The volume waveform generated by a ventilator remains the same against changing lung me-chanics. Which of the following parameters might this device be controlling? 1. Volume 2. Flow 3. Pressure

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

ANS: A
If the ventilator controls flow, the flow and volume waveforms will remain consistent, but pres-sure will vary with changes in respiratory mechanics. Flow can be controlled directly using something as simple as a flow meter or as complex as a proportional solenoid valve. Flow can be controlled indirectly by controlling volume.