Pediatric emergency medicine trisk 1660 1660
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Adapted from Martinati LC, Boner AL. Clinical diagnosis of wheezing in early childhood. Allergy
1995;50:701–710.
The intensity of wheezes and their pitch and duration are a function of the
degree of airway narrowing and the velocity of airflow at the site(s) of
obstruction. In patients with minimal airway obstruction, wheezing may be
difficult to detect. When such instances are suspected, forced exhalation may
reveal low-pitched wheezes limited to the end of expiration. Subtle wheezes can
be accentuated further by combining forced exhalation with simultaneous manual
compression applied by the examiner in the anteroposterior dimension of the
chest (the so-called “squeezing the wheeze”). As airway narrowing and minute
ventilation increase, wheezes become louder and higher pitched. However, when
airway obstruction becomes more severe, airflow and wheezes will diminish
proportionately. A “quiet chest” in the face of significant respiratory distress may
indicate impending respiratory failure. Conversely, in patients with reversible
bronchospasm, air exchange and wheezes are often noted to increase in response
to bronchodilator therapy.
Auscultation of the neck may be used to determine the source of wheezing.
Wheezing heard only in the chest, and not the neck, is more likely to be
associated with intrathoracic airway obstruction, whereas wheezing heard over
the neck, but not in the chest, is more likely associated with upper airway causes
of wheezing, such as psychogenic wheezing.
The clinical evaluation of a patient with obstructive lower airway disease will
invariably reveal a prominent cough. To the experienced clinician or parent, this
cough will usually be perceived as having a characteristic whistling or “wheezy”
quality that is distinct from the “seallike” barky cough of croup. Physical
examination of the wheezing child may also reveal inspiratory and expiratory
crackles, which are far more often attributable to subsegmental atelectasis than to
an associated pneumonia and parenchymal consolidation.
DIAGNOSTIC TESTS
Most diagnoses can be made based on the clinical history and physical
examination alone, but a limited number of diagnostic modalities may support the
emergency department (ED) evaluation of the wheezing child. The primary
measurement that should accompany any patient with respiratory complaints is
respiratory rate from pulse oximetry, which measures oxygenation. Noninvasive
end-tidal carbon dioxide measurements may also be used to assess ventilation.
When bronchiolitis or asthma is the clear diagnosis and the course is
uncomplicated, a chest radiograph is not routinely indicated. The available data
