Thorax 1983;38:778-784 Pattern of breathing during exercise in patients with interstitial lung disease

ABSTRAcr The responses to exercise were studied in 41 patients with pulmonary fibrosis, in whom vital capacity (VC) was reduced to 62 % of predicted normal values. Maximum power out-put (POmax) was 53 % predicted; there was a significant relationship between POma0 and VC (r = 0.564). The maximum ventilation achieved during exercise was also related to VC (r = 0.614). Although arterial oxygen saturation (Sao2) fell by more than 5 % in 13 of 31 patients, there was no relationship between either Sao2 at POmax or the exercise related fall in Sao2 and POmax. Heart rate responses were higher than normal predicted values in seven patients, all of whom showed a low POmax (36 % predicted); this finding was due only in part to a fall in Sao2. The ven-tilatory response to exercise was within normal limits for the patients as a whole; those subjects with the lowest POm, showed relatively higher ventilatory responses to exercise but the differ-ence was not significant. The pattern and timing of breathing was studied in 32 patients and com-pared with control subjects matched by sex, age, and size. Tidal volume (VT) was low in the patients; maximum VT was related to VC (r = 0.761), but at low values of VC VTmax was higher than in healthy subjects with comparable VC. The total breathing cycle time (Ttot) fell with prog-ressive exercise in patients and controls; Ttot for a given ventilation was shorter in the patients