PURPOSE: Upper airway inflammation has been implicated in the pathogenesis of obstructive sleep apnea (OSA) and may be linked to cardiovascular consequences. Fractional exhaled nitric oxide (FeNO), a surrogate marker of airway inflammation, measured non-invasively with non-portable machines has been shown inconsistently to be high in OSA patients and decreased following continuous positive airway pressure (CPAP) therapy. Using a recently FDA approved portable NIOX MINO(r) NO analyzer (aerocrine ; Sweden), we examined FeNO levels in otherwise healthy OSA patients and assessed its utility as a bedside monitoring tool.
METHODS: We prospectively enrolled 31 consecutive non-smokers ≥ 18 years with polysomnographically-confirmed OSA and without cardio-respiratory, allergic or systemic diseases. We measured FeNO levels immediately before (prePSGno) & after PSG (poPSGno); before (preCPAPno) & after CPAP titration (poCPAPno); and within 1-3 months following initiation of CPAP therapy (Tno). Compliance was confirmed in all subjects based on PAP download data.
RESULTS: Mean age of the population was 45.9 ± 14.2 years and 51.6% were males. Mean BMI and AHI were 39.0 ± 11.6 kg/m2 and 31.0 ± 23.0 h-1 respectively. Mean poCPAPno (22.9 ± 7.9 ppb) was higher than mean preCPAPno (20.8 ± 7.7 ppb, p<0.05) and poPSGno (19.0 ± 7.7 ppb, p<0.05). Mean Tno (13.4 ± 6.7 ppb) was significantly reduced compared to mean preCPAPno and poCPAPno. Levels of ∆CPAPpost-pre, ∆ poCPAPno -Tno and ∆ preCPAPno -Tno were not associated with any anthropometric & polysomnographic parameters. Of all variables, only the presence of dry mouth on awakening emerged significant for higher mean FeNO levels at all time points of measurements.
CONCLUSION: FeNO levels rose after 1 night of CPAP application and declined after 1 to 3 months of compliant use which further supports the role of upper airway inflammation in the pathogenesis of OSA. The association of dry mouth with elevated FeNO levels remains to be investigated.
CLINICAL IMPLICATIONS: Measuring FeNO with a portable analyzer may be a simple way to monitor airway inflammation and CPAP adherence in otherwise healthy OSA patients.
DISCLOSURE: Ai-Ping Chua, No Financial Disclosure Information; No Product/Research Disclosure Information