Wheeze and stridor
Wheeze and stridor are respiratory sounds caused by air-flow limitation
– when predominantly expiratory these musical sounds are wheezes, inspiratory
sounds that do not clear on coughing are only caused by upper airway
obstruction and this is called stridor.
A wheeze is described according to where it is best heard and whether it is monophonic (limitation of a specific size of airway – usually one bronchus) or polyphonic (widespread airway limitation). Asthma is one of the major causes of polyphonic wheeze, but not all asthma attacks are accompanied by wheeze. Other causes include chronic obstructive airways disease and acute bronchitis.
Stridor is due to upper airway obstruction. It occurs because in inspiration, a valve-like effect worsens obstruction in
the major airways. On expiration, the in creased airway pressure opens the
valve, so expiratory wheeze may be minor.
Acute stridor: Laryngeal trauma or smoke/toxic gas inhalation, acute
epiglottitis (drooling, unwell), anaphylaxis, inhaled foreign body.
Gradual onset: Obstruction by tumours of the upper airway (larynx,
pharynx or trachea), extrinsic compression (lymph nodes, retrosternal thyroid),
bilateral vocal cord palsy.