Are peak flow and symptom measures good predictors of asthma hospitalizations and unscheduled visits?†

Epidemiologic studies of pediatric respiratory health often include objective measures such as peak expiratory flow (PEF), and subjective measures such as symptom reports. These measures, however, are poorly correlated with each other, and there is little evidence that PEF is useful in predicting important health outcomes. Within a cohort of 791 inner-city children with asthma, we examined correlations between a series of five peak flow measures and five symptom scores obtained from 2-week diaries. The strongest correlations were found between "total peak flow lability" defined as: [(diary maximum - diary minimum)/diary mean] and "% of days with chest tightness" (r = 0.31). Logistic models evaluated peak flow and symptoms as predictors of an important health outcome: hospitalization or emergency department or unscheduled clinic visit for asthma within 30 days of starting the diary. Each of the peak flow and symptom measures was significantly related to utilization. However, the predictive power of each measure was low (range of area under ROC curve, 0.54-0.67). Models including only peak flow or symptoms had greater prediction than models with risk factors such as atopy, asthma persistence, and age. The prediction from a model with the risk factors and symptoms was not improved by adding a peak flow measure to the model (increase in area under ROC, 0.67-0.68). Stratified analyses suggest that prediction was similar in the fall vs. winter, spring, and summer months. Greater prediction of health outcomes was found among more persistent asthmatics and children who were nonatopic. These findings suggest that in a research setting, peak flow monitoring in children did not add prediction beyond that obtained from symptom reports. Pediatr Pulmonol. 2001; 31:190-197. Published 2001 Wiley-Liss, Inc.     

Mechanisms of exercise-induced asthma

In a previous review in this journal McFadden eloquently presented the findings which led him and his colleagues to propose that respiratory heat loss and the subsequent cooling of the airways are the initial reaction sequence leading to airway obstruction in hyperventilation and exercise-induced asthma [62]. He further concluded that: “Exercise per se is not essential and serves only as means to increase ventilation”. Our interpretation of currently available data has led us to conclude that while respiratory heat loss may play an important permissive role in initiating the bronchoconstriction which follows exercise, the weight of evidence indicates that exercise per se serves as the trigger mechanism and is not just a tool to increase ventilation. Moreover, we believe that the role of exercise in releasing chemical mediators has been established, although pathways by which the airway smooth muscle is affected are still uncertain.     

普米克令舒、博利康尼雾化吸入治疗轻中度支气管哮喘的临床研究

目的探讨联合雾化吸入普米克令舒、博利康尼对轻中度支气管哮喘的治疗作用。方法51例支气管哮喘患者随机分为对照组（25例）和治疗组（26例）。两组均予吸氧、抗感染、静脉氨茶碱及对症等治疗。治疗组加用普米克令舒及博利康尼氧气雾化吸入。两组均于治疗前及治疗7天后测定肺功能及动脉血气。结果两组肺功能及PaO2较治疗前均有明显改善（P〈0．01或P〈0．05）。结论联合雾化吸入普米克令舒和博利康尼治疗轻、中度支气管哮喘安全有效，并有协同作用。