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Temporal Dynamics of Fractional Exhaled Nitric Oxide (FeNO) During CPAP Therapy in Obstructive Sleep Apnea: A Prospective Follow-Up Study

Year: 2025

Type: article

Abstract: Background: This study aimed to assess: (i) whether long-term continuous positive airway pressure (CPAP) reduces fractional exhaled nitric oxide (FeNO) in obstructive sleep apnea (OSA), and (ii) how FeNO change relates to baseline OSA severity. Unlike prior cross-sectional work, we performed a prospective longitudinal follow-up with FeNO at baseline, after short-term titration, and at three months. Primary and secondary endpoints were prespecified. Methods: We enrolled 62 patients with moderate-to-severe OSA; 43 completed CPAP titration and three-month follow-up. FeNO was measured preCPAP, after two nights (postCPAP1), and at three months (postCPAP2). Secondary analyses examined correlations between FeNO change and baseline indices—apnea–hypopnea index (AHI), oxygen desaturation index (ODI), percent sleep time with SpO₂ < 90% (TS90%), and Epworth Sleepiness Scale (ESS)—and the effect of CPAP adherence. Statistics: normality (Shapiro–Wilk); t -test or Mann–Whitney U; χ²/Fisher’s exact for categorical data; repeated-measures ANOVA with Huynh–Feldt for longitudinal change; Spearman correlations. Missing data were handled by complete-case analysis with multiple imputation (m = 5) as sensitivity. Results: At baseline, FeNO was higher in OSA than in AHI < 15 reference subjects from our earlier cohort (21.49 ± 5.56 vs 13.28 ± 3.70 ppb, P < 0.001). Within the OSA cohort, FeNO rose slightly after titration (22.84 ± 4.58 ppb, P > 0.05) but decreased significantly after 3 months of treatment (17.95 ± 3.27 ppb, P < 0.001 vs baseline).FeNO reduction correlated with AHI ( r = 0.674), ODI ( r = 0.617), TS90% ( r = 0.461), and ESS ( r = 0.552; all P < 0.001). Greater reductions occurred with adherence ≥ 6 h/night. Conclusion: Sustained CPAP significantly lowers FeNO, reflecting reduced airway inflammation in OSA. FeNO may serve as a promising non-invasive candidate biomarker for monitoring CPAP response, but larger multicenter studies are needed. Keywords: obstructive sleep apnea, fractional exhaled nitric oxide, CPAP, airway inflammation, polysomnography, candidate biomarker

Source: Nature and Science of Sleep

DOI: 10.2147/nss.s554641