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 5Formula: see textcmH 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 15Formula: see textcmH2O and in bi-level modes with inspiratory positive airway pressures (IPAPs) of 10, 12, and 15Formula: see textcmH2O (with PEEP fixed at 5Formula: see textcmH2O), compared to spontaneous breathing. The mean differences and confidence intervals for these comparisons were as follows: CPAP 15[Formula: see textcmH2O versus spontaneous breathing (SB) (Formula: see text3.81Formula: see textmm; 95% CI: 0.95–6.67), IPAP 10 Formula: see text PEEP 5 cmH2O versus SB (Formula: see text3.44Formula: see textmm; 95% CI: 0.58–6.30), IPAP 12 Formula: see text PEEP 5Formula: see textcmH2O versus SB (Formula: see text3.96Formula: see textmm; 95% CI: 1.10–6.82), and IPAP 15 Formula: see text PEEP 5Formula: see textcmH2O versus SB (Formula: see text6.21Formula: see textmm; 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.
Ferreira et al. (Fri,) studied this question.