Estimation of condensed pulmonary parenchyma from gas exchange parameters in patients with multiple trauma and blunt chest trauma.

Pulmonary gas exchange in correlation with condensed lung volume was prospectively studied in 10 patients with multiple injuries and blunt chest trauma. The purpose was to find nomograms that allow the estimation of the extent of pulmonary density from gas exchange parameters. The condensed lung volume was determined planimetrically from serial transverse sections of chest computed tomographic scans. There was no correlation between condensed lung volume and mean pulmonary artery pressure, pulmonary vascular resistance, systemic vascular resistance, or cardiac index and a week negative correlation to the oxygenation index (PaO2/FIO2) (r2 = 0.46) and to the total static lung compliance (r2 = 0.29). A strong correlation between pulmonary density and intrapulmonary shunt fraction (Qs/Qt) (r2 = 0.95) as well as alveoloarterial PO2 difference (P[A-a]O2) (r2 = 0.86) was evident. By using linear regression equations (linear regression line with 95% confidence interval), nomograms were calculated. The extent of pulmonary density can easily be obtained from these nomograms by measuring Qs/Qt or P(A-a)O2. The presented nomograms may be helpful in monitoring the effect of treatment in patients with blunt chest trauma.