Importance

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Abstract

A mechanism is provided for a respiratory ventilator by which the gas-delivery mechanism of the ventilator can be caused to deliver gas to the patient either at a predetermined flow rate or at a rate directly controlled by the patient's instantaneous demand. The mechanism includes a pressure-responsive device adapted to produce an analog signal indicative of the difference between a reference pressure and the patient's airway proximal pressure. The analog signal has a first polarity when the proximal pressure is less than the reference pressure in response to an inhalation effort, and a second polarity when the proximal pressure is greater than the reference pressure in response to an exhalation effort. A first control mechanism is provided which causes the gas-delivery system to deliver gas at a rate which is proportional to the absolute value of the analog signal when the signal has the first polarity and an absolute value at least equal to a predetermined threshold value. The control mechanism responds to the second polarity of the analog signal by causing the gas-delivery system to recharge itself with a fresh supply of gas. The same gas-delivery mechanism can also be operated in an assist mode to deliver gas at a predetermined flow rate by a second control mechanism responsive to the analog signal.

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First Claim