Answer to Question 1
ANS: D
P(Aa)O2 = (age/4) + 4
P(Aa)O2 = (56/4) + 4
P(Aa)O2 = 18 mm Hg
Answer to Question 2
ANS: D
In intubated patients, sources of imposed work of breathing include the endotracheal tube, ven-tilator circuit, and auto-PEEP due to dynamic hyperinflation with airflow obstruction, as is commonly seen in the patient with COPD.