buffer and added to the rbc suspension the rbc polymer mixture was then rocked gently at room temperature for 30 minutes after which the rbc was washed twice in buffer the coated rbc were resuspended at 40 hematocrit in autologous plasma after peg coating rbc showed normal morphology i e biconcave discs as evaluated by optical microscopy except when very high peg concentrations were used which resulted in echinocytosis rbc deformability was measured using the cell transit analyzer cta abx montpellier france which measures the time taken for rbc to deform and pass through 5 micron diameter pores the deformability of peg coated rbc was unchanged from control except at high peg concentrations and only when the morphology was also compromised oxygen uptake and release measured using a hemox analyzer model b tcs medical products co huntingdon pa was found to be identical to control rbc referring to fig2 the effect of peg coating on whole blood viscosity is shown the viscosity of control rbc and peg coated rbc were compared over a range of shear rates using a couette viscometer contraves ls30 contraves ag switzerland the control rbc show a typical steep change in viscosity with shear rate in contrast the viscosity for the peg coated rbc lower curve showed very little shear dependence i e the blood behaved in a nearly newtonian manner consistent with the complete elimination of rbc rbc aggregation at the higher shear rates 10 100 sec u2212 1 the curves for control and peg coated rbc exactly converged given that the hematocrit and plasma viscosity were identical for the two samples this confirms that the rbc deformability was not altered by the peg coating note that the amount.