This post will clarify the difference monophonic and polyphonic wheeze. You will be able to differentiate between the two and also make a differential based on type of wheeze.
What is a wheeze?
Wheeze is a very common sign found in respiratory system examination. It is the main/most common sign found in asthma patients.
Wheeze is a continual, high-pitched ‘musical’ quality sound, which is audible at the end of inspiration or at the start of expiration. It usually indicates obstruction in the airways.
How is it produced?
Airway narrowing allows airflow induced oscillation of airway walls, producing acoustic waves. As the airway lumen becomes smaller, the airflow velocity increases, resulting in vibration of the airway wall and the tonal quality.
MONOPHONIC WHEEZE
A monophonic wheeze is wheeze with a single note, which starts and ends at different points in time.
– The pitch and timings are fixed & a classic example is wheeze caused by a tumor in the bronchi. This is because the tumor itself is static, causing a fixed obstruction.
– A child with a fixed foreign body may also have a monophonic wheeze.
POLYPHONIC WHEEZE
Polyphonic wheezes are wheezes with several different tones starting and finishing at the same time. It is heard when narrowing of airways occur in multiple bronchi and bronchioles at the same time.
– It is found in obstructive airway diseases such as, COPD, asthma, bronchiectasis.
– It is caused by second- or third-order bronchi closing at the same time at end-expiration, because the pressures within the airway keeping them patent are reduced.
– Polyphonic can also be heard in healthy people at end-expiration during forceful expiration.
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