Summary of findings for the main comparison. Low tidal volume compared to high tidal volume for surgery.
| Low tidal volume compared to high tidal volume for surgery | ||||||
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Patient or population: adults (aged > 16 years) without acute lung injury needing mechanical positive pressure ventilation during their surgery and undergoing any type of open or laparoscopic surgery, elective or emergency Settings: university hospital (16) or in‐hospital (3). Trials were conducted in China (3), France (1), Germany (1), India (1), Italy (1), Japan (1), Russia (1), South Korea (2), The Netherlands (1), Turkey (1) or USA (6) Intervention: low tidal volume Comparison: high tidal volume | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| High tidal volume | Low tidal volume | |||||
| Mortality Follow‐up: 0 to 30 days after surgery | Study population | RR 0.80 (0.42 to 1.53) | 1207 (12 studies) | ⊕⊕⊝⊝ Lowa | Participants were undergoing abdominal surgery (6 studies), heart surgery (1 study), pulmonary thromboendarterectomy (1 study) or various surgeries (1 study) | |
| 30 per 1000 | 24 per 1000 (13 to 46) | |||||
| Low | ||||||
| 20 per 1000 | 16 per 1000 (8 to 31) | |||||
| High | ||||||
| 80 per 1000 | 64 per 1000 (34 to 122) | |||||
| Pneumonia Follow‐up: 0 to 7 days after surgery | Study population | RR 0.45 (0.25 to 0.82) | 778 (7 studies) | ⊕⊕⊕⊝ Moderateb | Participants were undergoing abdominal surgery (5 studies) or spine surgery (2 studies) | |
| 84 per 1000 | 43 per 1000 (23 to 79) | |||||
| Low | ||||||
| 20 per 1000 | 10 per 1000 (5 to 19) | |||||
| High | ||||||
| 120 per 1000 | 61 per 1000 (32 to 113) | |||||
| Need for postoperative non‐invasive ventilatory support Follow‐up: 0 to 7 days (between discharge from the postoperative care unit and 7 days after the surgery) | Study population | RR 0.31 (0.15 to 0.64) | 506 (3 studies) | ⊕⊕⊕⊝ Moderateb | Participants were undergoing abdominal surgery (1 study), spine surgery (1 study) or knee surgery (1 study) | |
| 115 per 1000 | 36 per 1000 (17 to 73) | |||||
| Low | ||||||
| 20 per 1000 | 6 per 1000 (3 to 13) | |||||
| High | ||||||
| 180 per 1000 | 56 per 1000 (27 to 115) | |||||
| Need for postoperative invasive ventilatory support Follow‐up: 0 to 7 days (between discharge from the postoperative care unit and 7 days after the surgery) | Study population | RR 0.33 (0.14 to 0.77) | 957 (11 studies) | ⊕⊕⊕⊝ Moderateb | Participants were undergoing abdominal surgery (5 studies), heart surgery (3 studies), spine surgery (2 studies) or knee surgery (1 study) | |
| 39 per 1000 | 13 per 1000 (6 to 30) | |||||
| Low | ||||||
| 8 per 1000 | 3 per 1000 (1 to 6) | |||||
| High | ||||||
| 60 per 1000 | 20 per 1000 (8 to 46) | |||||
| Intensive care unit length of stay (days) | The mean intensive care unit length of stay in the intervention groups was 0.06 standard deviations lower (0.22 lower to 0.10 higher) | 898 (5 studies) | ⊕⊕⊝⊝ Lowc | A standard deviation of 0.2 represents a small difference between groups Participants were undergoing abdominal surgery (2 studies), heart surgery (1 study), pulmonary thromboendarterectomy (1 study) or various surgeries (1 study) |
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| Hospital length of stay (days) | The mean hospital length of stay in the intervention groups was 0.15 standard deviations lower (0.29 lower to ‐0.00 lower) | 1298 (14 studies) | ⊕⊕⊝⊝ Lowc | A standard deviation of 0.2 represents a small difference between groups Participants were undergoing abdominal surgery (7 studies), heart surgery (3 studies), pulmonary thromboendarterectomy (1 study) spine surgery (1 study), knee surgery (1 study) or various surgeries (1 study) The difference was equivalent to 0.8 day |
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| Barotrauma: pneumothorax Follow‐up: 0 to 7 days | Study population | RR 1.77 (0.52 to 5.99) | 708 (5 studies) | ⊕⊝⊝⊝ Very lowd | Participants were undergoing abdominal surgery (4 studies) or pulmonary thromboendarterectomy (1 study) | |
| 11 per 1000 | 20 per 1000 (6 to 67) | |||||
| Low | ||||||
| 5 per 1000 | 9 per 1000 (3 to 30) | |||||
| High | ||||||
| 30 per 1000 | 53 per 1000 (16 to 180) | |||||
| The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; RR: risk ratio; SMD: standardized mean difference. | ||||||
| GRADE Working Group grades of evidence High quality: further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: we are very uncertain about the estimate. | ||||||
aDowngraded one level for risk of bias and by one level for imprecision. bDowngraded one level for imprecision. cDowngraded one level for risk of bias and by one level for heterogeneity.
dDowngraded one level for risk of bias and by two levels for imprecision.