Leak-compensated proportional assist ventilation

• US 8,978,650 B2
• Filed: 04/26/2013
• Issued: 03/17/2015
• Est. Priority Date: 03/20/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Jafari, Mehdi M., Jimenez, Rhomere S., Upham, Gail F., Aviano, Jeffrey K.
• Primary Examiner(s): Anderson, Lynne
• Assistant Examiner(s): PHILIPS, BRADLEY H
• Application Number:
  US13/871,075
• Publication Number:
  US 20130233314A1
• Time in Patent Office: 690 Days
• Field of Search: 128/200.24, 128/204.18, 128/204.21, 128/204.23
• US Class Current: 128/204.21
• CPC Class Codes: A61M 16/0051 with alarm devices
• CPC Class Codes: A61M 16/0057 Pumps therefor
• 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 16/04 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 16/0816 Joints or connectors
• CPC Class Codes: A61M 16/0875 Connecting tubes
• 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 2016/0033 electrical
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 2205/505 Touch-screens; Virtual keyboard or keypads; Virtual buttons; Soft keys; Mouse touches
• CPC Class Codes: A61M 2230/46 Resistance or compliance of the lungs

Abstract

This disclosure describes systems and methods for compensating for leakage when during delivery of gas from a medical ventilator in a proportional assist mode to a patient. The technology described herein includes systems and methods to compensate the delivery of PA ventilation for leakage in the patient circuit by using leak-compensated lung flows as well as leak-compensated respiratory mechanics parameters (lung compliance and lung resistance) estimated in a manner that compensates for elastic and inelastic leaks from the ventilation system.

Claims

1. A method of compensating for leakage in a ventilation tubing system during delivery of proportional assist ventilation to a patient, wherein the method is performed by a ventilation system having a memory storing a computer-readable instructions and a processor, the processor executing the computer-readable instructions for performing the method comprising:

receiving a support setting identifying an amount of proportional assistance to provide to the patient;

receiving at least one of a pressure measurement and a flow measurement in the ventilation tubing system;

modeling leakage from the ventilation tubing system as a first leakage through a first orifice of a fixed size that is estimated as a first function of at least one of the pressure measurement and the flow measurement and a second leakage through a second orifice of a varying size that is estimated as a second function of at least one of the pressure measurement and the flow measurement;

estimating a lung compliance of the patient and a lung resistance of the patient based on the first leakage, the second leakage, and the at least one of the pressure measurement and the flow measurement;

estimating patient effort based on the first leakage, the second leakage, the lung compliance, the lung resistance, and the at least one of the pressure measurement and the flow measurement; and

delivering ventilation to the patient based on the estimated patient effort and the support setting.

2. The method of claim 1, wherein one or more of modeling leakage, estimating lung compliance and lung resistance, and estimating patient effort occurs every computational cycle.

3. The method of claim 1, wherein estimating the lung compliance further comprises:

generating a plurality of leak-compensated lung flows associated with a period of time based on the first leakage, the second leakage, and the at least one of the pressure measurement and the flow measurement associated with the period of time;

generating a leak-compensated net lung volume for the period of time based on the plurality of leak-compensated lung flows; and

calculating the lung compliance using the leak-compensated net lung volume.

4. The method of claim 3, further comprising:

calculating the lung resistance based on the lung compliance and one or more of the plurality of leak-compensated lung flows, the leak-compensated net lung volume, and at least one pressure measurement.

5. The method of claim 1, wherein estimating the lung compliance and the lung resistance further comprises:

generating a plurality of leak-compensated lung flows associated with a period of time based on the first leakage, the second leakage, and the at least one of the pressure measurement and the flow measurement associated with the period of time;

generating a leak-compensated net lung volume for the period of time based on the plurality of leak-compensated lung flows; and

calculating the lung compliance and the lung resistance using the leak-compensated net lung volume, the plurality of leak-compensated lung flows for the period of time, and the at least one pressure measurement associated with the period of time.

6. The method of claim 1, wherein estimating the lung compliance comprises calculating a leak-compensated lung compliance comprising:

calculating a leak-compensated lung volume based on a leak-compensated lung flow during an inspiratory phase;

delivering a stable flow of gas at a stable pressure, wherein the stable flow and stable pressure are determined based on the estimated leakage at the stable pressure;

maintaining the stable flow of gas at the stable pressure for at least a predetermined time interval;

calculating the leak-compensated lung compliance based on the leak-compensated lung volume and the stable pressure; and

calculating a leak-compensated lung resistance based on the leak-compensated lung compliance and one or more of a previously calculated leak-compensated lung flow, a previously calculated leak-compensated lung volume, and a previously measured pressure.

7. A pressure support system comprising:

a pressure generating system adapted to generate a flow of breathing gas;

a ventilation tubing system including a patient interface device for connecting the pressure generating system to a patient;

one or more sensors operatively coupled to the pressure generating system or the ventilation tubing system, each sensor capable of generating an output indicative of a pressure or a flow of the breathing gas;

a leak estimation module that estimates leakage from the ventilation tubing system by identifying an inelastic leakage in the ventilation tubing system as a first function of an output of at least one sensor, and identifying an elastic leakage in the ventilation system as a second function of an output of at least one sensor;

a patient effort estimation module that estimates patient effort based on the leakage and an output of at least one sensor; and

a proportional assistance ventilation module that causes the pressure generating system to provide ventilation to the patient based on patient effort and a support setting.

8. The system of claim 7, further comprising:

a compensation module that generates a leak-compensated lung flow based on the inelastic leakage.

9. The system of claim 7, further comprising:

a respiratory mechanics module that uses a static respiratory mechanics model to determine at least one of a static lung compliance and a static lung resistance based on the leak-compensated lung flow and an output of at least one sensor.

10. The system of claim 7, further comprising:

a respiratory mechanics module that uses a dynamic respiratory mechanics model to determine at least one of a dynamic lung compliance and a dynamic lung resistance based on the leak-compensated lung flow and an output of at least one sensor.

11. The system of claim 10, wherein the patient effort estimation module estimates patient effort based on the leakage and at least one of the dynamic lung compliance and the dynamic lung resistance.

12. A controller for a medical ventilator comprising:

a microprocessor;

a leak estimation module that estimates instantaneous elastic leakage of breathing gas from a ventilation tubing system as a first function of and output of at least one sensor and instantaneous inelastic leakage of breathing gas from the ventilation tubing system as a second function of an output of at least one sensor;

a module that compensates calculations of lung compliance and lung resistance based on the instantaneous elastic leakage and the instantaneous inelastic leakage; and

a pressure generating module controlled by the microprocessor that provides proportional assist ventilation based on the compensated lung compliance and lung resistance.

13. A method of compensating for leakage in a ventilation tubing system during delivery of proportional assist ventilation to a patient, wherein the method is performed by a ventilation system having a memory storing a computer-readable instruction and a processor, the processor executing the computer-readable instruction for performing the method comprising:

receiving a support setting identifying an amount of proportional assistance to provide to the patient;

receiving at least one of a pressure measurement and a flow measurement associated with the ventilation tubing system;

estimating leakage from the ventilation tubing system based on the at least one of the pressure measurement and the flow measurement, comprising;

identifying an inelastic leakage in the ventilation system as a first function of the at least one of the pressure measurement and the flow measurement; and

identifying an elastic leakage in the ventilation system as a second function of the at least one of the pressure measurement and the flow measurement;

estimating a lung compliance of the patient and a lung resistance of the patient based on the estimated leakage and the at least one of the pressure measurement and the flow measurement;

estimating patient effort based on the estimated leakage, the lung compliance, the lung resistance, and the at least one of the pressure measurement and the flow measurement; and

delivering ventilation to the patient based on the estimated patient effort and the support setting.

14. The method of claim 13, wherein one or more of estimating leakage, estimating lung compliance and lung resistance, and estimating patient effort occurs every computational cycle.

15. The method of claim 13, wherein estimating the lung compliance further comprises:

generating a plurality of leak-compensated lung flows associated with a period of time based on the estimated leakage and the at least one of the pressure measurement and the flow measurement associated with the period of time;

generating a leak-compensated net lung volume for the period of time based on the plurality of leak-compensated lung flows; and

calculating the lung compliance using the leak-compensated net lung volume.

16. The method of claim 15, further comprising:

calculating the lung resistance based on the lung compliance and one or more of the plurality of leak-compensated lung flows, the leak-compensated net lung volume, and at least one pressure measurement.

17. The method of claim 13, wherein estimating the lung compliance and the lung resistance further comprises:

generating a plurality of leak-compensated lung flows associated with a period of time based on the estimated leakage and the at least one of the pressure measurement and the flow measurement associated with the period of time;

generating a leak-compensated net lung volume for the period of time based on the plurality of leak-compensated lung flows; and

calculating the lung compliance and the lung resistance using the leak-compensated net lung volume, the plurality of leak-compensated lung flows for the period of time, and the at least one pressure measurement associated with the period of time.

18. The method of claim 13, wherein estimating the lung compliance comprises calculating a leak-compensated lung compliance comprising:

calculating a leak-compensated lung volume based on a leak-compensated lung flow during an inspiratory phase;

delivering a stable flow of gas at a stable pressure, wherein the stable flow and stable pressure are determined based on the estimated leakage at the stable pressure;

maintaining the stable flow of gas at the stable pressure for at least a predetermined time interval; and

calculating the leak-compensated lung compliance based on the leak-compensated lung volume and the stable pressure.