Headbox or body/trunk box

This method of oxygen delivery is normally most suitable for infants and small children. The advantages of these types of device are that they give effective oxygen delivery, it is possible to reliably monitor the FiO₂ and they are totally non-invasive. Disadvantages are that carbon dioxide re-breathing will occur at low oxygen flow rates, <4 L/min (Frey & Shann 2003), removal of the box quickly dilutes the oxygen delivered and a cold gas supply will quickly cool an infant. It is also desirable to humidify when prolonged oxygen therapy is required (Chandler 2001, Frey & Shann 2003, Pilkington 2004). Normally, inspired gas is warmed and humidified in the nasopharynx and reaches the upper trachea with a relative humidity of about 90% and a temperature of 32–36°C; it has reached a temperature of 37°C by the time it reaches the alveoli (Hazinski 1998). Mucociliary transport is impaired when relative humidity falls below 75% at 37°C (Pilkington 2004).

Nasal cannula

Nasal cannulae are available in different sizes, suitable for neonates through to adults. Advantages of nasal cannula are that they are reasonably well tolerated by children (particularly in comparison with an oxygen mask) and carbon dioxide re-breathing does not occur (Chandler 2001). Humidification is not necessary as the gas is entering via the nasal passages where it is warmed and moistened in the normal way (Frey & Shann 2003). Disadvantages are that nasal cannula are only suitable for use with a low flow of oxygen, i.e. maximum 2 L/min in neonates. Higher flows (>4 L/min) may be uncomfortable and dry the nasal mucosa (McGloin 2008). It is usually only possible to achieve an oxygen concentration of approximately 40–60% (EPLS 2006). In addition, a child who mouth breathes will dilute the FiO₂ with air and oxygen concentrations are very dependent upon the infant or child’s breathing pattern.

One major hazard to be aware of is the risk of strangulation that nasal cannula can present if the child is not closely observed. This risk can be reduced by taking the tubing behind the child’s head and not underneath their chin as is common in adult practice.

Oxygen masks

They are available in two sizes; paediatric and adult. Advantages are that oxygen masks without a reservoir bag can deliver concentrations of up to 60% and with a reservoir up to 95% or higher (EPLS 2006). Humidification can also be provided. Disadvantages are that the mask needs to be well fitting which can be problematic if a baby or child is in-between sizes of mask. Additionally, they can become hot and uncomfortable leading to non-compliance.

Healthy children

Healthy children should have an arterial oxygen saturation level of 95–98% (Balfour-Lyn et al 2005). However, some children with chronic lung disease or who have cyanotic heart conditions may have an oxygen saturation level well below this, even when otherwise healthy. It is therefore essential for nurses to be aware of the child’s ‘norm’ and parents are a vital source of such information.

Neonates

Administration of continuous oxygen therapy to neonates must be monitored very carefully. High inspired oxygen concentrations have been clearly linked to the development of retinopathy of prematurity and prolonged exposure to high oxygen tensions may also cause pulmonary oxygen toxicity and permanent lung damage, e.g. bronchopulmonary dysplasia (BMA 2006, Kotecha & Allen 2002). However, very little is known about how much oxygen is safe to give and the target range of oxygen saturations in neonates is controversial (Tin & Gupta 2007). Recent studies have suggested that saturations of 92–94% in infants, particularly during the pre-term period, may be ideal (Askie et al 2003, Anon 2000).

Sick children

Children with respiratory problems may benefit from being nursed upright, well supported with pillows. An infant may benefit from being placed in a baby chair for periods of up to 4 h or longer if absolutely necessary. Any child should have a change of position 4-hourly if possible, to relieve pressure areas. If the child is too ill to sit up, consider tilting up the head of the bed or cot.

Recent studies have demonstrated that a child with chronic lung disease can and should have oxygen saturations maintained around 92–94% to provide a buffer zone against desaturation during sleeping and feeding. These targets also aim to reduce complications from pulmonary artery hypertension and promote growth (Kotecha & Allen 2002). However, in a small number of children with chronic lung disease, e.g. some children with cystic fibrosis, the dependence of respiratory drive on CO₂ and bicarbonate concentration is lost. In these children, inflammatory changes in the lungs result in increased alveolar CO₂ tension, which ultimately leads to a gross saturation of the chemoreceptors, making them dysfunctional. Administering high concentrations of oxygen to these children can cause carbon dioxide narcosis leading to unconsciousness (Chandler 2001). The BMA (2005) states that any patient with a chronic chest condition should not be administered more than 28% concentration of oxygen alongside repeated blood gas measurements.