Gas supply device for sleep apnea

• US 6,761,167 B1
• Filed: 11/08/2001
• Issued: 07/13/2004
• Est. Priority Date: 02/12/1999
• Status: Expired due to Term

• Current Assignee: Covidien AG (Medtronic Plc)
• Original Assignee: Mallinckrodt Developpement France
• Inventors: Nicolazzi, Pascal, Griller Lanoir, Véronique, Nadjafizadeh, Hossein
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US09/913,220
• Time in Patent Office: 978 Days
• Field of Search: 128/204.18, 128/204.21, 128/204.23
• US Class Current: 128/204.23
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit

Abstract

Methods and apparatus for controlling air supplied under pressure to a patient suffering from sleep disorders such as apnoea. Controlled pressurized air is supplied to the patient'"'"'s upper anatomical airways by the apparatus according to the methods of the present invention. The apparatus measures and/or calculates the inspiratory air flow, volume and pressure to the airway. The apparatus further determines whether to increase or decrease the airway pressure based on a determination of several factors, such as the occurrence events representing a sleep problem, duration of inspiratory air flow, correspondence of the inspiratory air flow curve to a sinusoidal curve, air leakage and acoustical vibrations. Occurrences of events representing a sleep problem may be stored by the apparatus and read by a clinician at a later date.

Claims

1. A method of controlling an apparatus for supplying air pressure to an airway of patient, comprising:

providing a flow of air under a maintenance pressure to a patient;

determining a pressure of the flow of air to the patient;

determining a rate of an inspiratory flow of air to the patient during a current respiratory cycle of the patient;

determining a volume of the inspiratory flow of air during the current respiratory cycle;

determining a duration of the inspiratory flow of air during the current respiratory cycle;

determining a duration of the current respiratory cycle;

determining whether the current respiratory cycle is a valid respiratory cycle, wherein the current respiratory cycle is determined as valid when the rate of the inspiratory flow of air is greater than a inspiratory flow rate threshold, the volume of the inspiratory flow of air is greater than an inspiratory volume threshold, the duration of the inspiratory flow is within an inspiratory duration interval and the respiratory cycle duration is within a respiratory cycle duration interval;

incrementing a respiratory cycle counter for each valid respiratory cycle since a last pressure adjustment;

detecting an event representing a sleep problem;

setting a problem appearance indicator to a problem appearance state when a sleep problem event is detected;

setting the problem appearance indicator to a problem absence state when a sleep problem event is not detected;

incrementing a problem appearance counter for each successive change of the problem appearance indicator from the problem absence state to the problem appearance state; and

increasing the pressure of the flow of air to the patient above the maintenance pressure when a current respiratory cycle has been determined to be a valid respiratory cycle, when the respiratory cycle counter is greater than a respiratory cycle threshold and when the problem appearance counter is greater than or equal to a problem appearance threshold.

2. The method according to claim 1, wherein detecting an event representing a sleep problem includes:

determining an equivalent sinusoidal curve corresponding to an inspiratory flow rate curve of a valid respiratory cycle;

calculating a correlation criterion between the inspiratory flow rate curve and the equivalent sinusoidal curve;

detecting an event representing a sleep problem when the calculated correlation criterion is less than a correlation criterion threshold;

calculating a surface criterion proportional to the ratio of an area delimited by the inspiratory flow rate curve to an area delimited by the equivalent sinusoidal curve; and

detecting an event representing a sleep problem when the calculated surface criterion is less than a surface criterion threshold.

3. The method according to claim 1, further comprising:

setting a high pressure time counter to zero when the pressure of the flow of air is less than a high pressure threshold;

incrementing the high pressure time counter when the pressure of the flow of air is not less than the high pressure threshold; and

reducing the pressure of the of the flow of air to a safety pressure value when the value of the high pressure time counter is greater than a maximum high pressure time threshold.

4. The method according to claim 3, further comprising setting the high pressure threshold to between about ten mbar and about twenty-five mbar, setting the maximum high pressure time threshold to between about one minute and about one hundred minutes, and setting safety pressure value to about eight mbar.

5. The method according to claim 1, further comprising measuring a leakage of flow of air to the patient during the current respiratory cycle, and maintaining the pressure of the flow of air to the patient when the measured air leakage is greater than a leakage level threshold.

6. The method according to claim 5, further comprising setting the leakage level threshold to substantially equal to an additive leakage value summed with a leakage coefficient multiplied by the measured flow of air to the patient.

7. The method according to claim 5, further comprising setting the additive leakage coefficient between about zero liters/minute and about one-hundred liters/minute, and setting the leakage coefficient between about zero liters/minute-mbar and about ten liters/minute-mbar.

8. The method according to claim 1, further comprising detecting oscillations of the inspiratory flow of air to the patient, analyzing the detected oscillations so as to identify acoustic vibrations within an acoustic frequency range, and increasing the pressure of the flow of air to the patient when acoustic vibrations are identified.

9. The method according to claim 8, further comprising setting the acoustic frequency range to between about thirty hertz and about three-hundred hertz.

10. The method according to claim 1, further comprising storing a chronology of each detected event representing a sleep problem, and reading the stored chronology.

11. The method according to claim 1, further comprising setting the respiratory cycle threshold to between about one and about 255.

12. The method according to claim 11, further comprising setting the respiratory cycle threshold to about ten.

13. The method according to claim 1, further comprising setting the problem appearance threshold to between about one and about one-hundred.

14. The method according to claim 13, further comprising setting the problem appearance threshold to about one.

15. The method according to claim 1, wherein increasing the pressure of the flow of air to the patient above the maintenance pressure includes increasing the pressure in an amount less than about ten mbar.

16. The method according to claim 15, wherein increasing the pressure of the flow of air includes increasing the pressure by about 0.3 mbar.

17. The method according to claim 1, further comprising setting the inspiratory flow rate threshold to about fifty ml/s, and setting the inspiratory volume threshold to about 0.05 liters.

18. The method according to claim 1, further comprising setting the inspiratory duration interval to about 0.5 seconds to about six seconds, and setting the respiratory cycle duration interval to about 1.5 seconds to about twenty seconds.

19. A method for supplying air under pressure to a patient, comprising:

providing a flow of air at a pressure to a patient;

determining a pressure of the flow of air to the patient;

determining a rate of an inspiratory flow of air to the patient during a current respiratory cycle of the patient;

determining a volume of the inspiratory flow of air during the current respiratory cycle;

determining a duration of the inspiratory flow of air during the current respiratory cycle;

determining a duration of the current respiratory cycle;

determining whether the current respiratory cycle is a valid respiratory cycle, wherein the current respiratory cycle is determined as valid when the rate of the inspiratory flow of air is greater than a inspiratory flow rate threshold, the volume of the inspiratory flow of air is greater than an inspiratory volume threshold, the duration of the inspiratory flow is within an inspiratory duration interval and the respiratory cycle duration is within a respiratory cycle duration interval;

incrementing a respiratory cycle counter for each valid respiratory cycle since a last pressure adjustment;

detecting an event representing a sleep problem;

setting a problem appearance indicator to a problem appearance state when a sleep problem event is detected;

setting the problem appearance indicator to a problem absence state when a sleep problem event is not detected;

incrementing a problem appearance counter for each successive change of the problem appearance indicator from the problem absence state to the problem appearance state;

setting a high pressure time counter to zero when the pressure of the flow of air is less than a high pressure threshold;

incrementing the high pressure time counter when the pressure of the flow of air is not less than the high pressure threshold;

measuring a leakage of air flow to the patient during the current respiratory cycle;

increasing the pressure of the flow of air to the patient when a current respiratory cycle has been determined to be a valid respiratory cycle, when the respiratory cycle counter is greater than a respiratory cycle threshold, when the problem appearance counter is greater than or equal to a problem appearance threshold and when the measured air leakage less than a leakage level threshold; and

reducing the pressure of the of the flow of air to a safety pressure value when the value of the high pressure time counter is greater than a maximum high pressure time threshold.

20. The method according to claim 19, wherein detecting an event representing a sleep problem includes:

determining an equivalent sinusoidal curve corresponding to an inspiratory flow rate curve of a valid respiratory cycle;

calculating a correlation criterion between the inspiratory flow rate curve and the equivalent sinusoidal curve;

detecting an event representing a sleep problem when the calculated correlation criterion is less than a correlation criterion threshold;

calculating a surface criterion proportional to the ratio of an area delimited by the inspiratory flow rate curve to an area delimited by the equivalent sinusoidal curve; and

detecting an event representing a sleep problem when the calculated surface criterion is less than a surface criterion threshold.

21. The method according to claim 20, further comprising detecting oscillations of the inspiratory flow of air to the patient, analyzing the detected oscillations so as to identify acoustic vibrations within an acoustic frequency range, and increasing the pressure of the flow of air to the patient when acoustic vibrations are identified.

22. An apparatus for supplying air pressure to a patient, comprising:

means for providing a flow of air under a maintenance pressure to an airway of a patient;

means for determining a pressure of the flow of air to the patient;

means for determining a rate of an inspiratory flow of air to the patient during a current respiratory cycle of the patient;

means for determining a volume of the inspiratory flow of air during the current respiratory cycle;

means for determining a duration of the inspiratory flow of air during the current respiratory cycle;

means for determining a duration of the current respiratory cycle;

means for determining whether the current respiratory cycle is a valid respiratory cycle, wherein the current respiratory cycle is determined as valid when the rate of the inspiratory flow of air is greater than a inspiratory flow rate threshold, the volume of the inspiratory flow of air is greater than an inspiratory volume threshold, the duration of the inspiratory flow is within an inspiratory duration interval and the respiratory cycle duration is within a respiratory cycle duration interval;

means for incrementing a respiratory cycle counter for each valid respiratory cycle since a last pressure adjustment;

means for detecting an event representing a sleep problem;

means for setting a problem appearance indicator to a problem appearance state when a sleep problem event is detected;

means for setting the problem appearance indicator to a problem absence state when a sleep problem event is not detected;

means for incrementing a problem appearance counter for each successive change of the problem appearance indicator from the problem absence state to the problem appearance state; and

means for increasing the pressure of the flow of air to the patient above the maintenance pressure when a current respiratory cycle has been determined to be a valid respiratory cycle, when the respiratory cycle counter is greater than a respiratory cycle threshold and when the problem appearance counter is greater than or equal to a problem appearance threshold.

23. The apparatus of claim 22, further comprising a detected event chronology memory.

24. The apparatus of claim 22, wherein the means for detecting an event representing a sleep problem includes:

means for determining an equivalent sinusoidal curve corresponding to an inspiratory flow rate curve of a valid respiratory cycle;

means for calculating a correlation criterion between the inspiratory flow rate curve and the equivalent sinusoidal curve;

means for detecting an event representing a sleep problem When the calculated correlation criterion is less than a correlation criterion threshold;

means for calculating a surface criterion proportional to the ratio of an area delimited by the inspiratory flow rate curve to an area delimited by the equivalent sinusoidal curve; and

means for detecting an event representing a sleep problem when the calculated surface criterion is less than a surface criterion threshold.

25. The apparatus of claim 22, further comprising:

means for setting a high pressure time counter to zero when the pressure of the flow of air is less than a high pressure threshold;

means for incrementing the high pressure time counter when the pressure of the flow of air is not less than the high pressure threshold; and

means for reducing pressure of the of the flow of air to a safety pressure value when the value of the high pressure time counter is greater than a maximum high pressure time threshold.

26. The apparatus of claim 22, further comprising means for measuring a leakage of flow of air to the patient during the current respiratory cycle, and means for maintaining the pressure of the flow of air to the patient when the measured air leakage is greater than a leakage level threshold.

27. The apparatus of claim 26, further comprising means for setting the leakage level threshold to substantially equal to an additive leakage value summed with a leakage coefficient multiplied by the measured flow of air to the patient.

28. The apparatus of claim 22, further comprising means for detecting oscillations of the inspiratory flow of air to the patient, means for analyzing the detected oscillations so as to identify acoustic vibrations within an acoustic frequency range, and means for increasing the pressure of the flow of air to the patient when acoustic vibrations are identified.