Wheezing

Wheezing (Wheezing): Whistling sound of narrowed airways

Wheezing that whistles on exhalation (wheezing, візинг) — is a high‑pitched, musical sound that occurs when air forcefully passes through narrowed lower airways (bronchi or bronchioles). It is not a disease but an important clinical sign that always indicates bronchial obstruction (narrowing of the bronchial lumen). The appearance of wheezing, especially if accompanied by shortness of breath, is a reason for immediate medical consultation.

Physics of the sound: How does the whistle form?

The mechanism of wheeze generation is similar to playing a flute or whistling. When an air stream passes through a narrow opening, it becomes turbulent and forces the airway walls to vibrate, producing sound. Because during exhalation the airways physiologically narrow even more, wheezes are most often heard on exhalation.

Mechanisms of airway narrowing (Bronchial obstruction)

Bronchial narrowing can be caused by three main mechanisms, often acting simultaneously:

1. Bronchospasm: Sudden contraction of the smooth muscle surrounding the bronchi. This is the key mechanism during an attack of bronchial asthma.
2. Mucosal edema: In response to a viral infection or allergen, the bronchial mucosa becomes inflamed and swollen, significantly reducing its lumen.
3. Hypersecretion of mucus: In response to inflammation, a large amount of thick, viscous mucus is produced, clogging already narrow bronchi.

Most common causes of wheezing

• Bronchial asthma: The most common cause of recurrent wheezing.
• Acute obstructive bronchitis / Bronchiolitis: The most common cause of wheezing in young children, usually viral.
• Chronic obstructive pulmonary disease (COPD): The most common cause in adult smokers.
• Allergic reactions: An acute reaction to an allergen can trigger bronchospasm.
• Aspiration of a foreign body.

Read more about wheezing in children on the page "Wheezing in children".