Tsoukias N M, George S C
Department of Chemical and Biochemical Engineering and Materials Science, University of California, Irvine, 92697-2575, USA.
Ann Biomed Eng. 2001 Sep;29(9):731-9. doi: 10.1114/1.1397786.
Exhaled endogenous nitric oxide (NO) holds promise as a potential biomarker of pulmonary inflammation. Previous experimental and theoretical work has concluded that the alveolar concentration approaches a constant steady state value at end exhalation due to both a constant maximum flux or release of NO (J(max,alv)) and a constant diffusing capacity (D(NO,alv)) in the alveolar region. We have recently demonstrated that D(NO,alv) is not constant, but increases with alveolar volume (VA) given by the following average relationship: D(NO,alv) =48*VA(2/3) ml/min/mmHg (where VA is expressed in liters, STPD). We investigated the potential impact of a variable D(NO,alv) on exhaled concentration by incorporating the volume dependence into the currently accepted two-compartment model for NO exchange dynamics. Our results suggest that the mechanism underlying the plateau in exhaled concentration is a constant ratio J(max,alv)/D(NO,alv) This constant ratio requires a volume dependence of J(max,alv) similar to D(NO,alv), and is likely due to a decreasing alveolar surface area during exhalation.
呼出内源性一氧化氮（NO）有望成为肺部炎症的潜在生物标志物。先前的实验和理论研究得出结论，由于肺泡区域中NO的最大通量或释放量（J(max,alv)）恒定以及扩散能力（D(NO,alv)）恒定，呼气末时肺泡浓度接近恒定的稳态值。我们最近证明，D(NO,alv)并非恒定不变，而是随肺泡容积（VA）增加，其平均关系如下：D(NO,alv)=48×VA(2/3) ml/min/mmHg（其中VA以升为单位，标准温度和压力下干燥气体体积）。我们通过将容积依赖性纳入目前公认的NO交换动力学双室模型，研究了可变的D(NO,alv)对呼出浓度的潜在影响。我们的结果表明，呼出浓度平台期的潜在机制是J(max,alv)/D(NO,alv)的恒定比值。这个恒定比值要求J(max,alv)的容积依赖性与D(NO,alv)类似，这可能是由于呼气过程中肺泡表面积减小所致。
