Statistical analysis
Statistical analyses were performed using Prism 5 (Graphpad software, San Diego, CA, USA) and Matlab R2018a (Mathworks, Natick, MA, USA). The Shapiro–Wilk test was used to test data for normality. Descriptive data were expressed as median [interquartile range (IQR)] or percentage (%) of total. The neuro-respiratory drive, neuro-mechanical coupling, and timing of the inspiratory muscles at each measurement series were compared using the Wilcoxon signed rank test. To assess if the changes in PS level induced significant changes in neuro-respiratory drive, neuro-mechanical coupling, and timing of the inspiratory muscles, one-way analysis of variance for repeated measures was performed (Skillings-Mack test). The relationship between neuro-respiratory drive and Pes-derived data (effort) in each ventilatory condition was assessed. For both inspiratory muscles, the correlation between EMG