Statistical analysis
HEAT
Data (raw scores) of Comfort and Symptom Scores are expressed as median (minimum–maximum) and interquartile range (IQR 75–25) and presented by boxplots (box: median, 25th-75th percentile; whiskers: 5–95 percentile).A generalized linear mixed (GLM) model, along with generalized estimating equations (GEE), was used on the logarithmized sum values of Comfort Score and Symptom Score as dependent variable. The GEE procedure extends the GLM to allow for analysis of repeated measurements. Here, load level and time of measuring were included as influencing factors. This approach allows intraindividual comparison at the different examination times (i.e., each subject is compared to him/herself). Least Squares Means were calculated based on these models. The situation without mask at each load level (pre, E1, E2, E3, post) or each time of measurement (pre, 30, 60, 90, 120, 150, 210, 240, post) was used as reference. Also considered were influencing factors such as sex, age (per 10 years) and height (per 10 cm). Further influencing factors on the sum of Comfort Score and cognitive function were tested by including them individually as potential factors to the model.Since the GLM model was only applicable to the sum of Comfort and Symptom Score, we processed the data for the single questions using analysis of variance (Friedman test, Dunn's multiple comparisons test as post-hoc test). For Comfort Score, at each load level (pre, E1, E2, E3, post) or each time of measurement (pre, 30, 60, 90, 120, 150, 210, 240, post) the data with mask were compared with the respective non-mask situation (reference).Pearson's chi-squared test was used to examine possible differences between men and women related to the different sensitivity scales. The Spearman rank correlation was calculated to predict the monotone association between parameters for correlations. This is further visualized by contrasting the parameters in a heat map.A p-value of < 0.05 was considered statistically significant. Analyses were performed using SAS 9.4 (SAS Institute, Cary, NC, USA). Figures were drafted with SAS 9.4 and GraphPad Prism version 9 (GraphPad Software, San Diego, CA, USA).