Table 2 Variables analyzed in the meta-analysis

Age*

59

23,426

Mean difference

3.43 [2.44, 4.41]

APACHE II score*

33

15,696

Mean difference

1.63 [0.92, 2.35]

Body mass index*

13

8483

Mean difference

− 0.64 [− 1.21, − 0.08]

Male sex

52

22,093

Odds ratio

0.90 [0.76, 1.07]

SAPS II*

15

7159

Mean difference

4.20 [2.75, 5.65]

History of cardiac disease*

16

7298

Odds ratio

1.35 [1.12, 1.64]

History of respiratory disease*

11

6303

Odds ratio

1.49 [1.18, 1.87]

COPD*

12

1984

Odds ratio

1.60 [1.16, 2.21]

Acute heart failure*

11

3947

Odds ratio

1.40 [1.04, 1.89]

ARDS

9

2842

Odds ratio

1.13 [0.75, 1.69]

COPD exacerbation*

18

4183

Odds ratio

1.26 [1.01, 1.58]

Glasgow Coma Scale before ext.*

13

5933

Mean difference

− 0.75 [− 1.06, − 0.43]

Pneumonia*

17

3692

Odds ratio

1.48 [1.21, 1.81]

Albumin

9

5481

Mean difference

− 0.21 [− 0.43, 0.02]

Hemoglobin*

18

7277

Mean difference

− 0.54 [− 0.72, − 0.35]

PaCO₂ before ext

34

12,328

Mean difference

0.81 [− 0.02, 1.64]

PaO₂ before ext.*

22

9677

Mean difference

− 8.02 [− 12.39, − 3.66]

PaO₂/FiO₂ before ext.*

30

11,960

Mean difference

− 19.38 [− 26.92, − 11.84]

SaO₂ before ext.*

7

1893

Mean difference

− 0.44 [− 0.87, − 0.01]

Duration of MV before ext.*

46

19,775

Mean difference

1.03 [0.62, 1.43]

Respiratory rate before ext.*

27

15,178

Mean difference

1.86 [1.19, 2.54]

RSBI*

44

20,301

Mean difference

8.51 [6.20, 10.81]

RSBI after 1 min SBT*

8

1606

Mean difference

10.26 [3.68, 16.84]

Tidal volume before ext.*

25

12,070

Mean difference

− 28.69 [− 44.61, − 12.78]

Heart rate before ext.*

20

9848

Mean difference

2.99 [1.49, 4.49]

Maximal expiratory pressure*

9

12,183

Mean difference

− 10.22 [− 17.70, − 2.73]

Negative inspiratory force*

14

13,448

Mean difference

5.30 [3.11, 7.48]

Cough*

7

3337

Odds ratio

0.33 [0.16, 0.66]

Cough peak flow*

8

1041

Mean difference

− 27.50 [− 38.95, − 16.04]

Moderate/abundant secretions*

7

2248

Odds ratio

1.98 [1.14, 3.43]

Acute respiratory failure

7

1249

Odds ratio

1.43 [0.88, 2.32]

Coma

8

2742

Odds ratio

0.77 [0.57, 1.03]

Creatinine

9

5422

Mean difference

0.11 [− 0.06, 0.29]

Diastolic blood pressure before ext

9

1651

Mean difference

− 1.03 [− 2.57, 0.50]

Diabetes

15

5976

Odds ratio

1.27 [0.96, 1.69]

FiO₂ during SBT

11

7818

Mean difference

0.00 [− 0.00, 0.01]

Glasgow Coma Scale upon admission

14

9113

Mean difference

− 0.28 [− 0.57, 0.00]

History of hypertension

8

998

Odds ratio

1.09 [0.78, 1.52]

Mean arterial pressure before ext

7

5161

Mean difference

− 0.95 [− 2.36, 0.45]

Minute ventilation before ext

17

14,383

Mean difference

0.00 [− 0.34, 0.34]

Neurologic diagnosis

9

3357

Odds ratio

1.19 [0.76, 1.87]

PEEP during SBT

11

7214

Mean difference

0.05 [− 0.00, 0.10]

pH before ext

27

11,392

Mean difference

− 0.00 [− 0.01, 0.00]

Postoperative respiratory failure

7

2713

Odds ratio

1.01 [0.69, 1.48]

SBP before ext

13

5240

Mean difference

− 0.41 [− 1.95, 1.13]

Sepsis

7

2903

Odds ratio

1.17 [0.92, 1.48]

Shock

8

1722

Odds ratio

0.87 [0.50, 1.50]

Steroids

7

3674

Odds ratio

0.84 [0.58, 1.24]

Trauma

7

4916

Odds ratio

0.83 [0.63, 1.09]