Perioperative respiratory risk in adults with class III obesity: predictors and management from preoxygenation to extubation

Class III obesity markedly reduces respiratory reserve during general anaesthesia. Lower functional residual capacity, early airway closure and increased oxygen consumption shorten the time available for airway interventions, while sleep-disordered breathing and adverse anatomy may add a separate risk of obstruction or difficult laryngoscopy. The aim of this review was to summarise clinically useful predictors of perioperative respiratory risk in adults with class III obesity and to examine current evidence for positioning, preoxygenation, apnoeic oxygenation, tracheal intubation, intraoperative ventilation and post-extubation respiratory support. A structured narrative review was performed using targeted PubMed/MEDLINE searches up to 17 August 2026. Reference lists of relevant guidelines, systematic reviews and clinical trials were also screened. Priority was given to professional-society guidance, systematic reviews and meta-analyses, randomised trials and prospective studies; older studies were retained when they established practices that remain clinically relevant. Body mass index alone does not reliably identify a difficult tracheal intubation. Risk assessment is more useful when it combines airway features such as Mallampati class, neck circumference, cervical mobility and previous airway difficulty with markers of limited physiological reserve, including resting hypoxaemia, obstructive sleep apnoea and suspected obesity hypoventilation syndrome. Head-up or ramped positioning improves the conditions for preoxygenation and laryngoscopy. Positive-pressure preoxygenation can improve lung recruitment and denitrogenation, whereas high-flow nasal oxygen has the distinct advantage of continuing oxygen delivery during laryngoscopy and apnoea. These techniques are not interchangeable: non-invasive ventilation may be preferable when derecruitment is prominent, whereas high-flow nasal oxygen is useful when a longer apnoeic interval is expected. Current airway guidance favours an intubation plan designed for first-attempt success, commonly with videolaryngoscopy, together with continuous attention to oxygenation and an explicit rescue plan. During maintenance of anaesthesia, tidal volume should be based on predicted rather than actual body weight; routine high positive end-expiratory pressure with recruitment manoeuvres improves some physiological variables but has not consistently reduced postoperative pulmonary complications. Extubation should be planned in the head-up position after complete neuromuscular recovery, with early resumption of continuous positive airway pressure or non-invasive respiratory support in selected high-risk patients. Overall, perioperative safety in class III obesity depends less on a single device than on matching the oxygenation and airway strategy to the patient's anatomical difficulty and physiological reserve.