Recommendations for the management of asthma include teaching patients how to monitor their peak expiratory flow rate and adjust their medications accordingly. Patients who are given this information may have a better awareness of their disease and may require urgent treatment for exacerbations of asthma less frequently. Cowie and associates performed a randomized, controlled trial to assess the effectiveness of an action plan based on peak expiratory flow measurements in preventing acute exacerbations of asthma.

The study included 150 adults and adolescents who had required emergency treatment for asthma in the preceding 12 months. All of the patients were given individualized instructions concerning the nature of their disease, asthma triggers, medication use and use of an inhaler.

The patients were randomly assigned to one of three groups. The first group (52 patients) received no action plan. The patients were given verbal information about the variability of asthma and were told that adjustment of their medications might be necessary periodically. The 50 patients in the second group were given written instructions with an action plan based on their symptoms of asthma. The plan included a series of steps whereby they would double the use of inhaled corticosteroids if they noted awakening at night because of asthma symptoms, a persistent cough or symptoms of a cold. They were instructed to begin taking oral corticosteroids if relief from the inhaled bronchodilator lasted less than two hours. They were also told to seek urgent treatment if the bronchodilator provided symptomatic relief for less than 30 minutes or if they were having difficulty speaking. The 48 patients in the third group were given an action plan based on their peak expiratory flow measurements. Each patient was given written instructions about peak flow readings at or below which each step in the action plan should be instituted. A doubling of inhaled corticosteroid dosage was recommended if the peak flow rate was less than 70 percent of the estimated best reading. If the peak flow rate was less than 50 percent, patients were instructed to start taking oral prednisone. If the peak flow rate was less than 30 percent of the predicted value, they were told to seek treatment in the emergency department.

During six months of follow-up, patients who were not given an action plan required 55 visits for urgent treatment of asthma exacerbations. Those following an action plan based on their asthma symptoms required 45 visits for urgent treatment. The difference in the number of urgent care visits was not statistically significant in these two groups. In contrast, only five visits for urgent care were required by the group that followed an action plan based on peak flow measurements. All three groups had a decrease in nocturnal symptoms and in the use of beta₂ agonists (an average decrease of 4.45 doses per day by the end of the study). The authors conclude that an action plan based on peak flow measurements is associated with a significant reduction in the need for urgent treatment of asthma.