Table 2.

Variables analyzed in the meta-analysis

Variables	n	N	Statistical method	Effect estimate [95%CI]
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]

N number of participants, n number of studies, ext extubation, SBT spontaneous breathing trial, SAPS severity acute physiologic score, APACHE acute physiology and chronic health evaluation, COPD chronic obstructive pulmonary disease, ARDS acute respiratory distress syndrome, PaCO2 partial pressure of carbon dioxide in the arterial blood, PaO2 partial pressure of oxygen in the arterial blood, SaO2 oxygen saturation in the arterial blood, FiO2 fraction of inspired oxygen, RSBI Rapid Shallow Breathing Index, PEEP positive end expiratory pressure, *statistically significant by meta-analysis