Table 2– Comparison of end-tidal and capillary blood gases, haematocrit and acid–base balance between chronic obstructive pulmonary disease (COPD) and control groups

	COPD	Controls
Subjects n	7	8
pH	7.44±0.02	7.46±0.09
P_c,CO₂ mmHg	37.1±4.8	34.9±4.3
P_c,O₂ mmHg	59.5±7.8	59.8±6.8
P_ET,CO₂ mmHg	32.5±2.7	33.6±2.8
P_ET,O₂ mmHg	90.3±4.0	89.4±6.2
[HCO₃^-] mmol·L⁻¹	25.7±2.9	24.7±4.9
[tHb] g·dL⁻¹	16.1±0.7	13.5±2.7

Data are presented as mean±sd unless otherwise stated. P_c,CO₂: capillary carbon dioxide tension; P_c,O₂: capillary oxygen tension; P_ET,CO₂: end-tidal carbon dioxide tension; P_ET,O₂: end-tidal oxygen tension; [HCO₃^-]: bicarbonate ion concentration; [tHb]: total haemoglobin concentration.