Little attention has been paid so far on the quantitative estimation of venous return during cardiopulmonary bypass. Hence, a new manometric method for measuring SVC/IVC flow ratio in the venous drainage conduit was proposed. Based on the structural features of Y-shaped conduit of venous drainage line, it was confirmed from the hydrodynamic considerations that the measurements of pressure difference between two branch tubes and flow rate after junction enabled the calculation of the flow ratio in the branch tubes. Results of in vitro flow experiments, a few clinical and animal heart lung bypass experiments substantiate the principle of the method.
