Which of the following factors is/are associated with an increased risk for auto-PEEP?

1. Mechanical ventilation of a patient with obstructive lung disease
2. High-minute volume during mechanical ventilation
3. Acute respiratory distress syndrome (ARDS) patients
4. Pulmonary fibrosis
a. 1 and 4 only
b. 1, 2, and 3 only
c. 3 only
d. 1, 2, 3, and 4

ANS: B
Patients receiving mechanical ventilation for obstructive airways disease have a large degree of inhomogeneity in the emptying of lung units, and auto-PEEP can develop even at relatively low-minute ventilation. Auto-PEEP is common in mechanically ventilated patients with high-minute ventilation and thus occurs in some patients with ARDS.