Effects of Inspiratory Exercise With Linear and Nonlinear Load on Respiratory Variables Post-Bariatric Surgery

Obesity leads to changes in respiratory function, causing reduced lung volumes and mechanical disadvantage of the respiratory muscles. We sought to evaluate the effect of breathing exercises using devices that impose linear and nonlinear load on reversing diaphragm dysfunction and the prevalence of atelectasis after bariatric surgery.

This was a blind randomized clinical trial. Preoperatively, we assessed the subjects' maximum inspiratory pressure by measuring nasal inspiratory pressure and respiratory muscle endurance with an incremental test based on sustained maximum inspiratory pressure (sustained P_Imax) and the prevalence of atelectasis by chest radiograph. Subjects were then randomized into 2 groups: a linear load pressure group and nonlinear load pressure group; both groups received conventional respiratory physiotherapy. Subjects were reassessed on the second day after bariatric surgery.

We included 40 morbidly obese women (body mass index > 40 kg/m²), age 25-55 years, who underwent bariatric surgery by laparotomy. The groups were homogeneous with respect to age (P = .11), body mass (P = .12), height (P = .75), body mass index (P = .75), nasal inspiratory pressure (P = .48), sustained P_Imax (P = .89), and absence of atelectasis at baseline. In the reassessment, both groups showed significant reduction in nasal inspiratory pressure (P < .001) and maintenance of sustained P_Imax (linear load pressure P = .51; nonlinear load pressure P = .055). The prevalence of atelectasis was 15% for linear load pressure and 25% for nonlinear load pressure, with no significant difference between groups (P = .69).

Both groups were able to maintain respiratory muscle endurance after bariatric surgery. In addition, the treatment contributed to controlling atelectasis so that it did not cause clinical repercussions to the subjects. (ClinicalTrials.gov registration NCT02298517).