Describe stridor and the management of acute upper airway obstruction.

Recognising and Grading Stridor

• Stridor is a harsh, noisy sound produced by turbulent airflow through a narrowed airway.
• It is a sign of airway obstruction, not a diagnosis, and its timing in the respiratory cycle localises the obstruction.
• The timing IS the most useful single observation:

Causes and Emergency Management

• Causes IN children, by age.
• Neonate and infant — laryngomalacia, which is much the commonest cause of chronic stridor in infancy, characteristically worse when supine, feeding, crying or with an upper respiratory infection, and better when prone, appearing in the first weeks and resolving spontaneously by 12 to 24 months in most; congenital subglottic stenosis; vocal cord palsy; laryngeal web, cyst or cleft; subglottic haemangioma, which appears at 3 to 6 months, may be associated with cutaneous haemangiomas, and responds dramatically to propranolol; tracheomalacia and vascular rings
• Age 6 months to 6 years — croup (acute laryngotracheobronchitis).
• Older children and adults — laryngeal trauma; foreign body; angio-oedema and anaphylaxis; deep neck space infection and LUDWIG angina; bilateral vocal cord palsy; laryngeal or thyroid malignancy; post-intubation subglottic stenosis; inhalation (thermal or chemical) burns; and laryngeal diphtheria.
• Emergency management — the principles:
• DO not distress the patient, particularly A child. Crying and struggling increase turbulent flow and oxygen demand and can precipitate complete obstruction — so leave the child on the parent’s lap, do not examine the throat, do not attempt cannulation or a lateral radiograph in a distressed child, and do not lie them flat
• Give oxygen in the least distressing way, held by the parent if necessary
• Call for help early — the senior anaesthetist and ENT surgeon, and move to a place where a definitive airway can be secured: the operating theatre, not the radiology department
• Nebulised adrenaline (epinephrine), which buys time by reducing mucosal oedema and works within minutes, but wears off in 1 to 2 hours with possible rebound — so a patient who has received it must be observed and not discharged
• Corticosteroid — dexamethasone orally or intramuscularly, or nebulised budesonide.
• HELIOX (helium-oxygen), which is less dense and so reduces turbulence, as a temporising measure
• Treat the cause — antibiotics, adrenaline and antihistamine for anaphylaxis, removal of a foreign body
• Securing the airway where obstruction is severe or progressing — inhalational (gas) induction with the patient breathing spontaneously, by an experienced anaesthetist, with a smaller tube than predicted; and the ENT surgeon scrubbed and ready with a rigid bronchoscope and tracheostomy set open
• Never give a muscle relaxant to a patient with critical stridor before the airway is secured — the obstruction may become complete and unrecoverable. This is the single most dangerous error in the management of the obstructed airway
• Cricothyroidotomy is the emergency surgical airway of choice in a "cannot intubate, cannot oxygenate" situation, being faster and more superficial than tracheostomy; it is converted to a formal tracheostomy within 24 to 48 hours, and is avoided in small children, in whom needle cricothyroidotomy with jet ventilation is used instead
• A quiet, sleepy child is tiring, not settling, which is the single most misread observation in paediatric airway obstruction
• Never paralyse a patient with critical stridor before the airway is secured; the obstruction may become unrecoverable
• Inspiratory stridor is above the cords, expiratory is below, and biphasic means a fixed subglottic narrowing
• Biphasic stridor is the most worrying, indicating a fixed and often critical narrowing at the transition
• Stertor is a different sign, arising above the larynx, and has its own differential
• A normal saturation must not reassure; oxygenation is maintained until obstruction is severe, particularly on oxygen
• Do not examine the throat of a distressed child, and do not send them for a radiograph unaccompanied
• Leave the child on the parent lap; crying increases turbulent flow and oxygen demand and may precipitate obstruction
• Nebulised adrenaline buys time but wears off in an hour or two.