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.
Stridor is a symptom, not a disease. It occurs when air is forced through breathing passages narrowed by the following:
- the presence of foreign objects
- congenital throat abnormalities
The sound is usually loud enough to be heard at a distance, although sometimes only during deep breathing and can occur on inhaling, exhaling, or both. It can be a symptom of a life-threatening respiratory emergency.
Stridor is most common in children. Croup, an inflammation of the trachea (windpipe) and larynx (voice box), is the most common cause of stridor in children under age two. Young children also frequently develop acute stridor by inhaling a foreign object, often food such as hot dogs, popcorn, or hard candy. Stridor as a complication of bacterial infections is also common in children under age eight.
Congenital stridor is caused by abnormalities in the airways that cause them to partially collapse when the child breathes. It is present at birth and usually becomes obvious within the first six weeks of life.
Causes and symptoms
During childhood, stridor is usually caused by infection of the cartilage flap (epiglottis) that covers the opening of the trachea to prevent material from entering the lungs and choking a person during swallowing. It can also be caused by foreign objects, such as a food or a coin, that a child has tried to swallow.
Laryngomalacia is the most common cause of congenital stridor, accounting for 75 percent of stridor in newborns. It seems to be caused by a collapse of tissue around the larynx and usually occurs in newborns that have no other health problems. It produces a rapid, low-pitched form of stridor that may be heard when a baby inhales. This condition develops soon after birth and usually does not require medical attention. It normally disappears as the child matures and almost always by the time the child is 18 months old.
Causes of stridor in adolescents and adults include the following:
- abscess or swelling of the upper airway
- paralysis or malfunction of the vocal cords
- enlargement of the thyroid gland goiter
- swelling of the voice box (laryngeal edema)
- narrowing of the windpipe (tracheal stenosis)
When to call the doctor
Acute stridor, especially when caused by inhaling a foreign object, can be a life-threatening emergency. Emergency medical care should be sought immediately if the individual is showing any signs of difficulty breathing or is turning blue, is unconscious, or is thought to have inhaled a foreign object. In other cases, a doctor should be consulted on a non-emergency basis whenever stridor develops in a newborn or when stridor accompanies other signs of illness such as a fever .
When stridor is present in a newborn, pediatricians and neonatologists also look for evidence of heart defects or neurological disorders that may cause paralysis of the vocal cords. Paralysis of the vocal cords can be life threatening. If examinations do not reveal other 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 timing and location of the noisy breathing, whether the sound is intermittent, occurs during eating, is better or worse when lying or standing, as well as the presence or absence of fever or other signs of infection and similar information help in determining the cause of stridor. It is sometimes difficult in children for doctors to differentiate between stridor and wheezing caused by asthma . However, a history of the breathing problem and careful examination can usually help them make the distinction.
The extent of the obstruction can be calculated by assessing several features in the patient:
- chest movements
- breathing rate
- level of consciousness
X rays and direct examination of the voice box (larynx) and breathing passages using a laryngoscope or bronchoscope indicate the exact location of the obstruction or inflammation. Computed tomography (CT) scans and magnetic resonance imaging (MRI) scans also may be useful, especially if surgery is needed.
Flow-volume loops and pulse oximetry are diagnostic tools used to measure how much air flows through the breathing passages and how much oxygen is available. Pulmonary function tests may also be performed.
Treatment of stridor depends on the underlying cause of the breathing difficulty. Life-threatening emergencies may require the insertion of a breathing tube through the mouth and nose (tracheal intubation) or the insertion of a breathing tube directly into the windpipe (tracheotomy) and surgery to remove a foreign object. Bacterial infections are treated with antibiotics . Congenital stridor is usually left untreated and resolves on its own.
The outcome of stridor depends on its cause. Death by suffocation may occur when a foreign object blocks the airway. Otherwise the outcome for most cases of stridor is good to excellent, depending on the cause.
Adults must keep small, easily swallowed objects such as coins, beads, and hard, round candies away from young children so that they do not try to swallow them. Taking precautions against colds and bronchial infections (washing hands, not sharing dishes, avoiding sick people) can cut down on stridor from infective causes. Congenital stridor is not preventable.
Congenital stridor in a newborn can sound frightening to parents, but it is rarely a cause for concern or medical intervention.
Congenital —Present at birth.
Laryngomalacia —A birth defect that causes the tissues around the larynx to partially collapse and narrow the air passageway, causing noisy breathing.
Laryngoscope —An endoscope that is used to examine the interior of the larynx.
Wyka, Kenneth, et al. Foundations of Respiratory Care. Albany, NY: Delmar Learning, 2002.
American Academy of Pediatrics. 141 Northwest Point Boulevard, Elk Grove Village, IL 60007–1098. Web site: http://www.aap.org.
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Tish Davidson, A.M. Maureen Haggerty