Table 3.

Hemodynamic, gas exchange, and blood gas measures while stationary on the cycle ergometer on day 1 and day 15

	Day 1 Normoxia	Day 15 Normoxia	Day 1 Hypoxia	Day 15 Hypoxia
Hemodynamic variables
Heart rate, beats/min	88 ± 5	85 ± 6	86 ± 6	93 ± 4*
Mean arterial pressure, mmHg	95 ± 3	95 ± 5	95 ± 4	95 ± 5
Cardiac output, L/min	8.7 ± 0.6	9.2 ± 0.7	8.8 ± 0.8	9.7 ± 0.6
Gas exchange variables
Oxygen uptake, mL/min	481 ± 67	452 ± 46	428 ± 26	440 ± 52
Carbon dioxide production, mL/min	491 ± 68	443 ± 50	435 ± 37	486 ± 88
Ventilation, L/min	23 ± 4	23 ± 4	21 ± 2	29 ± 9
Respiratory exchange ratio	1.04 ± 0.07	0.98 ± 0.07	1.04 ± 0.05	1.08 ± 0.08
Ventilatory equivalent for oxygen uptake	52 ± 7	51 ± 5	52 ± 3	61 ± 10
Ventilatory equivalent for carbon dioxide production	48 ± 3	52 ± 2	50 ± 2	54 ± 4
Alveolar oxygen partial pressure, mmHg	112 ± 3	113 ± 4	57 ± 3	60 ± 3
Alveolar-to-arterial oxygen difference, mmHg	8 ± 2	10 ± 2	9 ± 1	9 ± 1
Blood gas variables
Arterial oxygen saturation, %	96.8 ± 0.2	97.2 ± 0.2	82.9 ± 3.4	90.9 ± 1.8*
Arterial oxygen partial pressure, mmHg	103 ± 4	105 ± 5	49 ± 4	51 ± 3
Arterial carbon dioxide partial pressure, mmHg	32 ± 2	29 ± 2	29 ± 2	27 ± 2
Arterial oxygen content, mL O2/100 mL	19.8 ± 0.6	19.7 ± 0.5	17.3 ± 0.9	18.5 ± 0.7
Arterial-venous oxygen difference. mL O2/100 mL	5.6 ± 0.8	5.2 ± 0.8	5.2 ± 0.7	4.6 ± 0.5
Venous oxygen content, mL O2/100 mL	14.2 ± 0.8	14.8 ± 0.5	12.1 ± 1.3	13.8 ± 0.6
Fractional oxygen extraction, %	28 ± 4	25 ± 1	31 ± 5	25 ± 2
Carboxyhemoglobin, %hemoglobin	1.2 ± 0.1	1.6 ± 0.1*	1.2 ± 0.0	1.6 ± 0.1*
Bicarbonate, mmol/L	23 ± 1	21 ± 1	22 ± 0	20 ± 1
pH	7.46 ± 0.0	7.47 ± 0.0	7.50 ± 0.0	7.49 ± 0.0
Lactate, mmol/L	2.0 ± 0.3	1.9 ± 0.5	2.0 ± 0.3	2.2 ± 0.4

Data are means ± SE. Significance accepted at P < 0.05.

^*Significantly different from day 1.