Airway resistance variability and response to bronchodilator in children with asthma.
Variability of airway function is a feature of asthma, spanning timescales from months to seconds. Short-term variation in airway resistance (R(rs)) is elevated in asthma and is thought to be due to increased variation in the contractile activation of airway smooth muscle. If true, then variation in R(rs) should decrease in response to bronchodilators, but this has not been investigated. Using the forced oscillation technique, R(rs) and the variation in R(rs) from 4-34 Hz were measured in 39 children with well-controlled mild-to-moderate asthma and 31 healthy controls (7-13 yrs) before and after an inhaled bronchodilator (200 microg salbutamol) or placebo. In agreement with other findings, baseline R(rs) at all frequencies and the sd of R(rs) (R(rs) sd) below 14 Hz were found to be elevated in asthma while neither forced expiratory volume in one second nor the mean forced expiratory flow between 25 and 75% of forced vital capacity were different compared with controls. The present authors found that R(rs) sd changed the most of any measurement in asthma, and this was the only measurement that changed significantly more in children with asthma following bronchodilator administration. The present results show that like airway narrowing, short-term airway variability of resistance may be a characteristic feature of asthma that may be useful for monitoring response to therapy.
Lall
C A
CA
School of Biomedical Engineering, Dalhousie University, 5981 University Ave, Room 5241, Halifax B3H 1W2 NS, Canada. gmaksym@dal.ca.
Cheng
N
N
Hernandez
P
P
Pianosi
P T
PT
Dali
Z
Z
Abouzied
A
A
Maksym
G N
GN
D000293:Adolescent; D000403:Airway Resistance / Q000187:drug effects*; D000704:Analysis of Variance; D001249:Asthma / Q000188:drug therapy* / Q000503:physiopathology*; D001993:Bronchodilator Agents / Q000627:therapeutic use*; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D012129:Respiratory Function Tests; D013147:Spirometry; D016896:Treatment Outcome
D001993:Bronchodilator Agents