Responses to constant work rate exercise with different inspired oxygen concentrations in healthy subjects.
| Parameter | F I,O2 | ||||
| 0.21 | 0.30 | 0.50 | 0.75 | 1.00 | |
| Endurance min | 7.2±1.0 | 6.9±0.7 | 9.8±1.2* | 9.6±1.2* | 10.0±1.4* |
| Isotime values | |||||
| Breathlessness Borg | 5.6±0.8 | 5.1±0.9 | 3.7±0.7* | 3.6±0.7* | 3.4±0.6* |
| HR bpm | 151±5 | 150±5 | 142±7 | 141±8 | 144±6 |
| V'CO2 L·min−1 | 2.04±0.24 | 2.09±0.24 | 1.90±0.22 | 1.94±0.24 | 1.96±0.20 |
| PET,CO2 mmHg | 40.8±1.6 | 41.8±1.6 | 46.8±1.1* | 45.8±1.0* | 45.3±1.4* |
| IC L | 3.10±0.19 | 3.00±0.19 | 3.06±0.24 | 3.13±0.22 | 2.99±0.16 |
| IRV L | 0.95±0.11 | 0.89±0.12 | 0.94±0.09 | 0.99±0.11 | 1.09±0.08 |
| V'E L·min−1 | 57.7±6.9 | 59.1±8.0 | 46.5±5.0* | 48.7±6.1* | 50.5±6.2* |
| VT L | 2.15±0.25 | 2.11±0.25 | 2.13±0.25 | 2.14±0.29 | 1.92±0.17 |
| VT/IC % | 68.1±5.0 | 69.0±4.9 | 68.7±4.1 | 66.3±5.6 | 63.3±3.2 |
| TI/Ttot | 0.46±0.02 | 0.48±0.02 | 0.47±0.01 | 0.49±0.02 | 0.48±0.01 |
| TE s | 1.20±0.10 | 1.13±0.07 | 1.38±0.09* | 1.30±0.07 | 1.12±0.11 |
| VT/TI L·s−1 | 2.11±0.22 | 2.01±0.23 | 1.65±0.16* | 1.64±0.19* | 1.71±0.19* |
| Sa,O2 % | 97.3±0.5 | 99.6±0.3* | 99.9±0.1* | 99.9±0.1* | 100.0±0.0* |
Isotime refers to the time at which the room air test ended
HR: heart rate
V'CO2: carbon dioxide output
PET, CO2: end-tidal partial pressure for CO2
IC: inspiratory capacity
IRV: inspiratory reserve volume
V'E: minute ventilation
VT: tidal volume
VT/IC: tidal volume as a % of IC
TI/Ttot:duty cycle
TE: expiratory time
VT/TI: mean inspiratory flow rate
Sa,O2: arterial oxygen saturation
*: p<0.05 versus 0.21 FI,O2