Longitudinal observation of intraocular pressure variations with acute altitude changes

Table 1 Demographics of three groups (mean ± SD)

	LA group	HA group	VHA group	P value
n	17	22	19
Gender (male/ female)1	6/11	11/11	10/9	0.548
Age (yr)(range)2	28.1 ± 8.1(22-56)	29.6 ± 4.3 (20-37)	28.6 ± 6.0 (22-42)	0.716
Height (m)2	1.7 ± 5.7	1.7 ± 8.8	1.7 ± 6.3	0.19
Weight (kg)2	62.2 ± 8.7	64.9 ± 16.0	64.0 ± 10.6	0.898
BMI (kg/m2)2	21.8 ± 2.1	22.5 ± 3.9	23.6 ± 3.1	0.253
Waistline (cm)2	77.0 ± 8.4	80.7 ± 13.1	80.7 ± 9.7	0.492
Hipline (cm)2	93. 7± 5.3	90.3 ± 7.9	90.6 ± 7.1	0.279

¹Kruskal–Wallis test with post hoc Dunn multiple comparisons;

²One-way ANOVA with post hoc least significant difference analysis. BMI: Body mass index; LA: Low-altitude; HA: High altitude; VHA: Very high altitude.

Table 2 Comparison of baseline parameters among three groups measured at their native hospitals (mean ± SD)

Parameters	LA group	HA group	VHA group	P value	Post hoc analysis
n	17 (34 eyes)	22 (44 eyes)	19 (38 eyes)
SpO2 (%)1	97.06 ± 0.43	94.55 ± 1.18	90.05 ± 2.09	< 0.001	A > B > C
IOP (mmHg)2	18.4 ± 2.4	12.2 ± 2.4	11.5 ± 1.8	< 0.001	A > B, C
OPP (mmHg)2	36.5 ± 6.3	47.9 ± 7.3	49.2 ± 9.2	< 0.001	A > B, C
SBP (mmHg)3	109.7 ± 11.5	118.6 ± 14.9	118.3 ± 18.3	0.149	NS
DBP (mmHg)3	68.7 ± 10.3	76.1 ± 10.3	77.5 ± 14.5	0.069	NS
MBP (mmHg)3	82.4 ± 10.2	90.2 ± 11.2	91.1 ± 14.9	0.051	NS
Pulse rate (bpm)3	78.6 ± 9.1	79.6 ± 10.6	87.6 ± 8.5	0.009	A, B < C
Erythrocyte (1012/L)1	4.58 ± 0.6	5.24 ± 0.63	5.67 ± 0.62	< 0.001	A < B, C
Hemoglobin (g/L)1	137.63 ± 21.14	157.09 ± 20.26	180.84 ± 23.37	< 0.001	A < B < C

¹Kruskal–Wallis test with post hoc Dunn multiple comparisons.

²Mixed linear model analysis.

³One-way ANOVA with post hoc least significant difference analysis. SpO₂: Pulse oxygen saturation; IOP: Intraocular pressure; OPP: Ocular perfusion pressure; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; LA: Low-altitude; HA: High altitude; VHA: Very high altitude; A: Low-altitude group; B: High altitude group; C: Very high altitude group; NS: Not significant.

Table 3 Associations between intraocular pressure and vital as well as hematological parameters in two ascending groups

	LA group		HA group
	r	P value	r	P value
SpO2 (%)	0.388	< 0.001	0.117	0.223
Pulse rate (bpm)	–0.186	0.062	–0.176	0.065
Systolic blood pressure (mmHg)	–0.008	0.938	0.076	0.432
Diastolic blood pressure (mmHg)	–0.110	0.270	0.127	0.187
Erythrocyte (1012/L)	0.069	0.578	0.001	0.994
Hemoglobin (g/L)	0.099	0.427	–0.041	0.746

SpO₂: Pulse oxygen saturation; LA: Low-altitude; HA: High altitude.