PURPOSE: Pulmonary diffusion impairment and the development of precocious emphysema have been previously described in HIV-infected individuals in the pre-HAART era. We sought to investigate how widespread availability and use of HAART has influenced gas exchange in this population. In addition we sought to identify the structural etiologies underlying diffusion impairment using HRCT as a morphologic surrogate.
METHODS: Complete pulmonary function tests and high-resolution computed tomography of the chest were performed on 239 HIV-seropositive individuals (mean age = 42.8 +/− 8.7; mean pack years = 18.9 +/− 21.2). Diffusing capacity for carbon monoxide (DLCO) was performed using the single breath method and corrected for hemoglobin and race. Chest CT's were individually reviewed by a chest radiologist blinded to clinical status. Findings of emphysema, bronchial wall thickening, bronchial dilatation and pulmonary fibrosis were recorded. We specifically sought to identify chest CT findings in subjects with the lowest quartile of DLCO values.
RESULTS: Overall, the mean DLCO for the entire cohort was 76.9 +/− 15.8 % of predicted. The lowest quartile had diffusing capacities less than 68% of predicted (mean = 57.6 +/− 9.5 % of predicted). 53% of these individuals had evidence of emphysema on CT, generally a mild centrilobular pattern most prominent in the upper lobes. 31% had bronchial wall thickening, 24% had bronchial dilatation and 15% had evidence of air-trapping. Only 1.3% had any evidence of fibrosis (all focal changes).
CONCLUSION: The most common HRCT correlate of diffusion impairment among the HIV-seropositive population was pulmonary emphysema, followed by airway abnormalities. Interstitial fibrosis was uncommon.
CLINICAL IMPLICATIONS: Despite the widespread use of HAART, HIV-seropositive individuals commonly have reductions in diffusing capacity, most likely related to emphysema. Given the high smoking prevalence and advancing age of the HIV-seropositive population, COPD is likely to become an increasingly common clinical problem in this group of individuals.
DISCLOSURE: Dylan Wirtz, None.