Table 1.
Characteristics of study population by intraoperative ventilatory frequency. Data are expressed as n (%), mean (standard deviation), or median (inter-quartile range [25th–75th percentile], values separated by comma). ∗Score for Prediction of Postoperative Respiratory Complications. †ED95 dose of neuromuscular blocking agents (NMBA): median effective dose required to achieve a 95% reduction in maximal twitch response from baseline. Fio2, fraction of inspired oxygen; PEEP, positive end-expiratory pressure; PIP, peak inspiratory pressure; Spo2, peripheral oxygen saturation.
| Characteristics | Group 1 (n=24 392) |
Group 2 (n=23 574) |
Group 3 (n=28 125) |
Group 4 (n=26 541) |
|---|---|---|---|---|
| Intraoperative ventilatory frequency, median (IQR) | 8 (8, 9) | 10 (10, 10) | 12 (11.5, 12) | 15 (14, 18) |
| Intraoperative ventilatory frequency, range | 3–9.75 | 10–10.75 | 11–12.25 | 12.5–43 |
| Age, yr (range) | 55.9 (16.8) (18–104) | 53.9 (16.3) (18–102) | 52.2 (15.9) (18–102) | 50.6 (16.2) (18–102) |
| Sex, male | 7312 (30.0) | 8966 (38.0) | 13 477 (47.9) | 12 739 (48.0) |
| BMI, kg m−2 | 26.87 (5.7) | 28.33 (6.6) | 29.58 (7.4) | 28.98 (7.2) |
| ASA physical status classification | 2 (2, 3) | 2 (2, 3) | 2 (2, 3) | 2 (2, 3) |
| ASA ≥3 | 7826 (32.1) | 7933 (33.7) | 9954 (35.4) | 6928 (26.1) |
| Emergency surgery | 1433 (5.9) | 1703 (7.2) | 2234 (7.9) | 1428 (5.4) |
| Comorbidities | ||||
| Charlson comorbidity index | 1 (0, 2) | 1 (0, 2) | 1 (0, 2) | 0 (0, 2) |
| History of chronic obstructive pulmonary disease | 1093 (4.5) | 1153 (4.9) | 1379 (4.9) | 983 (3.7) |
| History of heart failure | 948 (3.9) | 993 (4.2) | 1059 (3.8) | 794 (3.0) |
| History of smoking | 2140 (8.8) | 2932 (12.4) | 4627 (16.5) | 3427 (12.9) |
| SPORC score,∗ ≥7 | 695 (2.8) | 702 (3.0) | 778 (2.8) | 535 (2.0) |
| Home oxygen therapy | 95 (0.4) | 122 (0.5) | 151 (0.5) | 141 (0.5) |
| Respiratory support at home | 105 (0.4) | 145 (0.6) | 173 (0.6) | 156 (0.6) |
| Intraoperative factors | ||||
| High-risk surgery | 10 548 (43.2) | 9803 (41.6) | 10 926 (38.8) | 7088 (26.7) |
| Work relative value units (RVU) | 13.99 (7.96, 18.23) | 13.99 (8.16, 18.88) | 13.18 (7.96, 19.02) | 8.57 (5.96, 15.26) |
| Duration of surgery, min | 124 (83, 180) | 127 (86, 186) | 129 (85, 195) | 87 (52, 144) |
| Fluids administered, ml | 2500 (2000, 4250) | 2500 (2000, 4250) | 2500 (2000, 4250) | 2125 (1500, 3000) |
| Total long-acting opioid dose (oral morphine equivalents), mg | 0.00 (0.00, 17.00) | 6.80 (0.00, 17.00) | 9.00 (0.00, 20.40) | 0.00 (0.00, 12.00) |
| Total short-acting opioid dose (oral morphine equivalents), mg | 37.50 (25.00, 62.50) | 37.50 (25.00, 62.50) | 31.25 (25.00, 62.50) | 25.00 (12.50, 37.50) |
| Minimum alveolar concentration of volatile anaesthetics and nitrous oxide | 0.99 (0.85, 1.14) | 1.00 (0.86, 1.14) | 1.00 (0.87, 1.14) | 1.01 (0.87, 1.15) |
| NMBA ED95 dose,† mg | 1.76 (0.00, 2.70) | 1.83 (0.27, 2.76) | 1.79 (0.00, 2.84) | 0.00 (0.00, 1.49) |
| Neostigmine dose, mg | 2.00 (0.00, 3.00) | 2.00 (0.00, 3.00) | 2.00 (0.00, 3.50) | 0.00 (0.00, 0.00) |
| Mean arterial pressure <55 mm Hg, min | 1 (0, 3) | 1 (0, 3) | 1 (0, 3) | 0 (0, 2) |
| Total vasopressor dose, mg | 0.00 (0.00, 0.04) | 0.00 (0.00, 0.05) | 0.00 (0.00, 0.06) | 0.00 (0.00, 0.02) |
| Packed red blood cell units | ||||
| 0 | 23 693 (97.1) | 22 975 (97.5) | 27 577 (98.1) | 26 302 (99.1) |
| 1 | 330 (1.4) | 264 (1.1) | 206 (0.7) | 76 (0.3) |
| 2 | 251 (1.0) | 202 (0.9) | 201 (0.7) | 81 (0.3) |
| ≥ 3 | 118 (0.5) | 133 (0.6) | 141 (0.5) | 82 (0.3) |
| Respiratory parameters | ||||
| Airway device | ||||
| Tracheal tube | 21 994 (90.2) | 21 847 (92.7) | 24 875 (88.4) | 9650 (36.4) |
| Laryngeal mask airway | 2323 (9.5) | 1625 (6.9) | 3110 (11.1) | 16 791 (63.3) |
| Combination | 75 (0.3) | 102 (0.4) | 140 (0.5) | 100 (0.4) |
| Median Fio2, % | 54.1 (14.7) | 55.4 (14.1) | 56.6 (14.0) | 55.6 (15.7) |
| Median PEEP, cm H2O | 2 (2, 5) | 3 (2, 5) | 4 (2, 5) | 2 (2, 5) |
| Median PIP, cm H2O | 20.5 (5.9) | 21.2 (5.9) | 21.8 (6.7) | 16.2 (8.8) |
| Median tidal volume, ml | 575 (115) | 566 (106) | 553 (111) | 394 (143) |
| Median tidal volume per kg, ml kg−1 | 9.9 (2.2) | 9.5 (2.0) | 8.9 (2.0) | 6.3 (2.2) |
| Median minute volume, L min−1 | 4.8 (1.0) | 5.7 (1.1) | 6.5 (1.3) | 6.2 (1.9) |
| Median end-tidal CO2, mm Hg | 34.6 (4.7) | 34.8 (4.1) | 36.1 (4.7) | 40.6 (6.6) |
| Spo2/Fio2 ratio | 195 (52) | 189 (48) | 184 (45) | 190 (51) |
| Non-protective ventilation | 11 640 (47.7) | 8583 (36.4) | 7857 (27.9) | 2967 (11.2) |