Statistical analysis
The LMM was used to estimate mean PCF, standard error, and confidence interval which described the changes in the PCF according to the position or maneuver. Applied position, maneuvers, TIV, and interaction between maneuver and position were included as fixed effects, and participant-specific random intercepts were included as a random effect to account for repeated measures within participants covering individual, different baseline pulmonary functions. The normality test was confirmed for residuals. The strength of the linear correlation between PCF and TIV was analyzed using Pearson’s correlation analysis after calculating the correlation coefficient R