RESUMEN
BACKGROUND: Pulmonary gas exchange impairment (GEI) is a common consequence of intrathoracic sarcoidosis presenting with important therapeutic and prognostic implications. OBJECTIVE: To determine the role of clinical, radiographic and functional variables in predicting GEI during moderate exercise at the estimated lactate threshold (theta(L)) in patients with sarcoidosis. METHODS: Fifty-four outpatients (29 females) with biopsy-proven sarcoidosis had clinical evaluation (baseline dyspnea index), lung function tests and an incremental cardiopulmonary exercise test with theta(L) estimation. On a separate day, patients underwent a constant work rate test at theta(L) with assessment of arterial blood gas tensions. RESULTS: There was no evidence of GEI [DeltaP (A - a) O(2)/VO(2) >20 mm Hg.l. min(-1)] in patients with radiographic stages 0-I (n = 13). In the remaining 41 patients, GEI was associated with more extensive radiographic involvement and reduced diffusing capacity of the lung for carbon monoxide (DL(CO)), forced expiratory volume in 1 s, total lung capacity and forced vital capacity (% predicted;p < 0.05); baseline dyspnea index and resting arterial blood gas tensions, in contrast, were not significantly related to GEI. DL(CO) correlated best with GEI. The negative predictive value of DL(CO) >70% predicted (absent-to-mild impairment) was 91.3% (sensitivity = 81.8%) and the positive predictive value of DL(CO)