The primary outcome was the change in global LUS score from pre-APP on day 1 to pre-APP on day 4. Secondary outcomes included changes in SpOratio, RR, and ROX index, as well as the differences in these variables between patients who were intubated and those who avoided intubation , and between responders and non-responders. Responders were defined as those patients whose SpOratio increased by ≥ 20% after the supine positioning of the first APP session.
], a confidence level of 95% and power of 95%, the number of patients was 70. Considering an attrition rate of 5%, we calculated the total sample size as 74.The normality of distribution for continuous variables was assessed by Kolmogorov–Smirnov test, and presented as mean ± SD or as median and interquartile range . Repeated measures ANOVA or Friedman’s test was used to compare differences of the variables pre-APP, post-APP, and post-supine.