Bronchial hyperresponsiveness to methacholine assessed by means of tracheal auscultation of healthy children aged under 4 years

Objective To assess the safety of the tracheal auscultation method for measuring bronchial hyperresponsiveness in healthy unsedated children aged less than 4 years and to establish a range of normal bronchial hyperresponsiveness values. Population And Methods The study population consisted of healthy children aged between 6 months and 4 years. A methacholine bronchial provocation test was administered to unsedated children, using the tidal volume breathing technique and applying an abbreviated protocol. The test was considered positive when wheezing was heard in the trachea, arterial oxygen saturation (SaO 2 ) fell by 5% or more, or respiratory rate increased by 50% or more. Results A total of 16 children were studied. Ages ranged from 8 to 47 months, with a mean (SD) of 23.5 (12.2) months. There was no response to the methacholine in 11 children. In the other 5 children, there was a positive response at a concentration of 8 mg/mL. Response to the test was considered positive on the basis of tracheal wheezing in 3 cases, tracheal wheezing and a fall in SaO 2 in 1 case, and a fall of more than 5% in SaO 2 in 1 case. SaO 2 never fell below 93%. Conclusions As a means for assessing bronchial hyperresponsiveness, the tracheal auscultation method is appropriate, is simple to apply, and can be safely administered to unsedated children aged less than 4 years. The lowest concentration at which a response to methacholine occurs in healthy children of this age group is 8 mg/mL.