Airway Management
Airway management is the cornerstone of anaesthetic practice, encompassing basic manoeuvres, supraglottic devices, and endotracheal intubation to maintain oxygenation and ventilation.
Key Facts
Head tilt-chin lift and jaw thrust are the fundamental basic airway manoeuvres Laryngeal mask airway (LMA/SGA) is a supraglottic device suitable for most routine anaesthetics — does NOT protect against aspiration Endotracheal intubation provides definitive airway protection and is required for aspiration risk, laparoscopy, and thoracic surgery DAS (Difficult Airway Society) guidelines provide structured algorithms for unanticipated difficult intubation Cormack-Lehane grading classifies laryngoscopic view: Grade 1 (full vocal cords) to Grade 4 (epiglottis not visible) Videolaryngoscopy improves first-pass success and is now recommended for all intubations by some guidelines Cannot intubate, cannot oxygenate (CICO) is a rare emergency (~1 in 50,000) requiring emergency front-of-neck access (eFONA) Pre-oxygenation with 100% O2 for 3 minutes provides an oxygen reserve of 3-8 minutes of apnoea in healthy adults
Overview
Key Facts
Airway management is the primary responsibility of the anaesthetist. Failure to maintain the airway is the leading cause of anaesthesia-related mortality. Structured assessment, planning, and use of algorithms are essential for safe practice.
Epidemiology
NAP4 (4th National Audit Project, 2011) found that airway complications accounted for approximately 60% of anaesthesia-related deaths. CICO events occurred in approximately 1 in 50,000 anaesthetics. Poor airway management in ICU was highlighted as a significant contributor to adverse outcomes.
Aetiology
Difficult airway situations arise from:
- Anatomical factors: Obesity, short neck, receding mandible, large tongue, limited mouth opening, cervical spine immobility
- Pathological factors: Head/neck tumours, previous radiotherapy, burns, trauma, infection (Ludwig's angina, epiglottitis)
- Physiological factors: Pregnancy (oedema, reduced FRC), obesity (rapid desaturation)
Pathophysiology
The upper airway functions as a conduit for ventilation. During anaesthesia, loss of muscle tone causes posterior displacement of the tongue and epiglottis, obstructing the airway. The goal of airway management is to maintain a patent airway for oxygenation and ventilation while protecting the lungs from aspiration.
Clinical Presentation
Airway Assessment (Pre-operative)
- Mallampati score (I-IV): Assess oropharyngeal view
- Thyromental distance: <6.5cm suggests difficult intubation
- Mouth opening: <3 finger-breadths concerning
- Neck mobility: Reduced extension limits intubation
- Body habitus: BMI, neck circumference
- Dental assessment: Loose teeth, prominent incisors, dental prosthetics
Signs of Airway Obstruction
- Snoring, gurgling, stridor
- See-saw (paradoxical) breathing
- Use of accessory muscles
- Desaturation
- Absent or reduced breath sounds
Airway Devices (Escalation)
- Basic manoeuvres: Head tilt-chin lift, jaw thrust
- Oropharyngeal (Guedel) or nasopharyngeal airway
- Supraglottic airway device (SGA/LMA)
- Endotracheal tube (ETT)
- Emergency front-of-neck access (cricothyroidotomy)
Red Flags
- Rapid desaturation despite airway manoeuvres — escalate immediately
- Cannot intubate, cannot oxygenate — declare CICO, perform eFONA
- Stridor pre-operatively — suggests significant airway compromise
- Expanding neck haematoma — secure airway urgently before complete obstruction
Differential Diagnosis
| Scenario | Key Features | Action |
|---|---|---|
| Unanticipated difficult intubation | Poor laryngoscopic view, multiple failed attempts | Follow DAS guidelines, maximum 3+1 attempts |
| Cannot intubate, can oxygenate | Failed ETT but SGA works | Maintain oxygenation via SGA, wake patient or proceed |
| CICO | Cannot intubate AND cannot oxygenate | Declare CICO, eFONA (scalpel cricothyroidotomy) |
| Laryngospasm | Complete airway obstruction, desaturation | Jaw thrust, CPAP, suxamethonium 1mg/kg if severe |
| Bronchospasm | Wheeze, raised airway pressures | Deepen anaesthesia, salbutamol, adrenaline if severe |
| Aspiration | Particulate matter or gastric contents in airway | Suction, head-down tilt, bronchoscopy if needed |
Diagnosis / Investigation
Bedside
- Airway assessment: Mallampati, thyromental distance, mouth opening, neck extension, dentition
- Capnography (ETCO2): Gold standard for confirming ETT placement — trace confirms tracheal position
- SpO2: Continuous monitoring during airway management
- Auscultation: Bilateral chest and epigastrium after intubation
Bloods
- Not specific to airway management
Imaging
- Neck X-ray/CT: If cervical spine injury or retropharyngeal abscess suspected
- CT neck: Pre-operative planning for known difficult airway (tumour, tracheal deviation)
- CXR: Post-intubation to confirm ETT position (tip at T2-T4 level)
- Nasendoscopy: For anticipated difficult airway — ENT assessment of upper airway anatomy
Special Tests
- Fibreoptic intubation: Awake fibreoptic nasotracheal intubation for anticipated difficult airway
- Point-of-care ultrasound: Identify cricothyroid membrane, assess airway anatomy
Management
Non-pharmacological
- Positioning: Ramped position (ear-to-sternal notch alignment) — improves laryngoscopy, essential in obese patients
- Pre-oxygenation: 100% O2 for 3 minutes (or 8 vital capacity breaths) — extends safe apnoea time
- Apnoeic oxygenation: Nasal high-flow O2 (THRIVE) during laryngoscopy — extends safe apnoea time
Pharmacological
- Induction: Propofol 2-3mg/kg or thiopental 3-5mg/kg
- Neuromuscular blockade: Rocuronium 0.6-1.2mg/kg or suxamethonium 1-1.5mg/kg (RSI)
- Sugammadex 16mg/kg: Immediate reversal of rocuronium in CICO/failed intubation scenarios
- Topical LA: 4% lidocaine spray for awake intubation
- Antisialagogue: Glycopyrrolate 200mcg IV for awake fibreoptic intubation
Surgical/Interventional
- Scalpel cricothyroidotomy (eFONA): For CICO — DAS recommends scalpel-bougie-tube technique
- Surgical tracheostomy: Planned or emergency for prolonged ventilation or known difficult airway
- Percutaneous tracheostomy: ICU — typically at 7-10 days of intubation
Referral Criteria
- Known or anticipated difficult airway — senior anaesthetist planning, ENT standby
- Failed intubation — follow DAS algorithm, consider wake-up or alternative plan
- CICO event — critical incident reporting, post-event debrief, psychological support for team
Prognosis
- NAP4 findings: Airway complications are responsible for ~60% of anaesthesia-related deaths
- CICO frequency: ~1 in 50,000 anaesthetics; eFONA success rate >90% when performed promptly
- Failed intubation: Occurs in ~1 in 2,000 routine anaesthetics; higher in obstetrics (~1 in 400)
- Aspiration: Mortality ~5% when it occurs; risk factors include emergency surgery, obesity, pregnancy
- Videolaryngoscopy: Reduces failed intubation rates by 50% compared with direct laryngoscopy
Other Relevant Information
Mallampati Classification
| Class | View |
|---|---|
| I | Soft palate, fauces, uvula, pillars visible |
| II | Soft palate, fauces, uvula visible |
| III | Soft palate, base of uvula visible |
| IV | Hard palate only visible |
DAS Failed Intubation Algorithm (Simplified)
| Step | Plan |
|---|---|
| Plan A | Facemask ventilation + intubation (max 3+1 attempts) |
| Plan B | Supraglottic airway device (max 3 attempts) |
| Plan C | Facemask ventilation |
| Plan D | CICO — emergency front-of-neck access |
Cormack-Lehane Grading
| Grade | View at Laryngoscopy |
|---|---|
| 1 | Full view of vocal cords |
| 2a | Partial view of cords |
| 2b | Arytenoids only visible |
| 3 | Epiglottis only visible |
| 4 | Neither epiglottis nor cords visible |