Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-03-10
2001-09-04
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204230
Reexamination Certificate
active
06283122
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to exhalation valves in general, and to the use of these valves in medical respirators, in particular.
BACKGROUND OF THE INVENTION
Exhalation valves are an essential part of respiration devices. They carry air or oxygen to the patient and carbon dioxide from the patient to atmosphere. The function of the exhalation valve in respiration devices is to allow a patients exhaled breath to vent to atmosphere, while preventing gas being supplied to the patient from venting to atmosphere before it reaches the patient. Exhalation valves currently In the art have a number of drawbacks.
Prior art valves generally are unable to function accurately as pressure control devices since they usually operate in two extreme positions only; namely open or closed. These valves are not well suited for any incremental operation.
Valves in the current art usually perform with a noticeable lag time between initialization of the respiration process and response time of the valves.
Exhalation valves known in the prior art exhibit a linear relationship between the control signal and the servo mechanism. They are noisy in operation and tend to malfunction. This is generally due to blockage of exhalation discharge to atmosphere, improper assembly after disassembly for cleaning and or sterilization, or a combination of these factors.
An example of a valve in the current art may be found in U.S. Pat. No. 4,717,117 to Cook entitled “Vacuum Valve Using Improved Diaphragm.” The subject valve employs a flexible diaphragm for opening and closing an exhalation port, and exhibits most of the drawbacks mentioned above.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a valve which is devoid of the abovementioned deficiencies found in the prior art.
There is thus provided, in accordance with a preferred embodiment of the invention, an exhalation assembly which includes a hollow flow-through body, having an air inlet port and an air outlet port. The inlet port is arranged to receive air for supplying to a patient and the air outlet port is arranged to provide air to a patient.
The device also includes an exhalation valve connected to the flow-through body, for facilitating selectable exhalation by a patient to whom air is being supplied. The exhalation valve includes an air exhalation port arranged to permit therethrough an outflow of exhaled air and a valve member arranged to selectably cover the exhalation port in response to a closure pressure applied thereto and to uncover the exhalation port in response to an exhalation pressure applied thereto from the flow-through body through the exhalation port.
Also included is a pressure source for selectably applying a closure pressure to the valve member, wherein the valve member is operative to cover the exhalation port in response to at least a minimum closure pressure which has a greater magnitude than an opposing exhalation pressure.
The present embodiment of the invention further includes apparatus wherein the valve member is a flexible diaphragm. The exhalation valve also has a housing formed integrally with the flow-through body, wherein the housing has a closure pressure inlet port associated with a working pressure source, and is arranged so as to receive air from the flow-through body through the exhalation port. The housing further has formed therein first and second diaphragm seating portions configured to support the flexible diaphragm therebetween.
The first valve seating portion is configured to support a first portion of the flexible diaphragm when the flexible diaphragm is in the uncovered position, and the second valve seating portion is configured to support a second portion of the flexible diaphragm when the flexible diaphragm is in the covered position.
The present embodiment of the invention further includes apparatus wherein the first and second portions of the flexible diaphragm, have effective working areas of different magnitudes, such that predetermined first and second transfer force ratios apply across the flexible diaphragm when the diaphragm is moving from the uncovered position to the covered position, and from the covered position to the uncovered position, respectively.
The present embodiment of the invention further includes apparatus wherein the first transfer force ratio is approximately 5:1 and the second transfer force ratio is approximately 8:1.
The present embodiment of the invention further includes apparatus for damping oscillation of the flexible diaphragm. The apparatus for damping includes an added mass formed on the first portion of the flexible diaphragm.
The present embodiment of the invention further includes apparatus wherein the flexible diaphragm has a resonant frequency substantially below the normal range of human hearing.
The present embodiment of the invention further includes a housing portion surrounding the closure pressure inlet port, so as to define together with the flexible diaphragm a servo chamber. The servo chamber housing is constructed with an annular rim member depending therefrom and internal to the servo chamber. The annular rim member includes a shoulder portion and a sidewall portion. The shoulder portion is parallel to the plane in which the flexible diaphragm is mounted and the sidewall portion extends angularly from the shoulder portion.
The present embodiment of the invention further includes apparatus wherein the flexible diaphragm has a central portion of varying thickness, surrounded by an annular portion of generally uniform thickness. The flexible diaphragm is also mounted between an annular rim constructed to retain an edge portion of the diaphragm, and the housing formed with the first and second diaphragm seating portions whereby the flexible diaphragm is supported.
The flexible diaphragm, when moving from the covered position to the uncovered position, undergoes a first lateral displacement towards the closure pressure inlet port, and while undergoing the first lateral displacement, the annular portion of the flexible diaphragm engages the shoulder portion so as to be prevented from further lateral displacement.
The present embodiment of the invention further includes apparatus wherein, while the flexible diaphragm is moving from the covered to the uncovered position, and after the engagement of the annular portion by the shoulder portion, the central portion of the diaphragm is operative to undergo a second further lateral displacement in the same direction as the first lateral displacement. When the flexible diaphragm is in the covered position, the central portion of the flexible diaphragm has an effective working surface whose area is less than the area of the flexible diaphragm.
The present embodiment of the invention further includes apparatus wherein the sidewall portion of the annular rib member delineates an effective volume of the servo chamber together with the flexible diaphragm while the central portion of the flexible diaphragm is undergoing a second further lateral displacement, thereby reducing the working volume of the servo chamber from a first volume defined by the entire area of the flexible diaphragm including the annular portion thereof, to a second smaller volume defined by the central portion of the diaphragm and the sidewall portions. This thereby permits rapid movement of the flexible diaphragm from the covered position to the uncovered operative position due to the lesser amount of air or working fluid necessary to be displaced from the second smaller volume.
The present embodiment of the invention further includes a housing formed about the air exhalation port so as to define a muffling chamber, and operative to permit a flow of exhaled air from the exhalation port to the muffling chamber. The housing that delineates the muffling chamber has formed therein a plurality of recessed discharge slits thereby facilitating discharge of exhaled air.
The present embodiment of the invention further includes apparatus wherein the hollow flow-through body has at least one monito
Davidson Davidson & Kappel LLC
Flight Medical Ltd.
Lewis Aaron J.
Mitchell Teena
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