Table 1.

Cardiorespiratory measurements during poikilocapnic and isocapnic exercise while breathing either normoxia or hyperoxia

	Stage
Measurement/Condition	BL1	BL2	20 %	40%	60%	80%
Poikilocapnic
V̇e, l/min
Normoxia	13.5 ± 1.7*	12.4 ± 2.4	22.0 ± 4.0*	30.3 ± 6.3*	41.0 ± 9.5*	57.0 ± 12.0*
Hyperoxia	13.4 ± 2.2*	13.7 ± 3.4	21.3 ± 5.0*	30.4 ± 5.8*	42.0 ± 8.2*	55.0 ± 13.0*
HR, beats/min
Normoxia	75 ± 13	74 ± 12	100 ± 15*	113 ± 15*	131 ± 13*	150 ± 13*
Hyperoxia	72 ± 16	68 ± 15	93 ± 17*	110 ± 18*	126 ± 19*	142 ± 22*
MAP, mmHg
Normoxia	88 ± 8	89 ± 10	97 ± 6*	103 ± 7*	108 ± 9*	112 ± 11*
Hyperoxia	89 ± 8	91 ± 6	97 ± 8*	99 ± 8*	106 ± 9*	110 9*
PetO2, mmHg
Normoxia	98 ± 13	99 ± 13	94 ± 14	93 ± 6	96 ± 5	100 ± 5
Hyperoxia	96 ± 3*	299 ± 8†	298 ± 5†	297 ± 6†	294 ± 7†	294 ± 6†
PetCO2, mmHg
Normoxia	40 ± 2	40 ± 2	41 ± 2	42 ± 3*	42 ± 3*	41 ± 3
Hyperoxia	40 ± 3*	36 ± 4§	39 ± 3*§	42 ± 3*§	42 ± 4*§	42 ± 4*§
Isocapnia
V̇e, l/min
Normoxia	13.5 ± 1.8*	16.5 ± 3.7‡	29.6 ± 4.7*‡	39.7 ± 7.2*‡	56.3 ± 13.4*‡	—
Hyperoxia	13.9 ± 2.2*	18.8 ± 4.8‡	30.0 ± 6.4*‡	39.4 ± 7.4*‡	53.8 ± 13.6*‡	—
HR, beats/min
Normoxia	73 ± 14	77 ± 13	101 ± 12*	116 ± 133*	133 ± 17*	—
Hyperoxia	71 ± 18	73 ± 20	97 ± 19*	113 ± 18*	128 ± 19*	—
MAP, mmHg
Normoxia	88 ± 6.7	89 ± 6.2	96 ± 6.0*	101 ± 8.0*	108 ± 11*	—
Hyperoxia	89 ± 7.5	91 ± 7.7	99 ± 7.8*	102 ± 9.1*	112 ± 13*	—
PetO2, mmHg
Normoxia	95 ± 4.2	99 ± 1.9	97 ± 5.7	97 ± 4.8	94 ± 4.2	—
Hyperoxia	96 ± 6.7	298 ± 5.3	298 ± 3.5	299 ± 5.2	310 ± 34	—
PetCO2, mmHg
Normoxia	40 ± 1.6	40 ± 1.7	40 ± 1.8	40 ± 1.9‡	41 ± 2.6‡	—
Hyperoxia	39 ± 3.8	39 ± 3.7‡	39 ± 3.5	39 ± 3.4‡	40 ± 4.0‡	—

>Values are means ± SD. BL, baseline; V̇e, ventilation; HR, heart rate; MAP, mean arterial pressure; Pet_O2 and Pet_CO2, partial pressure of arterial oxygen and carbon dioxide.

^*P < 0.05, from BL2;

^†P < 0.05, from normoxia;

^‡P < 0.05, from poikilocapnia;

^§P < 0.05, interaction effect between normoxia and hyperoxia.