Extravascular lung water and intrathoracic blood volume: double versus single indicator dilution technique

Objective: The accuracy of single thermodilution was assessed in measuring extravascular lung water (EVLW) and intrathoracic blood volume (ITBV). Design: Single thermodilution ((ST)) was prospectively compared with thermo -dye dilution ((TD)) in 13 mechanically ventilated pigs using the Pulsion C old Z-021 monitor. Interventions: Lung injury was induced with oleic acid injection. Results: EVLWITD increased from 4.3 +/- 1.4 to 11.3 +/- 4.5 ml/kg (p = 0.00 14) and ITBVTD decreased from 581 +/- 66 to 540 +/- 85 mi (p = 0.039) after induction of lung injury. EVLWST was systematically overestimated (0.5-1 m l/kg) and ITBVST was slightly underestimated (15-20 ml) when calculated aut omatically by the Pulsion Cold Z-021 monitor. This bias could be removed by adjusting two coefficients needed for the computation of ITBVST and EVLWST so that the following regression equations were obtained: EVLWIST = 0.98 . EVLWITD + 0.27 (r = 0.94, p < 10(-6)) and ITBVST = 1.0.ITBVTD + 0 (r = 0.8 7, p < 10(-6)). Conclusions: Single thermodilution allows estimation of ITBV and EVLW value s with reasonable accuracy and therefore provides useful information about the cardiac preload and the severity of lung injury. However, automatic cal culation of EVLWIST and ITBVST using the Pulsion Cold Z-021 might be biased . Therefore, researchers and clinicians should validate single thermodiluti on for the given settings, before employing this method to estimate EVLW an d ITBV.