Effects of isovolumetric venesection on blood viscosity, on red cell deformability, and on arterial flow velocity in chronic respiratory failure with secondary polycythemia.

Normovolemic hemodilution produced by isovolumetric venesection was done in 8 patients with polycythemia and respiratory failure secondary to chronic obstructive pulmonary disease. The 'deformability index' was studied by means of a filtration technique. The blood flow velocity in ascending aorta and right pulmonary artery was also studied by means of ultrasonic Echo-Doppler technique. The procedure showed in all patients an increase of oxygen tension and a decrease of carbonic gas tension in arterial blood. At the same time it was possible to demonstrate an improvement of red cell deformability and an increase of arterial flow velocity. Isovolumetric venesection is an important procedure in the management of patients with polycythemia secondary to respiratory failure.