Assessment Of Exhaled Nitric Oxide In Obstructive Sleep Apnea Hypopnea Syndrome

PART I Comparison of Two Exhaled Nitric Oxide AnalyzersObjective:As a simple and easy examination used in clinical practice, fraction of exhaled nitric oxide (FeNO) has been applied in many respiratory diseases. The principle of Sunvou Nano Coulomb Nitric Oxide Analyzer is different from the instruments used before. In this study, we compared it with Niox Mino to explore the consistency and association between these two anaylzers.Methods:Totally,45volunteers were enrolled in this study including:(1) healthy subjects;(2) patients diagnosed with asthma;(3) patients with COPD;(4) patients with respiratory symptoms but diagnosis had not been confirmed. FeNO(50ml/s) was measured with two devices randomly one after another in each subjects. Statistical analyses was performed by using SPSS19.0.Results:FeNO(50ml/s) measured with two analyzers did not show significant difference (P=0.1047), and there was a significant correlation between FeNO(50ml/s) by two devices (r=0.8647, P<0.0001). Besides, a conversion equation was developed by linear regression:FeNONiox Mino=0.6233(SE=0.0552)×FeNOSunvou+10.38(SE=2.78). A Bland-Altman plot showed low degree of consistency between these two devices, especially for the high-value of FeNO(50ml/s).Conclusions:There was a significant correlation between FeNO(50ml/s) measured with Sunvou Nano Coulomb Nitric oxide analyzer and with Niox Mino, though the agreement was low. The differences between two devices should be considered in clinical practice. Also, these results will provide a view on the conversion of FeNO(50ml/s) values measured by these devices and the reliability of measurement of FeNO in multi-expiratory flow rates with Sunvou Nano Coulomb Nitric Oxide Analyzer in the following researches. PART II Assessment of Central and Peripheral Airway Exhaled Nitric Oxide in Obstructive Sleep Apnea Hypopnea SyndromeObjective:This study aim to investigate the change and significance of exhaled nitric oxide derived from central and peripheral airway in obstructive sleep apnea hypopnea syndrome (OSAHS) patients by using two-compartment model (2CM).Methods:According to the inclusion and exclusion criteria,27Non-OSAHS subjects were enrolled in control group and32patients with OSAHS were included in OSAHS group. All the baseline information of each subjects were recorded, as well as the Epworth Sleepiness Scale (ESS) scores and indices in pulmonary function test. Measurement of exhaled nitric oxide at multiple flow rates were performed in each at the same segment of a day (20:00-21:00). In addition, the indices in polysomnography (PSG) were recorded in OSAHS. Statistical analyses were performed by SPSS19.0.Results:Comparing with non-OSAHS group, we found that:(1) FeNO(50ml/s) and J’awNO significantly elevated in patients with OSAHS; FeNO(50ml/s) correlated well with apnea-hypopnea index (AHI), mean nocturnal oxygen saturation (SaO2), percentage of sleep time that SaO2was less than90%and sleep time that SaO2was less than90%; also significant correlations were found between J’awNO with AHI, percentage of sleep time that SaO2was less than90%and sleep time that SaO2was less than90%.(2) CANO was slightly lower in OSAHS and did not correlate with indices in PSG.(3) FeNO(50ml/s), J’awNO or CANO did not show correlation with ESS score.Conclusions:Inflammation and oxidative stress levels elevated in central airway in OSAHS and related to the severity of the disease. Reduction of CaNO might be caused by hypoxia, and inflammation-induced endothelial dysfunction, while the potential mechanisms still need further research. Assessment of central and peripheral airway exhaled nitric oxide in OSAHS could help us to understand the pathogenesis of OSAHS and disease management as well. PART III Effect of Nasal Continuous Positive Airway Pressure Therapy on Central and Peripheral Airway Exhaled Nitric Oxide in severe OSAHS patientsObjective:To explore the effect and underlying significance of nasal continuous positive airway pressure (nCPAP) therapy on central and peripheral airway exhaled nitric oxide in severe OSAHS patients.Methods:30severe cases were enrolled in this part of the research according to the inclusion and exclusion criteria. Baseline information of each patients were recorded. Measurements of exhaled nitric oxide at multiple flow rates were performed before (before sleep,20:00-21:00) and after (early morning,06:00-07:00) each nCPAP therapy. Venous blood samples were also collected for plasma endothelin-1(ET-1) concentration examination before and after the three-night therapy. Evaluations of right ventricular function by echocardiography were also arranged before and after the treatment. Statistical analyses were performed by SPSS19.0.Results:Exhaled nitric oxide were measured in all subjects before and after nCPAP therapy;20patients agreed to blood collection; right ventricular function was evaluated in22patients and13of them received echocardiography evaluation both before and after nCPAP. Finally, we came to the results that:(1) FeNO(50ml/s), J’awNO markedly decreased after nCPAP therapy while CaNO increased significantly.(2) Morning serum ET-1concentration decreased after nCPAP and the decrease of ET-1showed a good consistency with the increase of CaNO, though their degree of change did not correlate well.(3) nCPAP treatment improved right ventricular function as Tei index decreased. Besides, Tei index positively and significantly correlated with plasma ET-1concentration.Conclusion:For patients with severe OSAHS, measurement of central and peripheral airway exhaled nitric oxide provided us a method which could evaluate local lung inflammation and oxidative stress, as well as endothelial dysfunction, change of vasoactive substances, pulmonary vascular resistance and right heart function. The exhaled nitric oxide derived from different regions of lung might be valuable molecular signatures and markers for the treatment and follow-up in OSAHS patients and monitoring long-term cardiovascular events.