title: Ratio between forced expiratory flow between 25% and 75% of vital capacity and FVC is a determinant of airway reactivity and sensitivity to methacholine.
abstract: OBJECTIVE
  The ratio between forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)) and FVC is thought to reflect dysanapsis between airway size and lung size. A low FEF(25-75)/FVC ratio is associated with airway responsiveness to methacholine in middle-aged and older men. The current study was designed to assess this relationship in both male and female subjects over a broader range of ages.
  
  
  METHODS
  Data analysis of consecutive subjects who had a >or= 20% reduction in FEV(1) after <or= 189 cumulative units of methacholine over a 7-year period.
  
  
  METHODS
  Pulmonary function laboratory in a university-affiliated hospital.
  
  
  METHODS
  A total of 764 consecutive subjects aged 4 to 91 years (mean +/- SD age, 40.8 +/- 19.6 years). There were 223 male (29.3%) and 540 female (70.7%) subjects.
  
  
  RESULTS
  Airway reactivity was assessed as the dose-response slope of the reduction in FEV(1) from baseline vs the cumulative dose of inhaled methacholine. The cumulative dose of methacholine causing 20% reduction in FEV(1) (PD(20)) was used as the indicator of airway sensitivity. In a linear regression model that included age, height, and percentage of predicted FEV(1), the FEF(25-75)/FVC ratio accounted for 7.6% of variability in airway reactivity (p < 0.0001, r(2) = 0.076). Subjects with higher airway sensitivity, indicated by lower PD(20), also had a lower FEF(25-75)/FVC ratio.
  
  
  CONCLUSIONS
  A low FEF(25-75)/FVC ratio, indicating small airway size relative to lung size, is associated with higher airway sensitivity and reactivity to methacholine in susceptible subjects.
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Memorial Hospital of Rhode Island and Brown Medical School, Providence, RI 02860, USA. Annie_Parker@brown.edu
authors.forename: Annie Lin
authors.initials: AL
authors.lastname: Parker
authors.forename: Muhanned
authors.initials: M
authors.lastname: Abu-Hijleh
authors.forename: F Dennis
authors.initials: FD
authors.lastname: McCool
mesh_terms: D000328:Adult; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D004305:Dose-Response Relationship, Drug; D005260:Female; D005540:Forced Expiratory Flow Rates; D005541:Forced Expiratory Volume; D006801:Humans; D016014:Linear Models; D008297:Male; D016210:Methacholine Chloride; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D013147:Spirometry; D014797:Vital Capacity
chemical_list: D016210:Methacholine Chloride