Figures
- Figure 1–
The Kaplan–Meier survival curves, adjusted for age, arterial oxygen partial pressure, Global Initiative for Chronic Obstructive Lung Disease classification, forced vital capacity (FVC) % pred, forced expiratory volume in 1 s to FVC ratio, total lung capacity (TLC) % pred, functional residual capacity % pred, inspiratory capacity to TLC ratio, residual volume % pred, body mass index and arterial carbon dioxide partial pressure for the four population groups, categorised by carbon monoxide transfer factor (TLCO) % pred quartiles.
- Figure 2–
The Kaplan–Meier survival curves, adjusted for age, arterial oxygen partial pressure, carbon monoxide transfer factor % pred quartiles, forced vital capacity (FVC) % pred, forced expiratory volume in 1 s to FVC ratio, total lung capacity (TLC) % pred, functional residual capacity % pred, inspiratory capacity to TLC ratio, residual volume % pred, body mass index and arterial carbon dioxide partial pressure for the four population groups, categorised by Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages. Survival only differed significantly between GOLD stage II and IV (p = 0.04).
Tables
- Table 1– Characteristics of the study population
Age years 61.9±9.7 Sex % Male 62.9 Female 37.1 BMI kg·m−2 24.2±5.3 FEV1 % pred 37±18.1 FVC % pred 84.5±22.4 FEV1/FVC 34.7±12.3 GOLD classification % Stage I 2.3 Stage II 17.0 Stage III 28.4 Stage IV 52.2 TLC % pred 124.9±18.4 RV % pred 205.1±58.4 IC/TLC % 26.9±8.8 FRC % pred 172.7±38.5 TLCO % pred 40.8±18 PaO2 kPa 9.4±1.4 PaCO2 kPa 5.2±0.9 Arterio-alveolar oxygen gradient kPa 5.1±1.3 LTOT % 17.1 Current smokers % 13.2 Smoking history pack-years 43.8±23 Exacerbations % 0–1 per year 39.1 2–4 per year 42.7 >4 per year 18.2 Data are presented as mean±sd, unless otherwise stated. n = 604. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; GOLD: Global Initiative for Obstructive Lung disease; TLC: total lung capacity; RV: residual volume; IC: inspiratory capacity; FRC: functional residual capacity; TLCO: carbon monoxide transfer factor; PaO2: arterial oxygen partial pressure; PaCO2: arterial carbon dioxide partial pressure; LTOT: long-term oxygen treatment.
- Table 2– Differences between survivors and non-survivors
Survivors Non-survivors p-value Subjects n 375 229 Age years 61.1±10.1 63±9.2 0.024 Sex % Male 62.4 63.8 ns Female 37.6 36.2 BMI kg·m−2 24.7±5.3 23.4±5.2 0.004 FEV1 % pred 40.6±18.8 30.9±15 <0.001 FVC % pred 88.4±22 78.2±21.6 <0.001 FEV1/FVC 36.4±12.8 31.8±11 <0.001 GOLD classification % <0.001 Stage I 3.2 0.9 Stage II 22.7 7.4 Stage III 33 20.5 Stage IV 41.1 71.2 TLCO % quartiles <0.001 Best quartile (>51) 31.3 13.9 Quartile 2 (51–37.3) 29.1 18.3 Quartile 3 (37.3–27.9) 22.2 29.3 Quartile 4 (<27.9) 17.4 38.5 TLCO % pred 44.7±18.4 34.1±15.2 <0.001 TLC % pred 123.4±17 127.5±20.5 0.015 FRC % pred 166.1±35.3 184.4±41.1 <0.001 RV % pred 195.6±53.2 220.9±63.1 <0.001 IC/TLC % 28.8±8.6 23.5±8 <0.001 PaO2 kPa 9.6±1.3 9.2±1.6 0.001 PaCO2 kPa 5.1±0.7 5.4±1 0.003 Arterio-alveolar oxygen gradient kPa 5±1.3 5.1±1.4 ns LTOT % 11.0 27.1 <0.001 Smoking status % Never or ex-smokers 88.4 83.4 ns Current smokers 11.6 16.6 Smoking history pack-years 45.6±25.1 41.1±19.4 ns Exacerbations % 0–1 per year 40.3 37.1 2–4 per year 40 47.2 ns >4 per year 19.7 15.7 Data are presented as mean±sd, unless otherwise stated. BMI: body mass index; FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; GOLD: Global Initiative for Obstructive Lung disease; TLCO: carbon monoxide transfer factor; TLC: total lung capacity; FRC: functional residual capacity; RV: residual volume; IC: inspiratory capacity; PaO2: arterial oxygen partial pressure; PaCO2: arterial carbon dioxide partial pressure; LTOT: long-term oxygen treatment; ns: nonsignificant.
- 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 PaO2 kPa 0.860 (0.755–0.979) 0.023 TLCO % 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 PaCO2 kPa 0.985 (0.796–1.218) 0.887 BMI kg·m−2 1.009 (0.970–1.036) 0.903 PaO2: arterial oxygen partial pressure; TLCO; 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; PaCO2: arterial carbon dioxide partial pressure; BMI: body mass index.
- Table 4– 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 1.030 (1.004–1.056) 0.021 PaO2 kPa 0.851 (0.748–0.969) 0.015 TLCO % pred 0.971 (0.957–0.984) <0.001 FEV1 % pred 1.016 (0.974–1.060) 0.463 FVC % pred 0.977 (0.950–1.004) 0.090 FEV1/FVC 0.988 (0.944–1.033) 0.582 RV % pred 0.987 (0.975–1.001) 0.055 FRC % pred 1.021 (0.998–1.045) 0.078 TLC % pred 1.011 (0.979–1.044) 0.507 IC/TLC % 2.009 (0.378–3.451) 0.628 PaCO2 kPa 0.991 (0.798–1.230) 0.932 BMI kg·m−2 1.006 (0.973–1.041) 0.710 Carbon monoxide transfer factor (TLCO) % pred and forced expiratory volume in 1 s (FEV1) % pred entered the analysis as continuous variables. PaO2: arterial oxygen partial pressure; FVC: forced vital capacity; RV: residual volume; FRC: functional residual capacity; TLC: total lung capacity; IC: inspiratory capacity; PaCO2: arterial carbon dioxide partial pressure; BMI: body mass index.
Supplementary results
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