OBJECTIVES: To investigate the agreement (and its potential dependency on extra-vascular lung water) between transpulmonary (TPID) and standard pulmonary artery (PAID) thermodilution cardiac output measurements. METHODS: One hundred and sixty simultaneous cardiac output measurements using transpulmonary and pulmonary artery thermodilution techniques were retrospectively compared in 18 patients with acute respiratory distress syndrome. In addition, extravascular lung water was determined using a double indicator technique (temperature and indocyanine green). RESULTS: Mean (+/- SD) difference ("bias") was 0.03 L/min (+/- 1.04 L/min), linear regression analysis resulted in TPID = 0.87 PAID + 1.16 (r = 0.91). Mean extra vascular lung water was 1625 mL (minimum-maximum: 403-3266 mL) and therefore markedly elevated as could have been expected in patients with ARDS. Bias (PAID-TPID) was not dependent on extravascular lung water. CONCLUSIONS: Transpulmonary and pulmonary artery thermodilution methods can be used interchangeably. The results demonstrate for the first time in humans that transpulmonary thermodilution provides valid cardiac output values in patients with markedly increased fluid content of the lungs.
