Abstract
ObjectiveAirway inflammation plays an important role in obstructive sleep apnea (OSA); exhaled nitric oxide is regarded as a noninvasive marker of airway inflammation. The aim of this study was to evaluate fractional exhaled nitric oxide (FeNO) and nasal nitric oxide (nNO) in patients with OSA.MethodsSeventy-five patients with OSA and 30 health controls were enrolled in this study. FeNO and nNO were measured before and after sleep. Nasal lavage was performed in 31 non-smoking individuals immediately after NO measurement in the morning. The sample of nasal lavage was taken for cell classification and analyzing interleukin 6 (IL-6) and interleukin 8 (IL-8).ResultsBoth FeNO and nNO were significantly higher in OSA (before sleep FeNO 21.08 ± 8.79 ppb vs.16.90 ± 6.86 ppb, p = 0.022; after sleep FeNO 25.57 ± 15.58 ppb vs.18.07 ± 6.25 ppb, p = 0.003; before sleep nNO 487.03 ± 115.83 ppb vs. 413.37 ± 73.10 ppb, p = 0.001; after sleep nNO 550.07 ± 130.24 ppb vs. 460.43 ± 109.77 ppb, p < 0.001). Furthermore, in non-smoking OSA, nNO levels were positively correlated with apnea hypopnea index (AHI) and average decrease of pulse arterial oxygen saturation (SpO2); after sleep, nNO was also positively associated to recording time with SpO2 < 90% and negatively associated to minimum SpO2. Both before and after sleep nNO levels were positively correlated with the percentage of neutrophils in nasal lavage (r = 0.528, p = 0.014; r = 0.702, p < 0.001, respectively). Additionally, before sleep nNO was also positively associated with IL-6 (r = 0.586, p = 0.005) and IL-8 (r = 0.520, p = 0.016) concentration.ConclusionThis study sustains the presence of airway inflammation in OSA patients with the increase of FeNO and nNO. The data suggests nNO might have greater value than FeNO since it positively correlated with OSA severity, and nNO is a potential bio-marker of nasal inflammation in non-smoking OSA patients.
Highlights
The most important characteristic of obstructive sleep apnea (OSA) is repeated pharyngeal collapses during sleep
This study sustains the presence of airway inflammation in OSA patients with the increase of fractional exhaled nitric oxide (FeNO) and nasal nitric oxide (nNO)
The data suggests nNO might have greater value than FeNO since it positively correlated with OSA severity, and nNO is a potential bio-marker of nasal inflammation in non-smoking OSA patients
Summary
The most important characteristic of obstructive sleep apnea (OSA) is repeated pharyngeal collapses during sleep. Pharyngeal, and laryngeal aggravates upper airway narrowing and increases the risk of OSA. The mechanical damage of recurrent upper airway closure and the oxidative stress caused by intermittent oxygen desaturation induce local and systemic inflammation in OSA patients. Non-invasive methods such as exhaled gases, exhaled breath condensate, and induced sputum can be used to detect these inflammation and oxidative stress in patients with OSA [1]. Exhaled nitric oxide is regarded as a non-invasive marker of airway inflammation [2]. Several studies have evaluated fractional exhaled nitric oxide (FeNO) in OSA, but they got controversial results. As nasal nitric oxide (nNO) is several times higher than FeNO [5], we hypothesize the difference of nNO level in OSA patients, and the health adults would be much greater. In the American Thoracic Society/European Respiratory Society (ATS/ERS) recommendations for standardized procedures for the measurement of nNO, the importance of velum closure was emphasized [12], to prevent loss of NO via the posterior velopharyngeal aperture or enter of lower respiratory air
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