Wheeze is a continuous, usually high-pitched whistling sound with a musical quality.The site of its production is restricted to the large and medium size airways, since it requires a sufficient airflow. It is of great clinical value, most commonly associated with airway obstruction, due to a various mechanisms, e.g. bronchoconstriction, airway wall oedema, intraluminal obstruction, extraluminal compression or dynamic airway collapse. The most common cause of intermittent episodes of polyphonic wheeze in children is asthma. The prompt response of wheeze to a trial of bronchodilator is of great importance since it strongly supports the diagnosis of asthma. In infants, especially if crepitations predominate on auscultation and particularly if it is the first episode of diffuse airway obstruction, bronchiolitis is the most likely diagnosis. Simple non-interventional studies, like chest x-ray, allergy testing and spirometry may be useful, while more elaborate studies are usually not necessery. On the contrary, monophonic recurrent or persistent wheeze needs a thorough investigetion with more advanced imaging (e.g. HRCT) and endoscopic (e.g. flexible bronchoscopy) evaluation.
In young children, wheezing, either trasient or persistent, represents a common disorder with a significant morbidity. Different phenotypes have been proposed for a more precise characterisation and personalised plan of treatment. For everyday practice it is suggested to treat intermittent wheezing with intermittent bronchodilators confirming efficacy. Controllers should be prescribed if bronchodilators work and under monitoring for the efficacy again. There are no data supporting the point of view that inhaled corticosteroids may prevent the progress of any phynotype of preschool wheeze to asthma. On the other hand, inhaled corticosteroids should be prescribed for as long as needed in the lower effective dose. Intermittent high-dose regiments might be useful.