Statistical analysis
Normality assumptions were verified with the Shapiro–Wilk test. Independent t test (for normally distributed variables), Mann-Whitney A two-way mixed, absolute agreement, single measures intraclass correlation coefficient (ICC) was used to determine the intra-rater reliability for the upper airway variables. Analyses of covariance (ANCOVA) were used to compare changes in sleep, respiratory, and upper airway variables between baseline and therapy evaluation between both groups. Significantly different baseline characteristics between responders and non-responders were controlled for as covariates [To test the robustness of the results of ANCOVA and correlation analyses, sensitivity analyses were performed by excluding the outliers of the primary variable (i.e., CSAmin) [Statistical analysis was performed using the SPSS software (SPSS version 26, Chicago, IL, USA). A post hoc power analysis was conducted for the primary outcome variable (i.e., CSAmin) using software G*power (version 3.1.9, Franz Faul, Universität Kiel, Germany).