Method and apparatus for providing ventilatory assistance

• US 8,051,853 B2
• Filed: 11/19/2009
• Issued: 11/08/2011
• 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): MATTER, KRISTEN CLARETTE
• Application Number:
  US12/621,991
• Publication Number:
  US 20100065057A1
• Time in Patent Office: 719 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. An apparatus for providing variable ventilatory assistance to a patient comprising:

means for delivering ventilation to a patient;

means for adjusting the level of ventilation to said patient;

means for determining an estimate of said patient'"'"'s respiratory airflow; and

processing means for calculating instantaneous inspired volume from said respiratory airflow;

wherein said processing means is controlled by coded machine instructions for calculating said instantaneous inspired volume as a function of said respiratory airflow, the fuzzy extent to which any leak is suddenly changing, and the fuzzy extent to which the recent peak leak is changing.

2. The apparatus of claim 1 wherein said fuzzy extent to which any leak is suddenly changing is calculated as the fuzzy extent to which the estimate of respiratory airflow is large for longer than expected.

3. The apparatus of claim 1 wherein said function of respiratory airflow is comprised of the time integral of the product of the fuzzy extent to which any leak is suddenly changing and said estimate of respiratory airflow.

4. In an apparatus for providing ventilation to a patient, a mechanism for calculating a patient'"'"'s instantaneous inspired volume, comprising:

means for delivering ventilation to a patient;

means for adjusting the level of ventilation to said patient;

means for determining an estimate of said patient'"'"'s respiratory airflow; and

processing means for calculating said patient'"'"'s instantaneous inspired volume from said estimate of respiratory airflow;

wherein said processing means is controlled by coded machine instructions for calculating said instantaneous inspired volume as a function of said respiratory airflow, an index dependent upon how leak is suddenly changing, and the extent to which the recent peak leak is changing.

5. The mechanism of claim 4 wherein said index is further based upon the extent to which said estimate of respiratory airflow is large for longer than expected.

6. The mechanism of claim 4 wherein said function is comprised of the time integral of the product of said index and said estimate of respiratory airflow.

7. A system for calculating the instantaneous inspired volume of a patient while providing ventilatory assistance comprising:

a mask;

a blower to supply pressurized air to said mask;

a servo-controller coupled to said blower;

a transducer to generate a flow signal representing respiratory airflow; and

a processor coupled to said transducer and said servo-controller, said processor controlled by programmed instructions;

wherein said programmed instructions include instructions to calculate instantaneous inspired volume as a function of the respiratory airflow, how any leak is suddenly changing, and an index based upon how the recent peak leak is changing, and

wherein said index is adjusted based upon how any leak is suddenly changing.

8. The apparatus of claim 7 wherein said how any leak is suddenly changing is based upon the extent to which the respiratory airflow is large for longer than expected.

9. The apparatus of claim 7 wherein said function is comprised of the time integral of the product of said first index and said respiratory airflow.