Method and apparatus for detecting ineffective inspiratory efforts and improving patient-ventilator interaction

• US 9,597,013 B2
• Filed: 11/06/2013
• Issued: 03/21/2017
• Est. Priority Date: 10/20/2004
• Status: Active Grant

• Current Assignee: ResMed Pty Ltd. (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Mulqueeny, Qestra Camille, Nava, Stefano
• Primary Examiner(s): Cheng, Jacqueline
• Assistant Examiner(s): PREMRAJ, ANGELINE L
• Application Number:
  US14/073,337
• Publication Number:
  US 20140066725A1
• Time in Patent Office: 1,231 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0871 Peak expiratory flowmeters
• CPC Class Codes: A61B 5/4205 Evaluating swallowing
• CPC Class Codes: A61M 16/0051 with alarm devices
• 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 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase

Abstract

A method and system for detecting an ineffective effort of a patient being mechanically ventilated by a ventilator comprises (i) monitoring a respiratory flow of air of the patient after said ventilator has cycled; (ii) creating a signal indicative of said flow; (iii) removing artifact from said signal; (iv) monitoring said signal for perturbations; and (v) determining that an ineffective effort has occurred when said perturbation is significant.

Claims

1. A method of detecting an ineffective effort of a patient being mechanically ventilated by a ventilator, the method comprising:

monitoring a respiratory flow of air of the patient during expiration by the patient after said ventilator has cycled and before the ventilator has triggered;

generating a signal indicative of said flow of the patient during expiration;

outputting the generated signal to a processing system;

determining a peak expiratory flow (PEF) of the patient based on the generated signal;

calculating, via a processing system that includes at least one processor, a value of a second derivative of the signal that is indicative of the respiratory flow;

determining an occurrence of a significant declivity within the signal when the value of the second derivative of the signal is greater than a negative threshold value;

detecting perturbations within the generated signal by classifying the perturbations between at least ineffective efforts and non-ineffective efforts based on determination of the occurrence of the significant declivity within the signal; and

adjusting at least one setting of the ventilator based on classification of the ineffective efforts.

2. The method of claim 1, further comprising removing a signal representative of cardiogenic oscillation from the generated signal.

3. The method of claim 2, further comprising down-sampling or noise-filtering the generated signal to remove the signal representative of cardiogenic oscillation from the generated signal.

4. The method of claim 2, further comprising distinguishing cardiogenic oscillations in the generated signal on the basis of amplitude.

5. The method of claim 4, wherein distinguished cardiogenic oscillations in the generated signal are assumed to have an amplitude of less than 4 L per minute.

6. The method of claim 1, further comprising determining whether a cough has occurred.

7. The method of claim 1, further comprising modifying the generated signal by removing signals that are indicative of secretions.

8. The method of claim 1, further comprising applying a noise filter to the generated signal.

9. The method of claim 1, further comprising detecting a local maximum within the generated signal.

10. The method of claim 9, further comprising determining a flow value that is associated with said local maximum.

11. The method of claim 10, further comprising determining that a potential swallow has occurred when the flow value associated with the local maximum is near zero.

12. The method of claim 11, further comprising starting a swallow timer when the flow value associated with the local maximum is near zero.

13. The method of claim 12, further comprising determining that a swallow has occurred when said swallow timer is greater than about 500 ms.

14. The method of claim 1, further comprising determining whether a potential swallow has occurred.

15. The method of claim 1, further comprising determining a time period since onset of a potential swallow.

16. The method of claim 1, further comprising determining that a cough has occurred when the PEF exceeds a threshold.

17. The method of claim 16, whereby said threshold is approximately 200 L per minute.

18. The method of claim 1, further comprising calculating a standard deviation of the second derivative of the generated signal, wherein said negative threshold is a percentage of the standard deviation.

19. The method of claim 18, whereby said percentage is 33%.

20. The method of claim 1, further comprising:

detecting a local minimum in the generated signal; and

determining an end of the significant declivity based on the detected local minimum.

21. The method of claim 20, further comprising determining an amplitude of the significant declivity.

22. The method of claim 21, further comprising determining that a cough has occurred when the amplitude of the significant declivity is greater than a threshold.

23. The method of claim 22, whereby said threshold is the PEF.

24. The method of claim 22, whereby said threshold is 200 L/min.

25. The method of claim 20, further comprising subtracting a flow value at said local minimum from a flow value at a local maximum.

26. The method of claim 1, wherein the adjustment of the at least one setting is automated.