Table 2. Quality of evidence by GRADE.
| Certainty assessment | № of patients | Effect | Certainty | Importance | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| № of studies | Study design | Risk of bias | Inconsistency | Indirectness | Imprecision | Other considerations | post-operative pulmonary complcations | placebo | Relative (95% CI) |
Absolute (95% CI) |
||
| complications | ||||||||||||
| 10 | randomised trials | serious a | not serious | not serious | not serious | none | 415/1361 (30.5%) | 511/1395 (36.6%) |
RR 0.66 (0.49 to 0.90) |
125 fewer per 1,000 (from 187 fewer to 37 fewer) |
⨁⨁⨁◯ MODERATE |
|
| complications—elder patients | ||||||||||||
| 4 | randomised trials | serious b | not serious | not serious | not serious | none | 13/99 (13.1%) | 36/122 (29.5%) |
RR 0.39 (0.22 to 0.68) |
180 fewer per 1,000 (from 230 fewer to 94 fewer) |
⨁⨁⨁◯ MODERATE |
|
| complications—Non-elder patients | ||||||||||||
| 7 | randomised trials | serious a | not serious | not serious | serious a,c | none | 398/1252 (31.8%) | 471/1266 (37.2%) |
RR 0.86 (0.77 to 0.95) |
52 fewer per 1,000 (from 86 fewer to 19 fewer) |
⨁⨁◯◯ LOW |
|
| complications—obese | ||||||||||||
| 2 | randomised trials | serious d | not serious | not serious | not serious | none | 5/35 (14.3%) | 2/35 (5.7%) |
RR 1.94 (0.49 to 7.74) |
54 more per 1,000 (from 29 fewer to 385 more) |
⨁⨁⨁◯ MODERATE |
|
| complications—Non-obese | ||||||||||||
| 8 | randomised trials | serious a | not serious | not serious | not serious | none | 387/1053 (36.8%) | 432/1093 (39.5%) |
RR 0.91 (0.81 to 1.02) |
36 fewer per 1,000 (from 75 fewer to 8 more) |
⨁⨁⨁◯ MODERATE |
|
| complications—LRMs+Non-Individual PEEP | ||||||||||||
| 10 | randomised trials | serious a | not serious | not serious | not serious | none | 201/584 (34.4%) | 212/615 (34.5%) |
RR 0.65 (0.46 to 0.91) |
121 fewer per 1,000 (from 186 fewer to 31 fewer) |
⨁⨁⨁◯ MODERATE |
|
| complications—LRMs with Individual PEEP | ||||||||||||
| 2 | randomised trials | not serious | not serious | not serious | not serious | none | 191/504 (37.9%) | 222/513 (43.3%) |
RR 0.88 (0.76 to 1.02) |
52 fewer per 1,000 (from 104 fewer to 9 more) |
⨁⨁⨁⨁ HIGH |
|
| complications-LRMs compare to ZEEP | ||||||||||||
| 6 | randomised trials | serious a | not serious | not serious | not serious | none | 37/372 (9.9%) | 80/372 (21.5%) |
RR 0.51 (0.25 to 1.05) |
105 fewer per 1,000 (from 161 fewer to 11 more) |
⨁⨁⨁◯ MODERATE |
|
| complications-LRMs compare to different level of PEEP | ||||||||||||
| 5 | randomised trials | serious a | not serious | not serious | not serious | none | 372/963 (38.6%) | 400/978 (40.9%) |
RR 0.94 (0.84 to 1.05) |
25 fewer per 1,000 (from 65 fewer to 20 more) |
⨁⨁⨁◯ MODERATE |
|
| complications-LRMs compare to low tidal volume | ||||||||||||
| 8 | randomised trials | serious a | not serious | not serious | not serious | none | 380/1051 (36.2%) | 417/1085 (38.4%) |
RR 0.92 (0.79 to 1.07) |
31 fewer per 1,000 (from 81 fewer to 27 more) |
⨁⨁⨁◯ MODERATE |
|
| complication-LRMs compare to high tidal volum | ||||||||||||
| 4 | randomised trials | serious a | not serious | not serious | not serious | none | 35/310 (11.3%) | 94/310 (30.3%) |
RR 0.66 (0.49 to 0.90) |
103 fewer per 1,000 (from 155 fewer to 30 fewer) |
⨁⨁⨁◯ MODERATE |
|
| complication-stepwise LRMs | ||||||||||||
| 7 | randomised trials | serious a | not serious | not serious | not serious | none | 379/1034 (36.7%) | 421/1068 (39.4%) |
RR 0.91 (0.77 to 1.06) |
35 fewer per 1,000 (from 91 fewer to 24 more) |
⨁⨁⨁◯ MODERATE |
|
| complication-sustain LRMs | ||||||||||||
| 4 | randomised trials | serious a | not serious | not serious | not serious | none | 32/315 (10.2%) | 86/315 (27.3%) |
RR 0.37 (0.21 to 0.66) |
172 fewer per 1,000 (from 216 fewer to 93 fewer) |
⨁⨁⨁◯ MODERATE |
|
CI: Confidence interval; OR: Odds ratio; MD: Mean difference
Explanations
a. because of different LRMs, and enrolled patients varied greatly.
b. different surgical procedure and fluid therapy
c. different frequency of LRMs
d. small sample siz