Inhalation technology: From the lab to the patient

Abstract

In most cases, the initial diagnosis and treatment of asthma and COPD takes place in the GP's surgery and also at home. Many inhalation devices and molecules are currently being applied in the treatment of these patients. Ideally, there is optimal matching between characteristics of the patient him/herself, the location of the disease process, and the specific inhalation device applied to target the disease process in that particular patient. The workshop on Inhalation Technology covers inhalation devices, factors influencing dose delivery and drug deposition, and ways of improving the deposition of inhaled drugs in the lungs. The aim of this module is to arm participants with the ability to judge inhalation therapy literature critically and make rational choices between devices for individual patients with asthma and COPD. This workshop is composed of four sections: - Devices - Flow and resistance as factors influencing drug dose delivery and deposition - Ways of improving drug deposition - Making a optimal choice for the individual patient Devices: In this section the participants are asked to describe the essential differences between pressurised metered-dose inhalers (pMDIs) and dry powder inhalers (DPIs), the principles of dose delivery in the two types of devices, and the significance of particle mass distribution in drug deposition. At the end of this section, participants will have learnt that in pMDIs delivery force is provided by propellant rather than, as it is in DPIs, the patient's inspiratory flow; that there is a larger variation between dose delivery with DPIs than pMDIs; and that with pMDIs, unlike DPIs, dose delivery and particle mass distribution are independent of inspiratory flow. Flow and resistance as factors for dose delivery and deposition: This section aims to discuss the relationships between the patient's inspiratory flow, resistance in the device, dose delivery, and deposition. It explains how some DPIs can have high internal resistance, such that the patient will have to exert more effort to achieve an adequate inspiratory flow. The slides present data illustrating how in DPIs but not pMDIs inspiratory flow is the most important factor in deposition as it determines dose delivery and particle size, and offer an opportunity to test participants' understanding of this relationship. The practical significance of the relationship is illustrated in an acute wheezing episode. Ways of improving deposition: In this section participants are invited to discuss when and how spacers can be best used to improve deposition of drug in the lungs. It demonstrates how spacers increase the respirable fraction of a dose of drug, while having little effect on respirable mass, and reduce oropharyngeal deposition. Some recommendations for optimal use of spacers are presented with clinical data illustrating the rationale behind them. This section also discusses how breath-actuated pMDIs, like spacers, can improve drug deposition in patients with poor coordination. Making a choice for the individual patient: In an interactive way, participants are invited to compose decision trees that will help them to select the most suitable inhaler for an individual patient according to the factors they have learnt to be relevant in the first three sections.