The Paediatric Airway: Physiology and Assessment
Airway management in children can be daunting, especially to those practitioners who deal with them only occasionally. In the next couple of steps we will be reviewing the main airway techniques used in paediatrics, and how to manage the child with a compromised airway. First, Dr Elena Fernandez, Consultant Paediatric Anaesthetist and Airway Lead at Great Ormond Street Hospital, London, will explore the unique anatomy and physiology of children and how they differ from adults.
What is different about paediatric airway anatomy?
At birth, the head is proportionally larger than the body with a prominent occiput. This causes neck flexion, leading to potential airway obstruction in the supine position . The larger occiput combined with a shorter neck makes laryngoscopy more difficult.
Children have a relatively large tongue that decreases the size of the oral cavity and can obstruct the airway.
The epiglottis in infants is longer, narrower, softer and more horizontally positioned than in adults. On direct laryngoscopy, the neonatal epiglottis has an inverted U-shape that may obscure the glottic view (see figure 1). Figure 1: View of the epiglottis on laryngoscopy in an infant, child and adult
Enlargement of the adenoids in childhood may cause nasal obstruction.
The above factors all contribute to loss of upper airway space which can lead to difficulty with mask ventilation and obstruction during spontaneous ventilation .
The cricoid cartilage lies at the level of the C4 vertebra at birth, C5 at 6 years and C6 in the adult. The more superior location of the larynx in small children can make visualization of the laryngeal inlet more difficult during laryngoscopy. External manipulation of the larynx is often required to improve the view .
The cricoid cartilage is functionally the narrowest part of the paediatric airway. The mucosa at this level is particularly vulnerable to trauma with the potential for oedema and stenosis .
The paediatric trachea is narrow and any reduction in its internal diameter by secretions or oedema will severely increase airway resistance and compromise airway flow.
The cartilaginous structures in the paediatric airway are soft and highly compliant. This leads to increased susceptibility to dynamic airway collapse especially in the presence of airway obstruction . Applying Continuous Positive Airway Pressure (CPAP) may relieve the obstruction.
Why are children at higher risk of airway obstruction and desaturation?
Infants are obligate nasal breathers until 5 months of age. Nasal breathing increases the resistance to airflow. Any reduction in airway diameter by secretions, oedema or blood will impede airflow and increase the work of breathing  .
High metabolic rate and low oxygen reserves make small children very intolerant to apnoea, such as during laryngoscopy, with rapid development of significant hypoxaemia and metabolic acidosis despite pre-oxygenation  .
How should we perform a paediatric airway assessment?
A 3-month-old twin baby presented for elective surgery. At the anaesthetic pre-operative visit, mother reported that compared with his twin brother his cry had always been very soft, almost inaudible.
Spend a few minutes reflecting on what information you would like to know about this child. What questions would you ask the mother? Would you perform any examinations or investigations?
The following factors should be identified in your preoperative airway assessment.
- Birth complications
- Difficulties in phonation, feeding, breathing
- Recent respiratory tract infection, stridor
- Symptoms of obstructive sleep apnoea: snoring, apneas, daytime somnolence, hyperactivity
- Previous airway trauma or airway surgery
- Syndromes associated with difficult airway
- Airway management in previous anaesthetics
- General appearance and body mass index
- Mouth opening, tongue, palate, pharynx
- Loose teeth common in 6-12 year olds
- Lateral profile to assess mandibular abnormalities
- Nasal flaring/ tracheal tug/ tachypnoea/ recession: signs of respiratory distress
- Mouth-breathing/ drooling: signs of enlarged tonsils or adenoids
- Neck deformity/ range of movement
- Shape of chest/ respiratory pattern/ auscultation
- Nasal endoscopy
- Imaging: CT-SCAN, MRI, Ultrasound
Now back to our clinical case:
The anaesthetist consulted ENT who decided to investigate with an airway endoscopy prior to surgery. A critical subglottic stenosis was diagnosed requiring an urgent tracheostomy.
Would you have gone ahead with this child without any further investigation? Spend some time discussing this with your fellow learners. Reflect also on how you think the different anatomy and physiology in children influence your choice of equipment and techniques?
In the next step Dr Fernandez will give you an overview of the principles of paediatric airway management.