Author Question: When is respiratory muscle fatigue likely to occur? a. When VE exceeds 20 of the maximum ... (Read 71 times)

PhilipSeeMore · **on:** Jul 16, 2018

When is respiratory muscle fatigue likely to occur?

a. When VE exceeds 20 of the maximum voluntary ventilation (MVV)
b. When VE exceeds 40 of the MVV
c. When VE exceeds 60 of the MVV
d. When VE exceeds 80 of the MVV

Question 2

Because an elevated PaCO2 increases ventilatory drive in normal subjects, the clinical presence of hypercapnia indicates which of the following?

1. Inability of the stimulus to get to the muscles
2. Weak or missing central nervous system response to the elevated PCO2
3. Pulmonary muscle fatigue
a. 1 and 2 only
b. 1 and 3 only
c. 2 and 3 only
d. 1, 2, and 3

stanleka1 · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: C
Comparing the spontaneous minute ventilation with MVV is a helpful index as fatigue and fail-ure are both likely to occur if the minute ventilation exceeds 60 of MVV.

Answer to Question 2

ANS: D
Because an elevated PaCO2 increases ventilatory drive in healthy subjects, the very existence of hypoventilation suggests other problems with the respiratory apparatus. Specifically, the presence of acute respiratory acidosis indicates one of three major problems: (1) the respiratory center is not responding normally to the elevated PaCO2, (2) the respiratory center is responding normally, but the signal is not getting through to the respiratory muscles, or (3) despite normal neurologic response mechanisms, the lungs and chest bellows are simply incapable of providing adequate ventilation due to parenchymal lung disease or muscular weakness.