Extravascular lung water to blood volume ratios as measures of pulmonary capillary permeability in nonseptic critically ill patients

Purpose

The aim of this study is to evaluate the value of extravascular lung water (EVLW) to intrathoracic blood volume, global end-diastolic volume, or pulmonary blood volume ratios as a reflection of pulmonary permeability in nonseptic critically ill patients with or at risk for acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

Methods

Pulmonary permeability was measured by the pulmonary leak index (PLI) for ⁶⁷gallium-labeled transferrin and EVLW and blood volumes by the transpulmonary indicator dilution technique in 20 mechanically ventilated patients, before and after fluid loading, guided by changes in central venous pressure.

Results

Nine (45%) patients had ALI/ARDS according to current criteria. The PLI was high (≥30.0 × 10⁻³/min) in 25% before and 30% after fluid loading. The EVLW was high (≥10 mL/kg) in 10% before and in none after fluid loading and did not increase with fluid loading, whereas blood volumes increased. Before fluid loading, PLI related to EVLW/blood volume ratios (minimum r = 0.48, P = .032). After fluid loading, PLI related to EVLW to pulmonary blood volume or intrathoracic blood volume ratios (minimum r = 0.46, P = .041). The relations were unaffected by fluid loading and pressure forces.

Conclusions

The EVLW/blood volume ratios are determined, at least in part, by moderately increased pulmonary permeability in nonseptic critically ill patients with or at risk for ALI/ARDS, independent of fluid status and pressure forces. Normal ratios may help to exclude high permeability.