Gas transfer in isolated lungs perfused with red cell suspension or hemoglobin solution

Rapid mixing experiments have shown that the reaction between oxygen and hemoglobin is faster in hemoglobin solutions than in red cell suspensions. In this study we tested whether this observation can also be made in the lung. Excised rabbit lungs were perfused either with washed human red cell suspensions or with hemoglobin solutions, each with 50 g hemoglobin/L, and steady-state diffusing capacities (DLO2) for oxygen elimination measured. Mean settings were a temperature of 29.5 degrees C of the inflowing and outflowing perfusate of the lung, a total ventilation of 1.7 L.min-1, and a perfusion rate of 116 ml.min-1. Under those conditions resulted a DLO2 with hemoglobin solution of 0.68 +/- 0.18 ml.min-1.mm Hg-1, and a significantly lower value of 0.50 +/- 0.06 ml.min-1.mm Hg-1 with red cell suspension (P less than 0.01). An extraerythrocytic diffusing resistance, formed by a plasma layer and/or arising from a dynamic diffusion boundary layer, which is also known as unstirred layer, could explain the lower value with red cell suspensions.