Table 3– Effects of hyperoxia (HOx) and helium-hyperoxia (HeHOx) on physiological and subjective responses to constant load exercise

	Isotime		T_lim
	HOx	HeHOx	HOx	HeHOx
Exercise time s	330 (234–462)	330 (234–462)	354 (234–462)	456 (288–738)*
Operating lung volumes
IC L	1.50±0.27	1.56±0.30	1.45±0.27	1.55±0.30*
EELV L	5.76±1.17	5.70±1.22	5.70±1.14	5.60±1.15*
IRV L	0.44±0.23	0.42±0.23	0.43±0.15	0.48±0.15
V_T/IC	0.71±0.12	0.74±0.11	0.72±0.09	0.71±0.06
Metabolic
V′_CO₂mL·min⁻¹	995±246	855±193*	997±248	878±187*
Cardiovascular
Cardiac output L·min⁻¹	11.8±2.4	11.5±2.6	12.0±2.4	12.3±2.9
Heart rate beats·min⁻¹	122±17	117±18*	123±17	122±18
Stroke volume mL	97±18	98±12	98±18	100±15
Ventilatory
V′_EL·min⁻¹	30.6±8.1	31.6±8.3	30.7±8.3	33.1±8.5*
V_T mL	1043±213	1140±209*	1040±211	1090±191
Breathing frequency breaths·min⁻¹	30±6	28±5	30±6	31±6
V′_E/MVV	0.92±0.20	0.82±0.18*	0.92±0.20	0.86±0.18
V′_E/V′_CO₂	31.4±6.3	37.6±7.8*	31.3±6.3	38.3±8.1*
t_I/t_TOT	0.30±0.03	0.28±0.04*	0.30±0.03	0.27±0.04*
V_T/t_I L·s⁻¹	1.71±0.42	1.94±0.46*	1.73±0.43	2.08±0.48*
V_T/t_E L·s⁻¹	0.73±0.21	0.73±0.21	0.73±0.22	0.76±0.21
Gas exchange
P_ETCO₂ mmHg	47±10	42±9*	47±10	41±10*
S_pO₂ %	98±1	98±1	100±16	97±2
Subjective
Dyspnoea scores	4.0 (3.0–5.0)	4.0 (3.0–5.0)	6.0 (5.0–7.5)	5.0 (3.3–7.0)
Leg effort scores	5.0 (3.0–7.0)	6.0 (4.0–7.8)	6.0 (3.0–8.0)	6.5 (4.3–8.0)

Data are presented as mean±sd or median (range). n = 21. T_lim: time to exercise intolerance; IC: inspiratory capacity; EELV: end-expiratory lung volume; IRV: inspiratory reserve volume; V_T: tidal volume; V′_CO₂: carbon dioxide output; V′_E: minute ventilation; MVV: maximal voluntary ventilation; t_I: inspiratory time; t_TOT: total respiratory time; t_E: expiratory time; P_ETCO₂: end-tidal carbon dioxide tension; S_pO₂: arterial oxygen saturation measured by pulse oximetry. *: p<0.05 for between-intervention differences at a given time point.