[Bronchial hyperreactivity in pediatric and adolescent asthmatics and healthy children]

The investigation of bronchial hyperreactivity (b.h.) represents the basic diagnostic test in asthmatics. In 515 asymptomatic pediatric and adolescent asthmatics (age 6-23 years) divided into various subgroups according to the study purposes, b.h. as an induced airway obstruction was assessed after inhalations of a single dose of acetylcholine (3 mg), histamine (3 mg), hypotonic and hypertonic solutions with jet nebulizer. B.h. was also studied following inhalations of distilled and mineral water, physiologic solution with ultrasonic nebulizer, and 5 min. free running outdoors. The induced airway obstruction was assessed by parameters measured from maximum expiratory flow-volume curve. The most potent stimuli were the inhaled acetylcholine (3 mg) and 5 min. free running outdoors. By the latter two tests similar incidence and magnitude of b.h. were revealed in our asthmatics without airway obstruction as well as with a mild obstruction (MEF50 and MEF25 below lower limits of predicted before both tests). For both tests (acetylcholine and 5 min. free running), recommended in practice, were given the expected limits of lung function parameters before starting the tests. The values of the parameters before the onset of provocation tests were unreliable predictors of the induced airway obstruction in our asthmatics. B. h. was also assessed in 426 healthy 9-years old children by inhalation of 1% carbachol (mean dose: 2.57 +/- 0.7 mg). Various lung function parameters showed different incidence of b.h. in the latter children. Both values of one- second vital capacity and respiratory resistance (interruption technique) revealed b.h. in 46% of our healthy children (decline of parameters more than 20%). Other parameters measured, except peak expiratory flow, proved b.h. more frequently. In the article the problems of respiratory resistance measured by interruption technique and higher incidence of b.h. in the studied healthy children are outlined.