Measuring cardiac output in one-lung ventilation: a comparison of pulmonary artery and transpulmonary aortic measurements in pigs.

Objective: The agreement between cardiac output measurements via pulmonary artery thermodilution (CO[PA]) and transpulmonary aortic thermodilution (CO[AT]) during one-lung ventilation was studied.

Design: Animal study with repeated simultaneous measurements comparing 2 cardiac output measurement techniques.

Setting: Experimental animal facility of a university department.

Participants: Forty-eight female pigs (26-42 kg).

Interventions: The pigs were anesthetized, tracheally intubated, and mechanically ventilated. After placement of an aortic thermistor catheter via the femoral artery and a pulmonary artery catheter, a double-lumen tube was placed via tracheotomy. During one-lung ventilation in each animal, 3 measurements with pulmonary artery thermodilution and transpulmonary aortic thermodilution were performed in different hemodynamic states. Both thermistors were connected to 1 computer system, and 144 simultaneous cardiac output measurements were analyzed.

Measurements And Main Results: Linear regression analyses revealed a close relationship between the 2 methods: CO(AT) = 0.81 CO(PA) + 1.04 (L/min) (r = 0.96, p < 0.0001). Bland-Altman analysis showed that CO(AT) was slightly higher than the CO(PA) with a bias of 0.2 +/- 0.5 L/min. However, in higher CO states, an inversion of this relationship was found, possibly because of indicator loss and recirculation.

Conclusions: The pulmonary artery thermodilution and the transpulmonary aortic thermodilution techniques both accurately measure cardiac output during one-lung ventilation.