Respiratory System in Children 2, Airways

Nose and nostrils

For the first few months of life, the nostrils are small meaning the communication from the outside air into the anterior nasal cavity is relatively narrow. Despite this, neonates and children of up to 3 to 6 months of age have long been thought to be obligate nose breathers. This means these young children would be unable to effectively breathe through their mouths. However, babies will breathe through the mouth when crying. In addition, recent studies have shown that infants can breathe through their mouths during both spontaneous breathing and nasal occlusion. If unable to breathe through the nose the soft pallet will lift, creating a passage between the tongue and the soft pallet meaning air can pass from the oral cavity, through to the oropharynx. This means it is better to describe children in the first 6 months of life as preferential nose breathers. Nevertheless, under normal circumstances, neonates and young children do breathe predominantly through the nose.

Observation of nasal patency however, remains an important clinical observation as upper respiratory infections are common in this age group and these will stimulate mucus production. Mucus may still block the nostrils leading to airway compromise. The advantage of nasal breathing is that young children are able to suckle for prolonged periods, while breathing normally through their noses. Nasal breathing also allows children to swallow without aspiration of milk into the airways.

Tongue

The tongue grows less than other parts of the body, therefore it is relatively larger in younger children. If an adult or child is unconscious, the tongue may fall back, obstructing the airway, leading to blockage of the airway with consequent asphyxiation. As the tongue is larger in children, in comparison to the surrounding anatomical structures, this risk of airway obstruction is increased in younger children.

Head and neck

Infants have a relatively short neck, combined with the large head this tends to cause neck flexion, making airway control difficult if the level of consciousness is reduced.

Floor of the mouth

Basically, all of the cartilages in the upper airway of an infant are softer and more flexible than older children and adults. This lack of rigidity means structures not fully maintain the anatomical architecture due to lack of rigidity, meaning distortions may be caused. The patency of the upper airway is more likely to be distorted. For example, the infant floor of the mouth is less rigid than in adults and the mandible is shorter and less well formed. This means the floor of the mouth is easily compressible. This is why care must be taken not to distort these tissues if airway management is required.Adenoids and tonsils

The adenoids and tonsils, like all lymphoid tissue, will enlarge when infected. Although lymphoid tissue does act to fight infection sometimes bacterial and viruses can lodge within the lymphoid tissue and survive. This will lead to chronic infection and subsequent swelling caused by hypertrophy. Three to eight-year olds are prone to this chronic adenotonsillar hypertrophy, partly obstructing the upper airways. This is the most common cause of obstructive sleep apnoea before puberty. If enlargement is an ongoing problem the adenoids and tonsils may need to be surgically removed.

Epiglottis

The size and the position of the epiglottis are different in children. In an adult the epiglottis is typically more broad and rigid. In infants and young children, the epiglottis is relatively large, long, floppy, and narrow. Positionally it also projects posteriorly over the glottis at an angle of about 45o. The combination of a relatively large epiglottis and the position just above the opening of the airway means that if it becomes inflamed, the swollen structure has the potential to occlude the upper airway leading to obstruction. Bacterial infection of the epiglottis in early life can therefore lead to swelling and oedema which may block off the airway. Epiglottitis is classically associated with Haemophilus influenzae type b, but with the Hib vaccination this presentation is much less common. However, a range of other bacterial or viral infections can also cause epiglottitis.