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Evaluation of the interrupter technique for measuring change in airway resistance in 5‐year‐old asthmatic children
Author(s) -
Phagoo S. B.,
Wilson N. M.,
Silverman M.
Publication year - 1995
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.1950200609
Subject(s) - repeatability , medicine , airway resistance , breathing , interrupter , methacholine , extrapolation , sensitivity (control systems) , oscillation (cell signaling) , forced oscillation , respiratory physiology , airway , anesthesia , cardiology , mathematics , statistics , respiratory system , physics , lung , electrical impedance , chemistry , biochemistry , respiratory disease , quantum mechanics , electronic engineering , engineering
The interrupter technique is a noninvasive method for measuring airway resistance during quiet breathing which requires minimal subject cooperation. It, therefore, has enormous potential for use in young children unable to cooperate with conventional lung function tests. We evaluated the interrupter technique during bronchial challenge with methacholine administered by the tidal breathing method in 10 5‐year‐old asthmatic children. The mouth pressure/time [P mo (t)] curve obtained following brief airflow interruption during the expiratory phase of quiet breathing was analyzed to determine the interrupter resistance R, int using four different methods: R intC , a smooth curve fit with back‐extrapolation; R intEO , calculated from the pressure change after the postinterruption oscillations had decayed (end‐oscillation); R intL two‐point linear fit with back‐extrapolation; and R intEL , calculated from the pressure change at the end of the period of interruption. The four R int methods were compared for repeatability and sensitivity with the direct measurement of resistance by the forced oscillation technique (R rs ) and with an independent method of measuring the response to challenge, utilizing the change in transcutaneous oxygen tension (P tcO2 ). The sensitivity of the methods was defined by a sensitivity index (SI), the change after challenge expressed in multiples of the baseline standard deviation. The P tCo2 method had the lowest variability and was by far the most sensitive method (geometric mean SI 18.9), at least 1 doubling concentration more sensitive than the other techniques in every subject (P < 0.05). R intL was more sensitive than the other interrupter methods (geometric mean SI: R intL 4.2; R intC 1.O; R intEO 2.7; R intEL 3.1; P < 0.05) and similar in sensitivity to R rs (geometric mean SI 4.6) in 7 out of 10 children in which this could be measured. We conclude that the interrupter method provides a simpler method than the oscillation technique for assessing airway obstruction in this age group. Pediatr Pulmonol. 1995; 20:387–395 . © 1995 Wiley‐Liss, Inc.