Method and apparatus for determining instantaneous leak during ventilatory assistance

• US 7,644,713 B2
• Filed: 03/08/2006
• Issued: 01/12/2010
• Est. Priority Date: 09/23/1996
• Status: Expired due to Fees

• Current Assignee: Resmed Limited (ResMed Incorporated)
• Original Assignee: Resmed Limited (ResMed Incorporated)
• Inventors: Berthon-Jones, Michael
• Primary Examiner(s): Yu; Justine R
• Assistant Examiner(s): MATTER, KRISTEN CLARETTE
• Application Number:
  US11/372,311
• Publication Number:
  US 20060150974A1
• Time in Patent Office: 1,406 Days
• Field of Search: 128/200.24, 128/204.18, 128/204.21, 128/204.23, 700/50, 706/1, 706 7- 9
• US Class Current: 128/204.21
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61B 5/087 Measuring breath flow
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61M 16/00 Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes stimulating the respiratory movement by mechanical, pneumatic or electrical means, iron lungs combined with gas breathing means A61H31/00
• CPC Class Codes: A61M 16/0003 Accessories therefor, e.g. sensors, vibrators, negative pressure
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/1055 bacterial
• CPC Class Codes: A61M 16/107 in the inspiratory path
• 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 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

The apparatus provides for the determination of the instantaneous phase in the respiratory cycle, subject'"'"'s average respiration rate and the provision of ventilatory assistance. A microprocessor (16) receives an airflow signal from a pressure transducer (18) coupled to a port (17) at a mask (11). The microprocessor (16) controls a servo (19), that in turn controls the fan motor (20) and thus the pressure of air delivered by the blower (10). The blower (10) is coupled to a subject'"'"'s mask (ii) by a conduit (12). The invention seeks to address the following goals: while the subject is awake and making substantial efforts the delivered assistance should be closely matched in phase with the subject'"'"'s efforts; the machine should automatically adjust the degree of assistance to maintain at least a specified minimum ventilation without relying on the integrity of the subject'"'"'s chemoreflexes; and it should continue to work correctly in the presence of large leaks.

Claims

1. A method for adjusting ventilatory assistance delivered to a subject by a ventilatory device comprising

determining the quantity of leak in said ventilatory device by determining an index equal to the fuzzy extent to which the leak is changing based at least in part on a measure of respiratory airflow and

adjusting ventilatory assistance delivered by said ventilatory device based on said quantity of leak,

wherein said ventilatory device is comprised of a ventilator, a patient interface, and connective tubing.

2. The method of claim 1 wherein said fuzzy extent to which the leak is changing is calculated as the fuzzy extent to which a measure of respiratory airflow is large for longer than expected.

3. The method of claim 1 wherein said fuzzy extent to which the leak is changing is a function of the fuzzy extent to which the leak has suddenly increased and a fuzzy extent to which the leak has suddenly decreased.

4. The method of claim 3 wherein said function is the fuzzy negation of a peak of a fuzzy union of said fuzzy extent to which the leak has suddenly increased and said fuzzy extent to which the leak has suddenly decreased.

5. The method of claim 3 wherein said fuzzy extent to which the leak has suddenly increased is the fuzzy intersection of the fuzzy extent to which a measure of respiratory airflow has been positive for longer than expected and the fuzzy extent to which a measure of respiratory airflow is large and positive.

6. The method of claim 1 wherein said fuzzy extent to which the leak has suddenly decreased is the fuzzy intersection of the fuzzy extent to which a measure of respiratory airflow has been negative for longer than expected and the fuzzy extent to which a measure of respiratory airflow is large and negative.

7. A method for adjusting ventilatory assistance delivered to a subject by a ventilatory device comprising

determining leak in said ventilatory device by calculating an index equal to a fuzzy extent to which the impedance of the leak is changing based at least in part on a measure of airflow, and

adjusting ventilatory assistance delivered by said ventilatory device based on said index,

wherein said ventilatory device is comprised of a ventilator, a patient interface, and connective tubing.

8. An apparatus for providing ventilatory assistance to a subject comprising

a ventilatory device comprised of a ventilator, a patient interface, and connective tubing and

means for determining a quantity of leak by calculating a fuzzy extent to which an impedance of the leak is changing as the fuzzy extent to which the respiratory airflow is large for longer than expected.

9. The apparatus of claim 8 wherein said fuzzy extent to which a leak is changing is a function of a fuzzy extent to which the leak has suddenly increased and a fuzzy extent to which the leak has suddenly decreased.