Is normobaric hypoxia an effective treatment for sustaining previously acquired altitude acclimatization?

Abstract

This study examined whether normobaric hypoxia (NH) treatment is more efficacious for sustaining high-altitude (HA) acclimatization-induced improvements in ventilatory and hematologic responses, acute mountain sickness (AMS), and cognitive function during reintroduction to altitude (RA) than no treatment at all. Seventeen sea-level (SL) residents (age = 23 ± 6 yr; means ± SE) completed in the following order: ) 4 days of SL testing;) 12 days of HA acclimatization at 4,300 m; ) 12 days at SL post-HA acclimatization (Post) where each received either NH ( = 9, [Formula: see text] = 0.122) or Sham ( = 8; [Formula: see text] = 0.207) treatment; and ) 24-h reintroduction to 4,300-m altitude (RA) in a hypobaric chamber (460 Torr). End-tidal carbon dioxide pressure ([Formula: see text]), hematocrit (Hct), and AMS cerebral factor score were assessed at SL, on HA2 and HA11, and after 20 h of RA. Cognitive function was assessed using the SynWin multitask performance test at SL, on HA1 and HA11, and after 4 h of RA. There was no difference between NH and Sham treatment, so data were combined. [Formula: see text] (mmHg) decreased from SL (37.2 ± 0.5) to HA2 (32.2 ± 0.6), decreased further by HA11 (27.1 ± 0.4), and then increased from HA11 during RA (29.3 ± 0.6). Hct (%) increased from SL (42.3 ± 1.1) to HA2 (45.9 ± 1.0), increased again from HA2 to HA11 (48.5 ± 0.8), and then decreased from HA11 during RA (46.4 ± 1.2). AMS prevalence (%) increased from SL (0 ± 0) to HA2 (76 ± 11) and then decreased at HA11 (0 ± 0) and remained depressed during RA (17 ± 10). SynWin scores decreased from SL (1,615 ± 62) to HA1 (1,306 ± 94), improved from HA1 to HA11 (1,770 ± 82), and remained increased during RA (1,707 ± 75). These results demonstrate that HA acclimatization-induced improvements in ventilatory and hematologic responses, AMS, and cognitive function are partially retained during RA after 12 days at SL whether or not NH treatment is utilized. This study demonstrates that normobaric hypoxia treatment over a 12-day period at sea level was not more effective for sustaining high-altitude (HA) acclimatization during reintroduction to HA than no treatment at all. The noteworthy aspect is that athletes, mountaineers, and military personnel do not have to go to extraordinary means to retain HA acclimatization to an easily accessible and relevant altitude if reexposure occurs within a 2-wk time period.

Acute mountain sickness and sleep disturbances differentially influence cognition and mood during rapid ascent to 3000 and 4050 m

“…As the differing timelines suggest (Banderet et al, 2002), AMS development and cognitive performance decrements do not seem to be related in the current study. While some have found correlations between AMS and cognitive performance decrements (Forster, 1985; Shukitt‐Hale et al, 1991), others have not (Abraini et al, 1998; Beidleman et al, 2017; Kramer et al, 1993) and it is generally believed they are not directly related (Shukitt‐Hale et al, 1991; Virues‐Ortega et al, 2004).…”

Hypoxia Conditioning for High-Altitude Pre-acclimatization

“…Upon re-exposure to a simulated altitude of 4300 m (hypobaric chamber) after a 12-day stay at sea level, only 17% developed AMS, indicating that a large acclimatization effect was retained. Interestingly, normobaric hypoxia exposure (3 h per day during the sea level stay) did not further reduce AMS development [9]. These findings, however, rather demonstrate a prolonged (12 days) effectiveness of prior acclimatization rather than corroborating ineffectiveness of normobaric hypoxia for pre-acclimatization.…”

“…In another study, out of 17 young sea level residents, 88% developed AMS (using the LLQ criteria) during the initial high-altitude exposure (4300 m), which declined to 0% during the 12-day acclimatization period [9]. Upon re-exposure to a simulated altitude of 4300 m (hypobaric chamber) after a 12-day stay at sea level, only 17% developed AMS, indicating that a large acclimatization effect was retained.…”

Impact of 2 days of staging at 2500–4300 m on sleep quality and quantity following subsequent exposure to 4300 m

“…Others have reported that sleep acclimatization occurs at altitudes above 4000 m (Fulco et al, 2011;Nussbaumer-Ochsner et al, 2012;Reite et al, 1975) but is questionable at lower altitudes (Fischer et al, 2004;Orr et al, 2018;Tseng et al, 2015). In addition, a decrease in AMS prevalence and severity over 4 days of exposure to 4300 m has been shown repeatedly by others (Beidleman et al, 2017;Fulco et al, 2011).…”