01Core principlesThe concepts and mechanisms needed to understand the subject.
A useful airway plan answers four different questions: can oxygen be delivered by facemask, can a supraglottic airway ventilate, can the trachea be intubated, and would emergency front-of-neck access be difficult? No single bedside sign answers all four. Mallampati class describes visible oropharyngeal structures, thyromental distance and jaw protrusion sample mandibular space and mobility, and mouth opening and neck movement affect device insertion and alignment. These findings alter preparation; none provides permission to proceed without rescue equipment.
History often carries more information than a score. Ask about previous airway difficulty, the device that succeeded, number of attempts, dental damage, awake intubation, postoperative ventilation and airway symptoms. Retrieve the chart rather than relying on the label difficult intubation. Examine dentition, mouth opening, jaw movement, tongue and palate, neck movement and front-of-neck anatomy. Add procedure-specific factors such as shared airway surgery, prone positioning or loss of access after draping.
Planning begins before induction. The 2025 DAS adult guidance emphasises preparation, peroxygenation, first-attempt success, continuous oxygen delivery, two-point confirmation of tracheal placement and prompt progression after failure. Prepare a skilled assistant, suction, facemask and adjuncts, a suitable videolaryngoscope, bougie or stylet, second-generation supraglottic devices, tubes and immediately accessible eFONA equipment. Optimise head and body position and physiology, agree who will call attempts and elapsed time, and tell the team when to move plans.
Anticipated and unanticipated difficulty are different decisions. Predictors of difficult airway management should lower the threshold for a planned awake technique, specialist help or altered location. DAS awake guidance requires supplemental oxygen, effective topicalisation that is tested, cautious minimal sedation rather than sedation as a substitute for topicalisation, a 3+1 attempt limit and visual plus capnographic confirmation before inducing anaesthesia. These details apply to awake adult tracheal intubation and should not be casually transferred to children or obstetric practice.
The rescue sequence protects oxygenation. Plan A is tracheal intubation with a maximum of 3+1 attempts. Failed intubation is declared and Plan B uses a second-generation supraglottic airway, with no more than three attempts, to restore ventilation and create a decision point. If Plan B fails, the eFONA kit is opened and Plan C is one final, fully optimised facemask strategy. Failed Plan C is declared cannot intubate, cannot oxygenate and triggers Plan D; delaying for further laryngoscopy or supraglottic attempts consumes the oxygen reserve the sequence is designed to preserve.
Airway management continues after placement. Sustained waveform capnography establishes ventilation and must continue through maintenance, transfer and emergence while an artificial airway remains. Fix and document tube depth, reassess after repositioning, monitor cuff pressure, anticipate obstruction or displacement, and maintain anaesthesia and neuromuscular block appropriate to the procedure. Before extubation, decide whether the airway is low or high risk, whether the patient can oxygenate and protect the airway, and where reintubation and rescue could be performed.
Key points
- Airway assessment predicts difficulty imperfectly. Combine prior records, symptoms, examination, aspiration risk, physiology, procedure and positioning with explicit plans for ventilation, intubation, extubation and failure.
- For an unanticipated difficult adult airway, preserve oxygen delivery, call for help early, optimise each attempt, confirm ventilation with waveform capnography and move forward when a plan fails.
- The 2025 DAS sequence is Plan A tracheal intubation, Plan B second-generation supraglottic-airway ventilation, Plan C final optimised facemask ventilation and Plan D emergency front-of-neck access.
- Plan A permits at most three attempts plus one by a more experienced operator; a repeat attempt must change a relevant factor such as position, device, operator, neuromuscular block or adjunct.
- If difficulty is predicted, awake tracheal intubation must be considered; it is a planned technique with oxygen, tested topicalisation, a checklist and its own attempt limit, not an improvised rescue after induction.
- Extubation is another airway procedure: assess whether reintubation would be difficult, ensure adequate recovery and oxygenation, select a location and technique, and state the post-extubation rescue plan.
02Mechanisms and patternsImportant relationships and how to distinguish them.
Identify exactly which component was difficult, what failed, what succeeded, the device and grade, attempts, complications and the documented recommendation for future anaesthesia.
Stridor, positional dyspnoea, voice change, dysphagia, drooling, sleep-related obstruction or progressive swelling may identify a dynamic airway that could worsen when consciousness and tone are lost.
Assess teeth, mouth opening, tongue and palate, jaw protrusion, thyromental space, neck movement, neck circumference and whether the cricothyroid membrane can be identified.
Beard, edentulous face, obesity, obstruction, limited jaw movement and altered upper-airway anatomy can impair rescue ventilation even when laryngoscopy appears feasible.
Limited oxygen reserve, severe hypotension, pulmonary hypertension, metabolic acidosis or right-heart compromise can make otherwise brief apnoea or positive-pressure ventilation hazardous.
Absent or inadequate capnogram, poor chest movement, falling saturation, leak, high resistance or absent expired volume means ventilation is not confirmed and requires immediate corrective action.
03Interpreting evidenceInformation, measurements and their limitations.
Consider the information, its meaning and its limitations before deciding what follows.
- 01
Prior anaesthetic documentation - Why
- Recover direct evidence of previous mask, supraglottic, laryngoscopic, intubation and extubation performance.
- Interpretation and limitations
- A specific successful technique and the circumstances of failure are more actionable than an unsupported difficult-airway alert; unresolved prior failure warrants senior review and an alternative plan.
- 02
Structured airway examination - Why
- Identify features affecting device insertion, glottic access, rescue ventilation and front-of-neck access.
- Interpretation and limitations
- Multiple abnormalities increase concern, but a reassuring examination cannot exclude difficulty. Translate findings into equipment, operator, location and awake-versus-asleep decisions.
- 03
Waveform capnography - Why
- Confirm alveolar ventilation after any airway device and monitor patency continuously.
- Interpretation and limitations
- A sustained waveform supports ventilation. A flat trace after tracheal intubation is oesophageal placement until excluded; during maintenance, abrupt loss suggests disconnection, displacement, complete obstruction or arrest and demands immediate patient-and-circuit assessment.
- 04
Targeted airway imaging or nasendoscopy - Why
- Define suspected upper-airway pathology when symptoms, examination or existing disease make anatomy uncertain.
- Interpretation and limitations
- Interpret with an airway specialist and the planned procedure. A static image does not establish that induction or rescue ventilation will be safe, and should not delay treatment of progressive obstruction.
- 05
Oxygenation and physiological reserve - Why
- Establish saturation, respiratory effort and cardiorespiratory stability before an airway intervention.
- Interpretation and limitations
- Poor reserve shortens safe apnoea time and increases the consequence of repeated attempts; optimisation, awake strategy or a higher-resource location may be required.
04Applied reasoningWorked examples connecting principles to decisions.
01Worked case: failed adult intubationUnexpected difficult intubation while oxygenation is maintainedAfter elective induction in an adult, the initial optimised videolaryngoscopy attempt fails but facemask ventilation and saturation remain adequate.+
- 1Announce the difficulty, call for help, continue facemask plus nasal oxygen, verify adequate anaesthetic depth and neuromuscular blockade, optimise position and ask the assistant to count attempts and elapsed time.
- 2For each further Plan A attempt, change a plausible cause of failure: improve laryngeal view or external manipulation, remove cricoid force if applied, use an introducer, change blade or device, or change to a more experienced operator.
- 3Stop after no more than three attempts plus one by a more experienced operator. Declare failed intubation, make the eFONA kit immediately accessible and move to Plan B rather than repeating laryngoscopy.
- 4Insert a second-generation supraglottic airway, limiting insertion to three attempts and confirming ventilation with waveform capnography. If ventilation succeeds, stop, think and communicate with senior input about waking, intubating through the device, proceeding without intubation, or planned surgical front-of-neck access.
- 5If supraglottic ventilation fails, declare failure, open the eFONA kit and move to the final optimised facemask attempt; if that does not oxygenate, declare CICO and proceed immediately to Plan D.
02Anticipated difficultyPlanning before loss of consciousnessHistory, examination or airway pathology predicts that asleep intubation or rescue ventilation may be difficult.+
- 1Retrieve prior records, define which airway components are threatened, assess aspiration and physiological risk, and involve an experienced anaesthetist and relevant surgical airway expertise.
- 2Consider awake tracheal intubation and agree primary and failure plans, oxygen delivery, topicalisation, minimal sedation if any, equipment, attempt limit and the point at which the procedure will stop.
- 3If awake intubation is used, administer continuous supplemental oxygen, establish and test effective topical anaesthesia, restrict attempts to 3+1, and induce general anaesthesia only after visual and waveform-capnographic confirmation.
03Failed rescue ventilationCICO and Plan DPlan A intubation and Plan B supraglottic ventilation have failed, and a final optimised Plan C facemask attempt cannot oxygenate the adult.+
- 1Ensure help is present, state cannot intubate, cannot oxygenate aloud, continue oxygen delivery, fully paralyse and open the eFONA equipment without further upper-airway attempts.
- 2Use the trained adult scalpel-bougie-tube technique with a size 10 scalpel, bougie and 6.0 mm cuffed tracheal tube; maximise neck extension when cervical safety permits and keep suction ready.
- 3Inflate the cuff, connect the circuit, confirm ventilation using a sustained waveform capnogram, stabilise physiology and document the emergency airway and subsequent surgical or critical-care plan.
04Extubation planningRemoving an artificial airway safelySurgery is ending and airway oedema, difficult reintubation, residual weakness or impaired consciousness could make extubation hazardous.+
- 1Reassess oxygenation, ventilation, airway swelling or contamination, neuromuscular recovery, consciousness and haemodynamics, and decide whether extubation or continued ventilation is safer.
- 2Choose the location, staff, position, oxygen strategy and reintubation equipment before removing the tube, with a stepwise plan for obstruction or failed reintubation.
- 3Continue close observation and capnography while an artificial airway remains, communicate the airway history to recovery staff and record information the patient and future teams will need.
05Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.
- Use continuous pulse oximetry and waveform capnography throughout airway insertion, maintenance, transfers and emergence until the artificial airway is removed and verbal contact is re-established.
- Count and announce intubation and supraglottic attempts, elapsed time and saturation trend; an attempt includes insertion of the device, and repeated unchanged attempts should not be normalised.
- Monitor airway pressure, expired tidal volume, respiratory rate and leak once ventilation begins, and recheck capnography, depth and fixation after every repositioning or circuit change.
- Use quantitative neuromuscular monitoring whenever blockade is given and confirm a train-of-four ratio above 0.9 before awakening and extubation.
- During recovery, observe airway patency, ventilation, oxygenation, consciousness and haemodynamics one-to-one until the adult can maintain their airway, communicate and remain respiratory and cardiovascularly stable.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
Prediction directs preparation
Bedside tests are useful when they change the airway strategy, equipment or expertise; their limited sensitivity means a rescue plan remains mandatory after a reassuring assessment.
Oxygenation is the endpoint
Laryngoscopic view and tube placement are intermediate goals. The algorithm moves to a different ventilation technique before repeated instrumentation converts a manageable airway into a hypoxic one.
Two-point confirmation
DAS uses visual confirmation of tube passage plus waveform capnography. Breath sounds, condensation or improved colour cannot safely overrule an absent sustained carbon-dioxide waveform.
Plan B creates choices
Successful ventilation through a second-generation supraglottic airway buys time for a senior decision; it does not automatically mean either waking or proceeding is safe.
Extubation needs resources
A high-risk tube should not be removed in a place where deterioration cannot be observed or where rapid oxygenation, reintubation and front-of-neck rescue are unavailable.
Scope changes algorithms
The DAS 2025 sequence is for unanticipated difficult tracheal intubation in adults; paediatric, obstetric, awake and critically ill populations have distinct physiology and guidance.
07Common pitfallsFrequent interpretation and management errors.
- 01
Calling the airway easy because one screening test is normal or because previous anaesthesia was undocumented.
- 02
Repeating laryngoscopy without changing position, device, operator, adjunct or another correctable cause.
- 03
Accepting chest movement or auscultation as confirmation when the waveform capnogram is absent or equivocal.
- 04
Continuing upper-airway attempts after CICO has been declared instead of performing trained emergency front-of-neck access.
- 05
Using heavy sedation to compensate for inadequate topicalisation during awake intubation.
- 06
Removing a difficult airway without a reintubation plan, appropriate recovery location and clear handover.