APPRAISING PULMONARY-EDEMA USING SUPINE CHEST ROENTGENOGRAMS IN VENTILATED PATIENTS

The role of portable, anteroposterior, supine chest X-rays (CXRs) in d istinguishing hydrostatic pulmonary edema (HPE) from permeability pulm onary edema (PPE) in mechanically ventilated patients is controversial . We prospectively obtained and evaluated such CXRs in 33 supine, mech anically ventilated intensive-care-unit patients with pulmonary artery catheters. Three chest radiologists independently reviewed CXRs witho ut clinical information and recorded the cardiothoracic (CT) ratio, va scular pedicle width (VPW), and other radiographic features commonly u sed to evaluate pulmonary edema. Hydrostatic pulmonary edema was assoc iated with a larger CT ratio (p < 0.001), subjective impressions of ca rdiomegaly (p < 0.01), and increased VPW (p = 0.02). There was a signi ficant correlation between the pulmonary artery occlusion pressure and the VPW (r = 0.45, p = 0.0076) and CT ratio (r = 0.52, p = 0.0016), a s well as between the VPW and CT ratio (r = 0.49, p = 0.0032). Despite this detailed evaluation of the CXRs, the mean accuracy of the radiol ogists' clinical diagnosis of HPE versus PPE was 41%, and 15 of 19 (79 %) of PPE patients showed one or more roentgenographic signs of volume overload. Receiver-operating-characteristic curves were constructed t o determine optimum cut-off values of VPW and CT ratio associated with HPE. Hydrostatic pulmonary edema was found to correlate best using a VPW > 63 mm coupled to a CT ratio > 0.52 (p = 0.027). With this combin ation of objective criteria, radiologists' diagnostic accuracy could h ave been increased to 73%. We therefore conclude that measurements of CT ratio and VPW correlate with pulmonary artery occlusion pressure in supine, mechanically ventilated patients. Distinction of hydrostatic from permeability pulmonary edema is difficult using portable, supine CXRs, but readily assessed radiologic signs may contribute to the corr ect diagnosis.