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. 2018 Jul 9;2018(7):CD011151. doi: 10.1002/14651858.CD011151.pub3

Soh 2018.

Methods RCT with parallel groups
Approved by the local ethics committee
Informed consents obtained
Site: Severance Cardiovascular Hospital, Yonsei University College of Medicine, 50 Yonsei‐ro, Seodaemun‐gu, Seoul, Republic of Korea
Setting: university hospital
Dates of data collection: January 2015 to January 2016
Clinicaltrials.gov: NCT02373475
Participants 78 participants at potential risk of postoperative pulmonary complications undergoing major lumbar spinal surgery in the prone position under general anaesthesia for > 2 hours, and preoperative risk index for postoperative pulmonary complications ≥ 2
Exclusion criteria: increased intracranial pressure or altered mental status before surgery; any neuromuscular disease; BMI > 35 kg/m2; previous lung surgery; repeated treatment for acute exacerbation of asthma or chronic obstructive pulmonary disease; congestive heart failure; use of mechanical ventilation within 2 weeks before surgery; sepsis; and pregnancy
Interventions Treatment group: tidal volume 6 mL/kg of predicted body weight, PEEP 6 cmH2O and recruitment manoeuvres (n = 39)
Control group: tidal volume 10 mL/kg, PEEP 0 cmH2O (n = 39)
Outcomes Relevant to this review

  1. Pneumonia

  2. Need for postoperative non‐invasive ventilation between discharge from the postoperative care unit and 7 days after the surgery

  3. Need for postoperative invasive ventilation between discharge from the postoperative care unit and 7 days after the surgery

  4. Length of hospital stay


Others

  1. Forced vital capacity

  2. Forced expiratory volume in 1 second

  3. Blood gas
Notes Funding: departmental resources
Declaration of interest: authors had no funding or conflicts of interest to disclose
Risk factors and points: age: ≥ 80 years = 17; 70–79 years = 13; 60–69 years = 9; 50–59 years = 4; functional status totally dependent = 10, partially dependent = 6; weight loss > 10% in past 6 month = 7; history of chronic obstructive pulmonary disease = 5; general anaesthesia = 4; impaired sensorium = 4; history of cerebrovascular accident = 4; blood urea nitrogen level < 2.86 mmol/L (< 8 mg/dL) = 4; 7.85–10.7 mmol/L (22–30 mg/dL) = 2; ≥ 10.7 mmol/L (≥ 30 mg/dL) = 3; transfusion > 4 units = 3; emergency surgery = 3; steroid use for chronic condition = 3; current smoker within 1 year = 3; alcohol intake > 2 drinks/day in past 2 weeks = 3
Class 1 = 0–15 points; Class 2 = 16–25 points; Class 3 = 26–40 points; Class 3 = 41–55 points; Class 5 ≥ 55 points
Volume per body weight: predicted body weight: men: 50 + 0.91 (height in cm – 152.4); women: 45.5 + 0.91
 (height in cm – 52.4)
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Computer‐generated randomization list using a permuted 2‐block strategy
Allocation concealment (selection bias) Low risk Concealment of the group allocation from primary physicians, nurses, participants and investigators was
 ensured by using non‐transparent envelopes
Blinding of participants and personnel (performance bias) 
 All outcomes High risk Envelopes opened on morning of surgery by an anaesthesiologist who was not involved in the investigation but was responsible for the intraoperative participant care and the recording of intraoperative variables
Blinding of outcome assessment (detection bias) 
 All outcomes Low risk Quote: "single‐blinded clinical trial"
Incomplete outcome data (attrition bias) 
 All outcomes Low risk No loss to follow‐up
Selective reporting (reporting bias) Low risk All results provided
Other bias Unclear risk Participants characteristics similar between the groups except that participants in the protective group were significantly older than those in the conventional group