Which of the following types of compressor can accommodate a mechanical ventilator? 1. Diaphragm 2. Liquid air 3. Rotary 4. Piston

a. 1 c. 3 and 4
b. 2 and 4 d. 1, 3, and 4

ANS: C
Rotary compressors use a rotating vane to compress air from an intake valve. As the rotating vane turns, gas is drawn into the cylinder through a one-way valve (Figure 3-16). The rotor turns, which causes the gas to be compressed as the oval-shaped cylinder becomes smaller. The com-pressed gas is then forced out of the compressor through another one-way outflow valve. Low-pressure rotary compressors are used in ventilators such as the Bennett MA-1. Piston com-pressors use the action of a motor-driven piston to compress atmospheric air. The piston is seated within a cylinder casing and is sealed to it with a carbon or Teflon ring. Figure 3-14 illustrates the operational principle of a typical piston air compressor used to power a mechanical ventilator.