Extravascular Lung Water and Acute Respiratory Distress Syndrome—Oxygenation and Outcome

Abstract

We studied eleven consecutive patients to assess the influence of extravascular lung water on clinical outcome. All patients were mechanically ventilated using a standardized protocol. Inspired oxygen concentration was adjusted to an initial target P_aO₂ of greater than 8.0 kPa (60.8 mmHg). All patients received inhaled nitric oxide (NO) at a concentration of 20 ppm. Extravascular lung water index (EVLWI) was measured by a dual indicator technique (COLD Z-021 monitoring system, Pulsion, Munich, Germany). Patients were managed with fluids and inotropes according to a standard protocol.

Median age was 45 (range 27–60) years, mean APACHE II score on admission 31 (range 17–36), duration of mechanical ventilation 15 (range 6–28) days, mean admission Murray lung injury score 2.5 (range 2–3) and admission EVLWI 20.8 (range 8.7 to 54.7) ml.kg⁻¹.

The only variables independently predictive of P_aO₂/FiO₂ ratio were serum albumin (B = 1.7±1.61) and EVLWI (B = −2.1 ±0.47), r²=0.33, P<0.0001. In severe ARDS, (P_aO₂/FiO₂<l50 mmHg), mean EVLWI was 24.4 (22.4 to 26.4, 95% confidence intervals) ml.kg⁻¹ compared with 15.1 (12.2 to 18.0) ml.kg⁻¹ during moderate ARDS (P<0.001). Serum albumin likewise differed, 29.4 (27.6 to 31.2) vs 35.1 (31.8 to 38.4) g.1⁻¹, P<0.005. PAOP was higher during periods of poor oxygenation, 12.7 (11.9 to 13.5) vs 9.3 (7.9 to 10.7) mmHg, P<0.001. The four survivors had greater initial EVLWI than non-survivors, 31 (24.1 to 37.9) vs 20.7 (16.0 to 25.4) ml.kg⁻¹, P=0.034 and showed a greater reduction in lung water, 15.2 (9.3 to 21.1) vs 5.4 (2.1 to 8.7) ml.kg⁻¹, P=0.013.