Effect of simulated altitude erythrocythemia in women on hemoglobin flow rate during exercise

The effect of simulated altitude erythrocythemia on hemoglobin flow rate and maximal O₂ uptake (V̇O(2max)) was determined for nine women sea-level residents. Test conditions included normoxia and normobaric hypoxia (16% O₂-84% N₂). Cycle tests were performed under normoxia (T₁-N) and hypoxia (T₁-H) at prereinfusion control and under hypoxia 48 h after a placebo infusion (T₂-H) and 48 h after autologous infusion of 334 ml of erythrocytes (T₃-H). Hematocrit (38.1-44.9%) and hemoglobin concentration (12.7-14.7 g·dl^-1) increased from control to postreinfusion. At peak exercise, V̇O(2max) decreased from T₁-N (2.40 l·min^-1) to T₁-H (2.15 l·min^-1) then increased at T₃-H (2.37 l·min^-1). Maximal arterial-mixed venous O₂ difference decreased from T₁-N to T₁-H and increased at T₃-H. Cardiac output (Q̇), stroke volume, heart rate, and total peripheral resistance during maximal exercise were unchanged from T₁-N through T₃-H. Hemoglobin flow rate (Hb flow) at maximum did not change from T₁-N to T₁-H but increased at T₃-H. When compared with submaximal values for T₁-N, V̇O₂ was unchanged at T₁-H and T₃-H; Q̇ increased at T₁-H and decreased at T₃-H; arterial-mixed venous O₂ difference decreased at T₁-H and increased at T₃-H; Hb flow did not change at T₁-N but increased at T₃-H. For young women, simulated altitude erythrocythemia increased peak Hb flow and decreased physiological altitude (227.8 m) but did not affect maximum cardiac output (Q̇(max)).