Pulmonary tuberculosis treated with directly observed therapy: serial changes in lung structure and function

(1) To correlate structure (CT) with function in pulmonary tuberculosis (TB), and (2) to describe the evolution of structural and functional abnormalities when pulmonary TB is treated with directly observed therapy.

Twenty-five patients with drug-susceptible pulmonary TB, 15 cavitary and 10 noncavitary, were studied prospectively. Conventional CT and pulmonary function testing (spirometry, diffusing capacity, and arterial blood gases) were performed at baseline, and after 1 and 6 months of directly observed therapy.

All but one patient with noncavitary miliary TB had CT evidence of endobronchial disease, and all patients with cavitary disease had coexistent reduced lung attenuation, the latter presumably a result of gas trapping, hypoxic vasoconstriction, and vascular injury. Functional impairment was minimal and in proportion to the number of diseased segments and cavitary volume. Bronchiectasis was significantly more likely to complicate cavitary than noncavitary disease (64 vs 11%; p<0.05).

CT findings correlate well with function in pulmonary TB. Physiologic data were consistent with the concept that pulmonary TB is an endobronchial disease that causes parallel reductions in ventilation and perfusion. This concurrent involvement of both airways and contiguous pulmonary blood supply offers an explanation for the minimal respiratory limitation experienced by these patients despite often extensive lung disease. Supervised therapy of drug-susceptible disease results in minimal structural and functional residua.