Overall success rate

8

1292

P < 0.01; I
^{2} = 97%

Risk ratio (MH, random, 95% CI)

0.86 [0.67–1.09] (P < 0.01)

Overall success rate (prehospital)

3

647

P = 0.04; I
^{2} = 69%

Risk ratio (MH, random, 95% CI)

0.58 [0.48–0.69] (P < 0.01)

Overall success rate (inhospital)

5

645

P = 0.008; I
^{2} = 71%

Risk ratio (MH, random, 95% CI)

0.86 [0.67–1.09] (P = 0.03)

Duration of intubation

10

2173

P < 0.01; I
^{2} = 88%

WMD (IV, random, 95% CI)

2.12[13.419.18] (P = 0.71)

Esophageal intubation rate

6

1245

P = 0.72; I
^{2} = 0%

Risk ratio (nonevent) (MH, random, 95% CI)

0.36 [0.16–0.80] (P = 0.01)

Inhospital mortality

6

1494

P = 0.89; I
^{2} = 0%

Risk ratio (nonevent) (MH, random, 95% CI)

1.12 [0.86–1.45] (P = 0.39)

Aspiration rate

6

1588

P = 0.007; I
^{2} = 69%

Risk ratio (nonevent) (MH, random, 95% CI)

1.01 [0.98–1.03] (P = 0.52)

Severe low oxygen saturation rate

4

664

P = 0.07; I
^{2} = 57%

Risk ratio (MH, random, 95% CI)

1.43 [0.51–3.96] (P = 0.50)

Proportion of C&L grade 1 classification

4

690

P < 0.01; I
^{2} = 20%

Risk ratio (MH, fixed, 95% CI)

1.54 [1.37–1.74] (P < 0.01)
