Lung function in former intravenous drug abusers: The effect of ubiquitous cigarette smoking

Purpose: To determine whether former intravenous drug abusera (IVDAs) demonstrate reductions in pulmonary function, especially in the diffusing capacity (DL_CO), after adjustment for the effects of their ubiquitous smoking habit. Knowledge of baseline DL_CO in this high-risk group is important in evaluating the effects of human immunodeficiency virus (HIV) and ensuing opportunistic infections. Patients and methods: Measurements of single-breath DL_CO, forced vital capacity (FVC), and forced expiratory volume in 1 second (FEV₁) were compared with predictive values that adjust for the effects of smoking. Patients were 98 ambulatory former IVDAs regularly attending a methadone maintenance program (62 men and 36 women; 94 current smokers, two exsmokers, and two nonsmokers). Results: When adjusted for smoking, FEV₁ and DL_CO were no different in the study sample than in cross sections of the general population: mean FEV₁ 105% predicted (men) and 97% predicted (women), mean DL_CO 95% predicted (men) and 99% predicted (women). Eleven percent of the IVDAs had abnormal values for DLco; only one subject had a value less than 50% of predicted. Conclusions: Most former IVDAs who regularly attend an ambulatory methadone program have normal DL_CO values when the effects of smoking are taken into account. A decrease in DL_CO in such subjects is presumptive evidence of superimposed disease, most likely related to opportunistic infections or HIV-associated malignancy or alveolitis.