Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-02-03
2001-04-24
Dawson, Glenn K. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S202120, C128S202130, C128S204180
Reexamination Certificate
active
06220245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is broadly concerned with an improved ventilator compressor system adapted for use with as a part of or in conjunction with a medical ventilator. More particularly, the invention is concerned with such compressor systems which include a hollow fiber membrane drying module for dehumidifying pressurized air from a compressor and significantly reducing the dew point pressure thereof; this insures that compressed air delivered to the ventilator is free of condensed water. Preferably, a recycle line is provided for delivery of pressurized, dehumidified air back to the compressor inlet during low demand operation of the system, to reduce the moisture level of incoming air to the compressor.
2. Description of the Prior Art
Many critically ill patients require breathing assistance by way of supplemental oxygen or through the use of a ventilator. A ventilator either forces pressurized gas into the lungs (a positive pressure ventilator) or expands the chest cavity of the patient to draw gas into the lungs (a negative pressure ventilator). Ventilators typically provide mixtures of pressurized air and oxygen to a patient according to a prescribed schedule, such as a specific pressure profile or a specific gas volume delivery profile over time. Moreover, many ventilators can be adjusted to either force breaths or respond only to a patient's attempts to breath and assist in such breathing, or operate in some more complex pattern.
In order to provide a source of pressurized air, ventilators may be coupled to hospital wall air which provides high quality, dehumidified and pressurized air. To this end, many hospital wall systems employ dryers in the pressurized air lines for dehumidification purposes, typically refrigerant or desiccant dryers. Membrane type dryers have also been used in this context. In addition, portable ventilators are commonly equipped with a portable compressor system either to meet the full demand of the ventilator or as a backup for ventilators using hospital wall air. A problem with such portable compressor systems is that they tend to provide high humidity air which can condense and cause damage to internal components of the ventilator and potentially loss of breath support to a patient. Previous methods for controlling humidity in such compressor systems has included the use of copper coils or heat exchangers for cooling and condensing of compressor output air. The cooling of such copper coil or heat exchanger occur within the confines of the compressor module itself, and is therefore warmer than ambient air outside the compressor module. Therefore, any outlet air that is exposed to ambient air can cool and cause condensation of the saturated air delivered to the ventilator. A typical solution is to compress the gas to above the required output pressure, pass it through a heat exchanger/condenser, and then regulate it down to a lower pressure. This expands the partially de-humidified air to try to bring the dew point below the ambient temperature. The problems introduced by this approach are decreased efficiency (to overpressurize the air), added heat in the compressor, decreased compressor life, and potential for inadequate dew point depression if the heat balance and pressure ratios are not adequate for all potential environments and air demand conditions.
SUMMARY OF THE INVENTION
The present invention overcomes the problems outlined above and provides an improved compressor system which is equipped with a membrane dryer so as to materially dehumidify the pressurized gas (usually air) delivered to a ventilator with a significant reduction in the dew point temperature of such gas. Broadly speaking, the compressor systems of the invention include a compressor with a gas delivery assembly including a delivery conduit coupled with the compressor outlet and adapted for connection with a ventilator; a membrane dryer is operably interposed in the delivery conduit downstream of the compressor outlet for removing moisture from the pressurized gas.
In preferred forms, the overall compressor systems of the invention are in the form of self-contained, portable units which include a heat exchanger and coalescing filter between the compressor and membrane dryer. The heat exchanger and filter initially dehumidify the pressurized air prior to entrance thereof into the membrane dryer.
In addition, the dehumidified output air from the dryer is directed to a valve which delivers the pressurized, dehumidified air to an accumulator and to the ventilator; alternately, when the accumulator is full and during low ventilator demand (e.g., during patient exhale), the dehumidified air from the dryer is recycled back to the compressor inlet. This reduces the overall moisture load imposed on the compressor system.
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Product Brochure re Stealth® .
Product Brochure re Parker Filtration -Finite®Compressed Air and Gas Dryers.
Ellestad Raymond A.
Takabayashi Susumu
Dawson Glenn K.
Hovey Williams Timmons & Collins
Mallinckrodt Inc.
Srivastava V.
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