Paediatrics
Acute and chronic airway obstruction in children

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Abstract

Airway obstruction is more common in children than in adults. This is because of subtle anatomical differences in the childhood airway and an increased propensity to infection. Effects of obstruction manifest more quickly in children because of a smaller airway diameter, reduced physiological reserve and easily fatigued respiratory muscles. The signs of airway obstruction differ between upper and lower airway obstruction, and in the spontaneously breathing and ventilated child because of the differences in the mechanics of breathing in each of these situations. The anaesthetist must be able to recognize risk factors for airway obstruction such as a history of respiratory symptoms, including sleep-disordered breathing, and high-risk groups, such as ex-preterm infants. The anaesthetist must also be able to recognize the signs of airway obstruction in the awake, anaesthetized and paralysed child. Upper airway obstruction may be moderate, as in many cases of tonsillar or adenoidal hypertrophy and laryngomalacia, or severe, as in some upper respiratory tract infections such as epiglottitis, croup or bacterial tracheitis. Lower airway obstruction is most commonly seen in children with reactive airways secondary to atopic asthma, viral-associated wheeze or chronic lung disease of prematurity. It can also accompany chronic infection and bronchiectasis, as in cystic fibrosis or primary ciliary dyskinesia. Pulmonary hypertension can develop in any child with chronic airway obstruction and is an additional risk factor for complications including death during anaesthesia. This article outlines some of the issues in acute and chronic airway obstruction in children. Where possible up-to-date anaesthetic management or algorithms will be referenced.

Section snippets

Aetiology

Some of the causes of acute and chronic airway obstruction are outlined in Table 1.

Mechanics of airway obstruction

Upper and lower airway obstruction (Figure 1) produce different pictures because of the different pressures inside and outside the thoracic cavity during the breathing cycle. Anatomically, the thorax is separated from the neck at the thoracic inlet, or superior thoracic aperture, formed by the first thoracic vertebra, the first pair of ribs and the manubrium sterni. Anatomically, the upper airway is divided from the lower airway at the level of the subglottis. Physiologically, the upper airways

Recognizing airway obstruction in the spontaneously breathing child

In the spontaneously breathing child, extrathoracic airway obstruction produces inspiratory or biphasic stridor, which is usually monophonic. Increased effort is seen with accessory muscle use. Tracheal tug, sternal, subcostal and intercostal recession are exaggerated because of the high negative intrapleural pressures generated by the child in an attempt to overcome the obstruction. This is obvious in younger children with compliant, cartilaginous thoracic walls when even moderate upper airway

Recognizing airway obstruction in the ventilated or anaesthetized child

The ventilatory responses which generate the signs of airway obstruction outlined above are blunted in the anaesthetized child and absent in the paralysed child. The anaesthetist needs to remain alert to changes in tidal volumes or airway pressures as well as hypercarbia and hypoxaemia. Monitoring of tidal volumes, end-tidal carbon dioxide and oxygen saturations are vital. The only clinical signs may be reduced chest expansion and diminished breath sounds. The ‘feel’ during hand ventilation

Nose and nasopharynx

Bilateral choanal atresia usually presents within hours of birth with breathing difficulties, apnoea or cyanotic episodes often associated with feeding. Unilateral choanal atresia can present later in childhood with persistent unilateral rhinorrhoea. Adenoidal and tonsillar hypertrophy are the commonest cause of chronic upper airway obstruction in pre-school children, manifest usually by disordered breathing in sleep or breathing difficulties during upper respiratory tract infections. A

Larynx and upper trachea

Laryngomalacia is the commonest laryngeal cause of upper airway obstruction in young children and is characterized by inspiratory stridor of variable degree developing usually days to weeks after birth and improving as the child grows.1 In laryngomalacia the negative airway pressure normally generated during inspiration drags the epiglottis or aryepiglottic folds into the laryngeal inlet obstructing the airway. The problem is usually less marked if positive airway pressure is applied. The

Bronchospasm

Asthma remains the commonest chronic illness in childhood and the commonest cause of lower airway obstruction. Children can have hyper-reactive airways without satisfying the other criteria of classic atopic asthma. Pre-school children can have severe and recurrent wheeze in response to viral infections without symptoms in the intervening period (known as viral-associated wheeze or wheezy bronchitis). Other children may have an idiosyncratic reaction to anaesthetic gases, or an allergic

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