Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Patent
1991-12-31
1993-09-07
Burr, Edgar S.
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
12820524, A61M 1600
Patent
active
052419550
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a breathing apparatus for supplying pulses of breathable gas to a patient, e.g. for emergency resuscitation or as a ventilator for patients during anesthesia.
BACKGROUND ART
GB-2,170,409 describes a breathing apparatus including a gas passage having an inlet to receive gas, an outlet to pass gas to the patient and a valve in the passage to control the flow of gas to provide the desired pulsed flow of gas. A variable throttle is included downstream of the valve which, when gas is flowing in the passage, diverts part of it into a reservoir. The reservoir includes a leak valve which allows gas to leak from the reservoir to atmosphere and a check valve that prevents gas in the reservoir from returning to the gas supply system of the apparatus. The valve includes a piston for opening and closing the valve; the piston is biassed (a) by pressure in the reservoir to move in one direction and (b) by a spring to move in the opposite direction. When the valve is open, gas flows through the passage to the patient, who inhales; at the same time, gas is diverted into the reservoir from the passage at a faster rate than it leaks out of the reservoir through the leak valve and so the pressure in the reservoir increases until it reaches a value at which it can move the piston to close the main valve causing the flow of gas to the patient to the patient to cease, allowing him to exhale (expiratory period). Since there is no gas flowing through the passage, no gas is diverted into the reservoir and the leakage of gas through the leak valve to atmosphere causes the pressure in the reservoir to fall; when the pressure reaches such a low level that the force it exerts on the piston is less than that exerted by the spring, the spring moves the piston to open the valve and resume the flow of gas in the passage thereby causing the patient to inhale once more (inspiratory period). The cycle of the inspiratory expiratory periods are repeated for as long as required. In order to adjust the duration of the inspiratory and expiratory periods, the leak valve needs to be made as a needle valve and a further needle valve needs to be provided in the duct diverting gas into the reservoir.
DISCLOSURE OF THE INVENTION
The present invention provides a simpler arrangement than that described above.
According to the present invention, there is provided a breathing apparatus for supplying pulses of a breathable gas to a patient, which apparatus comprises a gas inlet connectable to a source of breathable gas, an outlet connectable to provide gas to the patient, a gas flow passage extending between the inlet and the outlet, a main valve located in the gas flow passage for interrupting the flow of gas to the outlet, a throttle in the flow passage downstream of the main valve, a gas reservoir and a valved duct connected to supply gas to the reservoir from the part of the flow passage between the main valve and the throttle, wherein the main valve includes a piston that is slidable within a cylinder to open and close the gas flow passage, which piston is biassed in one direction by a resilient member (which will usually be a spring) and biassed in the other direction by the gas pressure within the reservoir, wherein gas in the reservoir can leak out of the reservoir when the flow of gas in the flow passage is interrupted by the main valve, which leakage occurs to the said flow passage, preferably through the said valved duct and thus does not occur directly to ambient atmosphere.
The force exerted on the piston by the resilient member is preferably adjustable since in this way it is possible to alter the ratio of (a) the duration of the period in which the main valve is open and gas is supplied to the patient (the inspiratory phase) to (b) the duration of the period in which the main valve is closed allowing the patient to exhale (the expiratory phase). In a preferred embodiment the resilient member biases the piston to a position in which the gas flow passage is open.
Because the leakage occurs
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Dearman Peter T.
Smith Richard
Burr Edgar S.
Neotronics Medical Limited
Raciti Eric P.
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