Airway Obstruction

OVERVIEW

Airway obstruction can be incomplete or complete

• Complete obstruction of the upper airway occurs when there is inability to talk, cough or breath. Apnea and cyanosis are present and paradoxical respiration may be noted.
• Incomplete obstruction occurs when there is partial upper airway obstruction and ability to breath is maintained. Inspiratory stridor and increased work of breathing are the hallmarks.

Upper airway obstruction can be due to the following factors:

• luminal (e.g. foreign body)
• intramural (e.g. tumour, neuromuscular diseases)
• extramural (e.g. thyroid mass)

CAUSES

• Foreign body
• Infection
  • Epiglottis
  • Retropharyngeal abscess
  • Bacterial tracheitis
  • Ludwig’s angina
  • Laryngotracheitis
  • Diptheria
  • Tetanus
• Immune
  • Angioedema
  • Anaphylaxis
• Tumor
• Trauma
  • Neck hematoma, e.g. trauma, bleeding diathesis, anticoagulants
  • laryngeal fracture
  • Burns
  • Post-operative complications
• Poisoning and toxic exposures
  • Smoke inhalation
  • Caustic ingestion
  • Strychnine poisoning
• Laryngospasm
  • Physical or chemical stimuli
  • Drug-induced e.g. acute dystonic reaction, ketamine
• Congenital
  • Vascular rings
  • Laryngeal webs
• Other
  • Paradoxical motion of the vocal cords
  • Altered level of consciousness
  • Cranial nerve palsies
  • Paralysis
  • Hysterical stridor
  • Myoedema

ASSESSMENT

History

• Stridor = sound on inspiration associated with airway narrowing
• stridor @ rest implies a reduction in airway diameter of >50%
• progression of symptoms
• positional exacerbation
• whether patient wakes @ night having difficulty breathing
• dysphagia
• drooling
• severe obstruction -> coughing becomes difficult -> chest infections

Examination

• Airway assessment
• Neck examination
• Nasal endoscopy – photos helpful, doesn’t involve LA to cords which could precipitate total airway obstruction, beaware that a nice view in the sitting position doesn’t mean the same in the supine position.

Investigation

• CT – more helpful in subglottic assessment

Define site of obstruction

• Supraglottic
• Laryngeal
• Subglottic – mid tracheal & lower tracheal/bronchial

MANAGEMENT

Supraglottic & Laryngeal Lesions

1. Awake tracheostomy
2. Inhalational induction

INHALATIONAL INDUCTION

• 2 anaesthestists
• experienced assistance
• vasoconstrictor + LA to nose
• surgeon in theatre scrubbed for emergency tracheostomy
• sevo/O2 induction (may need halothane)
• don’t bag if becomes apnoeic (allow CO2 rise)
• insert N/P airway if required
• wait for pupils to become small and central
• laryngoscopy (long, McCoy)
• assess whether can intubate

1. attempt intubation only twice
2. tracheostomy while breathing spontaneously

• sudden complete airway obstruction
  -> immediate tracheostomy or single attempt @ rigid bronchoscope

AWAKE TRACHEOSTOMY

Indications

• severe stridor
• large tumour
• gross anatomical distortion
• larynx not visible on nasal endoscopy

Technique

• no sedation
• helium/O2 mix -> improves symptoms
• beaware of giving high FiO2 -> can precipitate CO2 narcosis
• prepare in sitting position
• once in place -> confirm with CO2

Post op

• Analgesia
• Humidification
• If intubated – leave Cook Airway catheter in place until patient fully awake
• Dexamethasone
• May need PEEP or IPPV post

Mid Tracheal Lesions

• ie. thyroid mass
• ensure that patient can be intubated to below level of obstruction
• normal induction may be appropriate
• any suggestion of malignant tracheal invasion -> AFOI

Lower Tracheal & Bronchial Obstruction

• mediastinal masses (lymphoma, invasive carcinoma)
• beaware of invading thyroid carcinomas -> tracheal collapse with muscle relaxation -> have a ridgid bronchoscope available.
• if obstruction close to the carina or invading the bronchus -> can’t do tracheostomy or give muscle relaxation -> may need bypass.

References and Links

• CEPD – October 2002 (Rees & Mason)
• Obstructed Airway in ENT Surgery – Anaesthesia 1999, 54, page 625-628 (Mason & Fielder)