Sleep apnea risk evaluation

• US 6,811,538 B2
• Filed: 12/28/2001
• Issued: 11/02/2004
• Est. Priority Date: 12/29/2000
• Status: Expired due to Term

• Current Assignee: Watermark Medical, Inc. (BioSerenity SAS)
• Original Assignee: ARES Medical Incorporated
• Inventors: Berka, Chris, Levendowski, Daniel J., Westbrook, Philip R., Cvetinovic, Milenko, Furman, Yury
• Primary Examiner(s): Jones, Mary Beth
• Assistant Examiner(s): Mallari, Patricia C.
• Application Number:
  US10/040,937
• Publication Number:
  US 20020165462A1
• Time in Patent Office: 1,040 Days
• Field of Search: 600/300, 600/301, 600/323, 600/324, 600/326, 600/529-543, 128/200.24, 128/204.18, 128/204.23
• US Class Current: 600/529
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/103 Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes A61B5/08 takes precedence; measuring aids for tailors A41H1/00; measuring instruments specially adapted for dentistry A61C19/04
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment
• CPC Class Codes: Y10S 128/923 by comparison of patient data to other data

Abstract

In a technique for collecting and analyzing physiological signals to detect sleep apnea, a small light-weight physiological monitoring system, affixed to a patient'"'"'s forehead, detects and records the pulse, oximetry, snoring sounds, and head position of a patient to detect a respiratory event, such as sleep apnea. The physiological monitoring system may contain several sensors including a pulse oximeter to detect oximetry and pulse rate, a microphone to detect snoring sounds, and a position sensor to detect head position. The physiological monitoring system also can contain a memory to store or record the signals monitored by the mentioned sensors and a power source. The physiological monitoring system may be held in place by a single elastic strap, thereby enabling a patient to use the system without the assistance of trained technicians.

Claims

1. A system that monitors respiratory events of a patient, the system comprising:

a physiological monitoring system;

means for removably affixing the physiological monitoring system to the patient'"'"'s forehead;

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient of the patient and produces corresponding pulse oximetry data signals;

a storage memory for storing the pulse oximetry data signals produced by said pulse oximetry sensor;

wherein said pulse oximetry sensor and said storage memory are mounted on the physiological monitoring system, eliminating all lead wires between the patient and the storage memory, and such that the pulse oximetry sensor detects said oxyhemoglobin saturation and pulse rate of the patient and produces said pulse oximetry data signals, thereby monitoring the patient'"'"'s condition; and

computing circuitry that receives said pulse oximetry data signals and identifies a respiratory event of the patient responsive to said pulse oximetry data signals, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a variable threshold level of oxyhemoglobin desaturation, and wherein the variable threshold level is based on at least one of the following criteria;

peak oxyhemoglobin saturation, nadir, and peak oxyhemolobin resaturation.

2. A system as defined in claim 1, wherein the system monitors sleep related obstructive respiratory events of a patient during sleep.

3. A system as defined in claim 1, further comprising a patient head position and movement sensor that produces a head position and movement signal that indicates position and movement of the patient'"'"'s head.

4. A system as defined in claim 1, further comprising means for producing a sound data signal that indicates detected sounds produced by said patient.

5. A system as defined in claim 1, wherein said means for removably affixing the physiological monitoring system to the patient'"'"'s forehead comprises an adjustable strap.

6. A system as defined in claim 1, further comprising a computing device that receives said pulse oximetry data signals and computes SpO₂ measurement from which a respiratory event may be identified.

7. A system as defined in claim 1, further comprising a data transfer interface that communicates the pulse oximetry data signals from the system to an external computing device.

8. A system as defined in claim 1, wherein said pulse oximetry sensor is a reflectance-type sensor.

9. A system as defined in claim 1, wherein the pulse oximetry sensor comprises an active pulse oximetry sensor that applies positive pressure on the patient.

10. A system as defined in claim 1, further comprising a patient respiratory airflow detector.

11. A system as defined in claim 10, wherein the airflow detector comprises a nasal cannula or a pressure transducer.

12. A system as defined in claim 1, further including:

a data transfer interface that communicates said pulse oximetry data signals to the computing circuitry;

wherein the computing circuitry analyzes the pulse oximetry data signals and computes time spent by the patient at each of a plurality of oxyhemoglobin saturation levels.

13. A system as defined in claim 1, further comprising a CPAP device, and wherein said system monitors effects of the CPAP device.

14. A system as defined in claim 1, whereby the threshold level of oxyhemoglobin desaturation is variable.

15. A system as defined in claim 1, wherein values of the pulse oximetry data signal that indicate the threshold level of oxyhemoglobin desaturation are variable.

16. A method of evaluating risk of sleep apnea in a patient, the method comprising:

attaching a physiological monitoring system to a patient'"'"'s forehead, wherein the physiological monitoring system includes (a) a pulse oximetry sensor and circuitry that detects oxyhemoalobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, and (b) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, thereby eliminating all lead wires between the patient and the storage memory;

providing the stored pulse oximetry data signals to an expert system that receives the stored pulse oximetry data signals, wherein the expert system performs an analysis and generates a sleep apnea risk evaluation report of the patient;

receiving light from multiple light sources of an SpO₂ measuring circuit at a photo diode that produces a photo diode current; and

producing a difference signal at an input of an analog-to-digital converter, wherein the difference signal comprises the difference between the photo diode current and a substantially constant current produced by a controlled current source, the difference input signal having an AC component and a DC component, the analog-to-digital converter producing a measurement current in response to the difference input signal, wherein the substantially constant current is selected such that the difference input signal AC component is substantially equal to the DC component.

17. A system that monitors respiratory events of a patient, the system comprising:

a physiological monitoring system;

means for removably affixing the physiological monitoring system to the patient'"'"'s forehead;

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient of the patient and produces corresponding pulse oximetry data signals;

a storage memory for storing the pulse oximetry data signals produced by said pulse oximetry sensor; and

computing circuitry that receives said pulse oximetry data signals and identifies a respiratory event of the patient responsive to said pulse oximetry data signals, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a threshold level of oxyhemoglobin desaturation;

wherein said pulse oximetry sensor and said storage memory are mounted on the physiological monitoring system, eliminating all lead wires between the patient and the storage memory, and such that the pulse oximetry sensor detects said oxyhemoglobin saturation and pulse rate of the patient and produces said pulse oximetry data signals, thereby monitoring the patient'"'"'s condition, wherein the threshold level of oxyhemoglobin desaturation is variable, and wherein the variable threshold level is based on a known relationship between the partial pressure of oxygen and oxyhemoglobin saturation.

18. A system that monitors respiratory events of a patient, the system comprising:

a physiological monitoring system;

means for removably affixing the physiological monitoring system to the patient'"'"'s forehead; and

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient of the patient and produces corresponding pulse oximetry data signals;

a storage memory for storing the pulse oximetry data signals produced by said pulse oximetry sensor;

wherein said pulse oximetry sensor and said storage memory are mounted on the physiological monitoring system, eliminating all lead wires between the patient and the storage memory, and such that the pulse oximetry sensor detects said oxyhemoglobin saturation and pulse rate of the patient and produces said pulse oximetry data signals, thereby monitoring the patient'"'"'s condition, and wherein said physiological monitoring system interfaces with and provides feedback to a neuromuscular stimulation device and that monitors efficacy of the neuromuscular stimulation device.

19. A risk evaluation system that monitors sleep-related obstructive respiratory events of a patient and provides a patient risk evaluation, the system comprising:

(a) a physiological monitoring system that includes (i) a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, thereby monitoring said patient'"'"'s condition, (ii) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, and (iii) means for removably affixing the physiological monitoring system to the patient'"'"'s forehead, whereby all lead wires between the patient and the storage means are eliminated;

(b) an expert system;

(c) a data transfer interface that communicates said pulse oximetry data signals to the expert system;

wherein the expert system receives and analyzes the pulse oximetry data signals and generates a sleep apnea risk evaluation report of the patient; and

(d) a computing system that receives and analyzes the pulse oximetry data signals and identifies any abnormal respiratory events of the patient, thereby producing at least one secondary respiratory event signal that is provided to the expert system.

20. A system that monitors respiratory events of a patient, the system comprising:

a physiological monitoring system;

means for removably affixing the physiological monitoring system to the patient'"'"'s forehead;

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient of the patient and produces corresponding pulse oximetry data signals;

a storage memory for storing the pulse oximetry data signals produced by said pulse oximetry sensor;

wherein said pulse oximetry sensor and said storage memory are mounted on the physiological monitoring system, eliminating all lead wires between the patient and the storage memory, and such that the pulse oximetry sensor detects said oxyhemoglobin saturation and pulse rate of the patient and produces said pulse oximetry data signals, thereby monitoring the patient'"'"'s condition;

a patient head position and movement sensor that produces a head position and movement signal that indicates position and movement of the patient'"'"'s head;

means for producing a sound data signal that indicates detected sounds produced by said patient;

a computing system;

a data transfer interface that communicates patient physiological data signals to the computing system, said patient physiological data signals including said pulse oximetry data signals, said head position and movement signal, and said sound data signal;

wherein the computing system analyzes the patient physiological data signals and identifies any abnormal respiratory events of the patient, classifying the analyzed data signals into one or more types of respiratory events; and

an expert system that analyzes one or more patient physiological signals and detects patient arousals that can be used to confirm the respiratory event type classification.

21. A system as defined in claim 20, wherein said expert system summarizes any identified patient respiratory events and generates a patient report.

22. A system as defined in claim 20, wherein the expert system receives patient client clinical information, receives said patient physiological signals, and utilizes said patient clinical information and said patient physiological signals to confirm the respiratory event type classification.

23. A system as defined in claim 20, wherein said expert system receives patient clinical information, receives said patient physiological data signals, analyzes the physiological data signals and patient clinical information against a database of sleep apnea risk data, and generates a sleep apnea risk evaluation report of the patient.

24. A method of evaluating risk of sleep apnea in a patient, comprising the steps of:

measuring a patient'"'"'s oxyhemoglobin desaturation; and

comparing the patient'"'"'s oxyhemoglobin desaturation with a threshold level of oxyhemoglobin desaturation required to determine a respiratory event, wherein the threshold level of oxyhemoglobin desaturation is variable, and wherein the variable threshold level is based on a known relationship between partial pressure of oxygen and oxyhemoglobin saturation.

25. The method of claim 24, wherein the variable threshold level is based on at least one of the following criteria:

peak oxyhemoglobin saturation, nadir, and peak oxyhemoglobin resaturation.

26. The method of claim 24, wherein the variable threshold level of oxyhemoglobin oxyhemoglobin desaturation is based at least in part on an automated detection of changes in patient snoring sounds, head movement, and pulse rate.

27. A physiological monitoring system comprising:

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of a patient and produces corresponding pulse oximetry data signals;

a power source that provides electrical energy to the sensor and circuitry for operation; and

a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor;

means for removably affixing said pulse oximetry sensor and circuitry, said power source, and said storage memory to the patient'"'"'s forehead, and wherein said pulse oximetry sensor and circuitry, said power source, and said storage memory are affixed on said patient'"'"'s body to detect the oxyhemolobin saturation and pulse rate and produce the corresponding data signals, provide electrical power, and store the data signals, respectively, thereby monitoring said patient'"'"'s condition, and whereby all lead wires between the patient and the storage memory are eliminated; and

an SpO₂ measuring circuit comprising multiple light sources, a photo diode that receives light from the light sources and produces a photo diode current, a controlled current source that produces a substantially constant current, and an analog-to-digital converter that receives a difference input signal comprising the difference between the photo diode current and the constant current, the difference input signal having an AC component and a DC component, the analog-to-digital converter producing a measurement current in response to said difference input signal, wherein the substantially constant current is selected such that the difference input signal AC component is substantially equal to the DC component.

28. A risk evaluation system that monitors sleep-related obstructive respiratory events of a patient and provides a patient risk evaluation, the system comprising:

(a) a physiological monitoring system that includes (i) a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, thereby monitoring said patient'"'"'s condition, (ii) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, and (iii) means for removably affixing the physiological monitoring system to the patient'"'"'s forehead, whereby all lead wires between the patient and the storage means are eliminated;

(b) an expert system; and

(c) a data transfer interface that communicates said pulse oximetry data signals to the expert system;

wherein the expert system receives and analyzes the pulse oximetry data signals and generates a sleep apnea risk evaluation report of the patient, wherein the expert system receives patient clinical information, and wherein the expert system analyzes the patient clinical information and compares the patient clinical information to a database such that the patient is assigned into one of a plurality of discrete risk categories for sleep apnea.

29. A system as defined in claim 28, further including:

a microphone that produces a sound data signal that indicates detected sounds produced by said patient.

30. A system as defined in claim 28, further including:

a patient head position and movement sensor that detects position and movement of the head of said patient and produces corresponding head position and movement data signals.

31. A system as defined in claim 28, further comprising computing circuitry that receives said pulse oximetry data signals and identifies a respiratory event of the patient, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a threshold level of oxyhemoglobin desaturation.

32. A system as defined in claim 31, wherein values of the pulse oximetry data signals that indicate oxyhemoglobin desaturation are variable.

33. A system as defined in claim 31, wherein the threshold level of oxyhemoglobin desaturation is variable.

34. A system as defined in claim 31, wherein the threshold level of oxyhemoglobin desaturation is variable, and wherein the variable threshold level is based on a known relationship between the partial pressure of oxygen and oxyhemoglobin saturation.

35. A system as defined in claim 31, wherein the threshold level of oxyhemoglobin desaturation is variable, and the variable threshold level is based on at least one of the following criteria:

peak oxyhemoglobin saturation, nadir, and peak oxyhemoglobin resaturation.

36. A physiological monitoring system comprising:

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of a patient and produces corresponding pulse oximetry data signals;

a power source that provides electrical energy to the sensor and circuitry for operation; and

a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor;

means for removably affixing said pulse oximetry sensor and circuitry, said power source, and said storage memory to the patient'"'"'s forehead, and wherein said pulse oximetry sensor and circuitry, said power source, and said storage memory are affixed on said patient'"'"'s body to detect the oxyhemoglobin saturation and pulse rate and produce the corresponding data signals, provide electrical power, and store the data signals, respectively, thereby monitoring said patient'"'"'s condition, and whereby all lead wires between the patient and the storage memory are eliminated; and

a computing device that receives patient SpO₂ data produced by the pulse oximetry sensor and identifies SpO₂ data that indicates desaturation related to abnormal respiratory events by identifying changes in patient physiological data that indicate patient arousal.

37. A system as defined in claim 36, further including:

a patient head position and movement sensor that produces a head position and movement data signal that indicates position and movement of the patient'"'"'s head.

38. A system as defined in claim 36, further including:

a microphone that produces a sound data signal that indicates detected sounds produced by said patient.

39. A system as defined in claim 36, further comprising a data transfer interface that communicates data from the system to an external computer.

40. A system as defined in claim 36, wherein the means for removably affixing the physiological monitoring system to the patient'"'"'s forehead comprises an adjustable strap.

41. A system as defined in claim 36, wherein the computing device smooths the SpO₂ data by performing at least one of the following smoothing operations:

(a) applying a moving window median filter that replaces a current data sample value with a median value selected from a predetermined number of data sample values, (b) applying a slew limitation filter that determines if two consecutive data sample values differ by more than a predetermined amount, and in response replaces a data sample value with a replacement value so as to limit the difference to no greater than the predetermined amount, and (c) applying an averaging technique that operates on multiple data sample values.

42. A system as defined in claim 41, wherein the averaging technique comprises a first-order infinite impulse response (IIR) filter that operates on a current data sample value and a previous data sample value.

43. A system as defined in claim 41, wherein the computing device performs multiple smoothing operations and one or more of the smoothing operations receives, as data input, smoothed data sample values produced by a different smoothing operation.

44. A system as defined in claim 36, wherein the computing device indicates desaturation occurrences in accordance with rate of change of SpO₂ desaturation data.

45. A system as defined in claim 36, wherein the pulse oximetry sensor comprises an active pulse oximetry sensor that applies positive pressure on the patient.

46. A system as defined in claim 36, wherein the changes in patient physiological data include at least one of changes in patient heart rate, patient position and movement, and patient produced sounds.

47. A system for monitoring respiratory events of a patient, the system comprising:

a physiological monitoring system including a pulse oximetry sensor and circuitry, and storage means for storing physiological data, the pulse oximetry sensor and circuitry detecting oxyhemoglobin saturation and pulse rate of a patient and producing corresponding pulse oximetry data signals, and the storage means storing a recording of the pulse oximetry signals; and

means for removably affixing said physiological monitoring system to the patient'"'"'s forehead, whereby all lead wires between the patient and the means for storing are eliminated, the means for removably affixing comprising an elastic strap and at least one foam pad mounted to said physiological monitoring system, said elastic strap and foam pad cooperating to apply a pressure of the pulse oximetry sensor against the patient'"'"'s forehead.

48. The system of claim 47, further comprising:

a power source that provides electrical energy to the pulse oximetry sensor and circuitry for operation; and

said means for storing comprises a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor;

wherein said power source and said storage memory are mounted on the physiological monitoring system.

49. The system of claim 47, wherein said pressure is optimized by adjusting the elastic strap and adjusting the thickness of said at least one foam pad.

50. The system of claim 49, further comprising means for measuring said pressure.

51. The system of claim 50, further comprising means for actively pressing the pulse oximetry sensor toward the patient'"'"'s forehead.

52. A method of evaluating risk of sleep apnea in a patient, the method comprising:

attaching a physiological monitoring system to a patient'"'"'s forehead, wherein the physiological monitoring system includes (a) a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, and (b) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, thereby eliminating all lead wires between the patient and the storage memory;

providing the stored pulse oximetry data signals to an expert system that receives the stored pulse oximetry data signals, wherein the expert system performs an analysis and generates a sleep apnea risk evaluation report of the patient; and

analyzing the pulse oximetry data signals and identifying any abnormal respiratory events of the patient, thereby producing one or more secondary respiratory event signals; and

providing the secondary respiratory event signals to the expert system for analysis in generating the evaluation report.

53. A method as defined in claim 52, wherein the physiological monitoring system further includes a patient head position sensor that detects the position of the patient'"'"'s head and produces corresponding head position data signals, and a microphone that detects snoring sounds produced by said patient and produces corresponding sound data signals, such that the physiological monitoring system thereby monitors said patient'"'"'s condition.

54. A method as defined in claim 52, further including the expert system receiving the pulse oximetry data signals and utilizing a database to perform an analysis and generate the evaluation report of the patient.

55. A method as defined in claim 54, wherein the expert system receives patient clinical information and the expert system analyzes the patient clinical information using discriminant function analysis developed using information from a database.

56. A method as defined in claim 54, further comprising providing said pulse oximetry data signals to computing circuitry that responds to the received pulse oximetry data signals by identifying a respiratory event of the patient, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a threshold level of oxyhemoglobin desaturation.

57. A method as defined in claim 56, wherein values of the pulse oximetry data signals that indicate the threshold level of oxyhemoglobin desaturation are variable.

58. A method as defined in claim 56, wherein the threshold level of oxyhemoglobin desaturation is variable.

59. A method as defined in claim 52, further including receiving patient SpO₂ data produced by the pulse oximetry sensor and identifying SpO₂ data that indicates desaturation occurrences in accordance with rate of change of SpO₂ desaturation data.

60. A method as defined in claim 52, wherein the pulse oximetry sensor comprises an active pulse oximetry sensor that applies positive pressure on the patient.

61. A method as defined in claim 52, wherein the step of attaching the physiological monitoring system to the patient'"'"'s forehead comprises affixing the physiological monitoring system to the patient'"'"'s forehead by an adjustable strap.

62. A method as defined in claim 52, further comprising:

receiving patient SpO₂ data produced by the pulse oximetry sensor; and

smoothing the SpO₂ data by performing at least one of the following smoothing operations;

(a) applying a moving window median filter that replaces a current data sample value with a median value selected from a predetermined number of data sample values, (b) applying a slew limitation filter that determines if two consecutive data sample values differ by more than a predetermined amount, and in response replaces a data sample value with a replacement value so as to limit the difference to no greater than the predetermined amount, and (c) applying an averaging technique that operates on multiple data sample values.

63. A method as defined in claim 62, wherein the averaging technique comprises a first-order infinite impulse response (IIR) filter that operates on a current data sample value and a previous data sample value.

64. A method as defined in claim 62, wherein more than one of the multiple smoothing operations is performed, and at least one of the smoothing operations receives, as data input, smoothed data sample values produced by a different smoothing operation.

65. A method of evaluating risk of sleep apnea in a patient, the method comprising:

attaching a physiological monitoring system to a patient'"'"'s forehead, wherein the physiological monitoring system includes (a) a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, and (b) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, thereby eliminating all lead wires between the patient and the storage memory; and

providing the stored pulse oximetry data signals to an expert system that receives the stored pulse oximetry data signals, wherein the expert system performs an analysis and generates a sleep apnea risk evaluation report of the patient, the expert system receiving the pulse oximetry data signals and utilizing a database to perform an analysis and generate the evaluation report of the patient;

wherein attaching the physiological monitoring system comprises attaching a system that further includes a patient head position and movement sensor that detects position and movement of the head of said patient and produces corresponding head position and movement data signals, and a microphone that produces a sound data signal that indicates detected sounds produced by said patient, wherein said pulse oximetry data signals, said head position and movement data signals, and said sound data signal comprise patient physiological data signals.

66. A method as defined in claim 65, further including receiving patient SpO₂ data produced by the pulse oximetry sensor and identifying SpO₂ data that indicates desaturation related to abnormal respiratory events by identifying changes in patient physiological data that indicate patient arousal.

67. A method as defined in claim 66, wherein the changes in patient physiological data include at least one of changes in patient heart rate, patient position and movement, and patient produced sounds.

68. A method as defined in claim 65, further including providing the patient physiological data signals to a computing system that analyzes the patient physiological data signals and identifies any abnormal respiratory events of the patient, thereby producing one or more secondary respiratory event signals that are provided to the expert system.

69. A method of evaluating risk of sleep apnea in a patient, the method comprising:

attaching a physiological monitoring system to a patient'"'"'s forehead, wherein the physiological monitoring system includes (a) a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, and (b) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, thereby eliminating all lead wires between the patient and the storage memory;

providing the stored pulse oximetry data signals to an expert system that receives the stored pulse oximetry data signals, wherein the expert system performs an analysis and generates a sleep apnea risk evaluation report of the patient, the expert system receiving the pulse oximetry data signals and utilizing a database to perform an analysis and generate the evaluation report of the patient; and

providing said pulse oximetry data signals to computing circuitry that responds to the received pulse oximetry data signals by identifying a respiratory event of the patient, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a threshold level of oxyhemoglobin desaturation;

wherein the threshold level of oxyhemoglobin desaturation is variable, and wherein the variable threshold level is based on a known relationship between the partial pressure of oxygen and oxyhemoglobin saturation.

70. A method of evaluating risk of sleep apnea in a patient, the method comprising:

attaching a physiological monitoring system to a patient'"'"'s forehead, wherein the physiological monitoring system includes (a) a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals, and (b) a storage memory that stores the pulse oximetry data signals produced by said pulse oximetry sensor, thereby eliminating all lead wires between the patient and the storage memory;

providing the stored pulse oximetry data signals to an expert system that receives the stored pulse oximetry data signals, wherein the expert system performs an analysis and generates a sleep apnea risk evaluation report of the patient, the expert system receiving the pulse oximetry data signals and utilizing a database to perform an analysis and generate the evaluation report of the patient; and

providing said pulse oximetry data signals to computing circuitry that responds to the received pulse oximetry data signals by identifying a respiratory event of the patient, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a threshold level of oxyhemoglobin desaturation;

wherein the threshold level of oxyhemoglobin desaturation is variable, and the variable threshold level is based on at least one of the following criteria;

peak oxyhemoglobin saturation, nadir, and peak oxyhemoglobin resaturation.

71. A physiological monitoring system comprising:

a pulse oximetry sensor and circuitry that detects oxyhemoglobin saturation and pulse rate of the patient and produces corresponding pulse oximetry data signals;

a patient head movement sensor that produces a head movement and position data signal that indicates position and movement of the patient'"'"'s head;

a microphone that produces a sound data signal that indicates detected sounds produced by said patient;

power means for providing electrical energy to said pulse oximetry sensor, said head movement sensor, and said microphone for operation; and

memory means for storing the data signals produced by said pulse oximetry sensor, said patient head movement sensor, and said microphone;

means for removably affixing said pulse oximetry sensor, said patient head movement sensor, said microphone, said power means and said memory means to the patient'"'"'s forehead, wherein said sensors and power means detect the patient'"'"'s oxyhemoglobin saturation, pulse rate, head movement and sounds, and produce the corresponding data signals, thereby monitoring said patient'"'"'s condition, and whereby all lead wires between the patient and the memory means are eliminated; and

computing circuitry that receives said pulse oximetry data signals and identifies a respiratory event of the patient, wherein the computing circuitry identifies said respiratory event in response to detecting pulse oximetry data signals that indicate a threshold level of oxyhemoglobin desaturation.

72. A system as defined in claim 71, wherein values of the pulse oximetry data signal that indicate a threshold level of oxyhemoglobin desaturation are variable.

73. A system as defined in claim 71, whereby the threshold level of oxyhemoglobin desaturation required to determine a respiratory event is variable.

74. A system as defined in claim 71, wherein the threshold level of oxyhemoglobin desaturation is variable, and wherein the variable threshold level is based on a known relationship between the partial pressure of oxygen and oxyhemoglobin saturation.

75. A system as defined in claim 71, wherein the threshold level of oxyhemoglobin desaturation is variable, and the variable threshold level is based on at least one of the following criteria:

peak oxyhemoglobin saturation, or nadir, or peak oxyhemoglobin resaturation.

76. A system as defined in claim 71, wherein the pulse oximetry sensor comprises an active pulse oximetry sensor that applies positive pressure on the patient.

77. A system as defined in claim 71, wherein said means for affixing said pulse oximetry sensor, said patient head movement sensor, and said power means to the patient'"'"'s forehead comprises an adjustable strap.