The aim of this study was to assess the patients' use of inhaled short acting bronchodilators as rescue therapy during a 4-week study period. In this study an electronic metered-dose inhaler compliance monitor (MDI-CM) was used to measure the time and date of actuations of the device and this information was then compared with the patients' self reporting diary card (DC). Salbutamol canisters were used in the compliance monitor. The study was approved by the local ethics committee, and written informed consent was obtained from all patients. Patients aged 18 years and over who were either receiving, or in the investigators opinion required, inhaled salbutamol on a PRN basis were enrolled for a 4-week monitoring phase during which all rescue salbutamol used was obtained from the MDI-CM. Patients were recording their use of salbutamol in the DC each morning and evening. There was a 2-week follow-up period following completion of the monitoring phase or withdrawal from the study. Forty-four patients were enrolled and 35 patients completed the study. The mean age (range) was 43 (20–76) years and mean FEV₁ 2·32 (0·7-4·0) 1, with male:female ratio of 19:25. Comparison of MDI-CM and DC recordings showed patients fell into three categories: (1) patients who used rescue salbutamol appropriately and whose MDI-CM and DC recordings matched closely; (2) patients who used rescue salbutamol for acute relief but whose MDI-CM and DC recordings did not correlate and (3) patients whose use of rescue salbutamol was inappropriate or erratic according to the MDI-CM but whose DC indicated good compliance. This category of patients include those who ‘dumped’ all their salbutamol before attending clinic appointments. There was no significant difference in the demographic details or the severity of disease in the three groups.

Recorded use of ‘rescue’ bronchodilator is frequently used as an indicator of efficacy for new anti-asthma therapies. This study comparing electronic data monitoring and remembered rescue salbutamol highlights the potential errors that can occur without accurate recording systems.