In this issue of CHEST (see page 2080), an interesting study by Sakka and colleagues reports the results of extravascular lung water measurements with a transpulmonary double indicator (thermal-dye) dilution technique. Each patient required a thermal artery sheath through which a 4F flexible catheter with an integrated thermistor and fiber-optic device was advanced into the infradiaphragmatic aorta. The study was carried out in 373 critically ill patients, and the data were analyzed retrospectively to determine whether there was any prognostic value in measuring extravascular lung water by this method in critically ill patients. The authors report that the maximum level of extravascular lung water was higher in nonsurvivors (14.3 mL/kg) than in survivors (10.2 mL/kg). When the data were analyzed in a univariate logistic regression model, extravascular lung water at baseline, acute physiology scores, and acute physiology and chronic health evaluation scores were significant predictors of mortality, although the r value was relatively low. As would be expected, patients with ARDS had a significantly higher extravascular lung water level (14.9 mL/kg) than other patients. When the authors used a cutoff approach for statistical analysis, they found that the mortality rate was approximately 65% in patients with an extravascular lung water level > 15 mL/kg, whereas the mortality rate was approximately 33% in patients with an extravascular lung water level < 10 mL/kg. Also, a subgroup analysis indicated that, in patients with sepsis, nonsurvivors had a significantly higher extravascular lung water level than survivors.