Nasal nitric oxide improved by continuous positive airway pressure therapy for upper airway inflammation in obstructive sleep apnea

Purpose

In this report, we examined the association between obstructive sleep apnea (OSA) and upper and lower airway inflammation based on nitric oxide (NO) measurements.

Methods

Study subjects included 51 consecutive participants. Sleep-disordered breathing was evaluated by a type 3 portable monitor and quantified by respiratory disturbance index (RDI). Airway inflammation was noninvasively analyzed by the measurement of nasally and orally exhaled NO; nasal value was presented as nasally exhaled NO minus orally exhaled NO. In 15 patients prescribed nasal continuous positive airway pressure (nCPAP) therapy, exhaled NO was re-evaluated in 10.7 ± 6.3 months after nCPAP therapy.

Results

Nasal NO was significantly higher in patients with severe OSA (RDI ≥ 30/h) than those with non-OSA (RDI < 10/h) (76.9 ± 26.0 ppb vs. 47.9 ± 22.0 ppb, respectively, p = 0.016) and correlated with RDI (rho = 0.36, p = 0.0099), whereas orally exhaled NO did not differ between non-OSA and OSA patients and was not correlated with RDI. In 15 patients, nasal NO after nCPAP therapy was significantly decreased than that before nCPAP therapy (81.9 ± 31.2 ppb vs. 53.7 ± 27.2 ppb, respectively, p = 0.0046); in 11 patients having good compliance to nCPAP therapy (nCPAP use >4 h per night on more than 70% of nights), this association was more remarkable.

Conclusions

In OSA, upper but not lower airway inflammation can be increased by repetitive collapse of the upper airway. Future studies are required to determine the role of nasal NO in OSA.