Table 1. Baseline characteristics. Abbreviations: ABG, arterial blood gas, IQR, interquartile range, SBT, spontaneous breathing trial.
| All (n=520) | T piece (n=260) | Low PSV (n=260) | P value | |
|---|---|---|---|---|
| Age, year, median (IQR) | 56(45 – 66) | 56(46 – 65) | 56(45 – 67) | 0.775 |
| BMI, kg/m2, median(IQR) | 21.0(19.3 – 22.9) | 21.2 (19.5 – 22.8) | 20.8 (18.8 – 23.1) | 0.419 |
| Male, n (%) | 295(56.73) | 142(54.62) | 153(58.85) | 0.330 |
| Duration of ventilator support before trial recruitment, hour, median(IQR) | 28(17 – 56) | 26(15.5 – 46) | 31(18 - 60.5) | 0.023 |
| 12 – 24 hours (%) | 88 (16.92) | 53 (20.38) | 35 (13.46) | 0.109 |
| 24 – 48 hours (%) | 141(27.12) | 68 (26.15) | 73 (28.08) | |
| > 48 hours (%) | 291(55.96) | 139 (53.46) | 152 (58.46) | |
| Primary surgical disorders, n (%) | ||||
| Gastrointestinal | 128(24.62) | 77(29.62) | 51(19.62) | 0.060 |
| Hepato-biliary-pancreas | 119(22.88) | 56(21.54) | 63(24.23) | |
| Vascular | 93(17.88) | 45(17.31) | 48(18.46) | |
| Soft tissue | 42(8.08) | 20(7.69) | 22(8.46) | |
| Chest (Non-cardiac) | 63(12.12) | 23(8.85) | 40(15.38) | |
| Others | 75(14.42) | 39(15.00) | 36(13.85) | |
| Comorbidity (%) | ||||
| Hypertension | 186 (35.77) | 90 (34.62) | 96 (36.92) | 0.583 |
| Asthma | 26 (5.00) | 14 (5.38) | 12 (4.62) | 0.687 |
| COPD | 41 (7.88) | 19 (7.31) | 22 (8.46) | 0.625 |
| Diabetes mellitus | 108 (20.77) | 49 (18.85) | 59 (22.69) | 0.280 |
| Chronic renal failure | 95 (18.27) | 44 (16.92) | 51 (19.62) | 0.427 |
| Malignancy | 112 (21.54) | 53 (20.38) | 59 (22.69) | 0.522 |
| HIV | 11 (2.12) | 5 (1.92) | 6 (2.31) | 0.761 |
| Severity, median (IQR) | ||||
| Charlson’s comorbidity index | 10(8 – 12) | 10(8 – 12) | 10(8 – 12) | 0.593 |
| APACHE II score | 11(9 – 13) | 11(9 – 13) | 11(9 – 13) | 0.316 |
| ABG at enrolling, median(IQR) | ||||
| pH | 7.40(7.37 – 7.42) | 7.40(7.37 – 7.42) | 7.40(7.38 – 7.42) | 0.419 |
| PaO2 | 177(113 – 219) | 179(115 – 216) | 176 (110 – 223) | 0.964 |
| PaCO2 | 38 (35 – 41) | 38 (35 – 41) | 38 (35 – 41) | 0.331 |
| HCO3 | 24 (22 – 28) | 24 (22 – 28) | 24 (22 – 28) | 0.622 |
| PF ratio | 443(282 – 547) | 446(288 -541) | 440(275 – 557) | 0.964 |
| ABG and respiratory parameter at the end of SBT, median(IQR) | ||||
| pH | 7.40(7.37 – 7.42) | 7.40(7.37 – 7.42) | 7.40(7.37 – 7.42) | 0.964 |
| PaO2 | 180(132 – 235) | 178 (140 – 229) | 189 (125 – 244) | 0.648 |
| PaCO2 | 38 (36 – 41) | 38 (36 – 41) | 38 (35 – 41) | 0.473 |
| HCO3 | 24(22 – 27) | 24(22 – 27) | 24(22 – 27.5) | 0.832 |
| PF ratio | 450(330 - 587) | 445(350 - 572) | 472(313 - 610) | 0.648 |
| Tidal volume, mL | 348(310 – 390) | 350(310 – 390) | 340(310 – 390) | 0.487 |
| Respiratory rate, per minute | 20(18 – 22) | 20(18 – 22) | 20(18 – 22) | 0.136 |
| Minute volume, L | 7.0 (6.1 - 8.1) | 7.2(6.2 – 8.1) | 6.8 (5.8 – 8.1) | 0.101 |
| RSBI | 57.9(49.3 – 66.7) | 58.1 (49.9 – 68.6) | 57.5(48.8 – 66.3) | 0.713 |