LEAK-COMPENSATED PRESSURE REGULATED VOLUME CONTROL VENTILATION

• US 20100236555A1
• Filed: 03/20/2009
• Published: 09/23/2010
• Est. Priority Date: 03/20/2009
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Jimenez, Rhomere S., Upham, Gail F., Jafari, Mehdi M., Aviano, Jeffrey K.
• Granted Patent: US 8,418,691 B2
• Time in Patent Office: Days
• US Class Current: 128/204.230
• 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 16/0875 Connecting tubes
• 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 2205/502 User interfaces, e.g. screens or keyboards
• 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 to a patient from a medical ventilator in a pressure regulated volume control (PRVC) ventilation mode. The technology described herein includes systems and methods that compensate the delivery of PRVC ventilation for leakage in the patient circuit by using leak-compensated lung flows as well as respiratory mechanics (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 system during delivery of pressure regulated volume control ventilation to a patient comprising:

monitoring an instantaneous flow in the ventilation system based on one or more measurements of pressure and flow in ventilation system;

modeling leakage as a first leakage component through a first orifice of a fixed size and a second leakage component through a second orifice of a varying size, wherein the first and second leakage components are different functions of instantaneous pressure in the ventilation system;

estimating a leak-compensated delivered lung volume for at least one breath based on the one or more measurements, the first leakage component and the second leakage component;

using the leak-compensated delivered lung volume and a predetermined respiratory mechanics model to estimate a leak-compensated lung compliance; and

calculating a target pressure to be delivered to the patient for a subsequent breath based on a desired lung volume, the leak-compensated delivered lung volume and the leak-compensated lung compliance.

2. The method of claim 1 further comprising:

estimating the leak-compensated lung compliance based on the leak-compensated delivered lung volume and a pressure difference.

3. The method of claim 2 wherein the pressure difference is a difference between an end inspiratory pressure of a first breath and an end expiratory pressure of the first breath.

4. The method of claim 1 wherein the method further comprises:

calculating the target pressure based on a difference between the desired lung volume and the leak-compensated delivered lung volume.

5. The method of claim 1 wherein the method further comprises:

determining a circuit compliance of ventilation system; and

estimating a leak-compensated delivered lung volume for at least one breath based on the one or more measurements, the circuit compliance, the first leakage component and the second leakage component.

6. The method of claim 1 wherein the method further comprises:

upon initiation of pressure regulated volume control ventilation, calculating an initial lung compliance from data obtained during a startup period; and

determining an initial target pressure to be delivered to the patient for at least one breath after the startup period.

7. A method of compensating for leakage in a ventilation tubing system during delivery of gas from a medical ventilator to a patient comprising:

measuring leakage from the ventilation tubing system during a first breath;

calculating a leak-compensated delivered lung volume for the first breath based on the leakage;

estimating a lung compliance of the patient based on the leak-compensated delivered lung volume and pressure measurements taken during the first breath; and

delivering ventilation to the patient in a second breath at a pressure determined based on a desired delivered lung volume, the leak-compensated delivered lung volume and the leak-compensated lung compliance.

8. The method of claim 7 wherein measuring leakage further comprises:

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

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

9. The method of claim 7 wherein calculating the leak-compensated delivered lung volume further comprises:

generating a plurality leak-compensated lung flows each associated with a different period of time within the first breath;

generating the leak-compensated delivered lung volume for the first breath based on the leak-compensated lung flows.

10. The method of claim 7 wherein estimating the lung compliance further comprises:

receiving the desired lung volume from an operator.

11. 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 flow of the breathing gas in the ventilation tubing system;

a leak estimation module that identifies leakage in the ventilation tubing system;

a delivered lung volume module that calculates a leak-compensated delivered lung volume for a first breath based on the leakage during the first breath and the flow of the breathing gas in the ventilation tubing system;

a respiratory mechanics calculation module that generates a leak-compensated lung compliance based on the leak-compensated delivered lung volume and at least one output indicative of a pressure of the breathing gas during the first breath; and

a pressure control module that causes the pressure generating system to deliver a second breath to the patient at a target pressure calculated based on the leak-compensated lung compliance and the leak-compensated delivered lung volume.

12. The system of claim 11 further comprising:

a memory storing a desired delivered lung volume provided by a user.

13. The system of claim 12 wherein the pressure regulated volume control module calculates the target pressure based on the desired delivered lung volume, the leak-compensated lung compliance and the leak-compensated delivered lung volume.

14. The system of claim 11 wherein the respiratory mechanics calculation module generates the leak-compensated lung compliance based on the leak-compensated delivered lung volume and a pressure difference.

15. The method of claim 14 wherein the pressure difference is a difference between an end inspiratory pressure of the first breath and an end expiratory pressure of the first breath.

16. The system of claim 11 wherein the leak estimation module further identifies an elastic leakage and an inelastic leakage in the ventilation tubing system.

17. The system of claim 16 wherein the delivered lung volume module calculates the leak-compensated delivered lung volume for a first breath based on the elastic and inelastic leakage during the first breath and the flow of the breathing gas in the ventilation tubing system.

18. A controller for a medical ventilator comprising:

a microprocessor;

a module that calculates leak-compensated delivered lung volume and leak-compensated lung compliance based on instantaneous elastic leakage and instantaneous inelastic leakage of breathing gas from a ventilation system; and

a pressure control module that provides pressure regulated volume control ventilation at a pressure determined based on the leak-compensated delivered lung volume and the leak-compensated lung compliance.

19. The controller of claim 18 further comprising:

a leak estimation module that identifies the instantaneous inelastic leakage and the instantaneous elastic leakage in the ventilator.

20. The controller of claim 18 further comprising:

a memory that stores an identification of a target volume of gas to be delivered during pressure regulated volume control ventilation; and

wherein the pressure control module provides pressure regulated volume control ventilation at a pressure determined based on the leak-compensated delivered lung volume, the leak-compensated lung compliance, and the target volume of gas.