"It is therefore desired to provide a treatment device which can replicate the cough function and which can be used in a person's home without necessarily requiring the assistance of a trained person, and which avoids or reduces the drawbacks of the above-described modified ventilators."
Supplementing the background information on this patent application, NewsRx reporters also obtained the inventors' summary information for this patent application: "According to the invention there is provided a treatment device having:
"a pump, the pump having an inlet side and an outlet side, the pressure at the inlet side in use being lower than atmospheric pressure, the pressure at the outlet side in use being higher than atmospheric pressure;
"a breathing tube for connection to a patient;
"a pressure sensor adapted to determine the pressure within the breathing tube;
"a valve which can selectively connect the breathing tube to the inlet side or the outlet side of the pump;
"a controller adapted to receive a pressure signal from the pressure sensor and to control the valve; and
"an indicator to indicate an operational status of the treatment device.
"Preferably the valve is a proportional servo valve. The use of a proportional servo valve permits the pressure in the breathing tube to be varied between zero and the maximum pump pressure. Thus, the pressure in the breathing tube is determined by the valve and not by the pump.
"Preferably the valve is a proportional solenoid valve, such valves being adapted to rapid movement whereby the pressure in the breathing tube can be set very accurately and can be adjusted quickly if the pressure in the breathing tube changes from the desired level due, for example, to the patient's face mask moving and consequently leaking air. A proportional solenoid valve can permit the pressure in the breathing tube to be adjusted substantially more quickly, and significantly more accurately, than by varying the output of the pump.
"Desirably, the proportional servo valve is a rotary proportional solenoid valve. The valve is designed to reciprocate (or oscillate) between operational positions, one operational position corresponding to the breathing tube connected to the inlet side of the pump, the other operational position corresponding to the breathing tube connected to the outlet side of the pump. By switching the valve between these operational positions the pressure within the breathing tube can be altered from positive to negative (and vice versa) very quickly.
"In order to replicate a cough function, it is desirable that the pressure profile comprises a gradual increase to a first (positive) pressure, and then a rapid decrease to a second (negative) pressure. This may be followed by a gradual increase to a third (negative) pressure which is maintained for a period of time before the pressure rises to the first pressure once again. The magnitude of the third (negative) pressure is smaller than the magnitude of the second (negative) pressure, i.e. it is closer to atmospheric pressure. The values of the first, second and third pressures, and the durations of each part of the cycle, can be pre-set by the user to match the requirements of a particular patient (although the third (negative) pressure may be pre-set by the device manufacturer).
"The second (negative) pressure is therefore ideally a rapid negative spike in pressure lasting for substantially less than one second (e.g. a couple of hundred milliseconds), and the third (negative) pressure is preferably maintained for several seconds. Such a pressure profile facilitates the removal of secretions from the patient's lungs whilst reducing the likelihood of collapsing of the patient's lungs and/or airways (as can occur in some patients if a large-magnitude negative pressure is maintained).
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