End-diastolic volume.

To the Editor .—I read with interest the article by Diebel et al 1 in the July 1992 issue of theArchives. Because of the lack of a constant or predictable relationship between pressure and volume, methods of determining ventricular volume have been of interest to physicians caring for the critically ill. This article, in showing a correlation between right ventricular end-diastolic volume (EDV) index and cardiac index (CI) derived from measurements from the same catheter, appears to add little new information regarding the accuracy of the right ventricular ejection fraction (RVEF) catheter in measuring right ventricular EDV. Showing correlations between CI and hemodynamic parameters as an approximation of the EDV index of the right and/or left ventricle begs the very question being addressed in the article. Even if one were to assume that CI is an appropriate correlate of true EDV, the use of a measurement derived from the RVEF