Affiliations: [a]
Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, The University of British Columbia, Kelowna, British Columbia, Canada
| [b]
Faculty of Kinesiology, University of Calgary, Calgary, Canada
Correspondence:
[*]
Corresponding author: Brian H Dalton PhD, Assistant Professor Faculty of Health and Social Development, School of Health and Exercise Sciences The University of British Columbia, Okanagan Campus 1147 Research Road, Kelowna BC, V1V 1V7 Canada. Tel.: +1 250 807 9513; E-mail: brian.dalton@ubc.ca.
Abstract: BACKGROUND:Hypoxia influences standing balance and vestibular function. OBJECTIVE:The purpose here was to investigate the effect of hypoxia on the vestibular control of balance. METHODS:Twenty participants (10 males; 10 females) were tested over two days (normobaric hypoxia and normoxia). Participants stood on a force plate (head rotated leftward) and experienced random, continuous electrical vestibular stimulation (EVS) during trials of eyes open (EO) and closed (EC) at baseline (BL), after 5 (H1), 30 (H2) and 55-min (H3) of hypoxia, and 10-min into normoxic recovery (NR). Vestibular-evoked balance responses were quantified using cumulant density, coherence, and gain functions between EVS and anteroposterior forces. RESULTS:Oxyhemoglobin saturation, end-tidal oxygen and carbon dioxide decreased for H1-3 compared to BL; however, end-tidal carbon dioxide remained reduced at NR with EC (p≤0.003). EVS-AP force peak-to-peak amplitude was lower at H3 and NR than at BL (p≤0.01). At multiple frequencies, EVS-AP force coherence and gain estimates were lower at H3 and NR than BL for females; however, this was only observed for coherence for males. CONCLUSIONS:Overall, vestibular-evoked balance responses are blunted following normobaric hypoxia >30 min, which persists into NR and may contribute to the reported increases in postural sway.
