Table 2.
Information on intraoperative characteristics of unmatched patients and matched patients after propensity scoring
| Unmatched patients | Matched patients | |||||
| Low PEEP (n=1032) | High PEEP (n=873) | P value | Low PEEP (n=643) | High PEEP (n=643) | P value | |
| Types of surgery | 0.529 | 0.669 | ||||
| Orthopaedic | 566 (54.8%) | 444 (50.9%) | 0.091 | 339 (52.7%) | 324 (50.4%) | 0.403 |
| Laparotomy | 144 (14.0%) | 117 (13.4%) | 0.727 | 97 (15.1%) | 87 (13.5%) | 0.426 |
| Laparoscopy | 128 (12.4%) | 141 (16.2%) | 0.019 | 83 (12.9%) | 105 (16.3%) | 0.082 |
| Others | 194 (18.8%) | 171 (19.6%) | 0.663 | 124 (19.3%) | 127 (19.8%) | 0.833 |
| Duration of anaesthesia (min) | 165 (130–220) | 170 (140–225) | 0.239 | 170 (130–225) | 175 (140–220) | 0.616 |
| Duration of surgery (min) | 120 (90–170) | 130 (95–172) | 0.156 | 120 (90–170) | 120 (100–170) | 0.441 |
| Intraoperative transfusion | 19 (1.8%) | 14 (1.6%) | 0.692 | 11 (1.7%) | 9 (1.4%) | 0.822 |
| Crystalloids (mL) | 1000 (700–1200) | 1000 (700–1200) | 0.790 | 1000 (700–1200) | 1000 (700–1200) | 0.687 |
| Colloid solution (mL) | 500 (500–1000) | 500 (500–1000) | 0.697 | 500 (500–1000) | 500 (500–1000) | 0.787 |
| Blood loss (mL) | 100 (100–200) | 100 (100–200) | 0.294 | 100 (100–200) | 100 (100–200) | 0.306 |
| VCV/PCV | 747/285 | 610/263 | 0.228 | 439/204 | 447/196 | 0.630 |
| Median FiO2 | 67 (61–73) | 66 (61–73) | 0.450 | 66 (61–72) | 65 (60–72) | 0.214 |
| Median SpO2 | 100 (100–100) | 100 (100–100) | 0.404 | 100 (100–100) | 100 (100–100) | 0.058 |
| VT (mL) | 465.8±28.0 | 461.7±30.0 | 0.002 | 466.5±26.0 | 465.7±28.0 | 0.563 |
| VT/PBW (mL/kg) | 8.4±1.0 | 8.5±1.0 | 0.028 | 8.4±1.0 | 8.5±1.0 | 0.518 |
| Median PEEP (cmH2O) | 2.1±0.7 | 5.7±0.8 | 0.001 | 2.5±0.8 | 5.7±0.9 | 0.001 |
| Median PIP (cmH2O) | 16.7±2.9 | 18.0±3.0 | 0.001 | 16.9±3.0 | 17.9±3.0 | 0.001 |
Data are presented as mean±SD or median and IQR. IQR: M (P25– P75).
PBW: predict body weight, male: kg=50+0.91×(height/cm−152.4); female: kg=45.5+0.91×(height/cm−152.4).
FiO2, fraction of inspired oxygen; PBW, predicted body weight; PCV, pressure-controlled ventilation; PEEP, positive end-expiratory pressure; PIP, Peak Inspiratory Pressure; SpO2, pulse oxygen saturation; VCV, volume-controlled ventilation; VT, tidal volume.