Acute Airway in a Child

Pathophysiology

The paediatric airway has distinct differences from the adult airway;

• Paediatric airway has a smaller diameter and shorter length
• Paediatric larynx is situated higher and more anteriorly
• Paediatric patients have a larger head relative to their body size
• Paediatric tongue is larger relative to the size of the oropharynx
• Paediatric epiglottis is large and floppy ^{1, 2}

Such structural differences increase the paediatric airway’s susceptibility to obstruction, hence, an acute airway presentation. With a narrower airway, small amounts of swelling or oedema result in a proportionately larger percentage decrease in airway diameter. ³ A decrease in airway diameter increases the resistance of the airway; Poiseuille’s Law explains that a fall in airway radius by half increases the resistance of the airway 16-fold. R=8ηl/πr^{4 2}

The paediatric population has a higher metabolic rate than adults. This physiological difference is explained by Kleiber’s Law, with younger children with a smaller mass having a higher metabolic rate and using more oxygen per gram of tissue accordingly. Babies have a faster heart rate, faster respiratory rate and feed more regularly due to their smaller body habitus and the ability to move blood very quickly from the heart to tissues. Babies are also obligate nasal breathers for the first few months of life.² The paediatric physiology predisposes paediatric patients to a low tolerance to airway pathology with rapid deterioration when the airway is compromised. ⁴

Clinical Presentation

Clinical features vary with the underlying pathology. An acute airway in a paediatric patient can be caused by any of the following:

• Croup (viral laryngotracheobronchitis)
• Anaphylaxis
• Obstructive foreign body
• Retropharyngeal abscess
• Peritonsillar abscess
• Epiglottitis or tracheitis
• Airway burn such as from smoke inhalation
• Trauma ^5,6

From history:

The history in a patient with an acute airway should be directed towards establishing the underlying pathology and any indications of a difficult-to-manage airway. It is vital to investigate the following:

• Potential for foreign body within the airway
• Symptoms of upper respiratory infection
• Feeding difficulties
• Any surgeries or trauma to the airway or surrounding structures
• Complications during birth or delivery or previous intubation

An acute airway may present on a background of an underlying airway condition predisposing to difficult airway management. Examples include subglottic stenosis, laryngeal atresia, laryngeal or tracheal webs, tonsillar hypertrophy and haemangioma. ³

From examination:

The presentation of an acute airway pathology is indicated by the patient’s breathing. Examination of a child with an acute airway should be done cautiously to avoid causing distress, which could potentially lead to laryngospasm. ⁷. Inspection alone can be very informative. Respiratory distress in infants can be classified as moderate or severe, based on patient clinical features (see Table 1).

Table 1. Classifications of Respiratory Distress ⁶

Congenital syndromes present in the paediatric population and can have associated abnormal anatomy predisposing to potential for airway problems. Table 2 summarises some structural abnormalities and some of their associated syndromes.

Table 2. Structural Abnormalities and Associated Syndromes ^2,3

Noisy Breathing:

Obstructive airway pathology presents with characteristic stridor breathing noises. Stridor is a high-pitched breathing noise indicating pathology around the level of the larynx. ⁷ Timing of the stridor noise is relative to the anatomical level of pathology. See table 3.

Table 3. Stridor noises

Other breathing noises include

• Stertor: Snoring sound from the level of the oropharynx or nasopharynx
• Wheeze: High-pitched expiratory sound from the lower airway
• Gurgling: Wet-sounding noise indicative of fluid in the airway

Investigations

Immediate management of the acute airway should not be delayed by performing investigations. Stable patients may require imaging, such as a chest X-ray in foreign body obstruction, or nasoendoscopy to help identify the underlying pathology.⁴

Cotton-Myer Grading of Subglottic Stenosis

Subglottic stenosis can be congenital or acquired. The former is an indication for tracheostomy. The latter is commonly caused by a prolonged period of intubation. Cotton-Myer Grading is used, mainly in paediatric patients, to classify the severity of subglottic stenosis.

Table 4. Cotton-Myer Grading.⁸

Management

Initial management of patients presenting with an acute airway should be an A-E assessment. Oxygen therapy can be delivered via face mask or nasal cannula in patients with subnormal oxygen saturation before further management to address the underlying pathology. Senior help from ENT, anaesthetics, or intensive care should be sought early.

Emergency airway manoeuvres

In a patient with airway compromise, a head tilt chin lift can open up the airway. Infants should have their chin lifted into a neutral position to avoid overextension of the neck, while a head tilt chin lift in children over 1 year would be appropriate. Alternatively, if a head tilt chin lift is found ineffective, or in the event of trauma, a jaw thrust can be performed to help maintain the airway. ^6,9,10

Medications

Steroids (oral, nebulized, or parenteral), heliox and nebulized adrenaline can be helpful in the management of an acute airway.

Airway adjuncts

Oropharyngeal airway: An oropharyngeal airway is sized from the level of the incisors to the angle of the mandible. ³ Insertion of an oropharyngeal airway in a patient less than 8 years should be under direct vision, concave side down, while those older than 8 years should have the adjunct inserted upside down before being rotated 180˚ at the back of the hard palate, as with adult patients.⁹

Nasopharyngeal airway: Use of a nasopharyngeal airway can be useful in the management of conscious patients to assist airway patency. A nasopharyngeal airway is more tolerable than the oropharyngeal airway in a conscious patient.

Supraglottic airway- Laryngeal mask airway: Laryngeal mask airways (LMA) sit above the level of the vocal cords. When a patient requires ventilation, with no intubation-skilled person available, LMA insertion should be considered.

Subglottic airway- Endotracheal tube: Endotracheal tube (ETT) intubation below the subglottis is the definitive airway for maintaining the airway and ventilation. Generally, there should be no more than 4 attempts of ETT intubation before failed intubation is declared. In a failed ventilation situation, a supraglottic airway adjunct should be inserted as a secondary attempt to ventilate the patient. If a supraglottic ventilation attempt fails at this stage, final attempts to ventilate via face mask should be made. If unsuccessful, the situation is declared a Can’t Intubate Can’t Oxygenate (CICO) scenario. ³

Cricothyroidotomy: In the situation of unsuccessful intubation and oxygenation, an emergency needle cricothyroidotomy or surgical cricothyroidotomy can be performed to re-establish an airway, usually by the ENT specialist. Cricothyroidotomy may be appropriate when airway obstruction is at the level of the larynx or above. The procedure involves creating an opening through the cricothyroid membrane and into the trachea.⁹

References