Effect of RBC shape and deformability on pulmonary O2 diffusing capacity and resistance to flow in rabbit lungs

Isolated rabbit lungs were perfused with washed and resuspended human red blood cells (RBCs) in the presence of drugs known to change the shape and deformability of RBCs. With sodium salicylate (0.5-2 g/l), which causes echinocytosis and increases RBC deformability, lung diffusing capacity for O2 (DLO2) increased by 21%. When chlorpromazine, which induces stomatocytosis and stiffens RBCs, was given (50 mg/l), DLO2 decreased by 18%. With sodium salicylate, the mean pulmonary artery pressure dropped by 14% from control values, whereas it increased by 18% under chlorpromazine. Comparative experiments with hemoglobin solutions did not reveal any effect of those two drugs either on DLO2 or on pulmonary arterial pressure, which indicates that the effects of sodium salicylate and chlorpromazine were due to changes in RBC shape and deformability. It is concluded that RBC shape and deformability affect pulmonary artery pressure and oxygen diffusing capacity, which may have an influence on oxygen transfer to tissue and hence be of clinical relevance.