Fig. 4

Associations of Albuterol and outcomes in subgroup analysis. The effect of Albuterol on the outcome variables was examined with a repeated measure design using mixed-effect linear regression modeling with the random subject effect and fixed effect variables including age, sex, height, weight, and the corresponding baseline measure of the outcome variable. The analysis was separately done within the whole group of participants and the subgroups based on RV/TLC and/or adherence. The number of participants (N), the summary statistics (mean ± standard deviation) for each outcome variables measured in the placebo visit and the albuterol visit as well as the resulted parameter estimate (PE) representing the adjusted difference and the corresponding 95% confidence interval (CI) are shown. In these subgroup analyses, N represents the number of participants in both arms of the study who met the air trapping and/or adherence criteria. The dot-and-whisker plots represent the PE and 95% CI with colors black (scaled on the top) and red (scaled on the bottom) to distinguish outcomes in which higher versus lower values are preferable. Abbreviations: VO_2Peak: oxygen uptake in peak exercise; V_TPeak: tidal volume in peak exercise; VFL: volume of the tidal breath that is flow limited on expiration; PE: parameter estimate; CI: confidence interval