Stridor

Definition

Stridor is a term used to describe noisy breathing in general, and to refer specifically to a high-pitched crowing sound associated with croup, respiratory infection, and airway obstruction.

Description

Stridor occurs when erratic air currents attempt to force their way through breathing passages narrowed by:

• illness

• infection

• the presence of foreign objects

• throat abnormalities

Stridor can usually be heard from a distance but is sometimes audible only during deep breathing. Someone who has stridor may crow and wheeze when:

• inhaling

• exhaling

• inhaling and exhaling

Most common in young children, whose naturally small airways are easily obstructed, stridor can be a symptom of a life-threatening respiratory emergency.

Causes and symptoms

During childhood, stridor is usually caused by infection of the cartilage flap (epiglottis) that covers the opening of the windpipe to prevent choking during swallowing. It can also be caused by a toy or other tiny object the child has tried to swallow.

Laryngomalacia is a common cause of a rapid, low-pitched form of stridor that may be heard when a baby inhales. This harmless condition does not require medical attention. It usually disappears by the time the child is 18 months old.

The most common causes of stridor in adults are:

• abscess or swelling of the upper airway

• paralysis or malfunction of the vocal cords

• tumor.

Other common causes of stridor include:

• enlargement of the thyroid gland (goiter)

• swelling of the voice box (largyngeal edema)

• narrowing of the windpipe (tracheal stenosis)

When stridor is caused by a condition that slowly narrows the airway, crowing and wheezing may not develop until the obstruction has become severe.

Diagnosis

When stridor is present in a newborn, pediatricians and neonatologists look for evidence of:

• heart defects inherent at birth (congenital)

• neurological disorders

• General toxicity.

If examinations do not reveal the reasons for the baby's noisy breathing, the air passages are assumed to be the cause of the problem.

Listening to an older child or adult breathe usually enables pediatricians, family physicians, and pulmonary specialists to estimate where an airway obstruction is located. The extent of the obstruction can be calculated by assessing the patient's:

• complexion

• chest movements

• breathing rate

• level of consciousness

X rays and direct examination of the voice box (larynx) and breathing passages indicate the exact location of the obstruction or inflammation. Flow-volume loops and pulse oximetry are diagnostic tools used to measure how much air flows through the breathing passages, and how much oxygen those passages contain.

Pulmonary function tests may also be performed.

Treatment

The cause of this condition determines the way it is treated.

Life-threatening emergencies may require:

• the insertion of a breathing tube through the mouth and nose (tracheal intubation)

• the insertion of a breathing tube directly into the windpipe (tracheostomy)

For Your Information

Books

• Berkow, Robert, ed. The Merck Manual of Medical Information: Home Edition. Whitehouse Station, NJ: Merck & Co., Inc., 1997.

• Clayman, Charles B., ed. The American Medical Association Encyclopedia of Medicine. New York: Random House, 1989.

• Dershewitz, Robert A., ed. Ambulatory Pediatric Care. Philadelphia: J. B. Lippincott Co., 1993.

• Pierson, David J., ed. Foundations of Respiratory Care. New York: Churchill Livingstone, 1992.

Sources: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group

The Essay Author is Maureen Haggerty.