Apnea and hypopnea detection

• US 9,668,692 B2
• Filed: 09/06/2013
• Issued: 06/06/2017
• Est. Priority Date: 09/06/2013
• Status: Active Grant

• Current Assignee: Breathe Technologies, Inc. (Baxter International Inc.)
• Original Assignee: Breathe Technologies, Inc. (Baxter International Inc.)
• Inventors: Baloa Welzien, Leonardo Alberto, Ahmad, Samir S., Bambrilla, Enrico
• Primary Examiner(s): Natnithithadha, Navin
• Application Number:
  US14/020,729
• Publication Number:
  US 20150073291A1
• Time in Patent Office: 1,369 Days
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/0871 Peak expiratory flowmeters
• CPC Class Codes: A61B 5/0878 using temperature sensing means
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7282 Event detection, e.g. detecting unique waveforms indicative of a medical condition A61B5/4094, A61B5/4818, A61B5/349, A61B5/0823 take precedence
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/107 in the inspiratory path
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 2205/3344 Measuring or controlling pressure at the body treatment site
• CPC Class Codes: A61M 2205/42 Reducing noise
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient

Abstract

The identification of obstructed breathing, including an apnea condition and a hypopnea condition, is disclosed. A signal representative of a flow rate of therapeutic gas being delivered to the patient is received. A peak flow value and a minimum flow value over a predetermined time window encompassing a plurality of respiration cycles is derived. A polynomial difference equation from the peak flow values and the minimum flow values is generated, and a respiration index from a minimum of the polynomial difference equation is derived. The apnea and/or hypopnea condition is indicated based upon a comparison of the respiration index to a predefined obstruction threshold over a predefined obstruction time period.

Claims

1. A method for identifying obstructed breathing by a patient undergoing continuous positive airway pressure therapy, including at least one of an apnea condition and a hypopnea condition, the method comprising:

receiving a signal representative of a flow rate of therapeutic gas being delivered to the patient for a predetermined time window over a plurality of respiration cycles;

deriving a peak flow value of each of the respiration cycles within the predetermined time window;

deriving a minimum flow value of each of the respiration cycles within the predetermined time window;

generating a polynomial difference function from the peak flow values of a plurality of the respiration cycles in the predetermined window and the minimum flow values of a plurality of the respiration cycles in the predetermined window;

deriving a respiration index from a minimum of the polynomial difference function;

indicating the at least one of the apnea condition and the hypopnea condition based upon a comparison of the respiration index to a predefined obstruction threshold over a predefined obstruction time period; and

actuating a ventilation source of the therapeutic gas in accordance with the indicated at least one of the apnea condition and the hypopnea condition.

2. The method of claim 1, wherein the signal representative of the flow rate is an actual measured flow rate from a flow sensor.

3. The method of claim 1, wherein the signal representative of the flow rate is a derived flow rate from a sensor measuring a respiration condition of the patient.

4. The method of claim 3, wherein the respiration condition is pressure, and the sensor is a pressure sensor.

5. The method of claim 3, wherein the respiration condition is temperature, and the sensor is a thermistor.

6. The method of claim 1, further comprising:

generating a peak flow polynomial function from the peak flow values of each respiration cycle in the predetermined time window; and

generating a minimum flow polynomial function from the minimum flow values of each respiration cycle in the predetermined time window;

wherein the polynomial difference function is generated from the peak flow polynomial function and the minimum flow polynomial function.

7. The method of claim 1, wherein:

the respiration index is an apnea index equal to the minimum of the polynomial difference function; and

the predefined obstruction threshold is an apnea threshold.

8. The method of claim 7, wherein the apnea condition is indicated when the apnea index is less than the apnea threshold.

9. The method of claim 1, wherein:

the respiration index is a hypopnea index that is a fraction of the minimum of the polynomial difference function; and

the predetermined obstruction threshold is a hypopnea threshold.

10. The method of claim 9, wherein the hypopnea condition is indicated when the hypopnea index is less than the apnea threshold.

11. The method of claim 1, wherein the polynomial difference function is a second order polynomial difference function.

12. A method for identifying obstructed breathing by a patient undergoing continuous positive airway pressure therapy, the method comprising:

receiving a signal representative of a flow rate of therapeutic gas being delivered to the patient for a predetermined time window over a plurality of respiration cycles;

deriving a peak flow value of each respiration cycle within the predetermined time window;

deriving a minimum flow value of each respiration cycle within the predetermined time window;

generating a polynomial difference function from the peak flow values of a plurality of the respiration cycles in the predetermined window and the minimum flow values of a plurality of the respiration cycles in the predetermined window;

deriving an apnea index from a minimum of the polynomial difference function;

if the apnea index is less than a predefined apnea threshold over a predefined time period, indicating an apnea condition; and

actuating a ventilation source of the therapeutic gas in accordance with the indicated apnea condition.

13. The method of claim 12, further comprising:

if the apnea index is greater than the predefined apnea threshold over the predefined time period, deriving a hypopnea index corresponding to a fraction of the minimum of the polynomial difference function; and

if the hypopnea index is greater than a predefined hypopnea threshold after an elapse of a hypopnea time threshold, indicating a hypopnea condition.

14. The method of claim 13, further comprising:

if the apnea index is less than the predefined apnea threshold over the predefined time period and if the hypopnea index is less than the predefined hypopnea threshold after an elapse of hypopnea time threshold, indicating a normal respiration condition.

15. The method of claim 12, further comprising:

generating a peak flow polynomial function from the peak flow values of each respiration cycle in the predetermined time window; and

generating a minimum flow polynomial function from the minimum flow values of each respiration cycle in the predetermined time window;

wherein the polynomial difference function is generated from the peak flow polynomial function and the minimum flow polynomial function.

16. The method of claim 12, wherein the signal representative of the flow rate is an actual measured flow rate from a flow sensor.

17. The method of claim 12, wherein the polynomial difference function is a second order polynomial difference function.

18. The method of claim 12, wherein the signal representative of the flow rate is a derived flow rate from a sensor measuring a respiration condition of the patient.

19. An article of manufacture comprising a program storage medium readable by a data processing apparatus, the medium tangibly embodying one or more programs of instructions executable by the data processing apparatus to perform a method for identifying obstructed breathing by a patient undergoing continuous positive airway pressure therapy, including at least one of an apnea condition and a hypopnea condition, the method comprising:

receiving from a signal representative of a flow rate of therapeutic gas being delivered to the patient for a predetermined time window over a plurality of respiration cycles;

deriving a peak flow value of each respiration cycle within the predetermined time window;

deriving a minimum flow value of each respiration cycle within the predetermined time window;

generating a polynomial difference function from the peak flow values of a plurality of the respiration cycles in the predetermined window and the minimum flow values of a plurality of the respiration cycles in the predetermined window;

deriving a respiration index from a minimum of the polynomial difference function;

indicating the at least one of the apnea condition and the hypopnea condition based upon a comparison of the respiration index to a predefined obstruction threshold over a predefined obstruction time period; and

actuating a ventilation source of the therapeutic gas in accordance with the indicated at least one of the apnea condition and the hypopnea condition.

20. The article of manufacture of claim 19 wherein:

the respiration index is an apnea index equal to the minimum of the polynomial difference function;

the predefined obstruction threshold is an apnea threshold; and

the apnea condition is indicated when the apnea index is less than the apnea threshold.

21. The article of manufacture of claim 19, wherein:

the respiration index is a hypopnea index that is a fraction of the minimum of the polynomial difference function;

the predetermined obstruction threshold is a hypopnea threshold; and

the hypopnea condition is indicated when the hypopnea index is less than the apnea threshold.

22. The article of manufacture of claim 19, wherein the signal representative of the flow rate is an actual measured flow rate from a flow sensor.

23. The article of manufacture of claim 19, wherein the signal representative of the flow rate is a derived flow rate from a sensor measuring a respiration condition of the patient.

24. The article of manufacture of claim 19, wherein the polynomial difference function is a second order polynomial difference function.