Apparatus for the diagnosis of sleep apnea

• US 5,891,023 A
• Filed: 01/27/1997
• Issued: 04/06/1999
• Est. Priority Date: 08/19/1992
• Status: Expired due to Term

• Current Assignee: Lawrence A. Lynn
• Original Assignee: Lawrence A. Lynn
• Inventors: Lynn, Lawrence A.
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US08/789,460
• Time in Patent Office: 799 Days
• Field of Search: 128/633, 128/670, 128/671, 128/716, 128/719, 128/721, 600/323, 600/324, 600/333, 600/483, 600/484, 600/529, 600/534, 600/537, 600/538, 600/595
• US Class Current: 600/323
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 7/003 Detecting lung or respiration noise

Abstract

A device for diagnosing sleep apnea by identifying desaturation and resaturation events in oxygen saturation of a patient'"'"'s blood. The slope of the events is determined and compared against various information to determine sleep apnea.

Claims

1. A method for diagnosing sleep apnea comprising:

disposing an oximeter adjacent to a single human body part and recording a continuous measurement of oxygen saturation as a function of time to derive an oxygen saturation waveform;

identifying a first event comprising a desaturation event in which said oxygen saturation falls away from a baseline level by a predetermined amount and for a predetermined time;

identifying a second event comprising a resaturation event in which said oxygen saturation rises immediately following said desaturation, the presence of a consecutive desaturation event and resaturation event defining a couplet event;

identifying a third event comprising a second desaturation event occurring within a predetermined time interval after said resaturation and in which said oxygen saturation falls away from near said baseline level by near said predetermined amount, the presence of said first, second and third consecutive events defining a triplet event;

determining the number of said couplet events occurring during at least a portion of said measurement; and

assessing the probability that a patient has sleep apnea based on said number of couplet events.

2. The method of claim 1 wherein said interval is defined as less than 2 minutes.

3. A method as in claim 1 further comprising the step of determining the number of said triplet events occurring during at least a second portion of said measurement and assessing the probability that a patient has sleep apnea based on said number of triplet events.

4. A method for diagnosing sleep apnea comprising:

determining an oxygen saturation of a patient'"'"'s blood;

identifying a first desaturation event in which said oxygen saturation falls away from a baseline level by at least a predetermined amount;

calculating a slope of said desaturation event represented as the rate of change per unit of time of the fall of oxygen saturation;

comparing said calculated slope with at least one other value of slope of another desaturation event determined at a different time than said first desaturation event;

defining an interval of time after said first desaturation event;

when said other desaturation event occurs within said interval, determining whether the slope of at least an initial portion of said other desaturation event is greater than the initial portion of said first desaturation event, whereby the effect of said preceding desaturation event on the slope of the other desaturation event is determined; and

diagnosing sleep apnea based on said comparing.

5. A method for identification of sleep apnea comprising the steps of:

disposing an oximeter adjacent to a single human body part and recording continuous measurement of oxygen saturation as a function of time to derive an oxygen saturation waveform as a function of time;

repetitively calculating slopes along said oxygen saturation waveform;

continuously comparing said slopes to a first predetermined range of slopes, and identifying a first slope comprising a desaturation slope which falls within said first predetermined range of slopes;

further comparing said slopes immediately following said desaturation slope to a second predetermined range of slopes and identifying a second slope comprising a resaturation slope which falls within the second predetermined range of slopes;

determining an area below a curve defined by the desaturation slope;

determining an area below the curve defined by the resaturation slope;

comparing said desaturation slope area with said resaturation slope area and using said comparison to determine said diagnosis of sleep apnea.

6. A sleep apnea treatment device, comprising:

an oximeter, having an output signal indicating an oxygen saturation of a patient'"'"'s blood;

a processor element, responsive to said signal indicating oxygen saturation, for identifying at least two consecutive desaturation events in which said oxygen saturation falls away from a base line level by a predetermined amount and for a predetermined time;

said processor element identifying each desaturation event when it also includes a resaturation immediately following said desaturation event to thereby define a couplet event;

said processor element calculating a slope of each said desaturation event of said couplet event representing a rate of change per unit of time of fall of oxygen saturation;

said processor element calculating a slope of each said resaturation event of said couplet event representing a rate of change per unit of time of rise of oxygen saturation; and

said processor element comparing said desaturation slopes with each other and for comparing said resaturation slopes with each other to identify slope similarity, and using said slope similarity to diagnose sleep apnea.

7. A sleep apnea diagnostic device, comprising:

an oximeter, having an output signal indicating an oxygen saturation of a patient'"'"'s blood;

a processor element, responsive to said signal indicating oxygen saturation, identifying at least two consecutive desaturation events, in which said oxygen saturation falls away from a baseline level by a predetermined amount and for a predetermined time;

said processor element identifying each desaturation event which also includes a resaturation that occurs immediately following said desaturation event to thereby define a couplet event;

said processor element calculating a slope of each said identified desaturation event representing a rate of change per unit of time of fall of oxygen saturation;

said processor element calculating a slope of each said identified resaturation event representing a rate of change per unit of time of rise of oxygen saturation;

said processor element calculating a mathematical index of at least three said identified desaturation and resaturation slopes; and

using at least the mathematical index to diagnose sleep apnea.

8. A method for evaluating a patient for diagnosis of sleep apnea using an oximeter having a sensor, the method comprising the steps of:

1) disposing said oximeter sensor adjacent a human body part, said oximeter having an output signal indicating an oxygen saturation of a patient'"'"'s blood;

2) generating an oxygen saturation waveform as a function of time;

3) using a computer for;

a) repetitively calculating positive and negative oxygen saturation slopes along said oxygen saturation waveform;

b) determining whether at least three consecutive negative slopes interrupted by positive slopes occur where a time interval between each positive slope and the next negative slope following said each positive slope is less than a predetermined time interval, said occurrence defining a slope cluster complex,

c) determining whether the value of said at least three negative slopes fall within a predetermined range, and

d) using both said determinations to determine said diagnosis of sleep apnea.

9. The method of claim 8 wherein said predetermined time interval is two minutes.

10. The method of claim 8 further including using a computer for;

a) comparing said negative slopes to said positive slopes,

b) determining whether at least a portion of said negative slopes define lower rates of change of oxygen saturation than are defined by said positive slopes, and

c) using said determination to determine said diagnosis of sleep apnea.

11. The method of claim 8 further including using a computer for the steps of:

a) calculating a mathematical index of said negative slopes in relation to said positive slopes;

b) determining whether at least a portion of said mathematical indices are within a predetermined range for said mathematical index; and

c) using said determination to determine said diagnosis of sleep apnea.

12. The method of claim 11 wherein said mathematical index is a ratio having a range of about 3.5 to 10.5.

13. The method of claim 8 further including the steps of:

a) upon both said determinations in steps b) and c), initiating a preset positive pressure to the nasal pharynx of said patient with a positive pressure device.

14. The method of claim 13 further including using a computer for the steps of:

after the initiation of the positive pressure to the pharynx, determining whether a cluster complex reoccurs; and

if said slope cluster complex reoccurs, repeating step d) at an increased level of said nasal positive pressure.

15. The method of claim 14 further including using a computer for the steps of:

determining whether no slope cluster complex has occurred for a predetermined period and, if so, withdraw at least a portion of said positive pressure.

16. A method for determining an effective preset fixed pressure setting of one of a fixed single level and a fixed dual level positive pressure generating device for the long term maintenance treatment of sleep apnea, the method using an oximeter having a sensor, the method comprising the steps of:

1) disposing said oximeter sensor adjacent a human body part, said oximeter having an output signal indicating an oxygen saturation of a patient'"'"'s blood and a processor element responsive to said signal indicating oxygen saturation and generating an oxygen saturation waveform as a function of time;

2) using a computer for repetitively calculating positive and negative slopes along said oxygen saturation waveform;

3) determining whether two consecutive negative slopes interrupted by positive slopes occur where the time interval between each positive slope is less than a predetermined interval; and

4) determining whether the value of said two negative slopes are within a predetermined range of each other so as to be characteristic of a slope cluster complex and using both said determinations to diagnose sleep apnea;

5) upon both said determinations in steps

     3) and

     4) initiating a preset amount of positive pressure to the nasal pharynx,

6) repetitively performing steps

     3) and

     4) to determine an effective positive pressure level which eliminates substantially all slope cluster complexes, and

7) using said computer to indicate an effective fixed preset positive setting for long term use of a pressure generating device in the treatment of sleep apnea.

17. A method as in claim 16 further including the step of using said computer to automatically preset said determined fixed pressure on said pressure generating device for long term use.

18. A method for diagnosing sleep apnea said apnea producing at least one grouping of at least one oxygen saturation parameter, the method comprising:

1) disposing said oximeter sensor adjacent a human body part, said oximeter having an output signal indicating an oxygen saturation of a patient'"'"'s blood and a processor element responsive to said signal indicating oxygen saturation and generating an oxygen saturation waveform as a function of time; and

2) using a computer for;

a) determining the presence or absence of at least one grouping of repeating parameters along said oxygen saturation waveform,

b) evaluating said at least one grouping and comparing said evaluation result to a range of evaluation results known to be consistent with sleep apnea,

c) determining the intervening interval between consecutive repeating parameters within said grouping,

d) comparing said intervening interval to a limiting range of intervening intervals known to be consistent with a sleep apnea related grouping, and

f) determining the diagnosis of sleep apnea based on at least said evaluation result and said comparing said intervening interval.

19. A method as in claim 18 wherein said repeating parameter is the slope of the measured oxygen saturation as a function of time.

20. A method as in claim 18 wherein said repeating parameter is a negative deflection of the waveform and wherein the intervening time interval comprises the interval between said negative deflection and the next negative deflection.

21. A method as in claim 18 wherein two different parameters are compared.

22. A method as in claim 21 wherein one of said parameters is a positive deflection of the waveform and wherein another of said parameters is a negative deflection of the waveform occurring after said positive deflection, the intervening interval comprising the interval between said positive deflection and said negative deflection.

23. A method for diagnosing sleep apnea, said apnea producing at least one grouping of at least one oxygen saturation parameter, the method comprising:

1) disposing said oximeter sensor adjacent a human body part, said oximeter having an output signal indicating an oxygen saturation of a patient'"'"'s blood and a processor element responsive to said signal indicating oxygen saturation and generating an oxygen saturation waveform as a function of time; and

2) using a computer for;

a) determining the presence or absence of at least one grouping of a repeating parameter along said oxygen saturation waveform,

b) evaluating said repeating parameter and comparing said evaluation result to a range of evaluation results known to be consistent with sleep apnea,

c) determining the intervening time interval between consecutive repeating parameters within said grouping,

d) comparing said intervening time interval to a limiting range of intervening time intervals known to be consistent with an sleep apnea related grouping,

e) determining the frequency of said repeating parameters wherein both said evaluation result and said intervening time intervals are consistent with said parameters being caused by sleep apnea, and

f) determining the diagnosis of sleep apnea based on at least said frequency determination.

24. A method for diagnosing sleep apnea, said apnea producing at least one grouping of at least one oscillating oxygen saturation parameter, the method comprising:

1) disposing said oximeter sensor adjacent a human body part, said oximeter having an output signal indicating an oxygen saturation of a patient'"'"'s blood and a processor element responsive to said signal indicating oxygen saturation and generating an oxygen saturation waveform as a function of time; and

2) using a computer for;

a) determining the presence or absence of said at least one grouping of said oscillating parameter along said oxygen saturation waveform,

b) evaluating said grouping and comparing an evaluation result to a range of evaluation results known to be consistent with sleep apnea,

c) determining the intervening interval between consecutive oscillating parameters within said grouping,

d) comparing said intervening interval to a predetermined range of intervening intervals known to be consistent with a sleep apnea related grouping,

e) determine the frequency of said oscillating parameters wherein both said evaluation result and said intervening intervals are consistent with said oscillating parameters being caused by sleep apnea, and

f) determining the diagnosis of sleep apnea based on at least said frequency determination.

25. A method as in claim 24 wherein said oscillating parameter comprises a negative oxygen saturation followed by a positive deflection of the oxygen saturation.

26. A device for diagnosing the sleep apnea disorder in a patient, comprising:

a sensing unit capable of measuring a respiratory parameter during sleep, said respiratory parameter being of the type which has consecutive cycles of variation in said parameter indicative of a sleep apnea disorder and wherein each said consecutive cycle is induced by a corresponding consecutive apnea; and

,

a processor operating to;

(a) record said parameter to derive a timed waveform indicative of said parameter,

(b) identify at least one portion of said waveform in which said cycles are closely spaced to each other and define a cluster of said cycles, said cluster corresponding to a plurality of closely spaced apneas, and

(c) diagnose sleep apnea based at least on said identifying of said cluster.

27. The device of claim 26 wherein said parameter is oxygen saturation of arterial blood.

28. The device of claim 27 wherein said cycle comprises a fall in oxygen saturation coupled to a rise in oxygen saturation.

29. The device of claim 28 wherein said fall in saturation defines a desaturation slope and wherein said desaturation slope falls within a specific slope range.

30. The device of claim 29 wherein said cluster includes at least three of said desaturation slopes.

31. The device of claim 30 wherein said cluster includes at least three of said resaturation slopes.

32. The device of claim 28 wherein said rise in saturation defines a resaturation slope and wherein said resaturation slope falls within a specific slope range.

33. The device of claim 26 wherein said cluster includes at least three of said cycles.

34. The device of claim 26 wherein, within said cluster, each consecutive cycle occurs within a maximum interval of the preceding cycle.

35. The device of claim 34 wherein said maximum interval is two minutes.

36. The device of claim 26 wherein said parameter is at least one property of exhaled gas.

37. The device of claim 36 wherein said parameter is maximum partial pressure of the carbon dioxide component of said exhaled gas.

38. A device for diagnosing a sleep apnea disorder in a patient, comprising:

a sensing unit and a processor, said device being capable of measuring a respiratory parameter during sleep and capable of recording said parameter as a function of time to derive a timed waveform of said parameter, said parameter being of the type wherein said sleep apnea disorder causes consecutive events of variation along said waveform, said events having a similar configuration, and wherein each of said consecutive events is induced by a corresponding consecutive apnea, said processor operating to;

(a) identify at least one portion of said waveform in which said events are closely spaced to each other to define a cluster of said events, said cluster corresponding to a cluster of closely spaced apneas, and

(b) diagnose sleep apnea based at least on said identifying of said cluster.

39. The device of claim 38 wherein said parameter is the oxygen saturation of arterial blood.

40. The device of claim 39 wherein said event comprises a fall in said oxygen saturation.

41. The device of claim 40 wherein said fall in saturation defines a desaturation slope and wherein said desaturation slope falls within a specific slope range.

42. The device of claim 41 wherein said cluster includes at least three of said desaturation slopes.

43. The device of claim 39 wherein said event comprises a rise in said oxygen saturation.

44. The device of claim 43 wherein said rise in saturation defines a resaturation slope and wherein said resaturation slope falls within a specific slope range.

45. The device of claim 44 wherein said cluster includes at least three of said resaturation slopes.

46. The device of claim 39 wherein said event comprises a fall in oxygen saturation coupled to a rise in oxygen saturation.

47. The device of claim 38 wherein, within said cluster, each consecutive event occurs within a maximum interval of the preceding event.

48. The device of claim 47 wherein said maximum interval is two minutes.

49. The device of claim 38 wherein said parameter is at least one property of exhaled gas.

50. The device of claim 49 wherein said parameter is the maximum partial pressure of carbon dioxide component of said exhaled gas.

51. A device for diagnosing a sleep apnea disorder in a patient, the device comprising an oximeter and a processor, said device being capable of measuring arterial oxygen saturation during sleep and of recording said saturation as a function of time to derive a timed waveform of oxygen saturation, said processor operating to:

(a) repetitively calculate slopes along said oxygen saturation waveform;

(b) repetitively compare said slopes to a first predetermined range of slopes, and to identify a first slope comprising a desaturation slope which falls within said first predetermined range of slopes;

(c) further compare said slopes immediately following said desaturation slope to a second predetermined range of slopes and to identify a second slope comprising a resaturation slope which falls within the second predetermined range of slopes, said desaturation and said resaturation comprising a coupled event;

(d) repetitively perform operations a through c to repetitively identify additional coupled events said waveform;

(e) identify along at least one portion of said waveform wherein said events are closely spaced to each other to define a cluster of said events;

(f) diagnose sleep apnea based on at least said identifying of said cluster.