Table 1.
Patient and surgical baseline characteristics within each group
| Variable | All patients | Low risk of PPCs | Increased risk of PPCs |
| Male sex (%) | 45.0 (4439/9864) | 43.6 (2937/6743) | 48.5 (1294/2670) |
| Age (years) (%) | 53.0 [39.0 to 66.0] | 50.0 [36.0 to 63.0] | 62.0 [50.0 to 72.0] |
| ≤50 | 45.0 (4440/9861) | 52.1 (3510/6742) | 25.5 (680/2669) |
| 51 to 80 | 51.0 (5033/9861) | 46.1 (3111/6742) | 65.2 (1741/2669) |
| >80 | 3.9 (388/9861) | 1.8 (121/6742) | 9.3 (248/2669) |
| BMI (kg m−2) | 26.2 [23.4 to 30.0] | 26.0 [23.2 to 29.7] | 26.8 [23.7 to 30.7] |
| ASA physical status classification system | |||
| ASA 1 | 30.6 (3013/9840) | 36.3 (2445/6734) | 14.0 (373/2663) |
| ASA 2 | 48.2 (4743/9840) | 49.1 (3305/6734) | 47.0 (1252/2663) |
| ASA 3 | 19.3 (1903/9840) | 13.8 (929/6734) | 34.5 (919/2663) |
| ASA 4 | 1.8 (173/9840) | 0.8 (53/6734) | 4.3 (115/2663) |
| ASA 5 | 0.1 (8/9840) | 0.0 (2/6734) | 0.2 (4/2663) |
| Functional status | |||
| Non dependent | 92.4 (9105/9858) | 94.7 (6385/6739) | 86.5 (2308/2669) |
| Partially dependent | 6.3 (621/9858) | 4.3 (291/6739) | 11.5 (307/2669) |
| Totally dependent | 1.3 (132/9858) | 0.9 (63/6739) | 2.0 (54/2669) |
| ARISCAT score | 15.0 [3.0 to 26.0] | 11.0 [3.0 to 16.0] | 34.0 [31.0 to 41.0] |
| <26 | 71.6 (6743/9413) | 100.0 (6743/6743) | - |
| 26 to 44 | 23.5 (2215/9413) | - | 83.0 (3315/2670) |
| >44 | 4.8 (455/9413) | - | 17.0 (455/2670) |
| Preoperative SpO2 (%) | 98.0 [96.0 to 99.0] | 98.0 [97.0 to 99.0] | 97.0 [95.0 to 98.0] |
| ≥96 | 83.4 (7254/8698) | 90.2 (5450/6043) | 65.9 (1609/2440) |
| 91 to 95 | 15.3 (1331/8698) | 9.8 (591/6043) | 29.5 (721/2440) |
| ≤90 | 1.3 (113/8698) | 0.0 (2/6043) | 4.5 (110/2440) |
| Preoperative anaemia (Hb ≤ 10 g dl−1) | 4.0 (329/8265) | 1.0 (53/5573) | 10.5 (265/2528) |
| Chronic comorbidity – a patient can have more than one comorbidity | |||
| Metastatic cancer | 4.0 (392/9864) | 1.8 (124/6743) | 9.7 (260/2670) |
| Chronic kidney dysfunction | 3.1 (310/9864) | 2.0 (137/6743) | 6.1 (162/2670) |
| COPD | 6.0 (596/9864) | 4.8 (322/6743) | 9.6 (256/2670) |
| Heart failure | 5.9 (585/9864) | 4.6 (313/6743) | 9.6 (255/2670) |
| Obstructive sleep apnoea | 2.1 (205/9864) | 2.0 (132/6743) | 2.5 (68/2670) |
| Neuromuscular diseaseb | 0.9 (88/9864) | 1.0 (66/6743) | 0.8 (21/2670) |
| Liver dysfunction | 1.0 (102/9864) | 0.8 (54/6743) | 1.6 (43/2670) |
| Surgical procedure – a patient can have more than one type of surgical procedure | |||
| Lower GI | 11.1 (1096/9864) | 6.9 (466/6743) | 21.7 (579/2670) |
| Upper GI, hepatobiliary, pancreas | 13.8 (1357/9864) | 11.2 (753/6743) | 21.3 (568/2670) |
| Vascular surgerya | 3.1 (309/9864) | 2.9 (197/6743) | 3.7 (99/2670) |
| Aortic surgery | 0.6 (64/9864) | 0.3 (18/6743) | 1.7 (45/2670) |
| Neurosurgery, head and neck | 20.3 (2006/9864) | 3.1 (1558/6743) | 12.8 (342/2670) |
| Urological and kidney | 8.7 (858/9864) | 6.7 (455/6743) | 13.8 (368/2670) |
| Gynaecological | 11.6 (1141/9864) | 10.9 (733/6743) | 12.9 (345/2670) |
| Endocrine surgery | 2.0 (194/9864) | 2.4 (159/6743) | 1.1 (30/2670) |
| Transplant | 0.3 (34/9864) | 0.1 (5/6743) | 1.0 (28/2670) |
| Plastic, cutaneous, breast | 10.5 (1037/9864) | 13.1 (885/6743) | 4.2 (113/2670) |
| Bone, joint, trauma, spine | 16.2 (1595/9864) | 18.6 (1253/6743) | 9.6 (255/2670) |
| Other procedure | 5.9 (585/9864) | 7.2 (483/6743) | 3.0 (79/2670) |
| Surgical technique – a patient can have more than one type of surgical procedure | |||
| Open abdominal surgery | 18.0 (1773/9864) | 7.6 (512/6743) | 44.8 (1195/2670) |
| Laparoscopic surgery | 17.6 (1737/9864) | 16.0 (1082/6743) | 22.0 (587/2670) |
| Laparoscopic assisted surgery | 1.7 (167/9864) | 1.1 (73/6743) | 3.4 (90/2670) |
| Peripheral surgery | 18.5 (1827/9864) | 22.2 (1500/6743) | 8.2 (218/2670) |
| Other | 44.9 (4427/9864) | 53.3 (3594/6743) | 23.5 (628/2670) |
| Urgency of surgeryc | |||
| Elective | 88.9 (8765/9862) | 91.1 (6141/6742) | 84.2 (2248/2670) |
| Urgent | 8.6 (845/9862) | 7.5 (508/6742) | 10.8 (288/2670) |
| Emergency | 2.6 (252/9862) | 1.4 (93/6742) | 5.0 (134/2670) |
| Duration of surgery (min)d | 73.0 [42.0 to 125.0] | 60.0 [35.0 to 95.0] | 131.0 [75.0 to 199.0] |
| Duration of anaesthesia (min)e | 103.0 [66.0 to 160.0] | 90.0 [60.0 to 128.0] | 170.0 [107.0 to 246.0] |
Data are presented as median [LQ to UQ] or % (n/N); low versus increased risk of PPCs, according to the Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) risk score (<26 versus ≥26, respectively). ASA, American Society of Anaesthesiology; COPD, chronic obstructive pulmonary disease; GI, gastrointestinal; Hb, haemoglobin; LQ, lower quartile; UQ, upper quartile; n, number with characteristic; PPC, postoperative pulmonary complication; N, number in group or subgroup; SpO2, peripheral oxygen saturation.
aVascular surgery is carotid endarterectomy, aortic surgery and peripheral vascular taken together.
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 of induction and tracheal extubation or discharge from operation room if mechanical ventilation continued.