Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-05-25
2002-02-12
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204180, C128S204230, C128S204260
Reexamination Certificate
active
06345619
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to control of the provision of Continuous Positive Airway Pressure (CPAP) treatment.
BACKGROUND OF THE INVENTION
Early forms of CPAP treatment provided pressurised air or breathable gas to the entrance of a patient's airways continuously at a pressure elevated above atmospheric pressure, typically in the range 4-20 cmH
2
O. CPAP treatment is a common ameliorative treatment for breathing disorders, including Obstructive Sleep Apnea (OSA) syndrome. In its simplest form, CPAP treatment provides a single pressure level to the patient throughout the inspiratory and expiratory phases of respiration. It is also known for the level to vary over the course of many breaths in accordance with patient need, that form being known as automatically adjusting CPAP treatment.
Another form of CPAP treatment is ‘bi-level’, in which a higher pressure of gas is provided to the patient during the inspiratory phase of respiration and a relatively lower pressure during the expiratory phase. Bi-level CPAP treatment requires a determination of the onset of a transition between the inspiratory and expiratory phases (the “I-E” and “EI” transitions). The detection of these transitions is vital in controlling operation of a flow generator to provide pressurised air or breathable gas to the patient to maintain the therapeutic effect of treatment. Bi-level CPAP is used to treat respiratory insufficiency and acute respiratory failure, for example.
Many known bi-level CPAP devices rely on the detection of a change in patient respiratory flow as a trigger for a transition between treatment pressures. Delays in sensing patient breathing patterns is known to cause an increase in the work of breathing and discomfort for the patient due to pneumatic asynchrony. Such delays can also result in the unintended occurrence of apneas when treatment should be effective.
It is an objective of the present invention to overcome or at least ameliorate one or more of the problems in the prior art.
SUMMARY OF THE INVENTION
Accordingly, the gist of the invention is to provide an intermediate treatment pressure for a period of time as a transitional state between selected changes from the inspiratory and expiratory phase pressures of CPAP treatment.
Therefore, invention discloses a CPAP flow generator comprising:
a blower for providing a supply of pressurised air or breathable gas; and
a controller having control over the blower to supply an inspiratory phase pressure and an expiratory phase pressure, and operable to set a first flow threshold and a second flow threshold, the controller further sensing flow due to a patient respiration and selectively triggering generation of a pressure intermediate of the inspiratory phase and expiratory phase pressures for a period of time as a transitional state upon the first flow threshold being crossed and selectively triggering generation of a pressure intermediate of the expiratory phase and the inspiratory phase pressures for a period of time as a transitional state upon the second flow threshold being crossed.
The invention further discloses CPAP treatment apparatus, comprising:
a patient mask coupled to an air delivery conduit, in turn coupled to a blower operable to provide a positive pressure of air or breathable gas to said conduit;
a blower for providing a supply of pressurised air or breathable gas; and
a controller having control over the blower to supply an inspiratory phase pressure and an expiratory phase pressure, and operable to set a first flow threshold marking transitions between the inspiratory phase pressure and the expiratory phase pressure, and to set a second flow threshold, the controller further sensing flow due to a patient respiration and selectively triggering generation of a pressure intermediate of the inspiratory phase and expiratory phase pressures for a period of time as a transitional state upon the first flow threshold being crossed and selectively triggering generation of a pressure intermediate of the expiratory phase and the inspiratory phase pressures for a period of time as a transitional state upon the second flow threshold being crossed.
The invention further discloses a method for the administration of CPAP treatment, comprising the steps of:
providing a source of pressured air or breathable gas to a patient;
controlling the pressure of gas between an inspiratory phase level and a lower expiratory phase level;
setting a first patient respiratory flow threshold;
setting a second patient respiratory flow threshold; and
selectively generating an intermediate pressure for a period of time as a transitional state upon the first flow threshold patient respiratory threshold being crossed; and selectively generating another intermediate pressure for a period of time as a transitional state upon the second patient respiratory flow threshold being crossed.
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Lewis Aaron J.
Pillsbury & Winthrop LLP
ResMed Limited
Weiss Joseph F.
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