Reliability of the partial CO/sub 2/ rebreathing technique for measurement of cardiac output

The partial CO/sub 2/ rebreathing technique has been suggested to accurately estimate cardiac output (Q/spl dot//sub t/) even in the presence of lung injury. Using a computer-based gas exchange measurement system and graphical and textual programming languages, the authors evaluated the reliability of this noninfective technique for measurement of cardiac output in the setting of lung atelectasis and lung injury. The error of estimating Q/spl dot//sub t/ with this method correlates with the right to left intrapulmonary shunt fraction (Q/spl dot//sub s//Q/spl dot//sub t/). It is concluded that this technique is not reliable in the setting of lung injury, but is useful for the mechanically ventilated patient with normal Q/spl dot//sub s//Q/spl dot//sub t/.