wheeze
Meaning of wheeze: A narrowed airway behaves like a reed instrument, and the note it plays says more about tightness than about which disease caused it.
Definition of wheeze
A wheeze is a high-pitched whistling or musical sound made by air forced through narrowed airways inside the lungs. It is usually loudest when breathing out, and it may be audible across the room or only through a stethoscope. The pitch reflects how tight the narrowing is rather than how much of the lung is affected.
How is the sound made?
Air moving through a wide tube is silent. Squeeze the tube and the airflow speeds up, the walls are drawn closer together, and they begin to flutter in much the way a reed does inside a wind instrument. The flutter produces a musical note whose pitch rises as the passage tightens. Breathing out makes it worse, because pressure rising inside the chest presses on the outside of the bronchial tubes while they are already narrowed. That is why most wheeze is heard on the way out, and why it lasts far longer than the brief crackles made by fluid-filled air sacs.
What narrows the airway?
| Mechanism | Examples | Pattern of the sound |
|---|---|---|
| Muscle spasm and swelling | Asthma, allergic reaction | Widespread across both lungs and variable |
| Mucus and fixed narrowing | Chronic obstructive lung disease, bronchiectasis | Widespread and more constant |
| Fluid in and around small airways | Heart failure, bronchiolitis in infants | Widespread, with other findings alongside |
| Blockage of one airway | Inhaled object, tumor, mucus plug | Localized to one spot and unchanging |
A wheeze confined to one part of the chest that never shifts is regarded quite differently from a wheeze heard everywhere, since blockage of a single tube behaves nothing like generalized narrowing. Not everything that wheezes is asthma, and a first wheeze in an adult who has never had one raises the question of what has changed.
How does it differ from stridor?
Both are whistling noises, but they come from different places and carry different weight. Stridor arises from the upper airway, the voice box or windpipe above the chest, is loudest on breathing in, and needs no instrument to hear. It signals narrowing of the single large passage through which all air must travel, which is why upper airway noise is treated as urgent. Wheeze comes from below, from many small tubes within the lungs. A wheeze that quietens as an attack worsens is not recovery, since too little air may be moving to generate any sound, and that finding is called a silent chest. A bronchodilator relieves wheeze driven by muscle spasm, and does much less for the fixed narrowing of COPD.
Also known as
Used in a sentence
An expiratory wheeze was audible throughout both lung fields.
Good to know
A wheeze that fades while breathing becomes more labored can reflect airflow too poor to produce sound rather than improvement, and a wheeze localized to one area suggests blockage of a single airway rather than generalized narrowing.