A wheeze is a continuous, coarse, whistling sound produced in the respiratory airways
during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed
or obstructed, or airflow velocity within the respiratory tree must be heightened. Wheezing
is commonly experienced by persons with a lung disease; the most common cause of recurrent
wheezing is asthma attacks, though it can also be a symptom of lung cancer.
The differential diagnosis of wheezing is wide, and the cause of wheezing in a given
patient is determined by considering the characteristics of the wheezes and the historical and clinical
findings made by the examining physician.
Characteristics Wheezes occupy different portions of the respiratory
cycle depending on the site of airway obstruction and its nature. The fraction of the respiratory
cycle during which a wheeze is produced roughly corresponds to the degree of airway obstruction.
Bronchiolar disease usually causes wheezing that occurs in the expiratory phase of respiration.
The presence of expiratory phase wheezing signifies that the patient's peak expiratory
flow rate is less than 50% of normal. Wheezing heard in the inspiratory phase on the other
hand is often a sign of a stiff stenosis, usually caused by tumors, foreign bodies or
scarring. This is especially true if the wheeze is monotonal, occurs throughout the inspiratory
phase, and is heard more proximally, in the trachea. Inspiratory wheezing also occurs
in hypersensitivity pneumonitis. Wheezes heard at the end of both expiratory and inspiratory
phases usually signify the periodic opening of deflated alveoli, as occurs in some diseases
that lead to collapse of parts of the lungs. The location of the wheeze can also be an
important clue to the diagnosis. Diffuse processes that affect most parts of the lungs are more
likely to produce wheezing that may be heard throughout the chest via a stethoscope. Localized
processes, such as the occlusion of a portion of the respiratory tree, are more likely to
produce wheezing at that location, hence the sound will be loudest and radiate outwardly.
The pitch of a wheeze does not reliably predict the degree of narrowing in the affected airway.
A special type of wheeze is stridor. Stridor — the word is from the Latin, strīdor — is
a harsh, high-pitched, vibrating sound that is heard in respiratory tract obstruction.
Stridor heard solely in the expiratory phase of respiration usually indicates an upper
respiratory tract obstruction, "as with aspiration of a foreign body." Stridor in the inspiratory
phase is usually heard with obstruction in the upper airways, such as the trachea, epiglottis,
or larynx; because a block here means that no air may reach either lung, this condition
is a medical emergency. Biphasic stridor indicates narrowing at the level of the glottis or subglottis,
the point between the upper and lower airways. Diagnosis
1 out of 3 preschool children and 2 out of 3 school children with recurrent wheezing/coughing
are allergic. The reaction creates an inflammation that, in turn, can lead to a variety of symptoms
such as wheezing. Over the last decade allergy has increased
by 18% in the United States. Today one child in four is allergic. Early diagnosis of allergy
is important for the development of the child later in life. There are many patients with
symptoms suggesting eczema, rhinitis, hay fever, asthma or wheezing.
See also Crackles
Rhonchi Squawk
References
Further reading Godfrey S, Uwyyed K, Springer C, Avital A.
"Is clinical wheezing reliable as the endpoint for bronchial challenges in preschool children?".
Pediatr Pulmonol. 37: 193–200. doi:10.1002/ppul.10434. PMID 14966812.
External links Audio Breath Sounds - Multiple case studies
with audio files of lung sounds. R.A.L.E. Repository - sound files of breath
sounds