Relationship between extravascular lung water and oxygenation indices in patients with acute respiratory failure
© BioMed Central Ltd 2005
Published: 7 March 2005
The main strategy to restore organ perfusion in critically ill patients is fluid administration, which increases the likelihood of acquiring pulmonary edema with detrimental effects on gas exchange. The thermal-dye dilution technique has been used to measure extravascular lung water (EVLW). Recently, this technique has been simplified using only the thermal indicator . The relationship between EVLW and the PaO2/FiO2 ratio has been sparsely studied and described as weak . Oxygenation index (OI) relates PaO2, FiO2, and mean airway pressure (Paw) by the following formula: OI = Paw × FiO2 × 100 / PaO2 . We are not aware of publications correlating EVLW with OI.
Simultaneous measurements of EVLW, arterial blood gases and Paw were performed in mechanically ventilated patients at different moments of their illness course. EVLW was measured by a single transpulmonary thermodilution technique using a PiCCO® monitor. The EVLW value was indexed (EVLWi) by the predicted body weight . PaO2/FiO2 and OI were calculated and correlated with EVLWi using linear regression analysis with a 95% confidence interval (CI).
There is a stronger correlation between EVLWi and OI than with PaO2/FiO2. This finding emphasizes the importance of incorporating Paw into the evaluation of patient oxygenation during mechanical ventilation.