Rees S E, Kjaergaard S, Andreassen S, Hedenstierna G
Department of Health Science and Technology, Center for Model-Based Medical Decision Support, Aalborg University, Denmark.
J Appl Physiol (1985). 2006 Sep;101(3):826-32. doi: 10.1152/japplphysiol.01481.2005. Epub 2006 Jun 8.
The multiple inert-gas elimination technique (MIGET) is a complex mathematical model and experimental technique for understanding pulmonary gas exchange. Simpler mathematical models have been proposed that have a limited view compared with MIGET but may be applicable for use in clinical practice. This study examined the use of a simple model of gas exchange to describe MIGET retention and excretion data in seven pigs before and following lung damage caused by oleic acid infusion and subsequently at different levels of positive end-expiratory pressure. The simple model was found to give, on average, a good description of MIGET data, as evaluated by a chi(2) test on the weighted residual sum of squares resulting from the model fit (P > 0.2). Values of the simple model's parameters (dead-space volume, shunt, and the fraction of alveolar ventilation going to compartment 2) compared well with the similar MIGET parameters (dead-space volume, shunt, log of the standard deviation of the perfusion, log of the standard deveation of the ventilation), giving values of bias and standard deviation on the differences between dead-space volume and shunt of 0.002 +/- 0.002 liter and 7.3 +/- 2.1% (% of shunt value), respectively. Values of the fraction of alveolar ventilation going to compartment 2 correlated well with log of the standard deviation of the perfusion (r(2) = 0.86) and log of the standard deviation of the ventilation (r(2) = 0.92). These results indicate that this simple model provides a good description of lung pathology following oleic acid infusion. It remains to be seen whether physiologically valid values of the simple model parameters can be obtained from clinical experiments varying inspired oxygen fraction. If so, this may indicate a role for simple models in the clinical interpretation of gas exchange.
多惰性气体消除技术（MIGET）是一种用于理解肺气体交换的复杂数学模型和实验技术。已经提出了一些更简单的数学模型，与MIGET相比，这些模型的视野有限，但可能适用于临床实践。本研究考察了一种简单的气体交换模型在七只猪身上的应用，该模型用于描述油酸输注引起肺损伤前后以及随后在不同呼气末正压水平下的MIGET潴留和排泄数据。通过对模型拟合产生的加权残差平方和进行卡方检验评估，发现该简单模型平均能很好地描述MIGET数据（P>0.2）。简单模型参数（死腔容积、分流以及进入第2区的肺泡通气分数）的值与类似的MIGET参数（死腔容积、分流、灌注标准差的对数、通气标准差的对数）相比，结果良好，死腔容积和分流差异的偏差值和标准差分别为0.002±0.002升和7.3±2.1%（占分流值的百分比）。进入第2区的肺泡通气分数的值与灌注标准差的对数（r² = 0.86）和通气标准差的对数（r² = 0.92）相关性良好。这些结果表明，该简单模型能很好地描述油酸输注后的肺部病理情况。通过改变吸入氧分数的临床实验能否获得简单模型参数的生理学有效数值还有待观察。如果可以，这可能表明简单模型在气体交换的临床解释中具有一定作用。
