An audit of antiasthmatic drug inhalation technique and understanding

Abstract

Inhaled rather than oral antiasthmatic therapy is accepted as more advantageous but depends on patient technique and understanding. In 74 asthmatic outpatients, technique using metered-dose inhaler (MDI) was poor; in 56 patients inhaling β-agonist, the mean peak expiratory flow rate (PEFR) increase was only 15 L/min (6%) greater than in 16 controls, p < 0.05, 95% confidence intervals 2-27 L/min or 2-11%. Tilting the head back and actuation 'stopping' inspiration produced the least favorable PEFR responses; taken together, regression analysis yielded a statistically significant negative correlation with absolute or percentage PEFR change (R2 = 0.15; p < 0.02). Patients were unclear about which drugs to inhale as required or regularly. Among 19 patients reassessed inhaling β-agonist, only 6 had baseline PEFR values with in 10% of each other during both assessments. In the latter, the mean postinhalation PEFR increase was 36 L/min (or 13%) greater than the corresponding increase (or % change) at first assessment, p = 0.05 (0.08), 95% confidence intervals 0-73 L/min (-2 to 29%). Thus, MDI users should avoid tilting the head back, actuation stopping inhalation, and be more aware of prophylactic (steroid) versus symptomatic (β-agonist) treatment.