A theoretical analysis of continuous flow blood warmers

An analysis of the design and operation of continuous flow blood warmers was performed based on an analytical solution to a semimacroscopic energy balance. The model leads to a new measure of the intrinsic blood-warming capability of various related devices called the apparent thermal clearance. It was demonstrated that the temperature profiles are a function only of the ratio of the apparent thermal clearance to the flow rate. This result is useful in comparing the various devices that have been tested in the literature, usually under widely diverse conditions, and to suggest the important design features that must be addressed to improve the clinical operation of such devices. Experimental data from the literature for both dry wall and water bath blood warmers were used to demonstrate the accuracy and versatility of the model.