Application of whole body plethysmography for assessment of pulmonary function in patients with asthma and obesity

The incidence of asthma and obesity is constantly increasing. It is commonly acknowledged that obesity can make asthma more severe and poorly controlled. Conventional spirometry, despite of being a “gold standard” in diagnostics of lung diseases, cannot provide information on residual lung volume and bronchial resistance, which can be a key to understanding the mechanics of spirometric deviations found in asthma-obesity phenotype.The aim. To evaluate pulmonary function in patients with asthma and obesity by non-invasive and safe clinical method – body plethysmography.Methods. 46 women with asthma were enrolled into the study, of which 21 were obese and 25 had normal body weight. 18 women with obesity and 20 women with normal body weight were selected as controls. All the patients were postmenopausal. Body plethysmography was performed with MasterScreen Body device, CareFusion, Germany.Results. Asthma is associated with a decrease in forced vital lung capacity and an increase in residual volume. Also, Gensler index and peak expiration flows at 25, 50, and 75% expiration were decreased. Interestingly, specific effective resistance in patients with asthma without obesity was 30 – 40% higher than in the control group. In patients with asthma and obesity, specific effective resistance was 2,5 times higher than in the control group. Residual volume and bronchial resistance were found to have a strong positive correlation.Conclusion. despite of similar spirometric changes, only asthma in obesity was marked by an increase of specific bronchial resistance. This finding can be related to higher energy load of breathing process in obese asthma.