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Asthma patients often use peak expiratory flow meters, a short tube they blow into to measure the force of expiration (peak expiratory flow rate, PEFR), to determine how well their lungs are functioning. The National Institutes of Health (NIH) guidelines for assessing and treating asthma suggest that clinicians routinely measure PEFR and inquire about symptoms such as wheezing or shortness of breath. However, a study of adults receiving asthma medications from 35 community drugstores found that a quality-of-life measure was a much better predictor of subsequent asthma exacerbations (breathing-related emergency department visits or hospitalizations) than an isolated measurement of PEFR.
This finding supports the NIH recommendations for assessing asthma symptoms and their impact on patients, but it certainly does not mean that monitoring PEFR has no role in asthma care, explains William M. Tierney, M.D., of Indiana University School of Medicine, Regenstrief Institute for Health Care. Dr. Tierney and his colleagues administered the McMaster Asthma Quality of Life Questionnaire (AQLQ) and measured PEFR for each patient to determine their ability to predict breathing-related emergency department (ED) visits and hospitalizations within 4 and 12 months after study enrollment. Their work was supported in part by the Agency for Healthcare Research and Quality (HS09083).
A red zone PEFR (50 percent of predicted PEFR based on age and other factors) indicated nearly twice the likelihood of asthma-related ED visits and hospitalizations within 12 months. However, neither a red zone PEFR, the raw PEFR, or percent of predicted maximal PEFR were significantly predictive when controlling for AQLQ scores, clinical characteristics, or demographic data. In contrast, the four subscales of the AQLQ (activities, symptoms, emotion, and environment) were each significant predictors of asthma exacerbations. A patient with an overall AQLQ score greater than 5 was almost three times as likely to have an asthma-related ED visit or hospitalization during the year as a patient with a score of less than 4.
See "Assessing symptoms and peak expiratory flow rate as predictors of asthma exacerbations," by Dr. Tierney, J. Franklin Roesner, M.D., Roopa Seshadri, Ph.D., and others, in the March 2004 Journal of General Internal Medicine 19, pp. 237-242.
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