Abstract: An air/oxygen blender, optionally with an associated oxygen analyzer, is provided with an exhaust valve in fluid communication with one or more of a proportioning valve and a gas outlet which periodically opens to vent gas therefrom. The exhaust valve is preferably an electrically actuated valve, most preferably a solenoid valve, controlled by a control unit which periodically opens the exhaust valve. In another embodiment, an oxygen analyzer is provided with an exhaust valve in fluid communication with an oxygen sensing chamber. Preferably, the control unit controls the frequency of exhaust valve opening and the time period of exhaust valve opening. A method of prevention of contamination of a lower pressure source air or source oxygen connected to an air/oxygen blender is accomplished by periodically venting of gas from the exhaust valve.

Abstract: Respirator techniques are described for measuring the linear slope of the inspiratory phase to monitor lung compliance. The measurements of the slope characterize a pressure wave index which is recorded at regular intervals to provide a clear record from which a warning of the patient's pulmonary condition such as lung compliance can be derived. Several techniques are shown and described. In one, the pressure wave index is determined by sensing the times when the pressure-time signal reaches predetermined pressure levels above a base line. In another technique, the linear slope segment is searched for and its slope then measured.

Abstract: A respirator is described wherein a plurality of pneumatic bistable elements are employed in an automatically operated pneumatic circuit. A constant inspiratory to expiratory ratio pneumatic circuit is provided to simplify respirator control. A demand sensing circuit interrupts an oscillator to commence an inspiratory phase in response to pressure changes introduced in a patient gas supply circuit. A manual control is provided to enable manual dispensing of respiratory support. A pneumatic circuit is provided for generating an end inspiratory plateau period. During this period gas equilibration in different compartments of the lung is permitted and in addition a measurement of peak intraalveolar pressure is made.

Abstract: A respirator is described using pneumatic elements to generate a variety of operating modes. A gas mixture is passed through a patient connection which is coupled to supply the gas through a patient port to a patient. After passing the patient port the gas is controllably exhausted to atmosphere through an exhaust port in a control valve. The control valve regulates the closure of the exhaust port to provide inspiration and expiration control at the patient port. Pneumatic logic elements are combined to provide automatic inspiration and expiration support with different modes such as volume limited or pressure limited and with selection over the duration of the respective breathing phases. Various operating modes are obtained with variable restrictors selectively placed with the pneumatic logic elements.

Abstract: A respirator is described using pneumatic elements to generate a variety of operating modes. A gas mixture is passed through a patient connection which is coupled to supply the gas through a patient port to a patient. After passing the patient port the gas is controllably exhausted to atmosphere through an exhaust port in control valve. The control valve regulates the closure of the exhaust port to provide inspiration and expiration control at the patient port. Pneumatic logic elements are combined to provide automatic inspiration and expiration support with different modes such as volume limited or pressure limited and with selection over the duration of the respective breathing phases. Various operating modes are obtained with variable restrictors selectively placed with the pneumatic logic elements.