Rate of Elimination of Divinyl Ether

Abstract

We have found that the rate of elimination of divinyl ether from an anesthetized dog does not follow the formula first developed for acetone by Widmark 1 , 2 C_t = C_o.e^—Vλt/m where C_o is the original concentration of volatile substance in the blood; C_t the concentration after time t; t, the time; V, the alveolar ventilation; λ., the partition coefficient between air and blood; and m, the “reduced volume”. A mathematical treatment has also been applied to the elimination of ethyl ether by Henderson and Haggard. 3 , 4 Widmark's simplified formula is C_t = C_o.e ^—αt where α is the “elimination constant” and which in the logarithmic form becomes log C_t = log C_o -αt. If, therefore, the rate of elimination of a substance which follows this formula is plotted on semi-logarithmic paper with log C_t plotted against t a straight line should be obtained the slope of which is determined by the elimination constant.

Curve I in Fig. 1 is the typical straight line obtained for ethyl ether with dogs based on the data of Haggard. 4 Curve II, also from Haggard's data, shows the effect of administering carbon dioxide on the rate of elimination by increasing the alveolar ventilation. At point (A) on the curve the administration of carbon dioxide was stopped and the subsequent portion is essentially parallel to Curve I.

Curve III shows a result obtained in our laboratory for divinyl ether (the technic of these blood concentration studies will be published elsewhere). This curve does not become a straight line until after 30 minutes and hence we must infer that some new factor is in operation which is not accounted for by the Widmark expression.