Author Question: What will result from applying positive pressure below the critical opening pressure to alveoli that ... (Read 55 times)

student77 · **on:** Jul 16, 2018

What will result from applying positive pressure below the critical opening pressure to alveoli that are collapsed?

A. The patient's hypoxemia may be corrected.
B. The collapsed alveoli become overdistended.
C. The lung's pressure-volume relationship changes sharply.
D. Ventilation fails to enter these alveoli.

Question 2

Calculate a patient's alveolar ventilation (A) when the respiratory rate (f) is 12 breaths/minute, the tidal volume (VT) is 600 ml, and the dead space volume (VD) is 150 ml.

A. 7,200 ml/minute
B. 5,400 ml/minute
C. 4,000 ml/minute
D. 1,800 ml/minute

cclemon1 · **Reply #1 on:** Jul 16, 2018

Answer to Question 1

ANS: D
A. Incorrect response: Perfusion will continue past collapsed alveoli.
B. Incorrect response: The collapsed alveoli do not inflate at all when the critical opening pressure is not achieved.
C. Incorrect response: The lung's pressure-volume curve remains flat because volume does not change as no gas enters these alveoli.
D. Correct response: Because the critical opening pressure is not reached, these alveoli fail to open, and ventilation continues to be absent while perfusion persists. Consequently, the patient's hypoxemia remains uncorrected.

Answer to Question 2

ANS: B
A. Incorrect response: See explanation B.
B. Correct response: This patient's alveolar ventilation (A) is calculated as follows:
STEP 1: Determine the dead space ventilation (D).
D = f(VD)
= (12 breaths/minute)(150 ml)
= 1,800 ml/minute
STEP 2: Find the minute ventilation (E).
E = f(VT)
= (12 breaths/minute)(600 ml)
= 7,200 ml/minute
STEP 3: Calculate the alveolar ventilation (A).
A = E D
= 7,200 ml/minute 1,800 ml/minute
= 5,400 ml/minute
Alternatively,
12 breaths/minute (600 ml 150 ml) = 5,400 ml/minute

C. Incorrect response: See explanation B.
D. Incorrect response: See explanation B.