2. Additional information on the included studies.

Study	Criteria for extubation	ICU ventilation	Criteria for non‐invasive ventilation	Criteria for invasive ventilation
Bates 2015	Once participants were titrated down to an FiO2 ≤ 0.5 and PEEP 5 cmH2O, they were assessed twice daily with spontaneous breathing trials. Participants were considered ready for extubation from a pulmonary mechanics standpoint if their rapid shallow breathing index was < 105 for 30 minutes.	Same parameters for the first 3 after surgery if required	Unspecified	All participants admitted to ICU and kept on mechanical ventilation through an endotracheal tube after surgery
Chaney 2000	Normal ICU protocol: appropriate sensorium, normothermia, haemodynamic stability, adequate pulmonary function (PaO2 > 60 mmHg with FiO2 0.4), adequate urine output and minimal chest tube output	Same mode of ventilation for the first hour after surgery, then tidal volume 8 mL/kg, rate 10/minute, FiO2 1.0 and PEEP 5 cmH2O for all participants	Unspecified	Unspecified
Choi 2006	Unspecified	If the surgical procedure exceeded 5 hours, anaesthesiologists were allowed to change the ventilation strategy thereafter	Unspecified	Unspecified
Chugh 2012	Unspecified	Unspecified	Unspecified	Unspecified
Fernandez‐Bustamante 2014	Unspecified	Unspecified	Unspecified	Unspecified
Futier 2013	Recovery of a spontaneous ventilation with an expired tidal volume 5–8 mL/kg, respiratory rate 12–25 breaths/min, absence of residual neuromuscular blockade (assessed by a T4/T1 ratio ≥ 90%), peripheral oxygen saturation ≥ 95%, stable haemodynamics and body temperature ≥ 36°C	Unspecified	Unspecified	Unspecified
Ge 2013	Unspecified	Unspecified	Unspecified	Unspecified
Koner 2004	Unspecified	Unspecified	Unspecified	Unspecified
Kuzkov 2016	The criteria for discontinuation of respiratory support were as follows: the ability to tolerate 30 minutes of spontaneous breathing trial via the pressure support ventilation with pressure support level of 6–8 cmH2O, PaO2/FiO2 > 200 mmHg, spontaneous minute volume < 10 L/min, and respiratory rate < 30/minute (frequency/tidal volume < 65 1/L and tidal volume > 6 mL/kg predicted body weight) as well as normal body temperature, no obvious bleeding or anaemia, haemodynamic stability and adequate analgesia	Unspecified	Unspecified	Unspecified
Memtsoudis 2012	Unspecified	Unspecified	Unspecified	Unspecified
Park 2016a	Unspecified	None of the participants required postoperative ventilatory assistance	Unspecified	Unspecified
Sato 2016	Unspecified	All participants were extubated in the operating room and were spontaneously breathing when they arrived at the postanaesthesia care unit	Unspecified	Unspecified
Shen 2015	Unspecified	Unspecified	Unspecified	Unspecified
Soh 2018	Unspecified	Unspecified	Unspecified	Unspecified
Sundar 2011	Awake status (Riker Sedation‐Agitation Scale score of 3 or 4), haemodynamic stability (minimal doses of nitroglycerine or phenylephrine), and adequate gas exchange (PaCO2 100 mmHg, FiO2 0.4, PEEP 5 cmH2O) Participants were then placed in protocol sequence; they were placed on pressure support ventilation, assessed using the rapid shallow breathing index on PEEP, receiving pressure support levels of 5 cmH2O, followed by a spontaneous breathing trial of 30 min. Participants who passed this sequence were then extubated	Study ventilator settings were applied immediately after induction of general anaesthesia and continued throughout surgery and the subsequent ICU stay	Unspecified	Unspecified
Treschan 2012	Unspecified	Mechanical ventilation of participants who were transferred intubated to the ICU was continued according to group assignment under the discretion of the intensivist in charge	Unspecified	Unspecified
Weingarten 2010	Unspecified	Unspecified	Unspecified	Unspecified
Xiong 2016	Unspecified	Unspecified	Unspecified	Unspecified
Zupancich 2005	Participants were extubated when haemodynamically stable, fully rewarmed, awake, without surgical bleeding and with optimal blood gases	After chest closure, participants were transferred to the ICU and ventilated, with the ventilatory pattern selected randomly	Unspecified	Unspecified

Prophylactic use of non‐invasive ventilatory support was not mentioned in any of the studies.

cmH₂O: centimetres of water; FiO₂: inspired fraction of oxygen; ICU: intensive care unit; min: minute; mL/kg: millilitre per kilogram of body weight; mmHg: millilitre of mercury; n: number of participants; PaCO₂: arterial partial pressure in carbon dioxide; PaO₂: arterial partial pressure in oxygen; PEEP: positive end‐expiratory pressure.