Fig 1.
Climbing schedule of the expedition to Qinghai-Tibet Plateau.
The six red rhombuses represented the six time points for investigations that were performed at 500m altitude (1 plain), 3650m altitude (2 plateau), 3day (3 plateau), 1 month (4 plateau), and 3 (5 plateau) month post arriving at the base camp (4400m), and about 1 month (6 plain) after coming back to the 500m altitude respectively.
Fig 2.
Changes of heart rate, pulse oxygen saturation, and brain oxygen saturation.
The heart rate (HR) declined gradually after a rise during the stay at high altitude. Even at the sixth point, about 1 month after coming back to the 500m altitude, it continued to decrease. Pulse oxygen saturation (SPO2) displayed a downward state at high altitude, although it increased at 1 and 3 months post arriving at the base camp. The left and right brain oxygen saturation increased at the second, third, and fourth point, which was significantly higher than that at the first point. At the fifth and sixth point, left brain oxygen saturation nearly returned to normal, while the right brain oxygen was still at high level. *, p<0.05 compared with the first point; **, p<0.01 compared with the first point; #, p<0.05, compared with the second point; ##, p<0.01, compared with the second point; ΔΔ, p<0.01, compared with the third point.
Fig 3.
High altitude prolonged the latencies of auditory evoked event related potential (ERP).
The latencies of P300 prolonged at the second and third point, which were significantly longer than that of the first point respectively. At the fourth point, the latency shortened. In addition, the latencies at the fifth and sixth point nearly returned to normal. N200 latency went up at the second point and increased much more at the third point than at the second. At the sixth point N200 latency returned to normal. *, p<0.05 compared with the first point; #, p<0.05, compared with the second point; Δ, p<0.05, compared with the third point; ΔΔ, p<0.01, compared with the third point.
Fig 4.
High altitude increased plasma hypersensitive C-reactive protein (hsCRP) levels.
hsCRP augmented evidently at the second and third point. Then, it showed a downward tendency. At the sixth point it returned to normal. There was no obvious regularity in the alteration of homocysteine and IL-6. *, p<0.05 compared with the first point; **, p<0.01 compared with the first point; #, p<0.05, compared with the second point; ##, p<0.01, compared with the second point; Δ, p<0.05, compared with the third point; ΔΔ, p<0.01, compared with the third point.
Fig 5.
High altitude injured neurological cognitive functions.
Digit symbol substitution test (DSST) score reduced at the second point and decreased much more at the third point than at the second. Scores at the fourth, fifth, and sixth point increased, which have no statistical differences compared to that of the first point. **, p<0.01 compared with the first point; ##, p<0.01, compared with the second point; ΔΔ, p<0.01, compared with the third point.
Fig 6.
Associations among biochemical parameters, event related potential (ERP), and cognitive performance.
Overall, P300 and hsCRP displayed the same changing tendency, which was opposite to the alteration of DSST score. A strong inverse correlation was observed between hsCRP and DSST score. P300 latency was also inversely correlated with DSST score. In addition, P300 latency showed a positive association with hsCRP.