Fixed-Pressure vs Autoadjusting CPAP for BP Control in OSA: A Double-Masked, Randomized, Crossover Trial (FIXPAP Trial)

Background: Limited data exist concerning the impact of fixed-pressure positive airway pressure (FPAP) and autoadjusting positive airway pressure (APAP) on BP in patients with OSA. Research Question: In patients with hypertension with OSA, do FPAP and APAP lead to different effects on BP? Study Design and Methods: In this double-masked, randomized crossover clinical trial, patients with OSA and hypertension were treated with both FPAP and APAP. Ambulatory BP monitoring and autonomic function testing were performed before and after each treatment. The effect of positive airway pressure method on the change from baseline (4-week value minus baseline value) was analyzed using a Bayesian hierarchical linear model. Results: Forty-six patients (mean [SD] age, 48.8 [11.2] years) with OSA (median apnea-hypopnea index, 59 events/h [interquartile range, 34-99 events/h]) were enrolled, with 30 patients completing both treatment arms. Median device use was 6.2 h/night. In the primary Bayesian hierarchical analysis, FPAP showed a high probability of superior systolic BP control compared with APAP. For 24-hour systolic BP, the posterior median treatment effect was –4.41 mm Hg (95% credible interval [CrI], –11.11 to 2.00 mm Hg) with a probability of direction (pd) of 91.2%. This effect was more pronounced for nighttime systolic BP, with a posterior median change of –6.80 mm Hg (95% CrI, –15.37 to 1.76 mm Hg) and a pd of 94.0%. FPAP increased the likelihood of nocturnal diastolic BP dipping compared with APAP (posterior probability of benefit, 94.3%; OR, 4.09). Baseline characteristics, compliance, and satisfaction were similar between treatment sequences (typically, pd < 75%). Mean (SD) FPAP pressure was higher than APAP pressures: 12.51 (4.55) cm H2O vs 10.33 (2.66) cm H2O. Interpretation: Our analysis suggests a high probability that FPAP provides superior BP control compared with APAP in patients with OSA and hypertension. These findings challenge the assumption that APAP provides equivalent cardiovascular protection and suggest that fixed-pressure therapy, guided by manual titration, may be preferable for optimal BP management in this population. Clinical Trial Registration: Clinical Trials Registry of India; Nos.: CTRI/2022/11/047541 and CTRI/2022/11/047687; URL: www.ctri.nic.in © 2026 American College of Chest Physicians