Table 2—

Responses to constant work rate exercise with different inspired oxygen fractions in patients with chronic obstructive pulmonary disease.

Parameter	F _I,O₂
Parameter	0.21	0.30	0.50	0.75	1.00
Endurance min	4.2±0.5	7.8±1.0*	10.3±1.9*^†	10.8±1.0*^†	9.6±0.8*^†
Isotime values
Breathlessness Borg	6.7±0.6	4.4±0.4*	4.0±0.4*	3.3±0.4*	4.4±0.5*
HR bpm	121±4	111±5*	107±3*	105±3*	105±3*
V'_CO₂ L·min⁻¹	0.95±0.11	0.85±0.11	0.85±0.12	0.86±0.14	0.85±0.12
P_ET,CO₂ mmHg	41.2±1.4	43.7±1.5	42.9±1.3	41.5±1.3	41.5±1.3
IC L	1.39±0.14	1.59±0.14*	1.72±0.14*	1.68±0.12*	1.71±0.11*
IRV L	0.29±0.05	0.48±0.06*	0.54±0.06*	0.53±0.04*	0.55±0.07*
V'_E L·min⁻¹	30.6±3.3	26.4±3.4*	26.1±3.6*	25.4±2.9*	24.2±3.5*
V_T L	1.10±0.11	1.12±0.12	1.18±0.12	1.15±0.09	1.06±0.12
V_T/IC %	79.9±3.0	69.6±3.5*	65.5±4.3*	68.4±2.1*	64.0±4.7*
T_I T_tot	0.36±0.02	0.36±0.01	0.38±0.01	0.37±0.01	0.36±0.02
T_E s	1.44±0.12	1.69±0.16*	1.83±0.15*	1.75±0.11*	1.78±0.16*
V_T/T_I L·s⁻¹	1.47±0.14	1.20±0.11*	1.17±0.12*	1.11±0.11*	1.09±0.12*
S_a,O₂ %	91.0±1.1	98.0±0.8*	99.7±0.2*	99.7±0.2*	99.9±0.1*

Isotime refers to the time at which the room air test ended
HR: heart rate
V'_CO₂: carbon dioxide output
P_{ET, CO₂}: end-tidal partial pressure for CO₂
IC: inspiratory capacity
IRV: inspiratory reserve volume
V'_E: minute ventilation
V_T: tidal volume
V_T/IC: tidal volume as a % of IC
T_I/Ttot: duty cycle
T_E: expiratory time
V_T/T_I: mean inspiratory flow
S_a,O₂: arterial oxygen saturation
*: p<0.05 versus 0.21 F_I,O₂
^†: p<0.05 versus 0.30 F_I,O₂