Ratio between forced expiratory flow between 25% and 75% of vital capacity and FVC is a determinant of airway reactivity and sensitivity to methacholine.
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.
Parker
Annie Lin
AL
Department of Pulmonary and Critical Care Medicine, Memorial Hospital of Rhode Island and Brown Medical School, Providence, RI 02860, USA. Annie_Parker@brown.edu
Abu-Hijleh
Muhanned
M
McCool
F Dennis
FD
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
D016210:Methacholine Chloride