Table 1 Primary and secondary outcomes evaluated for each study

Bach et al. 1994 [19].

• PCF ≥ 160 L/min

• VC

• Age

Ceriana et al. 2003 [20].

• Clinical stability (no active infection and hemodynamic stability)

• Absence of psychiatric disorders

• Effective cough (MEP ≥ 40 cmH2O)

• PaCO2 < 60mmHg

• Adequate swallowing (evaluated by gag or blue dye test)

• Absence of tracheal stenosis (evaluated by endoscopy)

Stelfox et al. 2008 [26].

• Ability to tolerate tube capping (24h vs. 72h)

• Oxygenation (SaO2 95% with FiO2 0,3 vs. 0,5)

• Cough effectiveness (strong vs. weak)

• RR (18 bpm vs. 28 bpm)

• Secretions (scan thin vs. moderate thick)

• Swallowing (enteral nutrition via gastric tube and nothing p.o. vs. enteral nutrition via gastric tube and jelly and pudding)

• Level of consciousness (alert vs. drowsy but arousable)

• Indication for tracheostomy (pneumonia vs. COPD)

• Difficulty of intubation (easy vs. difficult)

• Comorbidities (no significant comorbidities vs. end-stage renal disease)

• Age (45 yo vs. 75 yo)

Stelfox et al. 2009 [27].

• Ability to tolerate tube capping (24h vs. 72h)

• Oxygenation (SaO2 95% with FiO2 0,3 vs. 0,5)

• Cough effectiveness (strong vs. weak)

• RR (18 bpm vs. 28 bpm)

• Secretions (scan thin vs. moderate thick)

• Swallowing (enteral nutrition via gastric tube and nothing p.o. vs. enteral nutrition via gastric tube and jelly and pudding)

• Level of consciousness (alert vs. drowsy but arousable)

• Indication for tracheostomy (pneumonia vs. COPD)

• Difficulty of intubation (easy vs. difficult)

• Comorbidities (no significant comorbidities vs. end-stage renal disease)

• Age (45 yo vs. 74 yo)

Budweiser et al. 2011 [23].

• Ability to tolerate tube capping > 24h/48h

• Serum creatinine

• Duration of former intubation and tracheostomy

• Oxygenation

• Age

O’Connor et al. 2009 [24].

• Shorter permanence at acute facility

• Ability to tolerate tube capping

• Cough effectiveness

Marchese et al. 2010 [28].

• Stability or respiratory conditions (dyspnea, RR, SaO2, PaO2, PaCO2, pH)

• Effective cough

• Indication for tracheostomy (underlying disease)

• Effective swallowing

• No or mild hypercapnia (PaCO2 level in stable state)

Choate et al. 2008 [21].

• Cough effectiveness

Leung et al. 2003 [22].

• Indication for tracheostomy (unstable or obstructed airways vs. others)

Tobin et al. 2008 [25].

• Ability to tolerate tube capping > 24h

• Cough effectiveness (no need of suctioning)

• Setting of cure (intensivist-led tracheostomy team vs. others)