Sibilant rhonchi (older term)
In one sentenceA musical sound in which several tones are heard at once. It occurs in widespread obstruction.
Listen to the same sound in another patient. Breathing rate, chest wall, the pitch of the sound and the number of adventitious sounds vary within realistic limits.
What does it sound like?
Several musical tones are heard at once. The tones overlap; one may end as another begins. Expiration is prolonged.
Where is it heard?
Widespread over both lungs.
What causes it?
In widespread narrowing, many airways vibrate at the same time. Each produces its own tone. The chest wall mixes these tones. The number of tones you hear is not an exact count of vibrating airways. It is a clue to how widespread the narrowing is.
Quantitative criteria
- Wheeze occupancy (Tw/Ttot): in 20 patients with acute asthma, it fell from 86% to 31% with a bronchodilator (Baughman and Loudon, 1984). In a monitoring study of 12 patients, it correlated with FEV₁ (r = 0.893) (1985).
- On the spectrogram, several narrow-band lines appear. The tones are not harmonics of one another. When the tones start and stop together, the type is a fixed polyphonic wheeze, which is typical of COPD. In asthma, the tones may start and stop at different moments, and the pitch of each may drift in its own direction; lower tones are louder. Evenly spaced parallel lines are often the harmonics of a single wheeze and should not be mistaken for polyphony. The example on this site was generated from the pattern in an adult asthma recording: the tones start and stop at different moments.
Clinical meaning
Typical of asthma and COPD. Its duration and intensity change with flow, airway diameter and treatment. If there is no wheeze, there are two possibilities. Either the disease is under control, or the obstruction is so severe that too little flow is left to produce oscillation (silent chest).
Sounds it can be confused with
A monophonic wheeze has a single tone. If it is focal and fixed, think of local obstruction.
A sound from the upper airway is louder over the neck.
Less wheeze after treatment does not always mean improvement. Assess the patient's work of breathing, ability to speak and oxygenation together.
See the reference list for sources.