Leak determination in a breathing assistance system

• US 8,707,952 B2
• Filed: 04/29/2010
• Issued: 04/29/2014
• Est. Priority Date: 02/10/2010
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Bernadet, Olivier, Jourdain, Cdric
• Primary Examiner(s): DOUGLAS, STEVEN O
• Application Number:
  US12/769,876
• Publication Number:
  US 20110196251A1
• Time in Patent Office: 1,461 Days
• Field of Search: 128/202.22, 128/204.18, 12820421-20423, 128/200.24
• US Class Current: 128/204.23
• CPC Class Codes: A61M 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/0063 Compressors
• 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 16/026 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 16/04 Tracheal tubes catheters in general A61M25/00
• CPC Class Codes: A61M 16/0666 Nasal cannulas or tubing devices for improving normal breathing through the nose A61F5/08; nose filters A62B23/06; outside holding devices A61M25/02
• CPC Class Codes: A61M 16/0883 Circuit type
• CPC Class Codes: A61M 16/20 Valves specially adapted to medical respiratory devices
• CPC Class Codes: A61M 2016/0015 inhalation detectors
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0027 pressure meter
• CPC Class Codes: A61M 2016/003 with a flowmeter
• CPC Class Codes: A61M 2016/0033 electrical
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• 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

Abstract

Systems and methods for estimating a leak flow in a breathing assistance system including a ventilation device connected to a patient are provided. Data of a flow waveform indicating the flow of gas between the ventilation device and the patient is accessed. A specific portion of the flow waveform is identified, and a linear regression of the identified portion of the flow waveform is performed to determine an estimated leak flow in the breathing assistance system.

Claims

1. A breathing assistance system for providing breathing assistance to a patient, comprising:

a pneumatic system for providing breathing assistance to a patient; and

a controller configured to control one or more operational parameters of the pneumatic system, the controller configured to estimate a leak flow in a breathing assistance system including a ventilation device connected to a patient by;

accessing data of a flow waveform indicating the flow of gas between the ventilation device and the patient;

identifying a specific portion of the flow waveform as a steady phase portion; and

performing a linear regression of the identified portion of the flow waveform to determine an estimated leak flow in the breathing assistance system;

wherein identifying the steady phase portion comprises;

identifying a reference period of the flow waveform;

determining a representative flow rate for the reference period;

determining a series of one or more consecutive qualifying periods of the flow waveform having representative flow rates that vary from the representative flow rate for the reference period by less than a predetermined amount; and

defining the steady phase portion as including the reference period and the series of one or more consecutive qualifying periods.

16. A breathing assistance system according to claim 1, wherein the controller is further configured to control at least one of the operational parameters of the pneumatic system based at least on the estimated leak flow.

17. A breathing assistance system according to claim 1, wherein identifying the specific portion of the flow waveform comprises determining a portion of the flow waveform having a flow variation within a predetermined variation threshold.

2. A controller for a breathing assistance system, the controller including logic instructions embodied in tangible computer readable media and executable by one or more processors to:

access data of a flow waveform indicating the flow of gas between the ventilation device and the patient;

identify a specific portion of the flow waveform as a steady phase portion; and

perform a linear regression of the identified portion of the flow waveform to determine an estimated leak flow in the breathing assistance system;

wherein identifying the steady phase portion comprises;

identifying a reference period of the flow waveform;

determining a representative flow rate for the reference period;

determining a series of one or more consecutive qualifying periods of the flow waveform having representative flow rates that vary from the representative flow rate for the reference period by less than a predetermined amount; and

defining the steady phase portion as including the reference period and the series of one or more consecutive qualifying periods.

3. A method for estimating a leak flow in a breathing assistance system including a ventilation device connected to a patient, the method comprising:

accessing data associated with a flow waveform indicating the flow of gas between the ventilation device and the patient;

identifying a steady phase portion near the end of an exhalation phase; and

performing a linear regression of the identified portion of the flow waveform to determine an estimated leak flow in the breathing assistance system;

wherein identifying the steady phase portion comprises;

identifying a reference period of the flow waveform;

determining a representative flow rate for the reference period;

determining a series of one or more consecutive qualifying periods of the flow waveform having representative flow rates that vary from the representative flow rate for the reference period by less than a predetermined amount; and

defining the steady phase portion as including the reference period and the series of one or more consecutive qualifying periods.

5. A method according to claim 3, wherein identifying the specific portion of the flow waveform further comprises identifying an end portion of an exhalation phase of the flow waveform.

6. A method according to claim 3, wherein identifying the steady phase portion further comprises determining a portion of the flow waveform having a flow variation within a predetermined variation threshold.

7. A method according to claim 3, wherein identifying the steady phase portion further comprises:

determining a first representative flow rate for a first portion of the flow waveform;

determining a second representative flow rate for a second portion of the flow waveform;

comparing the first representative flow rate with the second average flow rate; and

determining the steady phase portion based at least on the results of the comparison.

8. A method according to claim 3, wherein identifying the steady phase portion comprises:

identifying a reference period of the flow waveform;

determining a representative flow rate for the reference period;

for each of a plurality of additional periods of the flow waveform;

determining a representative flow rate for the additional period;

comparing the representative flow rate for the additional period to the representative flow rate for the reference period; and

identifying the additional period as a qualifying additional period if the representative flow rate for the additional period varies from the representative flow rate for the reference period by less than a predetermined amount; and

defining the steady phase portion to include the reference period and each qualifying additional period.

9. A method according to claim 3, further comprising:

determining whether an breath phase following the exhalation phase is a ventilator controlled inhalation or a patient-triggered inhalation; and

if the inhalation phase is a ventilator controlled inhalation, defining the end of the specific portion as the end of the exhalation phase; and

if the inhalation phase is a patient-triggered inhalation, defining the end of the specific portion as a predetermined time period before the end of the exhalation phase.

10. A method according to claim 3, comprising determining as the estimated leak flow a flow value corresponding to the end of the exhalation phase based on the results of the linear regression.

4. A method for controlling breathing assistance provided to a patient, comprising:

providing breathing assistance to a patient according to one or more operational parameters;

estimating a leak flow by;

accessing data of a flow waveform indicating the flow of gas between the ventilation device and the patient;

identifying a steady phase portion near the end of an exhalation phase;

performing a linear regression of the identified portion of the flow waveform to determine an estimated leak flow in the breathing assistance system; and

controlling at least one of the operational parameters based at least on the estimated leak flow;

wherein identifying the steady phase portion comprises;

identifying a reference period of the flow waveform;

determining a representative flow rate for the reference period;

determining a series of one or more consecutive qualifying periods of the flow waveform having representative flow rates that vary from the representative flow rate for the reference period by less than a predetermined amount; and

defining the steady phase portion as including the reference period and the series of one or more consecutive qualifying periods.

11. A method according to claim 4, wherein controlling at least one of the operational parameters based at least on the estimated leak flow comprises controlling at least one of a pressure and a gas flow rate based at least on the estimated leak flow.

12. A method according to claim 4, further comprising displaying the estimated leak flow on a display device.

13. A method according to claim 4, wherein identifying the steady phase portion comprises determining a portion of the flow waveform having a flow variation within a predetermined variation threshold.

14. A method according to claim 4, wherein identifying the steady phase portion comprises:

determining a first representative flow rate for a first portion of the flow waveform;

determining a second representative flow rate for a second portion of the flow waveform;

comparing the first representative flow rate with the second average flow rate; and

determining the steady phase portion based at least on the results of the comparison.

15. A method according to claim 4, wherein identifying the steady phase portion comprises:

identifying a reference period of the flow waveform;

determining a representative flow rate for the reference period;

for each of a plurality of additional periods of the flow waveform;

determining a representative flow rate for the additional period;

comparing the representative flow rate for the additional period to the representative flow rate for the reference period; and

identifying the additional period as a qualifying additional period if the representative flow rate for the additional period varies from the representative flow rate for the reference period by less than a predetermined amount; and

defining the steady phase portion to include the reference period and each qualifying additional period.