Non-invasive probe for detecting medical conditions

• US 20040116787A1
• Filed: 09/12/2003
• Published: 06/17/2004
• Est. Priority Date: 04/05/2001
• Status: Active Grant

• Current Assignee: Itamar Medical Ltd. (Asahi Kasei Corporation)
• Original Assignee: Itamar Medical Ltd. (Asahi Kasei Corporation)
• Inventors: Schnall, Robert P
• Granted Patent: US 7,374,540 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/1073 Measuring volume, e.g. of limbs
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

A non-invasive probe for application to a body part, such as a finger, toe or limb, for the detection of a medical condition of the subject includes a housing defining a compartment closed at one end and open at the opposite end for receiving the distal end of the subject'"'"'s body part including its terminal-most extremity, a sensor for sensing a predetermined condition of the body part after being received within the compartment, and a removable liner lining the inner surface of the housing, to facilitate the insertion of the body part into the compartment. The described probe is one which senses changes in the peripheral arterial tone as manifested by changes in the pulsatile arterial blood volume and/or changes in the oxygen saturation level in a terminal extremity of a body part, and includes a number of other features particularly useful in such probes.

Claims

1. A non-invasive probe for application to a body part of a subject for the detection of a medical condition of the subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving the subject'"'"'s body part;

a sensor for sensing a predetermined condition of said body part after received within said compartment;

and a removable liner lining the inner surface of said housing, said liner being of a low-friction sheet material to facilitate the insertion of said body part into said compartment and to be slideably withdrawable from between said body part and said housing after the insertion of said body part into said compartment.

2. The probe according to claim 1, wherein said housing includes two of said removable liners lining two inner surfaces of said housing to face opposite sides of the body part when received in said compartment, each of said liners including an internal portion located within said housing, and an external portion extending externally of said housing to facilitate the slidable withdrawal of each liner from the housing after the body part has been inserted into said compartment.

3. The probe according to claim 2, wherein said internal portion of each liner located within said housing is folded upon itself to facilitate the slidable withdrawal of the liner from the housing after the body part has been inserted into said compartment.

4. The probe according to claim 2, wherein said external portion of each liner is temporarily adherent to the outer surface of said housing.

5. The probe according to claim 1, wherein said housing includes a casing and an inner membrane within said casing and defining an inner chamber for receiving a fluid to apply a predetermined static pressure to said body part when received within said compartment;

and wherein said liner lines the inner surface of said inner membrane to facilitate the insertion of said body part into said compartment.

6. The probe according to claim 5, wherein said housing is configured and dimensioned for receiving the distal end of the subject'"'"'s body part, including its terminal-most extremity;

and wherein said housing further includes a restraining member located within said compartment to restrain said membrane from expelling the body part from said compartment when the chamber is pressurized by said fluid;

said restraining member including an annular ring facing the open end of the housing, and a plurality of circumferentially-spaced arms extending axially within the compartment.

7. The probe according to claim 6, wherein there are two of said arms, said two arms being joined together in a U-shaped bend at their end adjacent the closed end of the housing.

8. The probe according to claim 6, wherein said arms terminate short of said closed end of the housing, and thereby short of said terminal-most extremity of the body part when received within said compartment.

9. The probe according to claim 6, wherein said annular ring is located adjacent to the open end of said housing.

10. The probe according to claim 6, wherein said annular ring is located inwardly of the open end of the housing to define, with an inner section of said inner membrane, an inner section of said compartment for receiving said body part;

said inner membrane including an outer section defining an outer section of said compartment for receiving said body part, and an outer section of said inner chamber for applying said static pressure to said body part when received in said compartment.

11. The probe according to claim 6, wherein said arms of the restraining mount said sensor within said compartment, and connections to the sensor from locations externally of the compartment.

12. The probe according to claim 11, wherein said sensor is an optical sensor and includes a light source and a light detector located externally of said compartment;

and wherein said connections mounted on the arms of said restraining member include light guides for guiding light into the interior of the compartment from said light source located externally of the compartment and for guiding light from the interior of the compartment to said light detector located externally of the compartment.

13. The probe according to claim 6, wherein said housing also includes a transmitter for transmitting in a wireless manner data sensed by said sensor to a receiver externally of said compartment.

14. The probe according to claim 6, wherein said inner membrane is part of an inflatable elastic bag located within said housing and engaged by said restraining member to define said compartment for receiving the body part of the subject, said casing including an opening for venting to the atmosphere the space between said elastic bag and the inner face of said casing.

15. The probe according to claim 14, wherein said inflatable bag is of an elongated configuration, having a length many times its diameter, and is engaged in a folded condition by said restraining member to define said compartment.

16. The probe according to claim 14, wherein said inflatable bag is filled with a gas.

17. The probe according to claim 14, wherein said inflatable bag is at least partially filled with a liquid.

18. The probe according to claim 6, wherein said housing further includes an outer membrane over the outer surface of said casing and defining thereforth an outer chamber communicating with said inner chamber via an opening in said casing.

19. The probe according to claim 18, wherein said housing further includes an outer casing facing the outer surface of said outer membrane and defining therewith a third chamber;

and wherein said outer casing includes a vent opening venting said third chamber to the atmosphere.

20. The probe according to claim 19, wherein said probe further includes a pressure transducer communicating with an opening in said outer casing for monitoring pressure changes within said third chamber.

21. The probe according to claim 18, wherein said inner membrane and said outer membrane are parts of an inflatable elongated elastic bag;

one end of said elongated elastic bag being received over the outer surface of said casing to constitute said outer membrane defining said outer chamber;

the opposite end of said elongated elastic bag being received within said casing to constitute said inner membrane engageable by said restraining member and defining said inner chamber communicating with said outer chamber via an opening in said casing.

22. The probe according to claim 21, wherein said casing and elongated elastic bag are so dimensioned that said one end of the elongated elastic bag, when received over said casing to define said outer chamber, is pre-tensioned sufficient to reduce diffusion of the fluid through the elastic bag by said static pressure when the body part is not received within the compartment, but not to substantially affect the deformability of said inner membrane by pulsatile volume changes in the body part when received in said compartment.

23. The probe according to claim 21, wherein said inner chamber is partially filled with a supporting medium, and is at a fluid pressure below said predetermined static pressure, such that the added volume of the distal end of the subject'"'"'s body part, when received within said compartment, produces said predetermined static pressure applied to said body part.

24. The probe according to claim 23, wherein said supporting medium includes a spongy body.

25. The probe according to claim 21, wherein the probe includes a pair of bistable elastic spring leaves carried by said casing and disposed within said inner chamber on opposite sides thereof;

each of said bistable elastic spring leaves being movable to a first stable position projecting away from said casing inner surface into said inner chamber for pre-tensioning said membranes to reduce diffusion of the fluid through the membranes by the fluid pressure within said elongated elastic bag;

each of said bistable elastic spring leaves being movable to a second stable position in contact with said casing inner surface to accommodate the subject'"'"'s body part when introduced into said compartment.

26. The probe according to claim 1, wherein said housing includes a plurality of optical sensors for sensing optical properties of different portions of the body part received in said compartment.

27. The probe according to claim 1, wherein said housing further includes a movement detector for detecting movement of said body part.

28. The probe according to claim 1, wherein said housing is constructed and dimensioned to define a compartment for receiving the distal end, including the terminal-most extremity, of a digit of the subject.

29. The probe according to claim 1, wherein said housing is constructed and dimensioned to define a compartment for receiving the distal end, including the terminal-most extremity, of a limb of the subject.

30. The probe according to claim 1, wherein said sensor senses pulsatile volume changes in said body part.

31. The probe according to claim 1, wherein said sensor senses oxygen saturation level changes in said body part.

32. A probe for application to a body part of a subject for the non-invasive detection of a medical condition of the subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving the distal end of the subject'"'"'s body part including its terminal-most extremity;

and a sensor for sensing a predetermined condition of said body part after received within said compartment;

said housing including;

an inner casing;

an inner membrane within said inner casing and defining an inner chamber for receiving a fluid to apply a predetermined static pressure to said body part when received within said compartment;

an outer membrane over the outer surface of said inner casing and defining herewith an outer chamber communicating with said inner chamber via an opening in said inner casing effective to cause said predetermined static pressure applied by said inner membrane to be substantially unaffected by the size of the body part inserted into said compartment or by volume changes of the body part inserted therein;

and an outer casing facing the outer surface of said outer membrane and defining therewith a third chamber;

said outer casing including a vent opening venting said third chamber to the atmosphere.

33. The probe according to claim 32, wherein said probe further includes a pressure transducer for monitoring pressure changes within said third chamber via an opening in said outer casing.

34. The probe according to claim 32, wherein said inner and outer chambers are interconnected via said inner casing such that the uniformity of said predetermined static pressure applied by said inner membrane is substantially unaffected by the size of the body part inserted into said compartment or by volume changes of said body part inserted therein.

35. A probe for application to a body part of a subject for the non-invasive detection of a medical condition of the subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving a distal end of the subject'"'"'s body part including its terminal-most extremity;

said housing including a casing and an inner membrane within said casing defining, with the inner surface of said casing, an inner chamber for receiving a fluid to apply a predetermined static pressure to said body part when received within said compartment;

a restraining member within said compartment to restrain said membrane from expelling the body part from said chamber when the chamber is pressurized by said static pressure;

and a sensor for sensing a predetermined condition of said body part after received within said compartment;

said restraining member including an annular ring adjacent to the open end of the housing, and a plurality of arms extending axially within the compartment and terminating short of said closed end of the housing, and thereby short of the terminal-most extremity of the body part when received within said compartment.

36. The probe according to claim 35, wherein said annular ring is located adjacent to the open end of said housing.

37. The probe according to claim 35, wherein said annular ring is located inwardly of the open end of the housing to define, with an inner section of said inner membrane, an inner section of said compartment for receiving said body part;

said inner membrane including an outer section defining an outer section of said compartment for receiving said body part, and an outer section of said inner chamber for applying said static pressure to said body part when received in said compartment; and

wherein said housing further includes an outer membrane defining an outer chamber with the outer surface of said casing;

said inner and outer chambers being interconnected via an opening through said casing such that the uniformity of said predetermined static pressure applied by said inner membrane is substantially unaffected by the size of the body part inserted into said compartment or by volume changes of said body part inserted therein.

38. The probe according to claim 35, wherein said arms of the restraining mount said sensor within said compartment, and connections to the sensor from locations externally of the compartment.

39. The probe according to claim 38, wherein said sensor is an optical sensor including a light source and a light detector located externally of said compartment;

and wherein said connections mounted on the arms of said restraining member include light guides for guiding light into the interior of the compartment from said light source located externally of the compartment and for guiding light from the interior of the compartment to said light detector located externally of the compartment.

40. A probe for application to a body part of a subject for the non-invasive detection of a medical condition of the subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving a distal end of the subject'"'"'s body part including its terminal-most extremity;

said housing including a casing and a membrane within said casing and defining a chamber for receiving a fluid to apply a predetermined static pressure to said body part when received within said compartment;

a restraining member within said compartment to restrain said membrane from expelling the body part from said chamber when the chamber is pressurized by said static pressure;

and a sensor for sensing a predetermined condition of said body part after received within said compartment;

said membrane being part of an inflatable elastic bag located within said housing and engaged by said restraining member to define said compartment after receiving the body part of the subject;

said casing including an opening for venting the space between said elastic bag and the inner face of said casing.

41. The probe according to claim 40, wherein said inflatable bag is of an elongated configuration, having a length many times its diameter, and is engaged in a folded condition by said restraining member to define said compartment.

42. The probe according to claim 40, wherein said inflatable bag is filled with a gas.

43. The probe according to claim 40, wherein said inflatable bag is at least partially filled with a liquid.

44. A probe for application to a body part of a subject for the non-invasive detection of a medical condition of the subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving a distal end of the subject'"'"'s body part including its terminal-most extremity;

said housing including a casing, an inner membrane within said casing and defining an inner chamber for receiving a fluid to apply a predetermined static pressure to said body part when received within said compartment, and an outer membrane defining an outer chamber communicating with said inner chamber via an opening through said casing effective to cause said predetermined static pressure applied by the inner membrane to be substantially unaffected by the size Of the body part inserted into said compartment or by volume changes of the body part inserted therein;

a restraining member within said compartment to restrain said inner membrane from expelling the body part from said inner chamber when the inner chamber is pressurized by said static pressure;

and a sensor for sensing a predetermined condition of said body part after received within said compartment;

said restraining member including an annular ring facing the open end of the housing, and a plurality of arms extending axially within the compartment;

said annular ring being located inwardly of the open end of the housing to define, with an inner section of said inner membrane, an inner section of said compartment for receiving said body part;

said inner membrane including an outer section defining an outer section of said compartment for receiving said body part, and an outer section of said inner chamber for applying said static pressure to said body part when-received in said compartment.

45. The probe according to claim 44, wherein said retraining member includes two of said armsjoined together in a U-shaped bend at their end adjacent the closed end of the housing.

46. The probe according to claim 44, wherein said arms of the retraining member terminate short of said closed end of the housing, and thereby short of said terminal-most extremity of the body part when received within said compartment.

47. The probe according to claim 44, wherein said arms of the restraining mount said sensor within said compartment, and connections to the sensor from locations externally of the compartment.

48. The probe according to claim 47, wherein said sensor is an optical sensor and includes a light source and a light detector located externally of said compartment;

and wherein said connections mounted on the arms of said restraining member include light guides for guiding light into the interior of the compartment from said light source located externally of the compartment and for guiding light from the interior of the compartment to said light detector located externally of the compartment.

49. A probe for application to a body part of a subject for the non-invasive detection of a medical condition of the subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving a distal end of the subject'"'"'s body part including its terminal-most extremity;

and a sensor for sensing a predetermined condition of said body part after received within said compartment;

said housing including;

an inner casing;

an inner membrane within said inner casing and defining an inner chamber for receiving a fluid to apply a predetermined static pressure to said body part when received within said compartment;

an outer membrane over the outer surface of said inner casing and defining herewith an outer chamber communicating with said inner chamber via an opening in said inner casing;

and a restraining member within said compartment;

said inner and outer membranes being parts of an inflatable elongated elastic bag;

one end of said elongated elastic bag being received over the outer surface of said casing to constitute said outer membrane defining said outer chamber;

the opposite end of said elongated elastic bag being received within said casing to constitute said inner membrane engageable by said restraining member and defining said inner chamber communicating with said outer chamber via an opening in said casing.

50. The probe according to claim 49, wherein said casing and elongated elastic bag are so dimensioned that said one end of the elongated elastic bag, when received over said casing to define said outer chamber, is pre-tensioned sufficient to reduce diffusion of the fluid through the elastic bag by said static pressure when the body part is not received within the compartment, but not to substantially affect the deformability of said inner membrane by pulsatile volume changes in the body part when received in said compartment.

51. The probe according to claim 49, wherein said inner chamber is partially filled with a supporting medium, and is at a fluid pressure below said predetermined static pressure, such that the added volume of the distal end of the subject'"'"'s body part, when received within said compartment, produces said predetermined static pressure applied to said body part.

52. The probe according to claim 51, wherein said supporting medium includes a spongy body.

53. The probe according to claim 49, wherein the probe includes a pair of bistable elastic spring leaves carried by said casing and disposed within said inner chamber on opposite sides thereof;

each of said bistable elastic spring leaves being movable to a first stable position projecting away from said casing inner surface into said inner chamber for pre-tensioning said membranes to reduce diffusion of the fluid through the membranes by the fluid pressure within said elongated elastic bag;

each of said bistable elastic spring leaves being movable to a second stable position in contact with said casing inner surface to accommodate the subject'"'"'s body part when introduced into said compartment.

54. A probe for the non-invasive detection of a medical condition of a subject, comprising:

a housing defining a compartment closed at one end and open at the opposite end for receiving a limb of the subject including the distal end of the limb;

an inner membrane within said housing and defining an inner chamber for receiving a fluid to apply a predetermined static pressure to said limb including the distal end thereof within said compartment;

a restraining member within said compartment;

and a sensor within said compartment for sensing a predetermined condition of said distal end of the limb within said compartment.

55. The probe according to claim 54, wherein said predetermined static pressure is produced by a fluid self-contained within the probe and is of a magnitude to prevent distal venous blood pooling, to unload wall tension from arterial blood vessels, and to inhibit retrograde venous shock wave propagation to the sensor site.

56. The probe according to claim 54, wherein said predetermined static pressure is produced by a fluid supplied from a fluid system externally of said probe and is of a magnitude to prevent distal venous blood pooling, to unload wall tension from arterial blood vessels, and to inhibit retrograde venous shock wave propagation to the sensor site.

57. The probe according to claim 54, wherein said compartment defined by said housing, and said inner chamber defined by said inner membrane, are divided into a plurality of sections, including a distal section at said closed end of the compartment for receiving the distal end of the limb, and at least one proximal section at the opposite open end of the compartment for receiving a more proximal region of the limb;

said distal section of the compartment being subjected to said predetermined static pressure and including said sensor for sensing said predetermined condition of said distal end of the limb.

58. The probe according to claim 57, wherein said predetermined static pressure applied to said distal section of the compartment is produced by a fluid self-contained within the probe.

59. The probe according to claim 57, wherein said proximal section of the compartment is also subjected to a predetermined static pressure and also includes a sensor for sensing said predetermined condition of said more proximal region of the limb.

60. The probe according to claim 57, wherein both said proximal section and said distal section of the compartment are also subjected to a predetermined static pressure each includes sensing means for sensing said predetermined condition of the limb in the respective section of said compartment.

61. The probe according to claim 60, wherein said predetermined static pressure applied to one of said plurality of sections of the compartment is produced by a fluid supplied from a fluid system external of said probe and is of sufficient magnitude to occlude the flow of blood to effect an induced ischemia test for evaluating the of degree of induced reactive hyperemia in a patient.

62. A method of using the probe according to claim 61, to induce ischemia in a patient for evaluating the degree of induced reactive hyperemia for the purpose of determining the endothelial function state of the patient.

63. The method according to claim 62, wherein said ischemia is induced in the patient via at least one section of said compartment.

64. The method according to claim 62, wherein said ischemia is induced by applying pressure to at least one of said plurality of sections of the compartment by a fluid supplied from a fluid system external of said probe and of sufficient magnitude to occlude the flow of blood, the measurements of pulsatile volume changes taken during the application of counter-pressure for occluding blood flow being used to ensure that a sufficient level of counter-pressure is being applied to completely occlude the flow of blood.