Table 2.

Arterial blood gas and electrolyte data during rapid ascent to and residence at 3,800 m on days (D)0, (D)2, and (D)9

Variable, Means ± SD	Calgary (D0)	Barcroft Lab (D2)	Barcroft Lab (D9)
Altitude, m	1,045	3,800
${\text{P}}_{\text{ATM }}$, mmHg	665	487
${\text{Pl}}_{{\text{O}}_2}$, mmHg	130	92
Oxygenation and Acid-Base/Electrolyte Variables
${\text{Pa}}_{{\text{O}}_2}$, mmHg	80.8 ± 8.8	50.5 ± 5.2*	53.8 ± 4.1*‡
${\text{Sa}}_{{\text{O}}_2}$, %	95.8 ± 1.2	85.8 ± 3.8*	88.3 ± 1.9*‡
[Hb], g/L	148.4 ± 12.0	149.1 ± 9.4	158.3 ± 9.8*‡
Hct, %	43.7 ± 3.5	43.9 ± 2.8	46.6 ± 2.9*‡
${\text{Ca}}_{{\text{O}}_2}$, mL/dL	19.6 ± 1.5	17.5 ± 1.3*	19.2 ± 1.4‡
${\text{Pa}}_{{\text{CO}}_2}$, mmHg	38.4 ± 3.0	34.3 ± 2.8*	30.5 ± 1.8*‡
$\left[{\text{HCO}}_3^{-}\right]\text{a}$, mM	24.4 ± 1.8	22.5 ± 2.2*	19.8 ± 1.4*‡
pHa	7.412 ± 0.014	7.424 ± 0.017	7.420 ± 0.013
RR, $\Delta \left[{\text{HCO}}_3^{-}\right]\text{a}/\Delta {\text{Pa}}_{{\text{CO}}_2}$		0.46 ± 0.28	0.59 ± 0.14
SID, mEq/L	41.0 ± 2.2a	39.4 ± 1.7*	37.5 ± 1.5*‡
Base Excess, mM	−0.13 ± 1.8	−1.8 ±2.5*	−4.7 ± 1.5*‡
Anion Gap, mM	15.8 ± 1.8	16.3 ± 1.3	16.5 ± 1.1
Osmolality, mOsmol/kgH2O	283.2 ± 3.2	283.8 ± 1.8	282.3 ± 2.5
Lactate, mM	0.97 ± 0.5a	0.98 ± 0.5	0.74 ± 0.3
Creatinine, μM	73.3 ± 12.4	77.3 ± 12.4	81.6 ± 14.3*

${\mathrm{C}\mathrm{a}}_{{\mathrm{O}}_2}$, arterial oxygen content; [Hb], concentration of hemoglobin; $\left[{\mathrm{H}\mathrm{C}\mathrm{O}}_3^{-}\right]\mathrm{a}$, concentration of arterial bicarbonate; Hct, hematocrit; ${\mathrm{P}\mathrm{a}}_{{\mathrm{C}\mathrm{O}}_2}$, partial pressure of arterial carbon dioxide; ${\mathrm{P}\mathrm{a}}_{{\mathrm{O}}_2}$, partial pressure of arterial oxygen; P_ATM, atmospheric pressure; pHa, arterial pH; ${\mathrm{P}\mathrm{I}}_{{\mathrm{O}}_2}$, partial pressure of inspired oxygen; RR, renal reactivity; ${S\mathrm{a}}_{{\mathrm{O}}_2}$, arterial oxygen saturation; SID, strong ion difference.

^*Significant difference from baseline (1,045 m), P < 0.05.

^‡Significant difference from previous day, P < 0.05. Unless otherwise stated, n = 16.

^an = 15.