A 63-year-old man complains of a new cough and of breathlessness after walking up a flight of stairs. Chest examination reveals late inspiratory crackles but no wheezes. There is a mild clubbing of the fingers. His CXR is shown in figure. Which of the following would be found on pulmonary function testing (PFT)?
- increased arterial carbon dioxide pressure (PaCO2)
- normal compliance
- decreased carbon monoxide diffusing capacity (DLCO)
- increased vital capacity
- increased oxygen saturation with exercise
Answer(s): C
Explanation:
The CXR shown in Figure shows a diffuse reticulonodular pattern consistent with ILD. The hilar nodes are enlarged, suggesting lymphadenopathy. This is a nonspecific picture and may be caused by a large number of diseases. Occupational exposure to dust, gas, or fumes; sarcoidosis; idiopathic pulmonary fibrosis; and lung disease associated with the rheumatic diseases are the more common factors. Despite the diverse causes, there is a common pathogenesis: injury leads to alveolitis, which progresses to fibrosis.
Abnormalities on PFT are also similar: restrictive disease characterized by decreased lung volumes (vital capacity, TLC) and decreased compliance. Loss of the alveolar capillary bed leads to decreased carbon monoxide diffusing capacity. Arterial oxygen pressure (PaO2) may be normal at rest but is decreased with exercise. Arterial carbon dioxide pressure (PaCO2) may be normal or decreased because of hyperventilation, but it is not usually elevated in pure ILD.