Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-09-24
2001-08-07
Lewis, Aaron J. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S204180
Reexamination Certificate
active
06269811
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a pressure support system for providing a primary flow of gas and a supplemental flow of gas to a patient, and, in particular, to such a system wherein the primary flow of gas is provided by a pressure generator and wherein the supplemental flow of gas to the patient is controlled based on the operating conditions of the pressure generator.
2. Description of the Related Art
It is known to provide a gas flow to a patient using a pressure support system to treat a medical disorder. For example, is it known to use a continuous positive airway pressure (CPAP) device, which is a single-limb pressure support system having a passive exhaust, to supply a constant positive pressure to the patient to treat obstructive sleep apnea (OSA). It is also known to provide a positive pressure that varies with the patient's breathing cycle, patient's effort or based on the condition of the patient, such as whether the patient is experiencing or likely to experience snoring, an apnea, or hypopnea.
Such devices typically include a pressure generator, such as a blower or piston with a pressure regulator or pressure regulating capability, the pressure support device is a variable pressure device, that creates a flow of breathing gas having an elevated pressure. A single conduit, typically a flexible tube, is coupled to the pressure generator to carry the breathing gas to the patient. A patient interface, such as a nasal and/or oral mask, nasal cannula, trachea tube, intubation tube or full face mask, couples the gas flow from the conduit to the patient's airway. The conduit and/or patient interface generally includes a vent for exhausting exhaled gas to atmosphere. The vent is considered a passive exhaust system because there are no selectively actuatable valves that control the flow of exhaust gas associated with the vent.
It is also common to provide a control system to control the flow of pressurized gas to the patient. The control system ranges from the relatively simple, controlling the pressure generator based on inputs from the patient or from a few monitored parameters, to the relatively complex, controlling the pressure generator in a feedback fashion based on monitored conditions of the patient, such as the patient's respiration. In many applications, these devices are used in the home and positioned at the patient's bedside to provide the positive pressure therapy to the patient throughout the night while the patient sleeps wearing the patient interface device.
In many instances, it is also desirable to provide the patient with a supplemental gas, such as oxygen or an oxygen mixture, in addition to the primary flow of gas, which is typically air, provided by the pressure generating system. It is conventional to introduce the supplemental flow of gas into the conduit or at the patient interface device, both of which are downstream of the pressure generator in the pressure generating system.
When introducing a flammable gas or a gas, such as oxygen, which readily promotes combustion, into the pressure support system, safety concerns dictate that steps be taken to minimize the risk of fire. For example, if the pressure generator should fail or be shut off while the supplemental gas, such as oxygen, remains on, there is a chance that the supplemental gas will continue to fill the conduit and/or patient interface and backup into the pressure generator. Typically, pressure generators are designed with this eventuality in mind and are optimized for safety against fire even if oxygen backs up into the device through the conduit, for example, by using electrical circuits that will not produce a spark or reach temperatures exceeding 300° C. during single fault failures. It is also known to provide gas-tight internal airways in the pressure generator so that the supplemental gas can not enter the enclosure in which the pressure generator and its associated electronics are housed. Furthermore, it is also known to provide a check valve in the conduit (breathing circuit) between the pressure generator and the introduction point for the supplemental gas. This valve prevents gas from backing up into the pressure generator if the pressure generator ceases functioning by exhausting the gas in the breathing circuit to atmosphere.
It can be appreciated, however, that creating electrical circuits that will not produce a spark or reach temperatures exceeding 300° C. during single fault failures or creating gas-tight units increase the cost of the entire pressure support device. This is exacerbated by the fact that generally less than half of the pressure support systems on the market are used in conjunction with a supplemental supply of oxygen. Providing a check valve in the breathing circuit between the pressure generator and the introduction point for the supplemental gas, while effective in blocking the backup of the supplemental gas into the pressure generating device, does not prevent a buildup of such gas in the room where the device is located should the above-described scenario occur. This latter point is also true for the first two conventional safety precautions discussed above. The buildup of supplemental gas, such as oxygen, in a room is particularly disadvantageous because of the risk of sparks from other ignition sources, such as electronic equipment, e.g., televisions, telephones, radios, etc, pilot lights and electric or gas heaters.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a pressure support system that can be used in conjunction with a supplemental gas, such as oxygen, to deliver the supplemental gas to that patient and that does not suffer from the disadvantages of conventional systems discussed above. This object is achieved, according to one embodiment of the present invention, by providing a pressure support system that includes a pressure generating system having a pressure generator that provides a primary flow of gas to a patient and a supplemental gas system adapted to provide a supplemental flow of gas to the patient. The pressure support system also includes a selectively acuatable valve associated with the supplemental gas system and a control unit. The valve regulates the supplemental flow of gas to the patient provided by the supplemental gas system. The control unit is coupled to the pressure generating system and the valve, and controls actuation of the valve based on the conditions of the pressure generator in the pressure generating system, so that if, for example, the pressure generator fails or is shut off, the control unit causes the valve to close, thereby shutting off the supplemental gas flow.
It is a further object to provide the user of the above-described pressure support system the additional ability to easily and readily determine whether the supplemental flow of gas is being delivered. This object is achieved by providing a monitoring system coupled to the above-described supplemental gas system. The monitoring system monitors the supplemental flow of gas in and provides an output indicative of whether gas is flowing in the supplemental gas system.
It is another object of the present invention to operate the above-described pressure support system of the present invention so as to conserve the supplemental gas being delivered to the patient as the supplemental gas flow. This object is achieved by monitoring the respiratory cycle of the patient and causing the supplemental gas system to deliver the supplemental flow of gas to the patient only during a selected portion of the respiratory cycle, as opposed to the entire respiratory cycle. This is accomplished by causing the valve to open at an appropriate time to deliver the supplemental gas during the selected portion of a respiratory cycle, such as during inspiration, and closing the valve at all other times during the respiratory cycle.
It is a still further object of the present invention to operate the above-described pressure support system to control
Duff Winslow K.
Keeports Douglas W.
Truitt Patrick W.
Haas Michael W.
Lewis Aaron J.
Respironics Inc.
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