Which of the following devices are output control valves used to regulate the flow of gas to the patient? I. rack and pinion poppet valves II. proportional valves III. electromagnetic poppet valves IV. pneumatic poppet valves

A. I, II only
B. III, IV only
C. I, II, III only
D. II, III, IV only

?ANS: D?I. Incorrect response: The electric motor/rack and pinion is a ventilator drive mechanism. The drive mechanism of a ventilator produces the force needed to deposit gas into the lungs of the patient.
II. Correct response: A proportional valve resembles a solenoid valve. It is operated via an electric motor whose rotation can be controlled in discrete arcs, or steps. Proportional valves change the size of their openings, thus influencing the shape of the flow-time waveform during inspiration. In fact, because the size of the opening can vary significantly, a variety of waveforms can be produced.
III. Correct response: The electromagnetic poppet valve is the same as a solenoid valve. It uses magnetism created by an electric current to control pneumatic pressure.
IV. Correct response: The pneumatic poppet valve uses small pneumatic pressure to control large pneumatic pressure.