Author Question: If a rectangular (square) pressure waveform is generated during pressure-controlled ventilation, ... (Read 112 times)

wrbasek0 · **on:** Jul 16, 2018

If a rectangular (square) pressure waveform is generated during pressure-controlled ventilation, what type of waveforms will develop for volume and flow?

A. volume waveform: exponential rise; flow waveform: exponential decline
B. volume waveform: exponential decline; flow waveform: exponential rise
C. volume waveform: sinusoidal; flow waveform: ascending ramp
D. volume waveform: descending ramp; flow waveform: rectangular

Question 2

Which of the following terms describe the configuration of a ventilator waveform? I. hyperbolic II. sinusoidal III. rectangular IV. exponential

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

dominiqueenicolee · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: AA. Correct response: A rectangular pressure waveform is accompanied by an exponentially rising volume waveform and an exponentially decaying (declining) flow waveform. The volume rises exponentially to a value equal to the product of the lung compliance and the difference between the PIP and the PEEP. That is,
volume = CL (PIP PEEP)
L = L/cm H2O (cm H2O)
The inspiratory flow declines exponentially from its peak level, which is equal to the difference between change in airway pressure multiplied by the airway resistance. Hence,
flow = Raw (PIP PEEP)
L/sec = cm H2O/L/sec (cm H2O)

B. Incorrect response: The choice has the waveforms opposite of what they actually are.
C. Incorrect response: When the pressure waveform is sinusoidal, the volume and flow waveforms are also sinusoidal.
D. Incorrect response: See explanation for choice A above.

Answer to Question 2

ANS: DI. Incorrect response: None of the ventilator waveforms is hyperbolic.
II. Correct response: The most common types of waveform produced by mechanical ventilators are:
Rectangular
Ramp
Exponential
Sinusoidal
III. Correct response: See explanation II.
IV. Correct response: See explanation II