Practical problems with aerosol therapy in COPD

Inhaled aerosol drugs commonly used by patients with chronic obstructive pulmonary disease include short-acting and long-acting bronchodilators, as well as corticosteroids. These agents are available in a variety of inhaler devices, which include metered-dose inhalers (MDI), breath-actuated MDIs, nebulizers, and, currently, 5 different models of dry powder inhaler (DPI). There is evidence to suggest that multiple inhaler types cause confusion among patients and increase errors in patient use. Problems with MDIs include failure to coordinate inhalation with actuation of the MDI, inadequate breath-hold, and inappropriately fast inspiratory flow. Lack of a dose counter makes determining the number of remaining doses in an MDI problematic. Patient misuse of MDIs is compounded by lack of knowledge of correct use among health-care professionals. Several factors often seen with elderly patients have been identified as predictive of incorrect use of MDIs. These include mental-state scores, hand strength, and ideomotor dyspraxia. Holding chambers and spacers are partially intended to reduce the need for inhalation-actuation coordination with MDI use. However, such add-on devices can be subject to incorrect assembly. Possible delays between MDI actuation and inhalation, rapid inspiration, chamber electrostatic charge, and firing multiple puffs into the chamber can all reduce the availability of inhaled drug. Because they are breath-actuated, DPIs remove the need for inhalation-actuation synchrony, but there is evidence that patient errors in use of DPIs may be similar to those with MDIs. One of the biggest problems is loading and priming the DPI for use, and this may be due to the fact that every DPI model in current use is different. Medical personnel's knowledge of correct DPI use has also been shown to be lacking. The optimum inhalation profiles are different for the various DPIs, but, generally, chronic obstructive pulmonary disease patients have been shown to achieve a minimum therapeutic dose, although the inhaled amount may be suboptimal. A limitation of DPIs that have multidose powder reservoirs (eg, the Turbuhaler) is ambient humidity, which can reduce the released dose. Small-volume nebulizers are limited by bulk, treatment time, and variable performance, but are easy for patients to use. Important features identified by patients for an ideal inhaler are ease of use during an attack, dose counter, and general ease of use and learning. A breath-actuated-pMDI, such as the Autohaler, ranked at the top of inhaler preference in a study of 100 patients with airflow obstruction, compared to DPIs and MDIs. Short of a universal simple inhaler, patient and caregiver education remains the best solution to correct patient errors in use.