Dry Powder Inhalers: Which Factors Determine the Frequency of Handling Errors?

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Abstract
Dry powder inhalers are often used ineffectively, resulting in a poor level of disease control. To determine how often essential mistakes are made in the use of Aerolizer, Discus, HandiHaler and Turbuhaler and to study the effects of age, severity of airflow obstruction and previous training in inhalational technique by medical personnel on the error rate. Two hundred and twenty-four newly referred outpatients (age 55.1 +/- 20 years) were asked how they had been acquainted with the inhaler and to demonstrate their inhalational technique. The inhaler-specific error rates were as follows: Aerolizer 9.1%, Discus 26.7%, HandiHaler 53.1% and Turbuhaler 34.9%. Compared to Aerolizer, the odds ratio of an ineffective inhalation was higher for HandiHaler (9.82, p < 0.01) and Turbuhaler (4.84, p < 0.05). The error rate increased with age and with the severity of airway obstruction (p < 0.01). When training had been given as opposed to no training, the odds ratio of ineffective inhalation was 0.22 (p < 0.01). If Turbuhaler is used, the estimated risks range from 9.8% in an 18-year-old patient with normal lung function and previous training to 83.2% in an 80-year-old patient with moderate or severe obstruction who had not received any training. Dry powder inhalers are useful in the management of younger patients with normal lung function or mild airway obstruction. In older patients with advanced chronic obstructive pulmonary disease, the risk of ineffective inhalation remains high despite training in inhalational technique. A metered-dose inhaler with a spacer might be a valuable treatment alternative in a substantial proportion of these patients.