Abstract: Normal breathing cycles of a ventilator cause an alarm controller circuit to emit a periodic pulse which resets a timer circuit thereby maintaining an alarm device in an "off" condition. Patient disconnect is sensed by an alarm trigger circuit which sends an inhibit pulse to the controller circuit inhibiting the timer circuit reset pulse. This causes the timer to "time out" thereby turning on an alarm actuator circuit which causes an audible and/or visual alarm condition.

Abstract: An improved patient ventilator for providing a mode of operation wherein mandatory breaths are supplied to a patient intermittently, and wherein those mandatory breaths are synchronized with the patient's normal breathing cycle. An adjustable timer provides an output signal for controlling the duration between mandatory breaths, and a delay circuit prevents the output signal from the timer from initiating the mandatory breath for a predetermined delay period to permit the patient to initiate that breath himself. The intermittent mandatory breaths are made "mandatory" by closing off an exhalation valve while a fixed quantity or pressure level of oxygen is supplied to the patient.