[Measurement of V/Q distribution by inert gas elimination method]

Wagner & West (1974) developed the new method for determination of ventilation-perfusion ratio (V/Q) distribution of the lung using multiple inert gases and multicompartmental computer analyses (inert gas elimination method), and attracted attention of researchers of pulmonary diseases. But there are some unsolved problems in this method, and its physiological value has not been completely determined. In this study, I evaluated mathematical methods and computer algorithm precisely and determined its limits on the clinical application by showing pattern reforming abilities using error-free data. Then I measured V/Q distributions of normal mongrel dogs and dogs with pulmonary fibrosis due to paraquat poisoning. 1). Pattern Reforming Error-free data were obtained by calculation based on some mathematical functions showing various distribution patterns. Using these error-free data, reforming abilities were examined. Unimodal and bimodal distributions were recovered well but trimodal ones were not recovered satisfactorily. 2). Appropriate Value of Smoothing Coefficient, Z With the changes of Z value (0.05-999), reforming patterns changed. When Z value was about 40, the recovered pattern was most similar to the original one. 3). Gas-chromatographic Analyses of Multiple Inert Gases In order to stabilize the baseline and to make the calculation more accurate, I changed the column packing from Porapak -K to Porapak -Q and calculated the peak areas. By these minor changes, more stable analytic values were obtained. 4). V/Q Distribution of Normal Mongrel Dogs 17 normal mongrel dogs were examined and 6 of them were proved normal by autopsy. They showed nearly log normal distribution pattern with mean V/Q of 0.5-1.0. Some of these dogs also showed faint blood flow to very low V/Q areas (V/Q less than 0.1), and very high V/Q areas (V/Q greater than 10.0). 5). V/Q Distribution of mongrel Dogs with Pulmonary Fibrosis Experimental models of pulmonary fibrosis were made by giving paraquat orally to the dogs. V/Q distributions were measured in 2 of pathologically proved fibrosis dogs. They characteristically showed increased blood flow to the low V/Q areas (V/Q less than 0.1) (about 10% of total blood flow).