Detection of expiratory airflow limitation in ventilated patient

• US 10,064,583 B2
• Filed: 08/07/2013
• Issued: 09/04/2018
• Est. Priority Date: 08/07/2013
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Nakai, Richard, Sanborn, Warren, Hyde, David
• Primary Examiner(s): WESTON, TIFFANY C
• Application Number:
  US13/961,316
• Publication Number:
  US 20150045687A1
• Time in Patent Office: 1,854 Days
• Field of Search: None
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• 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 16/0063 Compressors
• 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 16/12 by mixing different gases
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/0042 in the expiratory circuit
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2202/025 Helium
• CPC Class Codes: A61M 2205/505 Touch-screens; Virtual keyboard or keypads; Virtual buttons; Soft keys; Mouse touches
• CPC Class Codes: A61M 2205/52 with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2230/46 Resistance or compliance of the lungs

Abstract

This disclosure describes systems and methods for monitoring and evaluating data associated with ventilatory parameters to detect expiratory airflow limitation in a ventilated patient. For example, a ventilator may monitor flow and/or pressure during ventilation of the patient. Based on the flow and/or pressure measurements, or ventilatory data derived therefrom, the ventilator may calculate expiratory resistance. Moreover, the ventilator may trend expiratory resistance over time to produce an expiratory resistance waveform. In embodiments, the ventilator may calculate the slope of the expiratory resistance waveform during an initial part of exhalation. If the slope of the expiratory resistance waveform during the initial part of exhalation breaches a defined slope threshold, the ventilator may determine that the patient exhibits expiratory airflow limitation.

Claims

1. A ventilator-implemented method for determining whether a ventilated patient exhibits an expiratory airflow limitation, the method comprising:

delivering a flow of gases to a patient;

monitoring ventilatory parameters;

trending airflow resistance over time during an expiratory phase to produce a resistance waveform, wherein airflow resistance is a measure of frictional forces hampering the delivered flow of gases;

calculating a slope of the resistance waveform for an initial portion of the expiratory phase;

comparing the slope of the initial portion of the expiratory phase of the resistance waveform to a defined slope threshold;

determining that the patient exhibits an expiratory airflow limitation when the slope of the initial portion of the expiratory phase of the resistance waveform is greater than or equal to the defined slope threshold; and

in response to a determination that the patient exhibits the expiratory airflow limitation, adjusting at least one ventilatory setting.

2. The method of claim 1, further comprising:

determining that the patient does not exhibit an expiratory airflow limitation when the slope of the initial portion of the expiratory phase of the resistance waveform is less than the defined slope threshold.

3. The method of claim 1, wherein the airflow resistance is lung resistance.

4. The method of claim 1, wherein the airflow resistance is total resistance.

5. The method of claim 1, further comprising:

determining that the patient exhibits an expiratory airflow limitation when the slope of the resistance waveform is greater than or equal to the defined slope threshold for a threshold number of breaths.

6. The method of claim 1, further comprising:

determining that the patient exhibits expiratory airflow limitation when the slope of the resistance waveform is greater than or equal to the defined slope threshold for a threshold percentage of breaths.

7. The method of claim 1, wherein the defined slope threshold is a lung resistance slope threshold (slope_R_L threshold).

8. A system, comprising:

at least one processor; and

at least one memory, communicatively coupled to the at least one processor and containing instructions that, when executed by the at least one processor, cause a controller to determine whether a ventilated patient exhibits expiratory airflow limitation, the controller comprising;

a gas source for delivering a flow of gases to a patient;

a monitoring module for monitoring ventilatory parameters;

an expiratory resistance detection module for;

calculating airflow resistance during an expiratory phase;

trending airflow resistance over time during the expiratory phase to produce a resistance waveform, wherein airflow resistance is a measure of frictional forces hampering the delivered flow of gases;

an expiratory airflow limitation detection module for;

calculating a slope of the resistance waveform for an initial portion of the expiratory phase;

comparing the slope of the initial portion of the expiratory phase of the resistance waveform to a defined slope threshold; and

determining that the patient exhibits an expiratory airflow limitation when the slope of the initial portion of the expiratory phase of the resistance waveform is greater than or equal to the defined slope threshold; and

a ventilation module for;

in response to the determination that the patient exhibits the expiratory airflow limitation, adjusting at least one ventilatory setting.

9. The system of claim 8, the expiratory airflow limitation detection module further configured for determining that the patient does not exhibit an expiratory airflow limitation when the slope of the initial portion of the expiratory phase of the resistance waveform is less than the defined slope threshold.

10. The system of claim 8, wherein the airflow resistance is lung resistance.

11. The system of claim 8, wherein the airflow resistance is total resistance.

12. The system of claim 8, the expiratory airflow limitation detection module further configured for determining that the patient exhibits an expiratory airflow limitation when the slope of the resistance waveform is greater than or equal to the defined slope threshold for a threshold number of breaths.

13. The system of claim 8, the expiratory airflow limitation detection module further configured for determining that the patient exhibits an expiratory airflow limitation when the slope of the resistance waveform is greater than or equal to the defined slope threshold for a threshold percentage of breaths.

14. The system of claim 8, wherein the defined slope threshold is a total resistance slope threshold (slope_R_TOT threshold).

15. A computer storage device storing instructions that, when executed by a processor, cause a controller to determine whether a ventilated patient exhibits an expiratory airflow limitation comprising:

delivering a flow of gases to a patient;

monitoring ventilatory parameters;

trending airflow resistance over time during an expiratory phase to produce a resistance waveform, wherein airflow resistance is a measure of frictional forces hampering the delivered flow of gases;

calculating a slope of the resistance waveform for an initial portion of the expiratory phase;

comparing the slope of the initial portion of the expiratory phase of the resistance waveform to a defined slope threshold;

determining that the patient exhibits an expiratory airflow limitation when the slope of the initial portion of the expiratory phase of the resistance waveform is greater than or equal to the defined slope threshold;

in response to the determination that the patient exhibits the expiratory airflow limitation, adjusting at least one ventilatory setting.

16. The computer storage device of claim 15, the controller further configured for determining that the patient does not exhibit an expiratory airflow limitation when the slope of the initial portion of the expiratory phase of the resistance waveform is less than the defined slope threshold.

17. The computer storage device of claim 15, wherein the airflow resistance is lung resistance.

18. The computer storage device of claim 15, wherein the airflow resistance is total resistance.

19. The computer storage device of claim 15, the controller further configured for determining that the patient exhibits an expiratory airflow limitation when the slope of the resistance waveform is greater than or equal to the defined slope threshold for a threshold number of breaths.

20. The computer storage device of claim 15, the controller further configured for determining that the patient exhibits an expiratory airflow limitation when the slope of the resistance waveform is greater than or equal to the defined slope threshold for a threshold percentage of breaths.