A ventilator's pressure waveform changes when a patient's lung ...

[Yi-Chen]

A ventilator's pressure waveform changes when a patient's lung mechanics change, but its vol-ume waveform remains the same. The device does not directly control the delivered volume. What is this ventilator?
 
  a. Volume controller
  b. Pressure controller
  c. Time controller
  d. Flow controller

Question 2

Which of the following are true of the relationship between flow and volume? 1. Volume is the integral of flow. 2. Volume is the derivative of flow. 3. Flow is the derivative of volume.
 
  a. 1 and 2 only
  b. 1 and 3 only
  c. 2 and 3 only
  d. 1, 2, and 3

[Laurenleakan]

Answer to Question 1

ANS: D
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.

Answer to Question 2

ANS: B
This follows from the fact that volume and flow are inverse functions of time (i.e., volume is the integral of flow and flow is the derivative of volume).