Mishima M, Kawakami K, Sugiura N, Fukunaga T, Sakai N, Hirai T, Kuno K
Department of Clinical Physiology, Kyoto University, Japan.
Front Med Biol Eng. 1993;5(3):185-99.
We have previously reported that the phase difference between chest and mouth flows was a useful indicator of obstructive lung disease. In this paper, we calculated the effects of (i) airway reactance, (ii) extrathoracic airway shunt impedance, (iii) heating and humidification of the inspired air, (iv) abdominal gas volume, and (v) respiratory quotient on the measurement of the phase difference between chest flow (Vc) and mouth flow (Vm) using computer simulations. When the airway impedance was approximated as simple airway resistance, the phase difference (theta r) was calculated to be 0.8% less than the phase difference (theta s) calculated from the airway impedance (Za), including airway inertance and shunt compliance, in the normal lung. theta s became larger than theta r when the peripheral resistance increased, but did not exceed 5%. The extrathoracic airway shunt impedance effect did not exceed 0.1%, regardless of the respiratory frequency, airway impedance or thoracic gas volume. The influence of heating and humidification of the inspired air on the phase difference was calculated to be within 5%. The effect of abdominal gas was highly dependent on the abdominal gas volume and the respiratory pattern, but was calculated to be within 5%. The influence of the respiratory quotient was calculated to be negligible. As a result, it was concluded that none of the factors discussed above are an obstacle to the clinical application of this method for the evaluation of pathological changes in obstructive airway disorders.
我们之前曾报道，胸部气流与口腔气流之间的相位差是阻塞性肺病的一个有用指标。在本文中，我们利用计算机模拟计算了以下因素对胸部气流（Vc）与口腔气流（Vm）之间相位差测量的影响：（i）气道电抗，（ii）胸外气道分流阻抗，（iii）吸入气体的加热和加湿，（iv）腹部气体量，以及（v）呼吸商。当气道阻抗近似为简单气道阻力时，在正常肺中，计算得出的相位差（θr）比根据包含气道惯性和分流顺应性的气道阻抗（Za）计算出的相位差（θs）小0.8%。当外周阻力增加时，θs大于θr，但不超过5%。无论呼吸频率、气道阻抗或胸腔气体量如何，胸外气道分流阻抗的影响均不超过0.1%。计算得出吸入气体的加热和加湿对相位差的影响在5%以内。腹部气体的影响高度依赖于腹部气体量和呼吸模式，但计算得出在5%以内。呼吸商的影响经计算可忽略不计。结果得出结论，上述因素均不会妨碍该方法在临床上用于评估阻塞性气道疾病病理变化。
