An isoflow-volume technique for assessing airway dynamics in children and adults.
BACKGROUND
We propose a new approach to the measurement of small airway function as an alternative to recordings of maximal expiratory flow-volume (MEFV) curves.


OBJECTIVE
A newly developed technique to record isoflow-volume (IFV) curves to be tested against maximal respiratory flow curves.


METHODS
An isoflow whistle (IFW; Iflopen) measures the length of a constant expiration after full inspiration. The note of the whistle enables a subject to generate an even expiration, and the isoflow maintenance times at 1 l x s(-1) (IFMT1) and 2 l x s(-1) (IFMT2) are recorded. The accuracy and reproducibility of the IFV technique were evaluated in 17 healthy adults (age 17-55 years) and in 14 asthmatic children (age 6-14 years). Comparisons with standard lung function parameters, such as forced expiratory volume in 1 s (FEV1), maximal expiratory flow at 50% (MEF50) and 25% (MEF25) vital capacity and peak expiratory flow (PEF), obtained with a Wright Peakflow Meter were undertaken in 102 healthy (aged 8-14 years) and 101 asthmatic children (aged 6-17 years). A bronchial challenge test was performed in 13 asthmatic children.


RESULTS
The expired volume measured by the IFW showed an acceptable agreement with that of a pneumotachograph (mean error of 4.32% for IFMT1 and 5.93% for IFMT2). In healthy and in asthmatic children, the correlations between FEV1 and IFMT1 or IFMT2 (r = 0.92 and 0.94, respectively) were found to be greater than that between FEV1 and PEF (r = 0.68). During bronchial challenge tests in 13 asthmatic children, the FEV1 decreased to 69% of baseline and IFMT1 to 58% of baseline.


CONCLUSIONS
The IFV technique accurately measured airway obstruction and closely followed changes in standard parameters of the MEFV curve.
Schibler
A
A
Division of Pediatric Respiratory Medicine, Department of Pediatrics, University of Berne, Inselspital, Berne, Switzerland. andreas.schibler@insel.ch
Frey
U
U
Kraemer
R
R
D000293:Adolescent; D000328:Adult; D000402:Airway Obstruction / Q000175:diagnosis* / Q000503:physiopathology*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008449:Maximal Expiratory Flow-Volume Curves; D008875:Middle Aged; D012123:Pulmonary Ventilation; D015203:Reproducibility of Results