Jones H A, Davies E E, Hughes J M
J Appl Physiol (1985). 1986 Jan;60(1):311-6. doi: 10.1152/jappl.1986.60.1.311.
We have developed a rapid gas-dilution technique, with which pulmonary gas volume can be measured in only 20 s, even in the presence of maldistribution of ventilation. The subject rebreathes from a 0.75-liter anesthetic bag filled with 10% He and 30% O2 in argon. Breath-by-breath flow-weighted inspired concentrations of all gases present are calculated from continuous measurement by mass spectrometry. Insoluble gas concentrations are corrected continuously for shrinkage of the system volume. By use of these corrected values a mathematical extrapolation predicts the equilibrium concentration for He in the absence of complete mixing. Validation of the technique was carried out by comparing volumes calculated from the predicted equilibrium value with those obtained by whole-body plethysmography in 7 normal subjects and 12 patients with lung disease. In normal subjects equilibrium was usually attained within the 20 breaths and no extrapolation was required. In most of the patients, however, equilibrium was not reached and the use of the extrapolation technique increased the proportion of the lung volume measured by gas dilution from 0.82 +/- 0.16 (SD) to 0.95 +/- 0.12 of that measured by plethysmography.
我们开发了一种快速气体稀释技术，即使在通气分布不均的情况下，也能在仅20秒内测量肺气体容积。受试者从一个装有10%氦气、30%氧气和氩气的0.75升麻醉袋中进行重复呼吸。通过质谱连续测量，逐次计算所有存在气体的流量加权吸入浓度。不溶性气体浓度会根据系统体积的收缩情况进行连续校正。利用这些校正值，通过数学外推法预测在未完全混合情况下氦气的平衡浓度。通过比较7名正常受试者和12名肺病患者根据预测平衡值计算出的容积与通过全身体积描记法获得的容积，对该技术进行了验证。在正常受试者中，通常在20次呼吸内达到平衡，无需外推。然而，在大多数患者中，未达到平衡，使用外推技术使气体稀释法测量的肺容积比例从体积描记法测量值的0.82±0.16（标准差）增加到0.95±0.12。
