Table 2 Definitions of postoperative pulmonary complications (PPCs)

Sudre [32] (2015)

Atelectasis, pleural effusion, acute pulmonary edema

Chest radiograph findings.

Respiratory failure

Not defined

Ahmed [30] (2009)

Hypoxemia

SpO₂ > 4% below preoperative baseline values for > 10 s in duration.

Pereira [31] (2013)

Hypoxemia

Mild-moderate hypoxia (SpO₂ of 93–90%) on 3 L nasal cannula O_2, not improved after active interventions (increasing O₂ flows to > 3 L/min, application of high-flow face mask O₂, verbal requests to breathe deeply and tactile stimulation);

Severe hypoxia (SpO2 < 90%) on 3 L nasal cannula O2 not improved after active interventions (increasing O₂ flows to > 3 L/min, application of high-flow facemask O2, verbal requests to breathe deeply, and tactile stimulation).

Respiratory failure

Signs of respiratory distress or impending ventilatory failure (respiratory rate > 20 breaths per minute, accessory muscle use, and tracheal tug).

Airway obstruction

Patient complaining of symptoms of respiratory or upper airway muscle weakness (difficulty breathing, swallowing, or speaking), requiring reintubation in the PACU.

Residual NMB

TOFR < 0.9 and was quantified at PACU admission using acceleromyography of the adductor pollicis muscle (TOF-Watch®).

Others (airway obstruction, muscle weakness, decreased inspiratory capacity, bronchospasm)

Not defined.

Unal [33] (2015)

Hypoxemia

SpO₂ ≤ 90% in PACU.

Airway obstruction

Requiring an intervention (jaw thrust, oral or nasal airway, intubation).

Apnea

Not defined.

Re-intubation & invasive postoperative mechanical ventilation.

Patient whose hypoxemia and airway obstruction did not improve despite the application of oxygen through a mask and airway maneuvers.

Llaurado [34] (2014)

Atelectasis, pleural effusion

Chest radiograph finding.