Comparison of measured and calculated colloid osmotic pressure of serum and pulmonary edema fluid in patients with pulmonary edema

Serum and pulmonary edema fluid samples of 26 patients with pulmonary edema were examined. The correlation coefficient comparing measured colloid osmotic pressure (COPm) to calculated colloid osmotic pressure (COPc) (Landis and Pappenheimer equation) was 0.84. Significant differences between COPm and COPc were noted when total protein (TP) concentrations were less than or greater than 5 g/dl (p < 0.001 and p < 0.01, respectively). Twenty-one of 69 samples (30%) had a greater than 4 mm Hg difference between measured and calculated values. COP should be measured rather than calculated for accurate determinations.