Dawson W T, Johnson R L
J Appl Physiol Respir Environ Exerc Physiol. 1983 May;54(5):1427-33. doi: 10.1152/jappl.1983.54.5.1427.
Plethysmographic (box) methods using N2O uptake to measure pulmonary capillary blood flow, right ventricular stroke volume, and pulmonary arterial flow pulse conduction time have been complicated by the presence of so-called "cardiogenic oscillations" in the box flow records on air and N2O breathing. The exact cause of these oscillations is unknown but believed to be secondary to instantaneous changes in net blood flow into and out of the thorax during the cardiac cycle. We examined these oscillations and pulmonary capillary blood flow in normal human subjects in a flow plethysmograph using a pressure compensation circuit to extend the frequency response. The cardiogenic oscillations in flow recorded at the mouth (with glottis open) are much greater in amplitude and 90 degrees out of phase from those recorded from the plethysmograph. We derived a theoretical analysis of this and designed an analogue electrical circuit to enable us to eliminate these oscillations by electrical subtraction from the box flow record generated by N2O uptake in the pulmonary capillary bed. Measurements of pulmonary capillary blood flow and ventricular stroke volume using our method correlate with measurements made with acetylene-rebreathing blood flow measurements performed sequentially at the same sitting.
使用氧化亚氮摄取来测量肺毛细血管血流量、右心室每搏输出量和肺动脉血流脉冲传导时间的体积描记法（箱式法），因在空气呼吸和氧化亚氮呼吸时箱式血流记录中存在所谓的“心源性振荡”而变得复杂。这些振荡的确切原因尚不清楚，但据信是由于心动周期中进出胸腔的净血流量的瞬时变化所致。我们在正常人体受试者中，使用压力补偿电路来扩展频率响应的血流体积描记仪中检查了这些振荡和肺毛细血管血流量。在口腔（声门开放）记录的血流中的心源性振荡，其幅度比从体积描记仪记录的振荡大得多，并且相位相差90度。我们对此进行了理论分析，并设计了一个模拟电路，使我们能够通过从肺毛细血管床中氧化亚氮摄取产生的箱式血流记录中进行电减法来消除这些振荡。使用我们的方法测量的肺毛细血管血流量和心室每搏输出量与在同一次就诊时依次进行的乙炔再呼吸血流测量结果相关。
