Pulmonary permeability index predicts progression to acute lung injury in patients with increased risk

Introduction

Early identification of progression to acute lung injury (ALI) in patients at risk may change therapy and potentially improve outcome. Central to the pathogenesis of ALI is pulmonary microvascular injury and increased permeability resulting in pulmonary edema. We proposed that the pulmonary vascular permeability index (PVPI) (extravascular lung water (EVLW) (ml)/pulmonary blood volume (PBV) (ml)) reflects the severity of this injury and predicts progression to ALI in patients at risk.

Methods

The PVPI was measured prospectively in 27 patients who either were at increased risk to develop ALI (n = 17) or who had ALI on presentation (n = 10) for the first 5 days after admission to the ICU.

Results

Ten out of 17 patients at risk for ALI progressed to it. The mean (± SEM) PVPI on day 1 was lower in patients who did not develop ALI vs. those that did (1.4 ± 0.1 vs. 2.6 ± 0.4, P = 0.01) in the 17 patients who did not have ALI on presentation (Figure 1). There was no difference in PVPI for those that developed ALI vs. those that had it on presentation (2.6 ± 0.4 vs. 2.7 ± 0.3, P = 0.5). A cutoff PVPI value of 1.9 or less discriminated those that would not develop ALI from those who did or who had it on presentation with a sensitivity and specificity of 100% and 85%, respectively (Figure 2).

Figure 1

Figure 2

Conclusion

Increased PVPI is a feature of early ALI and predicts progression to ALI in patients at increased risk. Early identification of patients with elevated PVPI and who are at risk to develop ALI may lead to consideration of early initiation of lung protective ventilator strategies.