically connected between said means for automatically adjusting said gain and said negative input.

76. The device in accordance with claim 75, wherein said filter includes a first resistor in parallel with a first capacitor;

and wherein the negative input of said first amplifier has a second resistor in parallel with a second capacitor, with said first and second resistors having equal resistances, and with said first and second capacitors having equal capacitances.

77. The device in accordance with claim 72, wherein said sensor signal has a variable amplitude;

and wherein said means for automatically adjusting said gain adjusts said gain as a function of said variable amplitude.

78. The device in accordance with claim 77, wherein said means for processing the digital output of said analog to digital converter includes means for employing a fixed value as a trigger point for processing said digital output.

79. The device in accordance with claim 67, wherein said means for controlling the gain of said first amplifier includes a diode having a cathode electrically connected to the output of said second amplifier and an anode;

a resistor in parallel with a capacitor, said resistor and said capacitor being electrically connected to the anode of said diode; and

a field effect transistor having a gate electrically connected to said anode.

80. The device in accordance with claim 79, wherein said at least one sensing element further has a sensor signal with a plurality of negative pulses;

and wherein each of said negative pulses causes a corresponding negative pulse at the output of said second amplifier which has a direct electrical path through said diode to the gate of said field effect transistor, thereby minimizing a delay between said output of said second amplifier and said means for controlling the gain of said first amplifier.

81. The device in accordance with claim 80, wherein said sensor signal has a peak;

and wherein said means for controlling the gain of said first amplifier includes means for adjusting said gain with respect to the peak of said sensor signal.

82. The device in accordance with claim 68, wherein said means for processing includes means for applying threshold detection to the digital signal of said analog to digital converter.

83. The device in accordance with claim 68, wherein said means for processing includes means for detecting a first peak of the digital signal of said analog to digital converter, and means for delaying a predetermined time before detecting a second peak of the digital signal of said analog to digital converter.

84. The device in accordance with claim 68, wherein said means for processing includes means for detecting a descending threshold of the digital signal of said analog to digital converter, and means for delaying a predetermined time before detecting an ascending threshold of said digital signal.

85. The device in accordance with claim 68, wherein the physiological process of said animal is selected from the group consisting of a heart beat, a respiratory event, a respiration in the upper airway, a respiration in the lungs, a blood pressure, a radial pulse, a carotid pulse and a temporal pulse;

and wherein said means for processing includes means for detecting said selected physiological process.

86. The device in accordance with claim 85, wherein said means for processing includes means for displaying said selected physiological process.

87. The device in accordance with claim 85, wherein said means for processing includes means for detecting said heart rate as said selected physiological process.

88. The device in accordance with claim 87, wherein said means for processing includes means for rejecting said heart rate which is below a first predetermined value and which is above a second predetermined value.

89. The device in accordance with claim 88, wherein said first predetermined value is 35 beats per minute;

and wherein said second predetermined value is above 210 beats per minute.

90. The device in accordance with claim 87, wherein said means for processing includes means for averaging a series of consecutively detected heart rates.

91. A wrist mountable self-contained heart rate monitor comprising:

means for displaying a heart rate; and

an assembly for automatically and continuously generating said heart rate for said means for displaying, said assembly comprising;

a sensing portion for sensing a heart rate signal;

a load transfer element in communication with the sensing portion;

an interface transition mechanism in communication with the load transfer element wherein said interface transition mechanism interfaces with a portion of the animal and at least a portion of the interface transition mechanism comprises a rigid stiffening member; and

a processing portion in communication with the sensing portion for processing said heart rate signal and outputting said heart rate to said means for displaying.

92. The heart rate monitor in accordance with claim 91, wherein said sensing portion comprises at least two sensors across an area of the wrist where said heart rate is sensed.

93. The heart rate monitor in accordance with claim 91, wherein said sensing portion comprises a piezoelectric bimorph.