TABLE 2 Selected peak exercise variables in healthy controls and chronic obstructive pulmonary disease patients separated by Global Initiative in Chronic Obstructive Lung Disease (GOLD)

	Controls	GOLD stage
	Controls	1	2	3	4
Subjects	69	81	112	84	39
Time min	10.1±2.0	9.8±1.9	8.5±1.5	7.8±2.3	6.1±1.3
WR % predicted	125.9±24.4	97.1±20.3*^,#	82.5±18.8*^,#	67.3±17.1*^,#	48.9±17.0*^,#
V′_O₂% predicted	118.4±18.3	91.9±23.5*^,#	78.4±22.7*^,#	60.9±17.5*^,#	40.8±11.5*^,#
V′_E/MVV	0.58±0.07	0.73±0.10*^,#	0.88±0.07	0.89±0.08	0.92±0.10
V_T L	1.90±0.42	1.79±0.56*^,#	1.39±0.46*^,#	1.11±0.36*^,#	0.95±0.30*^,#
f_R rpm	38±10	35±6*	34±9*	33±8*	25±6*^,#
EILV/TLC	0.82±0.04	0.86±0.06*^,#	0.91±0.05	0.93±0.04	0.95±0.03
P_ETCO₂mmHg	31.6±3.8	34.6±4.9*^,#	38.4±6.4*^,#	40.9±6.3*^,#	44.4±3.8*^,#
S_pO₂ %	95±3*	95±4*	93±4*	91±3*	89±3*^,#
Dyspnoea scores	3 (2)	4 (3)*	4 (3)*	5 (2)*^,#	5 (3)*^,#

Data are presented as n, mean±sdor median (interquartile range). WR: work rate; V′_O₂: oxygen production; V′_E: minute ventilation; MVV: maximal voluntary ventilation: V_T: tidal volume; f_R: respiratory frequency; EILV: end-inspiratory lung volume; TLC: total lung capacity; P_ETCO₂: end-tidal carbon dioxide tension; S_pO₂: arterial oxygen saturation measured by pulse oximetry. *: p<0.05 versus controls; ^#: p<0.05 versus other GOLD stages.