Lehtimäki L, Turjanmaa V, Kankaanranta H, Saarelainen S, Hahtola P, Moilanen E
Medical School, University of Tampere, Finland.
Ann Med. 2000 Sep;32(6):417-23. doi: 10.3109/07853890008995949.
The concentration of nitric oxide (NO) in exhaled air is increased in patients with asthma, suggesting that measuring fractional exhaled NO concentration (FE(NO)) may be used to monitor asthmatic airway inflammation. However, increased FE(NO) is not specific for asthma, as other inflammatory lung diseases may also increase FE(NO). To augment the specificity of FE(NO) measurement, we tested a novel theoretical modelling of pulmonary NO dynamics that allows the approximation of alveolar NO concentration and bronchial NO flux separately by measuring FE(NO) at several exhalation flow rates. We measured FE(NO) at four exhalation flow rates in 10 steroid-naive asthmatics, 5 patients with extrinsic allergic alveolitis, and in 10 healthy controls. Both the asthmatics and the patients with alveolitis had significantly higher FE(NO) than the healthy controls. The increased NO concentration originated from the bronchial level in the asthmatics and from the alveolar level in the patients with alveolitis. In the second part of the study we assessed the repeatability of FE(NO) test, within-day and day-to-day (during two weeks) variation in FE(NO), and the effects of mouth pressure and cigarette smoking on FE(NO) in healthy volunteers. Repeatability of 10 subsequent measurements was high (coefficient of variation (CV) 4.6% +/- 0.4%), and no diurnal variation was found. The day-to-day variation during a 2-week period gave a CV of 10.6% +/- 1.0%. The magnitude of mouth pressure (5-20 cmH2O in adults, 5-40 cmH2O in children) during measurement had no effect on FE(NO). Smoking a cigarette caused a small and transient but statistically significant increase in FE(NO) at 1 and 5 min after smoking. In conclusion, FE(NO) measurement is highly repeatable with low day-to-day variation among healthy subjects. Our results also suggest that the present novel method of measuring FE(NO) at several exhalation flow rates can be used to approximate alveolar and bronchial contributions to FE(NO) separately and thus increase the clinical value of this test.
哮喘患者呼出气体中一氧化氮（NO）的浓度升高，这表明测量呼出一氧化氮分数浓度（FE(NO)）可用于监测哮喘气道炎症。然而，FE(NO)升高并非哮喘所特有，因为其他肺部炎症性疾病也可能导致FE(NO)升高。为提高FE(NO)测量的特异性，我们测试了一种新的肺内NO动力学理论模型，该模型通过在多个呼气流量下测量FE(NO)，能够分别近似估算肺泡NO浓度和支气管NO通量。我们在10名未使用过类固醇的哮喘患者、5名外源性过敏性肺泡炎患者以及10名健康对照者中，于四种呼气流量下测量了FE(NO)。哮喘患者和肺泡炎患者的FE(NO)均显著高于健康对照者。哮喘患者中升高的NO浓度源自支气管水平，而肺泡炎患者中升高的NO浓度源自肺泡水平。在研究的第二部分，我们评估了FE(NO)测试的可重复性、FE(NO)的日内和日间（两周内）变化，以及口腔压力和吸烟对健康志愿者FE(NO)的影响。连续10次测量的可重复性很高（变异系数（CV）为4.6%±0.4%），且未发现日变化。两周内的日间变化CV为10.6%±1.0%。测量过程中口腔压力大小（成人5 - 20 cmH₂O，儿童5 - 40 cmH₂O）对FE(NO)无影响。吸烟后1分钟和5分钟时，FE(NO)出现小幅短暂但具有统计学意义的升高。总之，FE(NO)测量具有高度可重复性，在健康受试者中日间变化较小。我们的结果还表明，目前在多个呼气流量下测量FE(NO)的新方法可用于分别近似估算肺泡和支气管对FE(NO)的贡献，从而提高该测试的临床价值。
