3 The Technology

3 The Technology

3.1 It is important to ensure that an inhaler device delivers the drugs to the airways consistently and in the appropriate quantity. There are a variety of inhaler devices that can be used in the management of asthma: hand held inhalers i.e. pressurised metered dose inhalers (pMDIs) (which can be breath activated or manual) and dry-powder inhalation systems (DPIs) and nebulisers. All the metered dose inhaler systems require co-ordination of activation and inhalation and may be difficult to use, particularly for younger children. For this reason a pMDI should be combined with a spacer device in young children. The purpose of the spacer device is to act as an intermediary chamber into which the pMDI can discharge the drug allowing the child to inhale over several breaths.

3.2 The inhalation devices have different mechanical characteristics which, combined with child and carer factors, leads to variation in both the quantity of drug delivered by the device and the amount actually deposited in the lung. Using the appropriate inhalation device is important to ensure reproducibility and consistency of drug dosing, as well as compliance for which child and carer acceptability and education regarding device usage may also be major factors.

3.3 The 1997 BTS Guidelines recommend the following device choices for children of under 5 years of age:

Age Group

1st Choice Device

2nd Choice Device

3rd Choice Device

Breath-actuated

Dry-powder

0-2 years inclusive

MDI + spacer + face mask

MDI + spacer

Nebuliser (rarely needed)

Avoid

Avoid

3-5 years inclusive

MDI + spacer

MDI + spacer + face mask

Nebuliser (rarely needed)

Not proven

Possible use for ß2-agonist but not recommended for corticosteroids

3.4 Interpretation of the evidence base for effectiveness of inhaler devices is influenced by a number of potential factors – the drug being delivered by the device, the severity of asthma, whether the condition is acute or chronic and the ability of the child/carer to effectively use the device. Moreover it is not possible to directly extrapolate to children under the age of five years, data collected in older children and adults, as the young child's anatomy and physiology may substantially alter the amount of drug delivered.