Sample size
RECRUITMENT
Based on the results from our pilot study, the incidence of ED after FESS was 21.3%. We assumed that the preconditioning would result in reduction of ED occurrence with an odds ratio (OR) of 1/3. At the setting of α = 0.05, an estimated sample size of 164 could provide a 90% of statistical power. Considering a potential dropout rate of 20%, 197 patients were required. Therefore, recruitment of 200 patients was planned.