Distinguishing between closed and open airway apneas and treating patients accordingly

• US 8,360,060 B2
• Filed: 05/28/2010
• Issued: 01/29/2013
• Est. Priority Date: 11/05/1993
• Status: Expired due to Fees

• Current Assignee: Resmed Limited (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Berthon-Jones, Michael
• Primary Examiner(s): MATTER, KRISTEN CLARETTE
• Application Number:
  US12/789,976
• Publication Number:
  US 20100242965A1
• Time in Patent Office: 977 Days
• Field of Search: 128/204.18, 12820421-20423, 128/205.11, 128/205.23, 600/484, 600/481, 600/529, 600/533, 600/538
• US Class Current: 128/204.23
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61F 5/56 Devices for preventing snoring by influencing the respiratory system by gas treatment A61M16/00
• CPC Class Codes: A61M 16/0006 with means for creating vibrations in patients' airways
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• 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 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/0875 Connecting tubes
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2230/60 Muscle strain, i.e. measured on the user

Abstract

Methods and apparatus for determining the occurrence of an apnea, patency and/or partial obstruction of the airway are disclosed. Respiratory air flow from a patient is measured to give an air flow signal. The determination of an apnea is performed by calculating the variance of the air flow signal over a moving time window and comparing the variance with a threshold value. One determination of partial obstruction of the airway is performed by detecting the inspiratory part of the air flow signal, scaling it to unity duration and area and calculating an index value of the amplitude of the scaled signal over a mid-portion. Alternatively, the index value is a measure of the flatness of the air flow signal over the mid-portion. One determination of patency of the airway is performed by applying an oscillatory pressure waveform of known frequency to a patient'"'"'s airway, calculating the magnitude of the component of said air flow signal at the known frequency induced by the oscillatory pressure waveform and comparing the calculated magnitude with a threshold value. Alternatively, the air flow signal is analysed to detect the presence of a component due to cardiogenic activity.

Claims

1. A method for treating an airway disorder of a patient using a CPAP apparatus comprising:

delivering an airflow directed toward the patient'"'"'s airway;

determining whether air is flowing in the patient'"'"'s airway by generating a signal representing patient breathing;

if air is flowing in the patient'"'"'s airway, determining whether the patient'"'"'s airway has a flow restriction;

if air is not flowing in the patient'"'"'s airway, initiating an oscillating pressure waveform for a time period to determine whether conditions point to the presence of an obstructive apnea or a central apnea;

increasing the pressure of the delivered airflow in the same manner if (1) there is an airway flow restriction or (2) conditions are indicative of the presence of an obstructive apnea; and

not increasing the pressure of the delivered airflow if (1) air is flowing in the patient'"'"'s airway and the airway is not determined to be flow restricted or (2) conditions point to the presence of a central apnea

wherein a flow restriction or a type of apnea is detected based upon a function of said signal representing patient breathing.

2. The method of claim 1 wherein, upon determining the presence of a flow restriction or determining the presence of an apnea, introducing a delay followed by delivering an airflow with an oscillating pressure waveform.

3. The method of claim 1 wherein the step of determining whether air is flowing in the patient'"'"'s airway includes determining leak and subtracting said leak from said delivered airflow.

4. The method of claim 1 wherein the step of determining whether the patient'"'"'s airway has a flow restriction includes linearizing a signal representing flow in the patient'"'"'s airway.

5. The method of claim 1 wherein at least one condition which points to the presence of an obstructive apnea or a central apnea represents a parameter which exceeds a fixed threshold.

6. The method of claim 1 wherein upon determining the presence of a flow restriction or determining the presence of an apnea, delivering an airflow with an oscillating pressure waveform of known frequency and magnitude.

7. The apparatus of claim 1 wherein parameters relating to airflow are measured at a flow generator.

8. An apparatus for treating an airway disorder of a patient comprising:

a flow sensor for determining whether air is flowing in the patient'"'"'s airway;

a processor coupled to said flow sensor; and

means for delivering airflow directed toward the patient'"'"'s airway;

wherein said processor is programmed

(1) to determine if air is flowing in the patient'"'"'s airway by generating a signal representing patient breathing—

and

(2) if air is flowing in the patient'"'"'s airway, to determine whether the patient'"'"'s airway has a flow restriction;

(3) if air is not flowing in the patient'"'"'s airway, initiating an oscillating pressure waveform for a time period to determine whether conditions point to the presence of an obstructive apnea or a central apnea;

(4) to increase the pressure of the delivered airflow in the same manner if (a) there is an airway flow restriction or (b) conditions are indicative of the presence of an obstructive apnea; and

(5) to not increase the pressure of the delivered airflow if (a) air is flowing in the patient'"'"'s airway and the airway is not determined to be flow restricted or (b) conditions point to the presence of a central apnea

wherein a flow restriction or a type of apnea is detected based upon a function of said signal representing patient breathing.

9. The apparatus of claim 8 wherein upon determining the presence of a flow restriction or determining the presence of an apnea, introducing a delay followed by said means delivering an oscillating pressure waveform.

10. The apparatus of claim 8 wherein determining whether air is flowing in the patient'"'"'s airway includes determining leak and subtracting said leak from said airflow.

11. The apparatus of claim 8 wherein determining whether the patient'"'"'s airway has a flow restriction includes linearizing a signal representing flow in the patient'"'"'s airway.

12. The apparatus of claim 8 wherein at least one condition which points to the presence of an obstructive apnea or a central apnea represents a parameter which exceeds a fixed threshold.

13. The apparatus of claim 8 wherein, upon determining the presence of a flow restriction or determining the presence of an apnea, said means delivering an oscillating pressure waveform of known frequency and magnitude.

14. Using a CPAP device, a method for detecting the presence of a flow restriction or a type of apnea in the patient comprising:

delivering an airflow directed toward the patient'"'"'s airway,

determining whether air is flowing in the patient'"'"'s airway by generating a signal representing patient breathing;

if air is flowing in the patient'"'"'s airway, determining whether the patient'"'"'s airway has a flow restriction; and

if air is not flowing in the patient'"'"'s airway, initiating an oscillating pressure waveform for a time period to determine whether conditions point to the presence of an obstructive apnea or a central apnea;

wherein a flow restriction or a type of apnea is detected based upon a function of said signal representing patient breathing.

15. The method of claim 14 wherein, upon determining the presence of a flow restriction or determining the presence of an apnea, introducing a delay followed by delivering an airflow with an oscillating pressure waveform.

16. The method of claim 14 wherein the step of determining whether air is flowing in the patient'"'"'s airway includes determining leak and subtracting said leak from said delivered airflow.

17. The method of claim 14 wherein the step of determining whether the patient'"'"'s airway has a flow restriction includes linearizing a signal representing flow in the patient'"'"'s airway.

18. The method of claim 14 wherein at least one condition which points to the presence of an obstructive apnea or a central apnea represents a parameter which exceeds a fixed threshold.

19. The method of claim 14 wherein, upon determining the presence of a flow restriction or determining the presence of an apnea, delivering an airflow with an oscillating pressure waveform of known frequency and magnitude.

20. An apparatus for detecting flow restrictions and types of apneas in a patient comprising:

means for delivering an airflow directed toward a patient'"'"'s airway;

a flow sensor for determining whether air is flowing in the patient'"'"'s airway by generating a signal representing patient breathing; and

a processor coupled to said flow sensor and said means for delivering an airflow;

wherein said processor is programmed to detect flow restrictions and apneas and their types

(1) by determining if air is flowing in the patient'"'"'s airway;

(2) if air is flowing in the patient'"'"'s airway, determining whether the patient'"'"'s airway has a flow restriction; and

(3) if air is not flowing in the patient'"'"'s airway, initiating an oscillating pressure waveform for a time period to determine whether conditions point to the presence of an obstructive apnea or a central apnea; and

wherein a flow restriction or a type of apnea is detected based upon a function of said signal representing patient breathing.

21. The apparatus of claim 20 wherein upon determining the presence of a flow restriction or determining the presence of an apnea, introducing a delay followed by said means delivering an oscillating pressure waveform.

22. The apparatus of claim 20 wherein determining whether air is flowing in the patient'"'"'s airway includes determining leak and subtracting said leak from said airflow.

23. The apparatus of claim 20 wherein determining whether the patient'"'"'s airway has a flow restriction includes linearizing a signal representing flow in the patient'"'"'s airway.

24. The apparatus of claim 20 wherein at least one condition which points to the presence of an obstructive apnea or a central apnea represents a parameter which exceeds a fixed threshold.

25. The apparatus of claim 20 wherein upon determining the presence of a flow restriction or determining the presence of an apnea, said means delivering an oscillating pressure waveform of known frequency and magnitude.