[The measurement of extravascular lung water--significant in the follow-up of ARDS?].

In 40 adult patients suffering from severe ARDS stage III and IV (Morel) we examined the course of the extravascular lung water (EVLW) measured by the double indicator dilution method with 858 single measurements, during mechanical ventilation with PEEP, or extracorporeal CO2 elimination (ECCO2 R). No correlation could be found between EVLW and the values of alveolar arterial oxygen difference (AaDO2) and intrapulmonary right-left shunt (Qs/Qt) or haemodynamic values such as CVP, PCWP, mean pulmonary arterial pressure, or the 24 h fluid balance. It was, therefore, not possible to estimate a prognostic trend based on a single measurement of EVLW. However, the course EVLW was more appropriate to perceive the prognostic trend of ARDS because a rapid decrease of very high EVLW was correlated with a decrease of AaDO2 (r = 0.87); whereas lethal ARDS (fibrosis) was associated with moderately increased, unchanged EVLW. However, during the ECCO2-R treatment the repeated estimation of EVLW and AaDO2 is a useful tool to assess recovery because other parameters such as Qs/Qt and chest computer tomography during long-term bypass are very difficult or impossible to employ for this purpose. A change of EVLW with increasing PEEP level could not be found. The reproducibility of 858 EVLW values was excellent with a coefficient of variation of 4.9 +/- 3.5%.