Airway resistance and obesity are independent factors for the occurrence of dynamic hyperinflation in asthmatics

Background: Asthma is a chronic obstructive airway disease with high prevalence in obese subjects. During exercise, the dynamic hyperinflation (DH) has been described in both non-asthmatics obese and patients with obstructive airway disease; however, remain unknown the presence of DH in obese asthmatics. Aim: To assess if airway resistance (Raw) and obesity are involved in the DH in asthmatics. Methods: 48 moderate or severe asthmatics either with grade II obesity (OB;BMI≥35kg/m 2 ) or non obese subjects (NOB;BMI≤24,9kg/m 2 ) were evaluated on 3 distinct days when they performed a cardiopulmonary exercise test to quantify peak VO 2 (day 1) and a submaximal exercise test (75% of maximum load) to assess DH (day 2). Anthropometric measurement and pulmonary function tests were also evaluated (day 3).T-test was used to compare the continuous variables and chi-square test to compare the categorical ones. Results: OB asthmatics had a lower expiratory reserve volume (35±23 vs. 62±40% of pred.) and greater FEV 1 /FVC (74±8 vs . 68±9) compared with NOB, respectively (p vs. 4%, respectively; p vs. 12%(p vs. 0.79% compared to NOB with lower Raw. Conclusion: Our results suggest that airway resistance and obesity are independent factors for the occurrence of DH in asthmatics.