Breathing gas delivery method and apparatus

• US 6,305,374 B1
• Filed: 01/14/2000
• Issued: 10/23/2001
• Est. Priority Date: 09/22/1989
• Status: Expired due to Term

• Current Assignee: RIC INVESTMENTS LLC (Koninklijke Philips N.V.)
• Original Assignee: Respironics Incorporated (Koninklijke Philips N.V.)
• Inventors: Estes, Mark, Zdrojkowski, Ronald J.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US09/483,538
• Time in Patent Office: 648 Days
• Field of Search: 128/200.24, 128/202.22, 128/204.18, 128/204.21, 128/204.23
• US Class Current: 128/204.21
• 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 16/06 Respiratory or anaesthetic masks
• CPC Class Codes: A61M 16/204 used for inhalation control
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• 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: A61M 2205/3561 local, e.g. within room or hospital

Abstract

An improved methodology and systems for delivery of breathing gas such as for the treatment of obstructive sleep apnea through application of alternating high and low level positive airway pressure within the airway of the patient with the high and low airway pressure being coordinated with the spontaneous respiration of the patient, and improved methods and apparatus for triggering and for leak management in such systems.

Claims

1. A method of detecting changes in a respiratory state of a patient between inspiration and expiration, comprising:

monitoring a respiratory gas flow of such a patient;

determining, from the monitoring step, a respiratory gas flow characteristic at selected time intervals;

comparing selected pairs of said respiratory gas flow characteristics, wherein each selected pair of respiratory gas flow characteristics includes a predicted value of such a patient'"'"'s respiratory gas flow rate at a selected time, and such a patient'"'"'s actual respiratory gas flow rate at the selected time; and

identifying, from the comparing step, changes in the patient'"'"'s respiratory state between inspiration and expiration.

2. The method of claim 1, further comprising:

taking a derivative of a known patient respiratory gas flow rate; and

processing the derivative to determine the predicted value of such a patient'"'"'s respiratory gas flow rate.

3. The method of claim 2, wherein the processing step includes scaling the derivative with a scaling factor to obtain a scaled derivative.

4. The method of claim 3, wherein the processing step includes modifying the scaled derivative with an offset factor to determine the predicted value of such a patient'"'"'s respiratory gas flow rate.

5. The method of claim 3, wherein the scaling factor includes a time factor.

6. The method of claim 5, the time factor is determined, at least in part, by a time span between the selected time and a time prior to the selected time.

7. The method of claim 1, wherein the predicted value of such a patient'"'"'s respiratory gas flow rate is determined from an actual patient respiratory flow rate that occurred at a time prior to the selected time.

8. A method of determining a leak component of gas flow in a respiratory gas supply system for supplying respiratory gas to a patient, comprising:

determining a beginning and an end of an integral number of patient breaths;

integrating a patient respiratory gas flow rate throughout at least one breath to determine a total respiratory gas volume for the at least one breath; and

dividing the total respiratory gas volume for the at least one breath by a time duration of the at least one breath to determine a leakage rate for the at least one patient breath.

9. The method of claim 8, further comprising averaging the leakage rate for the at least one patient breath to determine an average respiratory gas leakage from such a respiratory gas supply system.