It is known that pulmonary function is impaired during the course of HIV infection even in early stages. In order to estimate the resulting reduction of exercise capacity, different groups of HIV patients were investigated. Group 1 consisted of 20 patients without a history of respiratory disease and without actual lung disease, group 2 of 18 patients with a former episode of Pneumocystis carinii pneumonia (PCP) without actual lung disease, and group III of 37 patients with different broncho-pulmonary complications including PCP 20 normal subjects served as controls. Spirometry, diffusing capacity (DL_CO) and exercise tests including arterial blood gas analysis (BGA) were performed in patients and controls. Compared to the controls group 1 patients revealed a decreased DLco (TCO: 83+15 vs. 67 ± 15%_Pred.norm.) while spirometric data were normal. VO₂ and O₂ pulse at the anaerobic threshold (17.7 ± 5.1 vs. 14.3 ± 2.6 ml/kg min and 10.8 ± 4.0 vs. 8.6 ± 1.9 ml/beat, respectively) and maximum exercise (33.9 ± 9.7 vs. 22.1 ± 3.4 ml/kg min and 15.0 ± 5.0 vs. 11.3 ± 2.5, respectively) were decreased, whereas AaDO₂, V_D/V_T, and the HR/VO2 slope were normal. The reserves of heart rate and ventilation were high. Except for a reduced maximum work rate in group 1, no significant difference was found between groups 1 and 2. Group 3 patients differed most from groups 1 and 2 with respect to spirometry, DLco and AaDO₂, rather than VO₂. VO_2max and maximum work rate correlated with the Walter Reed classification: r = 0.72 (p < 0.0001) and r = 0.78 (p < 0.0001), respectively, suggesting that a more advanced stage of immunodeficiency leads to a decreased exercise capacity. There was also a significant correlation between maximum work rate and the Broca index: r = 0.57 (p < 0.0001).We conclude that an impairment of DLco and exercise capacity is associated with the infection of HIV-1. Analysis of gas exchange patterns suggests that the cause of exercise limitation in groups 1 and 2 is due to anemia and a neuromuscular disorder in the exercising muscles, rather than pulmonary limitations, as were observed in group 3.

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