High Values of the Pulmonary Artery Wedge Pressure in Patients with Acute Lung Injury and Acute Respiratory Distress Syndrome

Objective: To determine the incidence and severity of pulmonary artery wedge pressure (PAWP) elevation in patients with ALI/ARDS. In addition, to examine the effects of clinical variables on the presence of a high PAWP (>18 mmHg) and the effect of an elevated PAWP on mortality.

Design And Patients: Post hoc analysis of 120 patients with or at high risk of ARDS, enrolled in a randomized controlled trial of pressure- and volume-limited ventilation. Patients with or at high risk of congestive heart failure were excluded from the original study.

Setting: Eight tertiary intensive care units.

Measurements And Results: Pulmonary artery catheters were inserted at the discretion of the attending physician, and PAWP was collected every 8 h when present. Of 120 subjects 71 (59%) had a pulmonary artery catheter (44 at randomization, 27 later). The mean maximum PAWP reading among patients was 22.5 mmHg (95% CI 21.2-23.8) and mean median was 16.6 mmHg (95% CI 15.6-17.5). Patients who met standard criteria for ARDS were more likely to develop a high PAWP. In a multivariate stepwise logistic regression model a persistently elevated PAWP (median >18 mmHg) was a strong predictor of mortality after correction for baseline differences (OR estimate 6.82; 95% CI 1.66-37.81).

Conclusions: We conclude that in this group of patients a PAWP higher than 18 mmHg is common. Mandating a PAWP of 18 mmHg or less may negatively impact clinical trials in which ARDS is an inclusion/exclusion criteria or an endpoint.