For each study, the square represents the mean difference in blood pressure between PAP and control arms and the width of the line represents the 95% confidence interval; a line crossing the 0 mm Hg vertical line indicates no significant difference at α = 0.05. The diamond summarizes the pooled effect; the apex represents the overall mean difference in diurnal SBP between PAP and control arms, and the width represents the 95% confidence interval. In both plots, the diamond does not cross the 0 mm Hg vertical line, hence there is a significant difference between PAP and control in terms of the change in diurnal SBP (−2.58 mm Hg, p ≤ 0.001) and diurnal DBP (−2.01 mm Hg, p ≤ 0.001). DBP, diastolic blood pressure; PAP, positive airway pressure; SBP, systolic blood pressure.