Effect of induced erythrocythemia on hypoxia tolerance during physical exercise.

The effect of induced erythrocythemia on hypoxia tolerance during physical exercise was determined for five male mountain climbers. Treadmill testing was performed under four conditions: 1) prereinfusion, normoxia (Pre-N); 2) prereinfusion, hypoxia (Pre-H); 3) postreinfusion, normoxia (Post-N); and 4) postreinfusion, hypoxia (Post-H). An altitude of 3,566.2 m was simulated by having subjects breath a gas mixture of 13.5% O2-86.5% N2 at normal barometric pressure. Tests were administered immediately before and 24 h after autologous transfusion of 750 ml of red blood cells. Hematocrit increased from 43.3% at prereinfusion to 54.8% at postreinfusion. Hemoglobin concentration increased from 13.80 g X 100 ml-1 at prereinfusion to 17.63 g X 100 ml-1 at postreinfusion. Maximal O2 uptake (VO2 max, 1 X min-1) increased (P less than 0.05) by 12.8% (3.28 to 3.70) from Pre-N to Post-N and 13.0% (2.62 to 2.96) from Pre-H to Post-H. Treadmill performance time (s) increased (P less than 0.05) by 15.8% (793 to 918) from Pre-N to Post-N and 8.9% (687 to 748) from Pre-H to Post-H. VO2 max decreased by 20.1% from Pre-N to Pre-H and by 9.8% from Pre-N to Post-H. Treadmill time decreased by 13.4% from Pre-N to Pre-H and 5.7% from Pre-N to Post-H. The calculated change in hypoxia tolerance following reinfusion indicated that physiological altitude was improved by 463.6 m. It was concluded that induced erythrocythemia increased hypoxia tolerance during physical exercise.