Cardiac Output Determinations with Ear piece Densitometry

Abstract

The results of cardiac output determinations by a dye dilution technique were compared using (a) a dichromatic earpiece which was calibrated as a flow-through cuvette, but also permitted automatic computing by virtue of a pressure capsule, and (b) an ordinary flow-through densitometer. Eleven subjects, some with cardio-pulmonary disease, were investigated. Cardiac outputs were systematically overestimated when automatically computed. The results obtained by manual calculation with the earpiece corresponded more nearly with those derived from the flow-through cuvette, but still with a deviation from the identity line and with a residual standard deviation of 0.8 1/min. Double determinations had a residual standard deviation of 0.7 1/min. Despite its ease of handling, an earpiece densitometer seems to be too unreliable to be suitable for routine use.