Predictors of correct technique in patients using pressurized metered dose inhalers

Background: Correct inhaler technique is recommended by guidelines for optimum asthma care. The objective of the study is to determine real life predictors of correct pressurized metered dose inhaler ( pMDI) technique in Asthma and COPD patients. Methods: Two hundred eight adult patients aged 18+ from respiratory outpatients ( 69.2%) and the community on regular pMDI for a diagnosis of Asthma ( 78.9%) or COPD, were recruited. A questionnaire containing 31 possible predictors was administered and pMDI technique with or without spacer was observed by trained researchers on 12 point steps, of which 4 were considered critical. Results: 23.1% of patients had no errors in inhaler technique and 32.2% had no critical errors. Patients had a median of 10 correct steps ( IQR9- 11), and 3( IQR2- 4) correct critical steps. Using binary logistic regression the predictors of 10 correct steps were, other healthcare professional ( pharmacist, nurse, physiotherapist) explained OR 3.73( 1.63- 8.54, p = 0.001), male gender 2.70( 1.35- 5.39, p = 0.004), self- score 1- 10 1.21( 1.05- 1.39, p = 0.007), spacer use 0.38( 0.19- 0.79, p = 0.007), inhaled steroid 3.71( 1.34- 10.25, p = 0.01), heart disease 0.31( 0.13- 0.77, p = 0.01), pneumococcal vaccine 2.48( 1.0- 6.15, p = 0.043), education level 1- 4 1.44( 1.00- 2.06, p = 0.05) and respiratory physician explained 0- 7 times, 1.11( 0.99- 1.26, p = 0.08). Using ordinal logistic regression, predictors for correct critical steps 0- 4, were: technique self- score 1- 10 1.2( 1.05- 1.42, p = 0.006), inhaled corticosteroid use 2.78( 1.1- 7.31, p = 0.03) and education level 1- 4 1.41( 1.02- 1.95, p = 0.03 Times respiratory physician explained inhaler technique 0- 7 1.1( 0.98- 1.24, p = 0.1), married status 1.55( 0.85- 2.82, p = 0.15), hypercholesterolaemia 0.52( 0.25- 1.01, p = 0.054) and male gender 1.76( 0.97- 3.18, p = 0.06). Conclusions: Known predictors of correct pMDI use, such as gender and education level were confirmed, while age and concomitant use of dry powder inhaler were not. Pneumococcal vaccination and awareness of steroid side effects were possible novel positive predictors, while the use of a spacer and co- morbidity with heart disease were found to be negative predictors. Patients' self- assessment correlated well with actual performance. This information may be useful in defining approaches to optimize inhaler techniques which are so susceptible to human error.