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

?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.