Which of the following factors would tend to increase the elastic component of the work of breathing?

1. Decreased compliance of the lungs or thorax
2. High frequencies of breathing
3. Increased VT
a. 1 and 3 only
b. 1, 2, and 3
c. 2 and 3 only
d. 1 and 2 only

ANS: A
When changing from quiet breathing to exercise ventilation, healthy subjects adjust their tidal volumes and breathing frequencies to minimize the work of breathing. Similar adjustments occur in individuals who have lung disease (Figure 11-12). Patients with "stiff lungs," i.e., decreased compliance, have increased elastic work of breathing. Large tidal volumes also increase the elastic component of work.