An analysis of submaximal exercise responses in patients with sarcoidosis and fibrosing alveolitis.

An increase work rate exercise test was performed by 15 patients with sarcoidosis and by 20 patients with fibrosing alveolitis. The patients with sarcoidosis had a moderate reduction in total lung capacity (TLC) and transfer factor (DLCO), with chest radiographs showing widespread pulmonary infiltration but no evidence of fibrosis. The patients with fibrosing alveolitis had a significantly greater reduction in TLC and DLCO than those in the sarcoidosis group. Values for cardiac frequency (fH) and ventilation(V) were interpolated to the standard oxygen uptakes of 0.75, 1.0 and, where possible, 1.5 litres/min (33.5, 44.6 and 67 mmol/min respectively). The tidal volume at the ventilation of 20 and 30 litres/min was also determined. The exercise responses were compared to two groups of 20 normal men; each group being age matched to one group of patients. The fH at oxygen uptakes of 0.75, 1.0 and 1.5 litres/min were significantly higher in both patient groups than in the normal men. The submaximal indices for V were significantly greater in both patients groups than in the normal subjects at all three levels of oxygen uptake, and significantly greater in patients with fibrosing alveolitis than in those with sarcoidosis. The tidal volumes at 20 and 30 litres/min were smaller than normal in both patient groups but differences were removed by normalizing for differences in vital capacity. The maximum exercise ventilation measured in the patients with fibrosing alveolitis was significantly correlated with measurements of lung volume. Submaximal indices detect significant abnormalities during exercise in patients with pulmonary fibrosis and represent an alternative method for documenting abnormal exercise responses. Despite comparable radiological abnormalities the functional impairment in fibrosing alveolitis is much greater than in sarcoidosis. Thus the physiological abnormalities are not comparable quantitatively although they share a common qualitative difference.