The Utility of Forced Expiratory Flow between 25% and 75% of Vital Capacity in Predicting Childhood Asthma Morbidity and Severity

Abstract

Objective The forced expiratory volume in one second (FEV1), felt to be an objective measure of airway obstruction, is often normal in asthmatic children. The forced expiratory flow between 25% and 75% of vital capacity (FEF25-75) reflects small airway patency and has been found to be reduced in children with asthma. The aim of this study was to determine if FEF25-75 is associated with increased childhood asthma severity and morbidity in the setting of a normal FEV1, and to determine if bronchodilator responsiveness (BDR) as defined by FEF25-75 identifies more childhood asthmatics than does BDR defined by FEV1. Methods The Children’s Hospital Boston Pulmonary Function Test database was queried and the most recent spirometry result was retrieved for 744 children diagnosed with asthma between 10–18 years of age between October 2000 and October 2010. Electronic medical records in the 1 year prior and the 1 year following the date of spirometry were examined for asthma severity (mild, moderate or severe) and morbidity outcomes for three age, race and gender-matched subgroups: group A (n= 35) had a normal FEV1, FEV1/FVC and FEF25-75; Group B (n= 36) had solely a diminished FEV1/FVC; and Group C (n=37) had a normal FEV1, low FEV1/FVC and low FEF25-75. Morbidity outcomes analyzed included the presence of hospitalization, emergency department visit, intensive care unit admission, asthma exacerbation, and systemic steroid use. Results Subjects with a low FEF25-75 (Group C) had nearly 3 times the odds (OR 2.8, p<0.01) of systemic corticosteroid use and 6 times the odds of asthma exacerbations (OR 6.3, p>0.01) compared with those who had normal spirometry (Group A). Using FEF25-75 to define bronchodilator responsiveness identified 53% more subjects with asthma than did using a definition based on FEV1. Conclusions A low FEF25-75 in the setting of a normal FEV1 is associated with increased asthma severity, systemic steroid use and asthma exacerbations in children. In addition, using the percent change in FEF25-75 from baseline may be helpful in identifying bronchodilator responsiveness in asthmatic children with a normal FEV1.

Association of FEF25-75% Impairment with Bronchial Hyperresponsiveness and Airway Inflammation in Subjects with Asthma-Like Symptoms

“…In the literature, FEF 25-75% was validated as a marker able to predict high Fe NO levels in asthmatic children [13] and correlated with Fe NO in terms of percent change in improvement after 6 weeks of inhaled corticosteroid treatment in controlled asthmatic children [29]. In addition, Rao et al [30] observed that in children, a low FEF 25-75% associated with a normal FEV 1 is linked to increased asthma severity, systemic steroid use and asthma exacerbations. Using the percent change in FEF 25-75% from baseline might be helpful in identifying bronchodilator responsiveness in asthmatic children with normal FEV 1 [30].…”

“…In addition, Rao et al [30] observed that in children, a low FEF 25-75% associated with a normal FEV 1 is linked to increased asthma severity, systemic steroid use and asthma exacerbations. Using the percent change in FEF 25-75% from baseline might be helpful in identifying bronchodilator responsiveness in asthmatic children with normal FEV 1 [30]. In our study, FEF 25-75% , expressed both as z-score and percent of predicted, is strongly related to sputum eosinophil and Fe NO values in subjects with asthma-like symptoms.…”

Forced expiratory flows’ contribution to lung function interpretation in schoolchildren

“…In a large population of asthmatic children aged 10-18 years, the authors used a 30% baseline increase (corresponding to one standard deviation from the mean without controlling for FVC changes) to define a meaningful post-BD increase in FEF25-75%, which increased by 53% the frequency of spirometry reversibility compared to the reversibility based on FEV1 changes [33]. However, the use of such a threshold in our healthy population would have led to diagnosing FEF reversibility in nine children (14.7%, of whom only two had FEV1 reversibility), a higher prevalence than that of asthma in French schoolchildren [34].…”

Small airway dysfunction is associated with poorer asthma control

“…In a prospective follow-up study [6] of initially controlled asthmatic children, the same authors observed a significant difference in FEV1/FVC but not FEF25-75% at baseline, but for both FEV1/FVC and FEF25-75% at follow-up after 3 months, comparing those who remained controlled with those who subsequently became uncontrolled. In a similar design to the present study, over 2 years, using electronic prescribing linkage, RAO et al [7] compared matched groups of asthmatic children who had a preserved FEV1 (.80% pred), an abnormal FEV1/FVC (,0.85) and FEF25-75% (,60%) with those with normal values, showing significantly increased odds ratios for loss of control in terms of oral steroid use, asthma exacerbations and controller use.…”