Variation of Cognitive Function During a Short Stay at Hypobaric Hypoxia Chamber (Altitude: 3842 M)

Abstract

Objective To observe the effects of a fast-acute ascent to high altitude on brain cognitive function and transcranial doppler parameters in order to understand the physiological countermeasures of hypoxia. Methods 17 high-altitude-naïve male subjects (mean age was 26.3 ± 8.1 years) participated in the study. We measured Critical Flicker Fusion Frequency (CFFF), blood oxygen saturation, Psychology Experiment Building (PEBL) including three tests (Modified Math Processing Task, Perceptual Vigilance Task, and Time Estimation Task), as well as Cerebral Blood Flow index (CBFi), mean cerebral artery Systolic and diastolic velocities, Cerebral Pulsatility index (CPi), and heart Rate. All were measured at sea level, at least 1 h after arrival at the hypobaric hypoxia equivalent of 3842 m and 1 h after return to sea level. Results Under acute exposure to hypobaric hypoxic conditions, significant decrease in CFFF [42.1 ± 1 vs. 43.5 ± 1.7 Hz at sea level (asl), p < 0.01], CBFi (611 ± 51 vs. 665 ± 71 asl, p < 0.01) and blood oxygen saturation (83 ± 4% vs. 98 ± 1% asl, p < 0.001) as compared to pre-ascent values were observed. Physiological countermeasures to hypoxia could be involved as there was no significant change in neuropsychometric tests, Systolic and Diastolic velocities and CPi. A significant increase in Heart Rate (81 ± 15 bpm vs. 66 ± 15 bpm asl, p < 0.001) was observed. All parameters returned to their basal values 1 h after regaining sea level. Conclusion Hypoxia results in a decrease in CFFF, CBFi and oxygen saturation and in an increase in heart rate. As it decreased, Cerebral Blood Flow index does not seem to be the physiological measurement of choice to hypoxia explaining the maintenance of cognitive performance after acute exposure to hypobaric hypoxia and requires further investigation. Cerebral oxygen delivery and extraction could be one of the underlying mechanisms.

A Prospective Evaluation of the Acute Effects of High Altitude on Cognitive and Physiological Functions in Lowlanders

“…Our study showed preserved psychomotor vigilance after HH exposure in line with the results of other studies performed below 4,000 m ( Thomas et al, 2007 ; De Bels et al, 2019 ; Heinrich et al, 2019 ) but is in contrast with those performed above 4,000 m ( Roach et al, 2014 ; Davranche et al, 2016 ; Pun et al, 2018 ). However, more false starts at the PVT were observed in individuals with a worse sleep quality measured with the ISI after the first night at altitude (ISI > 7).…”

“…In the 18 included studies the fraction of inspired oxygen ranged from 10 to 18%. Differences in altitude-exposure speed, duration and profile, the way of ascent, study population, cognitive tests employed, and test administration times at altitude ( Li et al, 2000 ; Pavlicek et al, 2005 ; De Bels et al, 2019 ; Loprinzi et al, 2019 ) can explain discrepancies and hinder the drawing of conclusions regarding the effects of altitude on the cognition of recreationists.…”

Simulated Acute Hypobaric Hypoxia Effects on Cognition in Helicopter Emergency Medical Service Personnel – A Randomized, Controlled, Single-Blind, Crossover Trial

“…Previous studies in astronauts (Basner et al, 2015), aircraft pilots (Asmaro et al, 2013;Bustamante-Sánchez et al, 2019;Legg et al, 2012) and military helicopter pilots (Bouak et al, 2018;Legg et al, 2016) have explored the influence of HH on multiple cognitive domains but the precise effects on cognition are still unclear (Jung et al, 2020;McMorris et al, 2017). Contradictory results have been reported in different studies (De Bels et al, 2019;Li et al, 2000;Loprinzi et al, 2019;McMorris et al, 2011;McMorris & Hale, 2012;Pavlicek et al, 2015;Taylor et al, 2016), especially at moderate altitude. Some studies have reported reduced psychomotor vigilance (i.e., slowing of reaction time, RT) after exposure to reduced oxygen availability (altitude between 4350 and 5260 m above sea level (asl)) (Davranche et al, 2016;Pun et al, 2018;Roach et al, 2014) while others reported no effects (altitude between 1630 to 3962 m asl) (De Bels et al, 2019;Heinrich et al, 2019;Latshang et al, 2013;Thomas et al, 2007).…”

Anodal tDCS over the left DLPFC but not M1 increases muscle activity and improves psychophysiological responses, cognitive function, and endurance performance in normobaric hypoxia: a randomized controlled trial

“…However, after exhaustion in the endurance task under hypoxia, the DLPFC tDCS condition had a significantly shorter CRT compared to sham. Recent studies have found mixed results regarding cognitive function while exercising in hypoxia, emphasizing that we are dealing with a more complex scenario than in normoxia [ 30 , 50 – 52 ]. It has been demonstrated that cognitive function is compromised as hypoxia severity increases, most likely due to hypoxia-induced impairment in neurovascular coupling, which is the primary mechanism of brain O 2 delivery [ 30 , 36 , 53 ].…”