Transition from Restrictive to Obstructive Lung Function Impairment During Treatment and Follow-Up of Active Tuberculosis
Received 16 December 2019
Accepted for publication 10 March 2020
Published 11 May 2020 Volume 2020:15 Pages 1039—1047
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 2
Editor who approved publication: Dr Richard Russell
Brian W Allwood,1,2 Elizna Maasdorp,3 Grace J Kim,4,5 Christopher B Cooper,6 Jonathan Goldin,4 Richard N van Zyl-Smit,2 Eric D Bateman,2 Rodney Dawson2
1Division of Pulmonology, Department of Medicine, Stellenbosch University, Cape Town, South Africa; 2University of Cape Town Lung Institute, and Division of Pulmonology, Department of Medicine, University of Cape Town, Cape Town, South Africa; 3DST/NRF Centre of Excellence for Biomedical Tuberculosis Research; South African Medical Research Council Centre for Tuberculosis Research; Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa; 4Center for Computer Visions and Imaging Biomarkers, Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA; 5Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, CA, USA; 6Departments of Medicine and Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
Correspondence: Brian W Allwood
Division of Pulmonology, Department of Medicine, Stellenbosch University, Rm 3013 3rd Floor; Clinical Building; Francie Van Zijl Drive; Medical School, Tygerberg 7505, South Africa
Background: Pulmonary tuberculosis (PTB) is associated with many forms of chronic lung disease including the development of chronic airflow obstruction (AFO). However, the nature, evolution and mechanisms responsible for the AFO after PTB are poorly understood. The aim of this study was to examine the progression of changes in lung physiology in patients treated for PTB.
Methods: Immunocompetent, previously healthy, adult patients receiving ambulatory treatment for a first episode of tuberculosis were prospectively followed up with serial lung physiology and quantitative computed tomography (CT) lung scans performed at diagnosis of tuberculosis, 2, 6, 12 and 18 months during and after the completion of treatment.
Results: Forty-nine patients (median age 26 years; 37.2% males) were included, and 43 were studied. During treatment, lung volumes improved and CT fibrosis scores decreased, but features of AFO and gas trapping emerged, while reduced diffusing capacity (DLco) seen in a majority of patients persisted. Significant increases in total lung capacity (TLC) by plethysmography were seen in the year following treatment completion (median change 5.9% pred., P< 0.01) and were driven by large increases in residual volume (RV) (median change +19%pred., P< 0.01) but not inspiratory capacity (IC; P=0.41). The change in RV/TLC correlated with significant progression of radiological gas trapping after treatment (P=0.04) but not with emphysema scores. One year after completing treatment, 18.6% of patients had residual restriction (total lung capacity, TLC < 80%pred), 16.3% had AFO, 32.6% had gas trapping (RV/TLC> 45%), and 78.6% had reduced DLco.
Conclusion: Simple spirometry alone does not fully reveal the residual respiratory impairments resulting after a first episode of PTB. Changes in physiology evolve after treatment completion, and these findings when taken together, suggest emergence of gas trapping after treatment likely caused by progression of small airway pathology during the healing process.
Keywords: tuberculosis, post-tuberculosis, chronic obstructive pulmonary disease, lung function, computed tomography, airflow obstruction
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