Correlation between peak oxygen consumption, lung function, radiographic imaging, dyspnea and quality of life in people with post-tuberculosis pulmonary sequelae

Abstract

Introduction: Tuberculosis (TB) is one of the main causes of chronic diseases in the world, but the true post-tuberculosis (TB) conditions are not yet fully defined. It is known to have a complex and varied evolution and individuals with post-TB lung disease (PTLD) face increased risks of lung function abnormalities even after treatment. Structural changes that cause damage to lung function impact the reduction of exercise capacity and quality of life (QoL) of these individuals. Objective: To evaluate the correlations of peak oxygen uptake (VO₂peak) with lung mechanics, radiographic abnormalities, and QoL in adults with PTLD. Methods: This is a cross-sectional observational study in which 60 patients who had TB treated for at least 3 years, of both sexes, were evaluated. Eligible participants responded to the WHOQOL-BREF quality of life questionnaire, dyspnea assessment using the Modified Medical Research Council (mMRC) scale and 54 of them obtained chest radiography assessment. Additionally, patients underwent pulmonary function tests, including spirometry and impulse oscillometry (IOS). Finally, they performed a functional assessment during exercise using cardiopulmonary exercise testing (CPET). Results: Thirty-four (56.7%) were women with a mean age of 55.1 ± 14.1 years and a median time since the end of TB treatment of 24 (20–27) months. The highest peak oxygen consumption (VO2peak) was in men (18.3 ± 7.8 vs. 14.5 ± 5.3 ml/kg/min, P = 0.038). Regarding QoL, the physical domain had the worst performance (57.6 ± 17.5) and a significant positive correlation with VO2peak (rs=0.275, P=0.033). In spirometry, the normal (36.7%), restrictive (23.3%) and obstructive (40%) patterns showed significant differences in relation to VO2peak (19.7 ± 6.7 vs. 16.5 ± 5.9 vs. 12.7 ± 5.6 ml/kg/min, P=0.001). In IOS, 49 (81.7%) participants had an abnormal exam and the diagnosis of small tract disease was detected in 31 (51.7%) of them, with a significant negative correlation of the frequency response (Fres, rs=-0.675, P<0.0001). Those who had DPVA had a lower VO2peak when compared to those without DPVA (12.8 ± 5.1 vs. 19.7 ± 6.5 ml/kg/min, P<0.0001). In the radiography evaluation, the findings that caused the greatest impact on VO2peak were lung cavitation (11 ± 5.1 vs. 17.7 ± 6.4 ml/kg/min, P=0.001) and nodular opacity (14.1 ± 5 vs. 18.3 ± 7.5 ml/kg/min, P=0.016). In the multivariable regression analysis, forced vital capacity, age, sex and Fres explained 65% of the VO2peak variability. Conclusion: Patients with PTLD have a reduced VO₂peak. IOS demonstrates greater sensitivity in detecting changes in lung mechanics compared to spirometry, including those associated with SAD. Furthermore, we observed a correlation between VO₂peak and radiographic abnormalities, especially lung cavitations and nodular opacities. However, the relationship between VO₂peak and QoL is small. Therefore, both CPET and IOS can be useful in monitoring patients with PTLD, contributing to the assessment of the impact of interventions.