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Airway resistance by the interrupter technique: Which algorithm for measuring pressure?
Author(s) -
Pao C.S.,
Healy M.J.R.,
McKenzie S.A.
Publication year - 2004
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.10364
Subject(s) - medicine , algorithm , confidence interval , asymptomatic , airway resistance , limits of agreement , airway , anesthesia , nuclear medicine , mathematics , surgery
Airway resistance using the interrupter technique (R int ) can be measured using commercial devices which employ different algorithms for estimating pressure change. We aim to describe differences in R int due to algorithm. We compared R int and change in R int after bronchodilator, using four algorithms to estimate pressure change following interruption: 1) two‐point back‐extrapolation to interruption from points 70 msec and 30 msec from interruption, and similarly 2) to 15 msec from interruption, 3) at two‐thirds from interruption, and 4) near end‐interruption. Flow was measured immediately before interruption. Our subjects were 39 asymptomatic children 2–5 years old with previous intermittent wheeze. R int differed significantly with algorithm. Geometric mean R int (95% confidence interval (CI)) for algorithms 1–4 were 1.21 kPa · l −1 · sec (1.18–1.24 kPa · l −1 · sec), 1.31 kPa · l −1 · sec (1.28–1.34 kPa · l −1 · sec), 1.57 kPa · l −1 · sec (1.54–1.61 kPa · l −1 · sec) and 1.71 kPa · l −1 · sec (1.67–1.75 kPa · l −1 · sec), respectively. Measurement of change in R int following bronchodilator (BDR) did not differ on average with algorithm. Geometric means (95% CI) for BDR measurements for algorithms 1–4 were 29.9% (26.0–34.0%), 30.4% (26.4–34.5%), 32.9% (28.8–37.1%), and 31.7% (27.6–35.8%), respectively. However, measurement of change in individuals could differ by up to 40%, depending on algorithm. In conclusion, there are significant differences in R int , depending on algorithm used to estimate pressure change. Measurement of change in R int is unaffected on average, although in individuals there could be significant differences. Each laboratory should state its method and use the same algorithm for longitudinal and group data. Pediatr Pulmonol. 2004; 37:31–36. © 2004 Wiley‐Liss, Inc.