Accuracy of transpulmonary thermodilution versus gravimetric measurement of extravascular lung water

Objective: Pulmonary edema is a severe and often life-threatening condition. The diagnosis of pulmonary edema and its quantification have great clinical significance and yet can be difficult. A new technique based on thermodilution measurement using a single indicator has recently been developed (PiCCO, Pulsion Medical Systems, AG Germany). This method allows the measurement of extravascular lung water and thus can quantify degree of pulmonary edema. The technique has not been compared with a gold standard, gravimetric measurement of estravascular lung water. Therefore, the objective of this study was to determine the ability of extravascular lung water measurement with the PiCCO to reflect the extravascular lung water as measured with a gravimetric technique in a dog model of pulmonary edema. Design: Prospective, randomized animal study. Setting: A university animal research laboratory. Subjects: Fifteen mongrel dogs (n = 5/group) weighing 20-30 kg. Interventions: The dogs were anesthetized and mechanically ventilated. Five dogs served as controls; in five dogs hydrostatic pulmonary edema was induced using inflation of a left atrial balloon combined with fluid administration to maintain a high pulmonary artery occlusion pressure; and in five dogs pulmonary edema was induced by intravenous injection of oleic acid. After a period of stabilisation in a state of pulmonary edema, extravascular lung water was measured with the PiCCO monitor. The animals were then killed, and extravascular lung water was measured using a gravimetric technique. Measurements and Main Results: There was a very close (r = .967, p < .001) relationship between transpulmonary thermodilution and gravimetric measurements. The measurement with the PiCCO was consistently higher, by 3.01 ± 1.34 mL/kg, than the gravimetric measurement. Conclusions: Measurement of extravascular lung water using transpulmonary thermodilution with a single indicator is very closely correlated with gravimetric measurement of lung water in both increased permeability and hydrostatic pulmonary edema.