Body plethysmography in chronic obstructive pulmonary disease patients: A cross-sectional study

Chronic obstructive pulmonary disease (COPD) is the fourth most common cause of death in the world, for which smoking is a common cause. It is preferable to diagnose COPD at an earlier stage and to assess its progression so that mortality and morbidity of the disease could be reduced. Hence, we conducted this study to assess parameters of body plethysmography in Indian population where the data are lacking and to assess whether the use of body plethysmography can detect COPD earlier.

The study was approved by the Ethics Committee at B. J Government Medical College, Pune. In this comparative randomized cross-sectional study, healthy control subjects (CN), smokers without COPD diagnosis (SM) who were smoking for more than 5 pack-years and smokers with COPD who were further classified depending upon GOLD criteria as mild COPD (C1), moderate COPD (C2), and severe COPD (C3) (n = 30 each group) were considered. All the participants were males who gave written informed consent. Subject underwent routine spirometry (FEV₁, FVC, FEV₁/FVC, PEFR, and FEF_25-75%) along with body plethysmography where sGaweff, sGawtot, residual volume (RV), total lung capacity (TLC), and inspiratory capacity (IC) were recorded.

The differences in lung function were compared between healthy controls and smokers and also between the three groups of COPD severity (GOLD guidelines) employing univariate analysis of variance and Bonferroni's post hoc test.

Spirometry could not differentiate between smokers without COPD and healthy controls. However, three parameters on body plethysmography (IC, sGawtot, and sGaweff) were sensitive enough to detect differences between smokers without COPD and healthy controls.

Using body plethysmography, the vexed question troubling the clinician, which of the smokers progress to COPD and who do not before they develop irreversible changes can perhaps be answered if further large-scale multicenter studies and long-term follow-up studies confirm the findings in this study.