Breathing is a process that is comprised of two distinct phases: inhalation and exhalation. During the inhalation process, air from the environment is taken into the lungs. The inhaled air passes through the nostrils or the mouth, down the throat, larynx and trachea, and into the lungs. During the exhalation phase, the air from the lungs is expelled out into the environment through the same route.
During both inhalation and exhalation phases, the movement of air through the airways results in the production of breathing sounds (also known as respiratory sounds). Depending on the phase of breathing cycle, these sounds are classified as inspiratory sounds or expiratory sounds. We often do not hear it or choose to ignore it until breathing problems arise or these sounds become abnormal.
Read more on abnormal breathing sounds.
Normal vs Abnormal Sounds
We are usually not aware of our breathing or breathing sounds till we are panting or something feels wrong with our breathing. Abnormal breathing sounds are of many different types. These include wheezing, stridor, crackles, ronchi, and pleural friction rub. Wheezing sounds during breathing are perhaps the most widely known. However, wheezing and stridor need to be distinguished because both are audible as whistling sounds.
Wheezing sounds during breathing are typically high-pitched whistling sounds that may be present either during the inspiration or the expiration phase. Depending on the phase of the breathing cycle during which wheezing sounds are heard, they are referred to as inspiratory wheezing or expiratory wheezing. The cause of wheezing sounds is typically a narrowing of the lumen in the lower airways.
Like wheezing, stridor also refers to breathing noises that sound like high-pitched whistling. However, unlike wheezing, the whistling sounds of stridor are produced by the narrowing of the lumen in the upper airways.
Since both wheezing and stridor produce similar high-pitched whistling sounds, people are apt to confuse one with the other.
Also, since more people are exposed to the term “wheezing”, even cases of stridor may be referred to as wheezing. In addition, causes and affected airway regions in wheezing and stridor may overlap, further blurring the distinction.
Reasons for Whistling Sounds
Abnormal breathing sounds, including whistling sounds, are produced when the flow of air through the airway passages gets disturbed. The high-pitched whistling sounds are usually caused when air is forced to flow though a narrow lumen, producing an air vortex. Air vortices are also produced when the flowing airstream encounters an obstruction (such as an object) that deflects the airflow.
The whistling sounds in wheezing or stridor usually indicate that there is some impediment to the flow of air in some region of the airways. Apart from the whistling sounds, this may also result in breathing difficulties and shortness of breath. Immediate medical attention must be sought if the breathing difficulty worsens and becomes severe. Signs of serious breathing difficulties are dizziness, bluish-pale skin, mental confusion and fainting. These signs should not be ignored.
Read more on noisy breathing.
Causes of Whistling Breathing Sounds
As mentioned previously, whistling sounds occur when there is a disturbance to the airflow in the airways. These disturbances can be caused by either a narrowing of the airways or due to the presence of some physical obstruction in the airway. The narrowing of the airways is usually a result of inflammation of the walls of the airways.
Physical obstruction of the airflow is usually due to the presence of some foreign object in the airways. A medical professional is required to diagnose the exact cause of the whistling sounds produced while breathing, and prescribe appropriate treatments.
The following are some conditions that are associated with whistling sounds during breathing:
- Asthma is the most common respiratory allergic condition that causes whistling sounds during breathing. Asthma is a result of hypersensitivity of the immune system to certain trigger factors, and is characterized by a narrowing of the bronchial tubes. This condition can affect people of any age group. However, children are most commonly afflicted by this ailment.
- Hypersensitivity pneumonitis causes wheezing due to an inflammation of the lung tissue. This condition is likely to be triggered by an occupational exposure to allergens. Allergic inflammation may also affect the upper airways.
- Allergic laryngitis is an example of an allergic condition that causes upper airway inflammation and whistling breathing sounds.
- Whistling sounds during breathing may also occur during anaphylactic reactions, which are serious life-threatening allergic reactions that lead to sudden closure of the airways. Emergency medical attention must be sought if anaphylaxis is suspected.
- Infection: Both upper and lower respiratory tracts may get infected by viruses and bacteria. Examples of respiratory infections that may result in whistling breathing sounds include laryngitis, bronchitis, epiglottitis, tracheitis, and bronchiolitis.
- Croup is a viral infection of the larynx and trachea. In some cases, the bronchi may also be involved. Apart from the whistling respiratory sounds, croup is also characterized by a cough that sounds like a bark.
- Pertussis is caused by the bacteria, Bordetella pertussis. This condition is also known as whooping cough due to its characteristic violent cough that is followed by a high-pitched inhalation sound.
- Chronic obstructive pulmonary disease (commonly abbreviated as COPD) is characterized by chronic inflammation of the bronchi and a destruction of the air sacs. Chronic smoking is thought to be the cause of this condition.
- Gastroesophageal reflux disease (commonly abbreviated as GERD) is characterized by a backward regurgitation of the stomach acid into the esophagus. The regurgitated acid may also enter the airways and cause inflammation, leading to whistling breathing sounds.
- Obstructive sleep apnea is a common condition that results in disturbed sleep patterns. This condition is characterized by a collapse of the airway passage in the throat, resulting in cessation of airflow. When this happens, the breathing stops and the affected person wakes up abruptly.
- Foreign body: Airway obstruction caused by the presence of a foreign object in the throat is a common occurrence in small children, who are apt to put foreign objects in their mouth during play.
- Lung cancer can also result in airflow disturbance due to destruction of the lung tissue and the airways.
- Heart failure causes accumulation of fluid in the lungs (technically known as pulmonary edema). Pulmonary edema can result in whistling sounds during breathing.