Effects of positive inspiratory and expiratory pressure on diaphragmatic mobility in asymptomatic individuals: Randomised, crossover clinical trial

Background: The application of positive pressure (CPAP) improves pulmonary ventilation, but may negatively impact diaphragm geometry and function. Diaphragm mobility and strength are essential for lung function. Consequently, impairment of the diaphragm can reduce respiratory capacity. Objective: This study aims to evaluate the effects of positive pressure on diaphragm mobility in healthy individuals during spontaneous breathing. Methods: This is a randomised, crossover, double-blind clinical trial involving asymptomatic individuals aged 18–50 years. Participants randomly received the following non-invasive ventilation: continuous positive airway pressure (CPAP) of 5, 10, and 15 cmH 2 O, or bi-level inspiratory positive airway pressure (IPAP) of 10, 12, and 15 cmH 2 O with Positive end-expiratory pressure (PEEP) of 5[Formula: see text]cmH 2 O. Diaphragm mobility was assessed using ultrasound imaging during spontaneous breathing and the six levels of positive pressure. Data were analysed using a mixed linear model and Dunn–Sidak post-test. Results: The study included 82 volunteers. Diaphragmatic mobility increased during CPAP at 15[Formula: see text]cmH2O and in bi-level modes with inspiratory positive airway pressures (IPAPs) of 10, 12, and 15[Formula: see text]cmH2O (with PEEP fixed at 5[Formula: see text]cmH2O), compared to spontaneous breathing. The mean differences and confidence intervals for these comparisons were as follows: [CPAP 15[Formula: see text]cmH2O versus spontaneous breathing (SB) ([Formula: see text]3.81[Formula: see text]mm; 95% CI: 0.95–6.67), IPAP 10 [Formula: see text] PEEP 5 cmH2O versus SB ([Formula: see text]3.44[Formula: see text]mm; 95% CI: 0.58–6.30), IPAP 12 [Formula: see text] PEEP 5[Formula: see text]cmH2O versus SB ([Formula: see text]3.96[Formula: see text]mm; 95% CI: 1.10–6.82), and IPAP 15 [Formula: see text] PEEP 5[Formula: see text]cmH2O versus SB ([Formula: see text]6.21[Formula: see text]mm; 95% CI: 3.35–9.07)]. Conclusion: The positive inspiratory and expiratory pressures were sufficient to increase diaphragmatic kinetics, particularly when higher positive pressures were used.