Breathing gas delivery method and apparatus

• US 6,539,940 B2
• Filed: 09/26/2001
• Issued: 04/01/2003
• 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: Sanders, Mark H., Estes, Mark, Zdrojkowski, Ronald J.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US09/966,547
• Publication Number:
  US 20020023645A1
• Time in Patent Office: 552 Days
• Field of Search: 128/200.24, 128/202.22, 128/204.18, 128/204.21, 128/204.23
• US Class Current: 128/204.23
• 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 apena 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 non-invasive pressure support system comprising;

a pressure generator adapted to provide a flow of breathing gas;

a conduit having a first end coupled to an output of the pressure generator and adapted to carry the flow of breathing gas and a second end;

a non-invasive patient interface device coupled to the second end of the conduit and adapted to communicate the flow of breathing gas with an airway of a patient responsive to the interface device being donned by a patient, wherein the conduit and the interface device define a pressurized system;

a continuously open exhaust vent defined in the conduit at a location near the patient interface or in the patient interface to provide a flow of exhaust gas from the pressurized system to ambient atmosphere;

a flow transducer operatively coupled to the conduit to measure a total flow of breathing gas passing therethrough;

a pressure sensor coupled to the conduit or the patient interface so as to measure a pressure P(t) of gas within the pressurized system; and

a controller adapted to receive an output of the flow transducer and the pressure sensor, wherein the controller calculates, based on the output of the flow transducer and the pressure sensor, a characteristic K of a hypothetical orifice, which represents an orifice through which all leakage of gas from the pressurized system occurs, and wherein the controller determines a total instantaneous flow of the leakage of gas from the pressurized system based on the characteristic K of the hypothetical orifice.

2. The system of claim 1, wherein the characteristic K of the hypothetical orifice is calculated as a measure of an average leak flow determined from the output of the flow sensor divided by a measure of the pressure within the pressurized system measured by the pressure sensor.

3. The system of claim 1, wherein the characteristic K of the hypothetical orifice is calculated over a period of time T as:

$K=\frac{{\int <br><br>}_0^T<br><br>\left(\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{flow}\right)<br><br><br><br>t}{{\int <br><br>}_0^T<br><br>f<br><br>\left(P<br><br>\left(t\right)\right)<br><br><br><br>t}.$

4. The system of claim 1, wherein the characteristic K of the hypothetical orifice is calculated as:

$K=\frac{{\int <br><br>}_0^T<br><br>\left(\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{flow}\right)<br><br><br><br>t}{{\int <br><br>}_0^T<br><br>\sqrt{P<br><br>\left(t\right)}<br><br><br><br>t}.$

5. The system of claim 1, wherein the instantaneous flow of leakage gas is calculated as K*{square root over (P(t))}.

6. A non-invasive pressure support system comprising:

pressure generating means for generating a flow of breathing gas;

a conduit having a first end coupled to an output of the pressure generating means and adapted to carry the flow of breathing gas and a second end;

a non-invasive patient interface device coupled to the second end of the conduit and adapted to communicate the flow of breathing gas with an airway of a patient responsive to the interface device being donned by a patient, wherein the conduit and the interface device define a pressurized patient circuit;

venting means associated with the patient circuit for providing a flow of exhaust gas from the patient circuit to ambient atmosphere;

flow sensing means for measuring a total flow of breathing gas passing through the patient circuit;

pressure sensing means coupled to the patient circuit for measure a pressure P(t) of gas within the patient circuit; and

processing means for (1) calculating, based on the output of the now sensing means and the pressure sensing means, a characteristic K of a hypothetical orifice, which represents an orifice through which all leakage of gas from the patient circuit occurs, and (2) for determining a total instantaneous flow of the leakage of gas from the patient circuit based on the characteristic K of the hypothetical orifice.

7. The system of claim 6, wherein the characteristic K of the hypothetical orifice is calculated by as a measure of an average leak flow determined by the processing means from the output of the flow sensing means divided by a measure of the pressure within the patient circuit measured by the pressure sensing means.

8. The system of claim 6, wherein the characteristic K of the hypothetical orifice over a period of time T is calculated by the processing means as:

$K=\frac{{\int <br><br>}_0^T<br><br>\left(\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{flow}\right)<br><br><br><br>t}{{\int <br><br>}_0^T<br><br>f<br><br>\left(P<br><br>\left(t\right)\right)<br><br><br><br>t}.$

9. The system of claim 6, wherein the characteristic K of The hypothetical orifice over a period of time T is calculated by the processing means as:

$K=\frac{{\int <br><br>}_0^T<br><br>\left(\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{flow}\right)<br><br><br><br>t}{{\int <br><br>}_0^T<br><br>\sqrt{P<br><br>\left(t\right)}<br><br><br><br>t}.$

10. The system of claim 6, wherein the instantaneous flow of leakage gas is calculated by the processing means as K*{square root over (P(t))}.

11. A method of providing non-invasive pressure support comprising:

generating a flow of breathing gas;

carry the flow of breathing gas from a source of the flow of breathing gas to an airway of a patient via a conduit;

communicating the flow of breathing gas from the conduit to an airway of a patient via a patient interface device donned by the patient, wherein the conduit and the interface device defines a patient circuit;

venting a flow of exhaust gas from the patient circuit to ambient atmosphere;

measuring a total flow of breathing gas passing through the patient circuit;

measuring a pressure P(t) of gas within the patient circuit;

calculating, based on the output of the flow sensing means and the pressure sensing means, a characteristic K of a hypothetical orifice, which represents an orifice through which all leakage of gas from the patient Circuit occurs; and

determining a total instantaneous flow of the leakage of gas from the patient circuit based on the characteristic K of the hypothetical orifice.

12. The method of claim 11, wherein the characteristic K of the hypothetical orifice is calculated by as a measure of an average leak flow determined from the measured flow divided by a measure of the measured pressure within the patient circuit.

13. The method of claim 11, wherein the characteristic K of the hypothetical orifice over a period of time T is calculated by the processing means as:

$K=\frac{{\int <br><br>}_0^T<br><br>\left(\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{flow}\right)<br><br><br><br>t}{{\int <br><br>}_0^T<br><br>f<br><br>\left(P<br><br>\left(t\right)\right)<br><br><br><br>t}.$

14. The method of claim 11, wherein the characteristic K of the hypothetical orifice over a period of time T is calculated by the processing means as:

$K=\frac{{\int <br><br>}_0^T<br><br>\left(\mathrm{total}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{flow}\right)<br><br><br><br>t}{{\int <br><br>}_0^T<br><br>\sqrt{P<br><br>\left(t\right)}<br><br><br><br>t}.$

15. The method of claim 11, wherein the instantaneous flow of leakage gas is calculated by the processing means as K*{square root over (P(t))}.

16. A method of providing breathing gas from a breathing gas source to an airway of a patient who is breathing in repeated breathing cycles, each breathing cycle including an inspiratory phase and an expiratory phase, comprising:

providing a flow of gas from a pressure generator to a patient via a conduit operatively coupled to an outlet of the pressure generator and a non-invasive interface device coupled to the conduit, wherein the interface device is adapted to be donned by a patient so as communicate the flow of gas from the conduit to an airway of a patient;

continuously exhausting a flow of exhaust gas from the conduit, the interface device, or both;

monitoring a characteristic associated with the flow of gas;

determining an instantaneous flow rate of the flow of gas from the monitored characteristic;

determining whether the patient is in an inspiratory phase or an expiratory phase of a breathing cycle by comparing the instantaneous flow rate to a reference value; and

controlling the flow of gas from the pressure generator to the patient based on whether the patient is in an inspiratory phase or an expiratory phase of a breathing cycle so as to maintain a positive pressure in the patient'"'"'s airway substantially continuously during a sequence of inspiratory and expiratory phases, where a magnitude of pressure maintained during an expiratory phase is less than a magnitude of pressure maintained during an immediately preceding inspiratory phase.

17. The method of claim 16, wherein the reference value is an average flow rate determined from the monitored characteristic.

18. The method of claim 16, wherein controlling the flow of gas from the pressure generator to the patient includes actuating a pressure control valve associated with the flow of gas in the conduit.

19. The method of claim 16, further comprising:

monitoring whether the patient has entered the inspiratory phase within a first predetermined period of time; and

automatically delivering the flow of breathing gas at a pressure corresponding to that delivered during an inspiratory phase responsive to the patient failing to enter the inspiratory phase within the first predetermined period of time.

20. The method of claim 19, further comprising:

continuing to deliver the flow of breathing gas at a pressure corresponding to that delivered during an inspiratory phase for a second predetermined period of time; and

delivering the flow of breathing gas at a pressure corresponding to that delivered during an expiratory phase responsive to elapse of the second predetermined period of time.