CARDIORESPIRATORY RESPONSES TO INCREMENTAL EXERCISE IN SARCOIDOSIS PATIENTS WITH NORMAL SPIROMETRY

Patients with sarcoidosis are known to have histologic pulmonary abnor malities despite normal lung fields or conventional pulmonary function or both. These patients permit a useful assessment of the alleged gre ater sensitivity of the various measurements made during incremental c ardiorespiratory exercise testing. Abnormal responses on such testing may provide insight into such complaints as dyspnea in these patients. Incremental exercise testing was performed on 30 patients with biopsy -proven sarcoidosis who had normal spirometry; 13 had clear lung field s radiographically. Of these patients, the 21 who had normal single-br eath diffusing capacity for carbon monoxide (Dsb; [group A]) were comp ared with the 9 who had decreased Dsb (group B). Half of the group A p atients had excessive ventilation and 38% had increased dead space to tidal volume ratio (V-D/V-T), but frequencies of these abnormalities w ere greater in group B, 89 and 78%, respectively. Ventilatory response , as minute ventilation to oxygen consumption ratios ventilatory equiv alents, and deadspace to tidal volume ratio (V-D/V-T) ratios were high er in group B. Widened alveolar-arterial oxygen pressure differences w ere seen in 7 of 9 group B patients but only 1 of 17 group A patients. This study supports the clinical impression that occult pulmonary imp airment may be present in patients (in this case, sarcoidosis patients ) with normal pulmonary function, and corroborates the utility of exer cise testing in demonstrating such impairment. Reduction in Dsb predic ted greater frequency of abnormal exercise responses, especially in ox ygenation.