OPTIMAL AEROSOL DELIVERY

Pressurised metered-dose inhalers (pMDIs), nebulisers and dry-powder inhalers (DPIs) aim to deliver aerosols to the lungs. With optimal technique, lung deposition ranges from below 10% to approximately 15%. pMDIs are the most frequently used device. Excellent hand-breath co-ordination is required for effective use of pMDIs. Optimal technique requires slow inspiratory flow of 30 l/min and a breath hold of 10 seconds. Deposition in crying infants is minimal. 'Blow-by therapy' of nebuliser or pMDI aerosol delivered close to the sleeping child's mouth and nose is ineffective. Spacers and valved holding chambers provide an additional volume in which medication is dispersed, before it is breathed into the lungs. DPIs overcome the difficulties of poor hand-breath co-ordination. Patients who are unable to generate sufficient inspiratory flow and depth of breathing to trigger DPIs should not use these devices. Patients must not exhale into the device prior to inspiration. Equivalent clinical results can be achieved from any delivery device, providing the patient can use it correctly. Selection of the appropriate device for each patient requires consideration of multiple factors. Inhaler technique should be demonstrated by the patient at each visit, assessed by the health-care provider, and where necessary, training to optimise aerosol delivery should be repeated.