Table 1.

Mean changes in arterial blood and ancillary variables with ascent

Variable (mean ± SD)	0 m (sea level)	1045/1400 m (n = 20)	3440 m (n = 18)	3820 m (n = 17)	4240 m (n = 15)	5160 m (n = 14)
Atm pressure (mmHg)	760	675/648	509	486	454	411
P iO 2 (mmHg)	160	141/136	107	102	95	86
$P_{\mathrm{a}{\mathrm{O}}_2}$ (mmHg)	75–1001	80.2 ± 8.3	48.9 ± 7.1*	52.4 ± 5.7*	47.9 ± 5.0*	35.9 ± 4.8*†
$S_{\mathrm{a}{\mathrm{O}}_2}$ (%)	96–1001	96.0 ± 1.5	85.4 ± 6.4*	87.6 ± 3.4*	85.2 ± 3.9*	72.9 ± 7.2*†
$S_{\mathrm{p}{\mathrm{O}}_2}$ (%)	94–1001	97.5 ± 1.2a	91.9 ± 4.6*	92.5 ± 3.0*	88.1 ± 5.0*†	79.4 ± 4.2*†
$P_{\mathrm{ETC}{\mathrm{O}}_2}$ (mmHg)	30–432	32.9 ± 4.9	27.4 ± 2.8*	25.6 ± 2.5*†	21.6 ± 2.6*†	18.9 ± 2.4*†
Creatinine (μmol L–1)	44–1051	73.4 ± 21.4	72.4 ± 13.3	69.9 ± 11.2	71.9 ± 13.6	75.1 ± 18.6
Haematocrit (%)	35–521	42.6 ± 3.6	42.9 ± 3.4b	42.9 ± 3.2	43.5 ± 3.2	45.1 ± 3.5*†
SID (mmol L–1)	403	39.8 ± 2.0a	38.3 ± 2.7*b	38.1 ± 2.4*	38.2 ± 2.3*	36.0 ± 2.1*†
Base excess (mmol L–1)	(−2)–(+2)4	−0.8 ± 2.2	−2.6 ± 2.9*	−4.1 ± 2.0*†	−4.4 ± 2.4*	−6.3 ± 3.3*†
Osmolality (mosmol kg–1)	285–2905	294.6 ± 3.8	290.6 ± 4.3* b	292.7 ± 3.3*	291.5 ± 3.4*	292.9 ± 2.1
$P_{\mathrm{aC}{\mathrm{O}}_2}$ (mmHg)	35–451	35.7 ± 3.8	30.7 ± 3.8*	30.3 ± 3.3*	29.0 ± 3.2*†	25.8 ± 2.4*†c
[HCO3 −]a (mmol L–1)	22–261	23.7 ± 2.1	21.4 ± 2.7*	20.2 ± 2.1*†	19.7 ± 2.2*	18.4 ± 1.8*†c
pHa	7.35–7.451	7.430 ± 0.020	7.451 ± 0.025*	7.432 ± 0.022†	7.441 ± 0.022	7.459 ± 0.018*

¹Chernecky & Berger (2004). ²Respironics (2004). ³Chawla & Drummond (2008). ⁴Berg & Meyer (2008). ⁵Gennari (1984).

P _{iO 2}, partial pressure of inspired oxygen; $P_{\mathrm{a}{\mathrm{O}}_2}$, partial pressure of arterial oxygen; $S_{\mathrm{a}{\mathrm{O}}_2}$, arterial oxygen saturation; $S_{\mathrm{p}{\mathrm{O}}_2}$, peripheral oxygen saturation; $P_{\mathrm{ETC}{\mathrm{O}}_2}$, partial pressure of end tidal carbon dioxide; $P_{\mathrm{aC}{\mathrm{O}}_2}$, partial pressure of arterial carbon dioxide; [HCO₃ ⁻]_a, concentration of arterial bicarbonate; pH_a, arterial pH; SID, strong ion difference. Values at 0 m (sea level) are normative values. ^*Difference in mean from baseline (1045 /1400 m), P < 0.05. ^†Difference in mean from prior altitude, P < 0.05. ^a n = 19. ^b n = 17. ^c n = 13.