What is stridor?

Stridor is a high-pitched sound that is usually heard best when a child breathes in (inspiration). It is usually caused by an obstruction or narrowing in your child's upper airway. The upper airway consists of the following structures in the upper respiratory system:

  • Nose

  • Nasal cavity

  • Mouth

  • Sinuses. Cavities, or air-filled pockets, that are near the nasal passage.

    • Ethmoid sinus. This sinus is located inside the face, around the area of the bridge of the nose. It is present at birth, and continues to grow.

    • Maxillary sinus. This sinus is located inside the face, around the area of the cheeks. It is also present at birth, and continues to grow.

    • Frontal sinus. This sinus is located inside the face, in the area of the forehead. It is present at birth, begins to develop between ages 1 and 2 years, but does not fully develop until around 7 years of age.

    • Sphenoid sinus. This sinus is located deep in the face, behind the nose. It is also present at birth, begins to develop between 2 and 3 years of age, but does not fully develop until adolescence.

Illustration of the sinuses

  • Larynx. Also known as the voice box, the larynx is a cylindrical grouping of cartilage, muscles, and soft tissue which contains the vocal cords. The vocal cords are the upper opening into the windpipe (trachea), the passageway to the lungs.

  • Trachea (windpipe). A tube that reaches from the voice box to the bronchi in the lungs.

The sound of stridor depends on location of the obstruction in the upper respiratory tract. Usually, the stridor is heard when the child breathes in (inspiration), but can also be heard when the child breathes out (expiration).

What are the causes of stridor?

There are many different causes of stridor. Some of the causes are diseases, while others are problems with the anatomical structure of the child's airway. The upper airway in children is shorter and narrower than that of an adult, and, therefore, more likely to lead to problems with obstruction. The following are some of the more common causes of stridor in children:

  • Congenital causes (problems present at birth):

    • Laryngomalacia. Parts of the larynx are floppy and collapse causing partial airway obstruction. The child will usually outgrow this condition by the time he or she is 18 months old. This is the most common congenital cause of stridor. Very rarely children may need surgery.

    • Subglottic stenosis. The larynx (voice box) may become too narrow below the vocal cords. Children with subglottic stenosis are usually not diagnosed at birth, but, more often, a few months after, particularly if the child's airway becomes stressed by a cold or other virus. The child may eventually outgrow this problem without intervention. Most children will need a surgical procedure if the obstruction is severe.

    • Subglottic hemangioma. A type of mass that consists mostly of blood vessels. Subglottic hemangioma grows quickly in the child's first few months of life. Some children may outgrow this problem, as the hemangioma will begin to get smaller after the first year of life. Most children will need surgery if the obstruction is severe. This condition is very rare.

    • Vascular rings. The trachea, or windpipe, may be compressed by another structure (an artery or vein) around the outside. Surgery may be required to alleviate this condition.

  • Infectious causes:

    • Croup. Croup is an infection caused by a virus that leads to swelling in the airways and causes breathing problems. Croup is caused by a variety of different viruses, most commonly the parainfluenza virus.

    • Epiglottitis. Epiglottitis is an acute life-threatening bacterial infection that results in swelling and inflammation of the epiglottis. (The epiglottis is an elastic cartilage structure at the root of the tongue that prevents food from entering the windpipe when swallowing.) This causes breathing problems that can progressively worsen which may, ultimately, lead to airway obstruction. There is so much swelling that air cannot get in or out of the lungs, resulting in a medical emergency. Epiglottitis is usually caused by the bacteria Haemophilus influenzae, and now is rare because infants are routinely vaccinated against this bacteria. The vaccine is recommended for all infants.

    • Bronchitis. Bronchitis is an inflammation of the breathing tubes (airways), called bronchi, which causes increased production of mucus and other changes. Acute bronchitis is usually caused by infectious agents, such as bacteria or viruses. It may also be caused by physical or chemical agents--dusts, allergens, strong fumes--and those from chemical cleaning compounds, or tobacco smoke.

    • Severe tonsillitis. The tonsils are small, round pieces of tissue that are located in the back of the mouth on the side of the throat. Tonsils are thought to help fight infections by producing antibodies. The tonsils can usually be seen in the throat of your child by using a light. Tonsillitis is defined as inflammation of the tonsils from infection.

    • Abscess in the back of the throat (retropharyngeal abscess). An abscess in the throat is a collection of pus surrounded by inflamed tissue. If the abscess is large enough, it may narrow the airway to a critically small opening.

  • Traumatic causes:

    • Foreign bodies in the ear, nose, and breathing tract may cause symptoms to occur. Foreign bodies are any objects placed in the ear, nose, or mouth that do not belong there. For example, a coin in the trachea (windpipe) may close off breathing passages and result in suffocation and death.

    • Fractures in the neck

    • Swallowing a harmful substance that may cause damage to the airways

How is stridor diagnosed?

Stridor is usually diagnosed solely on the medical history and physical examination of your child. It is important to remember that stridor is a symptom of some underlying problem or condition. If your child has stridor, your child's doctor may order some of the following tests to help determine the cause of the stridor:

  • Chest and neck X-rays. A diagnostic test which uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.

  • Bronchoscopy. Congenital, chronic, or severe stridor may require direct visualization of the airways with a flexible fiberoptic bronchoscope. This procedure is under sedation and local anesthesia, and may be performed on an outpatient, as well as an inpatient basis.

  • Pulse oximetry. An oximeter is a small machine that measures the amount of oxygen in the blood. To obtain this measurement, a small sensor (like a Band-Aid) is taped onto a finger or toe. When the machine is on, a small red light can be seen in the sensor. The sensor is painless and the red light does not get hot.

  • Sputum culture. A diagnostic test performed on the material that is coughed up from the lungs and into the mouth. A sputum culture is often performed to determine if an infection is present.

What Is the treatment for stridor?

Specific treatment of stridor will be determined by your child's doctor based on:

  • Your child's age, overall health, and medical history

  • Cause of the condition

  • Extent of the condition

  • Your child's tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

Treatment may include:

  • Referral to an ear, nose, and throat specialist (otolaryngologist) for further evaluation (if your child has a history of stridor)

  • Surgery

  • Medications by mouth or injection (to help decrease the swelling in the airways)

Hospitalization and emergency surgery may be necessary depending on the severity of the stridor.