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HEMOGLOBIN MASS DOES NOT INCREASE IN ABLE-BODIED INDIVIDUALS AFTER CONSECUTIVE DAYS OF ACUTE INTERMITTENT HYPOXIA

Abstract

Prolonged exposure to hypoxia can elevate serum erythropoietin (EPO) and may eventually increase hemoglobin mass. However, whether very short, intermittent exposures to hypoxic gas (acute intermittent hypoxia; AIH) lead to similar changes is not well understood. In a recent study, one session of AIH significantly increased serum EPO but not hemoglobin mass in healthy individuals. Interestingly, several days of AIH improves walking endurance in individuals with chronic incomplete spinal cord injury (iSCI). Given the link between hemoglobin mass and cardiorespiratory fitness, these improvements are potentially associated with increases in hemoglobin mass. As one session of AIH increases EPO, and several days of AIH improve walking endurance in individuals with iSCI, it remains plausible that consecutive days of AIH will increase hemoglobin mass in able-bodied individuals. PURPOSE: To investigate the effect of consecutive days of AIH on hemoglobin mass in able-bodied individuals. METHODS: Participants (n = 21) were exposed to 4 consecutive days of AIH consisting of fifteen 90s intervals of breathing ~9% O2 alternating with 60s of breathing room air (~21% O2). Hemoglobin mass was measured in each participant before the first and after the last exposure. In a subset of individuals (n = 3), we collected serum blood samples for EPO analysis before and 4.5 hours after two of the 4 AIH exposures. A separate group (n = 5) underwent two sessions of AIH per day for 4 days, with the same hemoglobin mass and EPO measurements as above. Hemoglobin mass and serum EPO comparisons were made using linear mixed model analyses. RESULTS: There was no significant increase in hemoglobin mass after 4 consecutive days of AIH (D hemoglobin mass = 2.81g; CI [-11.9, 17.6], p = .70). Further, pilot data indicate no difference in DEPO with AIH, as compared to control, in the individuals receiving one dose (DEPO (AIH) = -1.00 mIU/mL; CI [-11.25, 9.23], DEPO (control) = 0.07 mIU/mL; CI [-2.42, 2.56]) or two doses (DEPO (AIH) = 0.67 mIU/mL; CI [-0.61, 1.95], DEPO (control) = 1.56 mIU/mL; CI [-2.19, 5.30]) of AIH per day. CONCLUSION: Four consecutive days of AIH is not a sufficient hypoxia exposure to elicit increases in hemoglobin mass in able-bodied individuals. This is reinforced by pilot data indicating no increase in serum EPO after consecutive days of AIH. Poster Presentations

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