Focal wheeze and local obstruction
In one sentenceA single-tone wheeze that is always heard at the same site points to one narrowed spot rather than widespread airway disease.
- Site and persistence tell you more than pitch.
- Breath sounds may be diminished beyond the narrowing.
- A finding that does not change with coughing or suction, especially on one side, needs imaging and, if required, bronchoscopy.
Yes. A single point of narrowing vibrates at a single pitch.
Yes. Little air passes beyond the narrowing, and the sound is weaker there.
If the narrowing is complete, the region beyond it loses its connection with the central airways.
A fixed monophonic wheeze in the same place, with diminished breath sounds beyond the narrowing.
For the reasoning: Where does sound come from? · How does sound reach the chest wall? · How do adventitious sounds arise? · From sound to differential diagnosis
What do you hear?
Over one region you hear a wheeze with a single pitch. It is at the same site at every examination. Breath sounds may be diminished over the same region or beyond it.
Why does it sound like this?
A single narrowed segment means a single dominant source of vibration. This is why the sound is monophonic. Less air reaches the lung beyond the narrowing. Sound production there falls and the breath sound becomes weaker.
Possible causes
- Mucus plug
- Aspirated foreign body
- Endobronchial tumour
- Post-intubation or post-inflammatory stenosis
- Kinking or compression of a bronchus by a neighbouring disease
Distinguishing clues
- Does it change after coughing? A sound that changes after coughing, suction or airway clearance suggests mobile secretions.
- Phase can mislead: The phase in which the wheeze occurs depends on the level and mechanics of the narrowing. Rely on site and persistence.
- Louder over the neck? If the sound is loudest over the neck, think of upper airway obstruction.
Pitfalls
- A local wheeze can be lost within a general diagnosis of asthma or COPD. Consider this possibility when you see "asthma that does not respond to treatment".
- The sound does not tell you what the lesion is. It only shows you where to look.
Next step
If the finding persists on repeated examinations, especially on one side, plan imaging and, when needed, bronchoscopy.
Try this pattern in a case
Going deeperresidents · specialists · numbers and sources
One source, a mixed path
A persistent monophonic wheeze is consistent with a single dominant source of vibration. The chest mixes sounds from different sites. So the number of tones you hear cannot be used as a reliable count of sources. Pitch does not give the diameter of the narrowing directly either. Airflow, transmural pressure (the pressure difference across the airway wall), and the stiffness and mass of the wall determine it together.
The strength of regional measurement
Vibration response imaging was used in patients with central airway obstruction. A "gap index" was defined from the time difference between the sound intensity peaks of the right and left lungs. In patients with unilateral bronchial involvement, this index fell after bronchoscopic intervention. Spirometry, by contrast, showed no significant improvement. A regional acoustic measure can capture uneven mechanics that are averaged out in whole-lung measurements.
Confusion with the upper airway
Upper airway obstruction can be labelled as asthma. Stridor is much more prominent over the neck than the wheeze of asthma, and its phase distribution is often different.
See the reference list for sources.