Table 1.

Mean responses to the final minute of exercise (138 ± 14 W, 10.6 ± 0.7 min)

	Sea Level	Acute Hypoxia	Chronic Hypoxia
HR, beats/min	152 ± 5	174 ± 4*	166 ± 4*†
VE, l min−1	64 ± 4	113 ± 8*	133 ± 10*†
fR, breaths min−1	32 ± 2	50 ± 3*	54 ± 3*
VT, liter	2.0 ± 0.1	2.2 ± 0.2	2.6 ± 0.2*†
V̇o2, l min−1	2.58 ± 0.19	2.44 ± 0.19*	2.39 ± 0.16*†
V̇co2, l min−1	2.51 ± 0.22	2.81 ± 0.21*	2.40 ± 0.15*†
VE/V̇o2	25 ± 1	50 ± 4*	56 ± 3*†
VE/V̇co2	26 ± 1	41 ± 2*	58 ± 3*†
SpO2, %	94.1 ± 1.0	62.2 ± 1.8*	75.6 ± 1.2*†
CBFv, cm/s	59.1 ± 4.8	74.2 ± 3.8*	73.2 ± 3.4*
Cerebral O2 delivery, a.u.	1,105 ± 62	895 ± 40*	1,289 ± 42*†
Ti/Ttot	0.35 ± 0.01	0.39 ± 0.01*	0.39 ± 0.01*
Te, s	1.30 ± 0.08	0.74 ± 0.05*	0.70 ± 0.04*
Winsp, cmH2O · s−1 · min−1	387 ± 36	503 ± 53*	608 ± 67*†
IC, liter	3.29 ± 0.22	3.13 ± 0.23	3.60 ± 0.23*
VT/IC	0.60 ± 0.03	0.68 ± 0.02*	0.72 ± 0.02*†
IRV, liter	1.30 ± 0.14	0.99 ± 0.13*	0.96 ± 0.05*
ERV, liter	1.98 ± 0.25	2.14 ± 0.29	1.67 ± 0.25*†
EILV, %TLC	80.5 ± 1.6	85.4 ± 1.7*	85.2 ± 0.9*
EELV, %TLC	51.5 ± 1.8	53.8 ± 2.5	46.9 ± 2.1*†
Expiratory flow limitation, n out of 8 subjects	0/8	2/8	4/8
RPE	12.3 ± 1.0	19.8 ± 0.1*	17.9 ± 0.6*†
Dyspnea	11.5 ± 0.7	19.5 ± 0.2*	19.3 ± 0.2*

HR, heart rate; V_E, minute ventilation; f_R, breathing frequency; V_T, tidal volume; V̇o₂, maximum oxygen (O₂) uptake; V̇co₂, carbon dioxide production; S_pO₂, arterial O₂ saturation; CBFv, cerebral blood flow velocity; T_i, duration of inspiration; T_tot, duration of entire breath; T_e, duration of expiration; W_insp, inspiratory muscle work; IC, inspiratory capacity; IRV, inspiratory reserve volume; ERV, expiratory reserve volume; EILV, end-inspiratory lung volume; TLC, total lung capacity; EELV, end-expiratory lung volume; RPE, rating of perceived exertion.

^*P < 0.05 vs. sea level;

^†P < 0.05 vs. acute hypoxia, n = 8.