The unanticipated difficult airway: plans A to D

What it is

An unanticipated difficult airway is the moment, after induction of anaesthesia, when tracheal intubation fails despite a normal-looking assessment. The danger is not the failed tube itself but falling oxygen levels while the team keeps trying. Difficult airway guidelines therefore organise the response as a short chain of plans, each with a limited number of attempts. Plan A is tracheal intubation with the best first attempt: good positioning, preoxygenation, full muscle relaxation and, increasingly, a videolaryngoscope and a bougie. If it fails, Plan B is to oxygenate through a supraglottic airway, ideally a second-generation device with a gastric drain channel, and then decide whether to wake the patient, proceed carefully, or intubate through the device. If that fails too, Plan C is face-mask ventilation, with two hands, oral or nasal airways and full paralysis, and a decision to wake the patient if oxygenation is possible. When none of these oxygenates, the patient is in a «cannot intubate, cannot oxygenate» situation and Plan D is emergency front-of-neck access. Throughout, the priority is oxygenation, not intubation, and declaring failure early and calling for help are skills, not weaknesses.

How to recognise it

• Laryngoscopy shows little or none of the glottis, or the tube or bougie will not pass despite a good view.
• Several attempts have failed, or the person intubating says it is difficult.
• Oxygen saturation is falling, or no sustained capnography trace appears after the tube is placed.
• Bleeding, swelling or secretions build up in the airway with each attempt.
• Face-mask ventilation becomes difficult: poor chest rise, large leak, no capnography trace.

Why it happens

• Airway assessment is imperfect, so many difficult airways are not predicted beforehand.
• Each laryngoscopy can cause oedema and bleeding, turning a difficult airway into an impossible one.
• After induction, the apnoeic patient consumes oxygen stores; obesity, pregnancy, children and critical illness shorten the safe time.
• Task fixation: the team keeps trying to intubate and loses track of time and saturation.

What to do at once

1. Call for help and name the problem aloud — a clear declaration focuses the team and brings an experienced colleague and the difficult airway trolley.
2. Keep oxygen going between attempts with face mask and nasal oxygen — oxygenation buys time; intubation is only a means to it.
3. Optimise Plan A once: reposition, adjust blade, use a videolaryngoscope and a bougie, external laryngeal pressure — each change must alter something.
4. Stop after a limited number of attempts and insert a supraglottic airway (Plan B) — repeated laryngoscopy swells the airway and worsens the next try.
5. If the supraglottic airway oxygenates, stop and think: wake the patient, proceed, or intubate through it — the safest choice depends on the urgency.
6. If it fails, use two-person face-mask ventilation with adjuncts and full paralysis (Plan C) — better seal and relaxed muscles open the airway.
7. If mask ventilation works, wake the patient: reverse the neuromuscular block if possible — return of spontaneous breathing is the safest exit.
8. If nothing oxygenates and saturation falls, declare «cannot intubate, cannot oxygenate» and start front-of-neck access (Plan D) — delay causes brain injury.

The plans of a difficult airway algorithm and what each one aims for

Costly mistakes

• Making many attempts at intubation: each one swells the airway and uses up the safe apnoea time.
• Trusting chest movement, breath sounds or tube misting instead of a sustained capnography waveform.
• Not calling for help early, or calling only when saturation is already critically low.
• Repeating the same technique unchanged instead of changing device, position or operator.
• Delaying front-of-neck access while trying yet another device, or giving up because of fear of the procedure.

Next step

• Once the patient is safe, decide with a senior whether surgery goes ahead, is postponed, or needs an awake technique next time.
• Watch for airway swelling, bleeding, aspiration and pneumothorax in recovery; extubate with a plan, as for a difficult airway.
• Document the grade of view, the devices tried, what worked and what failed, in a clear airway note.
• Tell the patient, give a written difficult airway alert, and inform the primary care doctor so future anaesthetists are warned.
• Debrief the team and report the event to the department's safety system.

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Elsewhere in DurgiPedia

• Bag-mask ventilation
• Supraglottic airway devices
• Opening the airway: head tilt, jaw thrust and simple adjuncts
• Emergency front-of-neck access: cricothyroidotomy and tracheostomy

Connections

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Difficult Airway (StatPearls (NCBI Bookshelf), 2026); Video Laryngoscopy (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.