CHARACTERISTICS OF WHEEZE DURING HISTAMINE-INDUCED AIRWAYS OBSTRUCTION IN CHILDREN WITH ASTHMA

Background - An automated system has been developed for the detection of sound patterns suggestive of airways obstruction in long term recor dings. The first step, presented here, was tracheal sound recording du ring histamine-induced airways obstruction. Methods - The tracheal sou nds of 29 children aged 8-19 years with asthma were recorded during ai rways obstruction caused by histamine inhalation using a system for co ntinuous respiratory telemetry and computer analysis. Sound patterns w ere analysed, classified, and related to airways obstruction measured by lung function tests based on the forced expiratory volume in one se cond (FEV(1)).Results - Five sound patterns were identified, one domin ant sensitive and four specific to a fall in FEV(1) of >20%. The prese nce of at least one of three specific sound patterns during unforced r espiration predicted a fall in FEV(1) of >20% in 87.5% of the subjects . The inspiratory and expiratory sound patterns were almost equally in formative of airways obstruction. Conclusions - Wheezes can be differe ntiated with more precision than is currently accepted. Tracheal sound patterns are sensitive and specific predictors of histamine-induced a irways obstruction. These patterns are neither invariably nor proporti onally related to the results of lung function testing. However, they can be used for detection of airways obstruction on the basis of their presence or absence.