Transition from restrictive to obstructive lung function impairment during treatment and follow-up of active pulmonary tuberculosis

Pulmonary tuberculosis (PTB) is associated with the development of chronic airflow obstruction (AFO), but the nature, evolution and mechanisms responsible for the lung function abnormalities seen after PTB are poorly understood. We examined the progression of changes in lung physiology in patients treated for PTB. Adult patients receiving treatment for a first episode of tuberculosis were prospectively followed with serial lung physiology and quantitative CT lung scans performed at baseline, 2, 6, 12 and 18-months during and after completion of treatment. Forty-nine patients (median age 26 years; 37.2% males) were included, and 43 studied. During treatment, lung volumes improved and CT fibrosis score decreased, but features of AFO and gas trapping emerged, and reduced diffusing capacity, seen in a majority of patients persisted. One year after completion of treatment, seven patients (16.3%) had AFO and 14 (32.6%) had gas-trapping on CT imaging which increased over time evidenced by a progressive increase in residual volume (median change +19%pred.; P<0.01), without associated increase in CT emphysema scores. Taken together, these findings suggest emergence of gas-trapping caused by progression of small airway pathology during the healing process. Simple spirometry alone does not fully reveal the impairments resulting from episodes of PTB.