Table 3– Predictors of mortality in the total chronic obstructive pulmonary disease population, according to the multivariate Cox regression analysis

	HR (95% CI)	p-value
Age years	1.034 (1.009–1.059)	0.007
P_aO₂ kPa	0.860 (0.755–0.979)	0.023
T_LCO % pred		0.006
Best quartile (>51)	0.332 (0.172–0.639)	0.001
Quartile 2 (51–37.3)	0.515 (0.322–0.825)	0.006
Quartile 3 (37.3–27.9)	0.711 (0.477–1.059)	0.093
Quartile 4 (<27.9)	Reference
GOLD classification		0.125
Stage I	0.506 (0.087–2.94)	0.448
Stage II	0.407 (0.176–0.939)	0.035
Stage III	0.639 (0.408–1.002)	0.053
Stage IV	Reference
FVC % pred	0.989 (0.969–1.010)	0.250
FEV₁/FVC	1.015 (0.994–1.037)	0.170
RV % pred	0.988 (0.975–1.051)	0.079
FRC % pred	1.023 (0.999–1.048)	0.057
TLC % pred	1.008 (0.976–1.041)	0.633
IC/TLC %	2.15 (0.37–3.293)	0.418
P_aCO₂ kPa	0.985 (0.796–1.218)	0.887
BMI kg·m⁻²	1.009 (0.970–1.036)	0.903

P_aO₂: arterial oxygen partial pressure; T_LCO; carbon monoxide transfer factor; GOLD: Global Initiative for Obstructive Lung disease; FVC: forced vital capacity; FEV₁: forced expiratory volume in 1 s; RV: residual volume; FRC: functional residual capacity; TLC: total lung capacity; IC: inspiratory capacity; P_aCO₂: arterial carbon dioxide partial pressure; BMI: body mass index.