Table 1 Baseline characteristics of total and propensity score-matched patients
| Â | Total population | Propensity score-matched population | ||||
|---|---|---|---|---|---|---|
High oxygen saturation group (n = 458) | Low oxygen saturation group (n = 111) | P-value | High oxygen saturation group (n = 222) | Low oxygen saturation group (n = 111) | Standardized differences | |
Age, yr, mean (± SD) | 66.9 (13.9) | 67.0 (14.7) | 0.963 | 66.4 (15.2) | 67.0 (14.7) | 0.038 |
Female, n (%) | 146 (31.9) | 43 (38.7) | 0.206 | 80 (36.0) | 43 (38.7) | 0.056 |
Body mass index, mean (± SD) | 21.3 (4.2) | 22.4 (4.2) | 0.013 | 22.0 (4.7) | 22.4 (4.2) | 0.087 |
Smoking status | Â | Â | Â | Â | Â | Â |
 Current smoker, n (%) | 86 (18.8) | 18 (16.2) | 0.624 | 38 (17.1) | 18 (16.2) | 0.024 |
 Ex-smoker, n (%) | 124 (27.1) | 25 (22.5) | 0.391 | 52 (23.4) | 25 (22.5) | 0.021 |
 Never smoker, n (%) | 240 (52.4) | 68 (61.3) | 0.115 | 129 (58.1) | 68 (61.3) | 0.064 |
 PYs, median (IQR) | 0 (0–30) | 0 (0–20) | 0.120 | 0 (0–20) | 0 (0–20) | 0.015 |
Comorbidities, n (%) | Â | Â | Â | Â | Â | Â |
 Hypertension | 182 (39.7) | 43 (38.7) | 0.932 | 86 (38.7) | 43 (38.7) |  < 0.001 |
 Diabetes mellitus | 128 (27.9) | 24 (21.6) | 0.218 | 51 (23.0) | 24 (21.6) | 0.032 |
 Congestive heart failure | 51 (11.1) | 19 (17.1) | 0.119 | 32 (14.4) | 19 (17.1) | 0.074 |
 Arrhythmia | 19 (4.1) | 5 (4.5) | 1.000 | 11 (5.0) | 5 (4.5) | 0.021 |
 Cerebrovascular accident | 88 (19.2) | 15 (13.5) | 0.207 | 32 (14.4) | 15 (13.5) | 0.026 |
 Chronic kidney disease | 32 (7.0) | 10 (9.0) | 0.597 | 13 (5.9) | 10 (9.0) | 0.120 |
 Chronic liver disease | 25 (5.5) | 9 (8.1) | 0.405 | 9 (4.1) | 9 (8.1) | 0.170 |
 Connective tissue disease | 13 (2.8) | 3 (2.7) | 1.000 | 5 (2.3) | 3 (2.7) | 0.029 |
 Dementia | 43 (9.4) | 5 (4.5) | 0.141 | 21 (9.5) | 5 (4.5) | 0.195 |
 History of other malignancy | 80 (17.5) | 23 (20.7) | 0.508 | 37 (16.7) | 23 (20.7) | 0.104 |
Respiratory disease, n (%) | Â | Â | Â | Â | Â | Â |
 Chronic obstructive pulmonary disease | 81 (17.7) | 14 (12.6) | 0.253 | 28 (12.6) | 14 (12.6) |  < 0.001 |
 Bronchiectasis | 133 (29.0) | 28 (25.2) | 0.495 | 54 (24.3) | 28 (25.2) | 0.021 |
 Asthma | 15 (3.3) | 3 (2.7) | 0.994 | 10 (4.5) | 3 (2.7) | 0.096 |
 Interstitial lung disease | 13 (2.8) | 3 (2.7) | 1.000 | 5 (2.3) | 3 (2.7) | 0.029 |
 Tuberculosis destroyed lung | 84 (18.3) | 9 (8.1) | 0.013 | 22 (9.9) | 9 (8.1) | 0.063 |
 Nontuberculous mycobacteria | 14 (3.1) | 5 (4.5) | 0.640 | 7 (3.2) | 5 (4.5) | 0.070 |
 History of lung cancer | 35 (7.6) | 4 (3.6) | 0.193 | 19 (8.6) | 4 (3.6) | 0.208 |
 History of lung resection | 12 (2.6) | 3 (2.7) | 1.000 | 7 (3.2) | 3 (2.7) | 0.027 |
 History of thoracic radiation therapy | 15 (3.3) | 1 (0.9) | 0.299 | 7 (3.2) | 1 (0.9) | 0.160 |