Table 7.
Univariable and multivariable analyses using severe PPC as outcome
| Univariable analyses | Multivariable analyses | ||||||
| Severe PPC (n = 1004) | No PPC (n = 8693) | P | OR (95% CI) | P | OR (95% CI) | P | |
| Ventilator settings | |||||||
| Tidal volume (ml kg−1 PBW) | 8.0 [7.2 to 8.9] | 8.1 [7.2 to 9.1] | 0.580 | 1.01 (0.94 to 1.10) | 0.722 | 0.96 (0.84 to 1.11) | 0.621 |
| PEEP (cmH2O) | 4 [2 to 5] | 3 [0 to 5] | <0.001 | 1.11 (1.06 to 1.17) | <0.001 | 0.95 (0.88 to 1.02) | 0.153 |
| Peak pressure (cmH2O) | 18 [16 to 22] | 17 [15 to 21] | <0.001 | 1.05 (1.03 to 1.07) | <0.001 | 1.04 (1.01 to 1.08) | 0.012 |
| Plateau pressure (cmH2O)a | 17 [15 to 20] | 15 [13 to 18] | <0.001 | 1.06 (1.03 to 1.09) | <0.001 | - | - |
| Driving pressure (cmH2O)a | 13 [11 to 16] | 12 [10 to 15] | 0.001 | 1.04 (1.01 to 1.08) | 0.009 | - | - |
| FiO2 (%) | 50 [42 to 60] | 51 [45 to 70] | 0.001 | 0.99 (0.98 to 0.99) | <0.001 | 1.01 (0.99 to 1.02) | 0.080 |
| Respiratory rate (bpm) | 12 [12 to 13] | 12 [12 to 13] | 1.03 (0.98 to 1.09) | 0.204 | 1.00 (0.91 to 1.11) | 0.944 | |
| Patient characteristics | |||||||
| Male sex | 152/270 (56.3) | 4203/9427 (44.6) | <0.001 | 1.60 (1.25 to 2.04) | <0.001 | 0.036 | |
| Age (years) | 59 [45 to 69] | 53 [40 to 66] | <0.001 | 1.02 (1.01 to 1.02) | <0.001 | 0.99 (0.99 to 1.01) | 0.825 |
| ≤ 50 | 88/270 (32.6) | 4238/9424 (45.0) | |||||
| 51 to 80 | 164/270 (60.7) | 4821/9424 (51.2) | <0.001 | - | - | - | - |
| >80 | 18/270 (6.7) | 365/9424 (3.9) | |||||
| BMI (kg m−2) | 26.1 [23.2 to 29.9] | 26.2 [23.4 to 30.0] | 0.998 | 1.02 (0.99 to 1.04) | 0.065 | 1.00 (0.98 to 1.03) | 0.726 |
| ASA | 2 [2 to 3] | 2 [1 to 2] | <0.001 | 2.00 (1.69 to 2.29) | <0.001 | 1.14 (0.87 to 1.49) | 0.353 |
| 1 | 49/269 (18.2) | 2884/9405 (30.7) | |||||
| 2 | 101/269 (37.5) | 4585/9405 (48.8) | |||||
| 3 | 101/269 (37.5) | 1778/9405 (18.9) | <0.001 | - | - | - | - |
| 4 | 17/269 (6.3) | 151/9405 (1.6) | |||||
| 5 | 1/269 (0.4) | 7/9405 (0.1) | |||||
| Functional status | |||||||
| Independent | 224/270 (83.0) | 8729/9421 (92.7) | <0.001 | 1 (Reference) | 1 (Reference) | ||
| Partially dependent | 36/270 (13.3) | 573/9421 (6.1) | 2.45 (1.70 to 3.52) | <0.001 | 1.26 (0.69 to 2.29) | 0.451 | |
| Totally dependent | 10/270 (3.7) | 119/9421 (1.3) | 3.27 (1.69 to 6.33) | <0.001 | 1.70 (0.59 to 4.85) | 0.324 | |
| Smoker | 60/270 (22.2) | 2188/9423 (23.2) | 0.701 | 0.94 (0.71 to 1.26) | 0.702 | - | - |
| ARISCAT score | 27 [16 to 41] | 15 [3 to 26] | <0.001 | 1.04 (1.04 to 1.05) | <0.001 | 1.01 (0.99 to 1.03) | 0.165 |
| <26 | 104/260 (40.0) | 6571/9047 (72.6) | |||||
| 26 to 44 | 115/260 (44.2) | 2069/9047 (22.9) | <0.001 | - | - | - | - |
| >44 | 41/260 (15.8) | 407/9047 (4.5) | |||||
| Preoperative SpO2 (%) | 97 [95 to 99] | 98 [96 to 99] | 0.010 | 0.93 (0.89 to 0.97) | <0.001 | 0.99 (0.91 to 1.08) | 0.842 |
| ≥96 | 180/242 (74.4) | 6961/8316 (83.7) | |||||
| 91 to 95 | 48 242 (19.8) | 1261/8316 (15.2) | <0.001 | - | - | - | - |
| ≤90 | 14 242 (5.8) | 94/8316 (1.1) | |||||
| Preoperative anaemia | 25/259 (9.7) | 293/7885 (3.7) | <0.001 | 2.77 (1.80 to 4.25) | <0.001 | 1.83 (0.89 to 3.75) | 0.098 |
| Chronic co-morbidity | |||||||
| Metastatic cancer | 38/270 (14.1) | 350/9427 (3.7) | <0.001 | 4.25 (2.97 to 6.08) | <0.001 | 2.16 (1.28 to 3.62) | 0.004 |
| Chronic kidney dysfunction | 16/270 (5.9) | 291/9427 (3.1) | 0.008 | 1.98 (1.18 to 3.32) | <0.001 | 1.15 (0.64 to 2.05) | 0.643 |
| COPD | 35/270 (13.0) | 553/9427 (5.9) | <0.001 | 2.39 (1.66 to 3.44) | <0.001 | 1.50 (0.90 to 2.51) | 0.118 |
| Heart failure | 28/270 (10.4) | 546/9427 (5.8) | 0.001 | 1.88 (1.26 to 2.81) | 0.002 | 1.32 (0.75 to 2.31) | 0.327 |
| Obstructive sleep apnoea | 18/270 (6.7) | 187/9427 (2.0) | <0.001 | 3.53 (2.14 to 5.82) | <0.001 | 3.53 (1.72 to 7.26) | 0.001 |
| Neuromuscular diseaseb | 3/270 (1.1) | 84/9427 (0.9) | 0.705 | 1.25 (0.39 to 3.98) | 0.706 | - | - |
| Liver dysfunction | 3/270 (1.1) | 94/9427 (1.0) | 0.852 | 1.12 (0.35 to 3.54) | 0.853 | - | - |
| Surgical characteristics | |||||||
| Urgency of surgeryc | |||||||
| Elective | 195/270 (72.2) | 8447/9425 (89.6) | <0.001 | 1 (Reference) | 1 (Reference) | ||
| Urgency | 52/270 (19.3) | 764/9425 (8.1) | 2.95 (2.15 to 4.04) | <0.001 | 2.56 (1.64 to 3.99) | <0.001 | |
| Emergency | 23/270 (8.5) | 214/9425 (2.3) | 4.66 (2.96 to 7.32) | <0.001 | 5.83 (2.74 to 12.37) | <0.001 | |
| Type of incision | |||||||
| Peripheral | 111/270 (41.1) | 5369/9427 (57.0) | <0.001 | 1 (Reference) | 1 (Reference) | ||
| Abdominal | 159/270 (58.9) | 4058/9427 (43.0) | 1.89 (1.48 to 2.42) | <0.001 | 1.18 (0.73 to 1.89) | 0.501 | |
| Type of surgery | |||||||
| Nonlaparoscopic | 230/270 (85.2) | 7595/9427 (80.6) | 0.057 | 1 (Reference) | 1 (Reference) | ||
| Laparoscopic | 40/270 (14.8) | 1832/9427 (19.4) | 0.72 (0.51 to 1.01) | 0.059 | 0.49 (0.27 to 0.86) | 0.014 | |
| Duration of surgery (min)d | 115 [63 to 200] | 71 [40 to 121] | <0.001 | 1.00 (1.00 to 1.00) | <0.001 | 1.00 (0.99 to 1.01) | 0.644 |
| Duration of anaethesia (min)e | 155 [63 to 200] | 100 [65 to 160] | <0.001 | 1.00 (1.00 to 1.00) | <0.001 | 1.00 (0.99 to 1.01) | 0.328 |
| Intraoperative characteristics | |||||||
| Tube type | |||||||
| Endotracheal | 246/270 (91.1) | 7684/9421 (81.6) | 1 (Reference) | 1 (Reference) | |||
| Nasotracheal | 4/270 (1.5) | 122/9421 (1.3) | 1.02 (0.37 to 2.79) | 0.963 | 1.65 (0.44 to 6.21) | 0.458 | |
| Supra-glottic | 16/270 (5.9) | 1523/9421 (16.2) | 0.33 (0.20 to 0.55) | <0.001 | 0.57 (0.29 to 1.12) | 0.103 | |
| Other | 4/270 (1.5) | 92/9421 (1.0) | 1.36 (0.49 to 3.72) | 0.552 | 0.81 (0.11 to 6.21) | 0.843 | |
| Ventilation mode | |||||||
| Volume controlled | 181/267 (67.8) | 6518/9288 (70.2) | 1 (Reference) | 1 (Reference) | |||
| Pressure controlled | 55/267 (20.6) | 1498/9288 (16.1) | 0.237 | 1.32 (0.97 to 1.80) | 0.075 | 1.07 (0.71 to 1.61) | 0.740 |
| Assisted | 15/267 (5.6) | 607/9288 (6.5) | 0.89 (0.52 to 1.52) | 0.668 | 1.50 (0.67 to 3.34) | 0.322 | |
| Otherf | 16/267 (6.0) | 665/9288 (7.2 | 0.87 (0.52 to 1.45) | 0.587 | 1.54 (0.76 to 3.11) | 0.226 | |
| SpO2 (%) | 99 [98 to 100] | 99 [98 to 100] | 0.489 | 0.94 (0.86 to 1.02) | 0.135 | 0.84 (0.75 to 0.94) | 0.002 |
| EtCO2 (kPa) | 4.4 [4.0 to 4.8] | 4.5 [4.1 to 4.9] | 0.001 | 0.96 (0.94 to 0.99) | 0.005 | 1.03 (0.98 to 1.08) | 0.238 |
| Transfusion of PRBC | 39/270 (14.4) | 282/9427 (3.0) | <0.001 | 5.47 (3.82 to 7.84) | <0.001 | 1.82 (1.08 to 3.05) | 0.024 |
Data are presented as median [LQ to UQ] or n/N (%). Driving pressure = plateau pressure − PEEP.
ASA, American Society of Anaesthesiology; ARISCAT, Assess Respiratory Risk in Surgical Patients in Catalonia risk score; bpm, breaths per minute; CI, confidence interval; COPD, chronic obstructive pulmonary disease; EtCO2, expiratory carbon dioxide; FiO2, inspired fraction of oxygen; LQ, lower quartile; OR, odds ratio; PBW, predicted body weight; PEEP, positive end-expiratory pressure; PPC, composite endpoint of postoperative pulmonary complications; severe PPCs, same composite as total PPCs, without unplanned supplemental O2; PRBC, packed red blood cells; OR, odds ratio; SpO2, peripheral oxygen saturation; UQ, upper quartile.
aPlateau pressure and driving pressure was only reported and calculable in 60% of all patients; Peak pressure, plateau pressure, and driving pressure had high co-linearity, therefore only peak pressure was entered into the model, as plateau pressure had missing values.
bNeuromuscular disease affecting the respiratory system.
cUrgency of surgery: elective, surgery that is scheduled in advance because it does not involve a medical emergency; urgent, surgery required within <48 h; emergency, nonelective surgery performed when the patient's life or well being is in direct jeopardy.
dDuration of surgery is the time between skin incision and closure of the incision.
eDuration of anaesthesia is the time between start induction and extubation or discharge from operation room if mechanical ventilation remained.
fOther (e.g. high frequency oscillatory ventilation, jet ventilation, synchronised intermittent mandatory ventilation).