Limitations of portable roentgenography of the chest in patients with acute respiratory failure.

The ability of the portable roentgenography of the chest to define the amount of physiologic shunting and the severity of noncardiogenic pulmonary edema was evaluated in 37 observations of 11 patients. Ten of the 11 patients had acute respiratory failure. The roentgenologic assessment of the amount of pulmonary edema and the severity of left ventricular failure was compared with the physiologic shunt fraction, tracer measured lung water and the pulmonary arterial wedge pressure. The roentgenologic scores for edema did not predict the shunt fraction or tracer measured lung water. The roentgenologic score for congestive heart failure correlated with the wedge pressure but not well enough to be clinically useful. Five per cent of the roentgenograms were false-positive and 11 per cent were false-negative. Roentgenologic findings lagged behind physiologic derangements. Thus, the roentgenogram could predict the shunt value of the preceding day. Results indicate that it is hazardous to accept a portable roentgenographic diagnosis of congestive heart failure as a cause of pulmonary edema.