Effect of Acute, Subacute, and Repeated Exposure to High Altitude (5050 m) on Psychomotor Vigilance

FIGURE 1. Expedition schedule and data collection time points. The Y-axis depicts altitude (meters), and the X-axis depicts the days of the entire expedition with two cycles at high altitude interspersed with 1 week at LA. The numbers within the large black circles depict time points of data collection. The small black circles with checkmark indicate the sleep nights with actigraphy, i.e., actigraphic data collection time points. The gray shaded horizontal part at the base of each cycle indicates Cycle 1 and Cycle 2. “1-Week” with a dashed line connecting two cycles indicates time spent at LA. HA1, high altitude exposure at 5050 m asl on Day 1; HA6, high altitude exposure at 5050 m asl on Day 6 on the respective cycles of expedition; FL, familiarization; BL, baseline; REC, recovery; m, meters; n, numbers.

FIGURE 2. Effect of altitude exposure on PVT parameters during acute and acclimatization exposures. It illustrates changes in different PVT parameters during high altitude exposure. Four important time points of the expedition are illustrated (BL, baseline at LA; HA1, acute high altitude exposure; HA6, acclimatization exposure of both cycles; REC, recovery). The Y-axis depicts sleep parameters with the mean and standard deviation (Mean ± SD) of the PVT parameters. The X-axis depicts different expedition time points (BL1, HA1, HA6, and REC of Cycle 1 and Cycle 2). Solid bars represent Cycle 1 exposure while empty bars represent Cycle 2 exposure. Here, panel A illustrates number of errors/lapses while panel E represents PVT reaction speed. Panels B and F represent mean and median of reaction times respectively. Panels C and G show fastest and slowest 10% reaction times while D and H depict reciprocals of them in respective orders. The significance shown with dashed line indicates baseline comparisons of two cycles. The comparison with solid lines is between different time points of respective cycles. n, number; RT, reaction time; ms, milliseconds; s-1, per second; PVT-RS, psychomotor…

FIGURE 3. Effect of altitude on actigraphy sleep indices during acute and acclimatization exposure. It has two panels as Cycle 1 (Left, A,B) and Cycle 2 (Right, C,D). The Y-axis depicts sleep parameters with the mean ± standard deviation (Mean ± SD) at baseline, acute exposure (1st night altitude), and acclimatization night (5th night at altitude). The X-axis depicts different sleep parameters as reported from actigraphy during the first expedition of Cycle 1 and Cycle 2. Black bars, baseline sleep at Santiago, Chile (520 m asl); gray bars, acute exposure to altitude, i.e., 1st night sleep at high altitude (2900 m asl) and empty bars, sleep after acclimatization at high altitude, i.e., 5th night sleep at high altitude in each cycle. The significance shown with dashed line indicates baseline comparisons of two cycles. The comparison with solid lines is between different time points of respective cycles. TIB, time in bed; TST, total sleep time; SL, sleep latency; WASO, wake after sleep onset; Awak, awakenings; SE, sleep efficiency; SD, standard deviation; min, minute; p, level of significance; n, number; %, percentage; ∗p, level of significance value with less than 0.05.

FIGURE 4. Inverse correlation between reaction speed vs. AMS-C score and positive association with changes in reaction time (HA1 – BL) vs. AMS-C score. It has two panels, left panel (A) shows negative correlation between PVT-RS vs. AMS score and the right panel (B) shows positive correlation between changes in reaction time (HA1 – BL) vs. AMS score. The Y-axis depicts reaction speed during the first exposure at altitude in A and the changes in reaction times (HA1, reaction time of high altitude at Day 1 – BL, reaction time at baseline) in B during acute exposure at altitude during Cycle 1. In both panels, the X-axis depicts AMS-C score during the acute exposure Cycle 1. The vertical dashed red lines in both panels separates no AMS subjects from AMS with the cut-off of a ≥ 0.7 AMS-C score. In B, the horizontal dashed line passing through zero of Y-axis is a reference line separating negative (i.e., subjects with decreased reaction time at high altitude) and positive (i.e., subjects with increased reaction time at high altitude) values of changes in reaction times. PVT-RS, psychomotor vigilance test reaction speed; AMS, acute mountain sickness; AMS-C, acute mountain sickness – cerebral; BL,…