Supraglottic airway devices (LMA and SGAD): generations, applications and the difficult-airway rescue

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• A supraglottic airway is NOT a definitive airway. It does not isolate the trachea from the oesophagus, and it does not fully protect against aspiration — most importantly in the first-generation device, which has no gastric drainage channel. Reserve the elective use for fasted patients at low aspiration risk, and prefer a second-generation device with a gastric channel whenever the risk is borderline.
• The classic LMA has the lowest seal of the family — second-generation devices achieve higher oropharyngeal leak pressures (mean differences about +4 to +9 cm H2O in an adult network meta-analysis). In the patient with low pulmonary compliance or high airway resistance — obesity, bronchospasm, the head-down laparoscopic position — peak airway pressures exceed the lower seal and the device vents, leaks, and fails to ventilate. A second-generation device or an endotracheal tube is required.
• Displacement is the silent failure of the supraglottic airway. The device can rotate, migrate, or be knocked out during positioning, surgery, or transfer, and the leak that follows is easily missed without continuous capnography — in NAP4's ICU and emergency cases, failure to use capnography contributed to 74% of death-or-brain-damage events. Use continuous waveform capnography for every case managed with a supraglottic device.
• In the unanticipated failed intubation, the SGAD is the guideline's supraglottic-airway RESCUE (second generation recommended). If oxygenation is inadequate after SGAD placement, do not persist — proceed to front-of-neck access (scalpel cricothyroidotomy is the recommended rescue technique). Oxygenation that is adequate after the SGAD is a reason to stop, wake the patient, and not to persist with repeated attempts at intubation.
• High aspiration risk — the full stomach, obesity, pregnancy, gastro-oesophageal reflux disease, ileus, and the upper-airway obstruction or bowel obstruction — is a relative contraindication to a first-generation device and an indication for a rapid sequence induction with an endotracheal tube. The second-generation gastric channel partially mitigates but does not abolish the risk.