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Peak expiratory flow rate monitoring in asthma

INTRODUCTION

The management of asthma depends in part on the ability of patients to monitor their condition on a regular basis. Self-monitoring can be performed by subjectively evaluating the frequency and severity of symptoms (algorithm 1). Patients can gain further information by monitoring peak expiratory flow rates (PEFRs), which provide an objective measurement of airflow obstruction, and can performed accurately by most adults and children older than five years of age. Peak expiratory flow rate monitoring in patients with asthma will be reviewed here. Other aspects of asthma management are presented separately. (See "An overview of asthma management" and "Patient information: Asthma treatment in adolescents and adults".)

ROLE OF PEFR MONITORING

Long- or short-term daily PEFR monitoring can provide the patient and clinician with objective data upon which to base therapeutic decisions [1]. However, adherence to long-term monitoring is difficult to maintain [2]. According to some reports, adherence with home PEF recording is satisfactory in the short term, but falls off considerably after several months. This suggests a significant limitation to this form of monitoring [3,4]. While patient adherence to PEFR monitoring is highly variable, connecting its use to the production of data relevant to concrete self-management activities may increase adherence [5].

Further research on the efficacy of regular peak flow monitoring by patients is needed. To date, studies evaluating the efficacy of PEFR monitoring for improving various outcome measures in asthma have not consistently supported this practice [6-17]. A number of studies have failed to demonstrate an advantage of using PEFR monitoring over monitoring of symptoms to base self-management actions [6-8,11,13-15]. Studies that demonstrated an improvement in outcomes, such as decreased health care utilization and improved quality of life, included a comprehensive management approach, which did not separate out the specific effect of PEFR monitoring [9,12].

The most conservative approach is to have patients monitor their condition using both objective and subjective measures [18-20]. This can be accomplished by using a patient diary to record daily PFM readings and the presence of any asthma symptoms. This dual approach may help patients observe a cause-and-effect relationship between exposure to triggers and decrements in peak flow and/or exacerbations of asthma. The patient should understand that such monitoring is undertaken to check on the effectiveness of therapy and to give early warning of potential deterioration [20].

Patients with moderate-to-severe persistent asthma should monitor both the PEFR and their symptoms in an asthma monitoring diary. Examples of asthma monitoring diaries that can be printed and given to patients are provided (algorithm 1 and graph 1 and table 1) [21]. Note that the diary can also be used to track medication use. Values can be compared to age-, gender- and height-matched normal subjects (table 2A-C)(calculator 1). The predicted values for black and Hispanic minorities are approximately 10 percent lower than those shown in the tables [22].
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References Top
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