Changes in peak expiratory flow indices as a proxy for changes in bronchial hyperresponsiveness

Abstract

Guidelines for asthma management advocate home peak expiratory flow (PEF) monitoring. It is commonly stated that PEF variability is a good proxy of bronchial hyperresponsiveness (BHR), a hallmark of asthma. However, this has hardly been tested longitudinally, as required to monitor asthma. This study assesses which PEF index correlates best with BHR longitudinally and whether the correlation improves when correcting PEF values for the known nonlinearity of mini-Wright PEF meters.Every 6 months, for a period of 2 yrs, PEF diary cards were filled in and BHR to histamine was tested in 104 patients with BHR and reversible airways obstruction, who started treatment with bronchodilators with (n=33) or without (n=71) inhaled corticosteroids. Within each subject, PEF indices and BHR were correlated longitudinally.The highest median correlation coefficients were obtained in the group of patients using inhaled corticosteroids. The PEF indices providing the best correlation with BHR were: mean PEF bronchodilator response (r=-0.50) and within-day variation (% mean or % maximum) (with postbronchodilator values, r=-0.50; without postbronchodilator values, r=-0.40). Using PEF data corrected for the nonlinearity of the PEF meters did not result in higher correlation coefficients.Since current guidelines on asthma management recommend only bronchodilators on demand, the most useful peak expiratory flow index for reflecting bronchial hyperresponsiveness longitudinally is mean within-day peak expiratory flow variation (% mean or % maximum) (without postbronchodilator values). Since the correlation coefficients are not very strong, the authors suggest that peak expiratory flow measurements are not used as a proxy for bronchial hyperresponsiveness longitudinally but as a measurement in its own right. The use of corrections of peak expiratory flows for the nonlinearity of mini-Wright peak expiratory flow meters does not improve the correlation between peak expiratory flow and bronchial hyperresponsiveness. Eur Respir J 2000; 16: 220±225.

Targeting pCO2 in Asthma: Pilot Evaluation of a Capnometry-Assisted Breathing Training

“…Thus, improvement through training extended beyond patients' perception of their disease to a somatic outcome measure central to the pathophysiology of asthma. Although the relationship between PEF variability and airway hyperresponsiveness has been debated (Douma, Kerstjens, Roos, et al, 2000;Reddel, Salome, Peat, et al, 1995), such findings are compatible with prior findings of a negative correlation between pCO 2 and hyperresponsiveness to methacholine challenge (Osborne et al, 2000). It is likely that additional benefits of an adjunctive breathing training will be less apparent in basal lung function (or only be visible in more direct measures of airway obstruction) than in a reduction of fluctuations in symptoms.…”

Questionnaires, spirometry and PEF monitoring in epidemiological studies on elderly respiratory patients

“…Monitoring of PEF variability alone is not able to identify the deterioration in FEV1 as well as the provocative dose of histamine causing a 20% fall in FEV1 in patients on long-term inhaled corticosteroids, and the increase in symptom score is not always related to an increase in PEF variability [53]. Similar poor correlation is found when, within each subject, PEF variability and BHR are correlated longitudinally [54]. Thus, PEF variability may represent something different from symptoms and BHR, and PEF evaluation may be helpful in optimising asthma control.…”

Underestimation of the peak flow variability in asthmatic children: Evaluation of a new formula

“…5 Although many consensus statements recommend measuring PEF variability as a surrogate of bronchial hyperresponsiveness, only few cross-sectional studies yield some support to this advice 1,4,15 and, by contrast, some other works showed poor agreement between PEF variability and airway hyperresponsiveness or asthma diagnosis. [20][21][22][23][24] These contrasting reports, and the discrepancy between the clinical and functional patient classifications found in our study, pointed out that the usefulness of PEF variability will remain low as long as the timing for PEF measurements is not well standardized and, more important, comprehensive knowledge about how to interpret it can be gained.…”