Stridor is a high-pitched squeaking or whistling sound, usually due to an obstruction in an airway.

Stridor is a sign of an underlying health issue rather than a diagnosis or disease in itself.

This article outlines the causes of stridor in children and adults, along with information on diagnosis and treatments.

Symptoms of stridor include strange whistling or squeaking noises when a person breathes.

The following recording from Debra L. Weiner, MD, PhD, Emergency Medicine, Children’s Hospital Boston, Harvard Medical School shows how stridor sounds in a child with croup.

Stridor is the sign of a blockage within the upper airways.

Doctors divide stridor into three types, depending on the point at which the sound occurs in the breathing cycle.

The three types of stridor are:

  • Inspiratory, which occurs when breathing in, and indicates a blockage above the vocal cords.
  • Expiratory, which occurs when breathing out, and indicates a blockage in the windpipe.
  • Biphasic, which occurs when a person breathes in and out, and indicates narrow cartilage directly below the vocal cords.

Common causes of stridor include:

  • nhaling a foreign object
  • inhaling smoke
  • overproducing phlegm
  • laryngitis or swelling and irritation of the voice box
  • swollen tonsils
  • an injury to the airways
  • an allergic reaction
  • swelling of the face or neck
  • bronchoscopies and laryngoscopies
  • neck surgery
  • long-term use of a breathing tube
  • cancer of the vocal cords

Stridor is much more common among children than adults. This is because children have narrower airways that are more susceptible to blockages.

Sometimes, stridor in children is due to congenital abnormalities. In these cases, stridor and other symptoms usually appear within a few weeks or months of the child being born.

Doctors must treat severe stridor immediately to prevent the airway from closing off. A severely blocked airway can cause an inability to breathe, which could result in respiratory failure.

Respiratory failure is when blood oxygen levels become dangerously low or blood carbon dioxide levels become dangerously high.

Causes of stridor in children can include:


Croup is a condition that causes inflammation of the vocal cords and windpipe. The cause is usually viral.

Children between 6 months and 6 years of age are at the highest risk of croup. It is also more common in males.

Symptoms of croup include:

  • barking cough
  • hoarse voice
  • breathing difficulties

At-home treatment is sufficient for most cases of croup. However, arrangements should be made for children to see a doctor if they develop breathing difficulties.

Inhaled object

A child can accidentally inhale a small foreign object, which may become lodged in the windpipe or in the bronchi — the tubes that carry air to the lungs.

Symptoms to look for include:

  • stridor
  • difficulty breathing
  • wheezing
  • difficulty swallowing
  • throat or chest pain
  • drooling
  • loss of appetite

The child may need an X-ray or other tests to confirm the presence and location of a foreign object.

Large, sharp, or dangerous objects, such as magnets or batteries, may require surgical removal.


Laryngomalacia softens the floppy tissues of the voice box, allowing them to drop into the airways when the child breathes in.

The condition is usually present from birth. Signs appear within the first month of life, but most children outgrow it over time.

Symptoms of laryngomalacia include:

  • inspiratory stridor
  • difficulty feeding
  • choking while feeding
  • acid reflux
  • poor weight gain
  • stopping breathing
  • bluish skin color

In 90 percent of cases, laryngomalacia gets better without treatment by the time the child reaches 18–20 months of age.

Vocal cord paralysis

Vocal cord paralysis refers to a lack of movement in one (unilateral) or both (bilateral) vocal cords. This paralysis can be due to a nerve injury or an infection.

Paralysis may be present from birth or may develop after neck or heart surgery or surgery to the food pipe.

Symptoms of vocal cord paralysis include:

  • inspiratory stridor
  • weak voice
  • breathy crying
  • coughing or choking while feeding

A child may need surgery for unilateral vocal cord paralysis if the condition lasts 1 or 2 years.

Some children with bilateral vocal cord paralysis will require a breathing tube while waiting for the paralysis to improve.

Subglottic stenosis

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Surgery can correct subglottic stenosis.

Subglottic stenosis is a narrowing of the airways within the voice box. It is usually due to scarring in this area.

Congenital subglottic stenosis is present from birth, whereas acquired subglottic stenosis often occurs after long periods of using a breathing tube.

Symptoms of subglottic stenosis include:

  • stridor
  • breathing difficulties
  • recurring croup, or barking cough

Mild stenosis will often improve without treatment. However, children with severe stenosis will usually require a breathing tube and surgery to correct the condition.

Subglottic hemangioma

A subglottic hemangioma is a benign or noncancerous tumor made up of capillaries and other small blood vessels. These benign tumors may grow in the airway, causing a blockage.

Hemangiomas are common, affecting 4–5 percent of children, but it is rare for them to grow in the airway. The condition is more common in the first 3 months after birth.

Symptoms of a subglottic hemangioma include:

  • biphasic stridor
  • difficulty breathing
  • barking cough

Subglottic hemangiomas grow rapidly for the first 12–18 months, and then begin to shrink.

Doctors may treat severe subglottic hemangiomas with the drug called propanolol, which works to shrink the tumor. Other treatments can include steroids, surgery, or temporary placing a breathing tube in the airway.

Vocal cord lesions

Types of vocal cord lesions include:

Vocal cord nodules: Lesions that prevent the vocal cords from closing properly.

Vocal cord papillomas: Lesions caused by the human papillomavirus (HPV).

Nodules may develop after strenuous vocal activity, such as shouting, screaming, or repetitive coughing.

Children with vocal cord papillomas usually acquire the HPV virus during childbirth.

Symptoms of vocal cord lesions include:

  • stridor
  • changes to the voice
  • difficulty breathing
  • difficulty exercising
  • difficulty eating
  • acid reflux

A child may require surgery for vocal cord papillomas but not for vocal cord nodules.

Treatment for vocal cord nodules usually involves careful monitoring and a “wait and see” approach. In the meantime, children may receive medication to control acid reflux symptoms.

Vascular rings

Vascular rings are a type of congenital abnormality in which rings of blood vessels form around the windpipe or the food pipe.

As the blood vessels grow in size, they may compress the windpipe, causing stridor. Symptoms usually appear in infancy or early childhood.

Symptoms of vascular rings include:

  • noisy or labored breathing that worsens when eating
  • difficulty eating and swallowing
  • choking
  • a feeling of something being stuck in the throat
  • a persistent cough

Doctors may use an MRI scan to help diagnose vascular rings. Surgery for vascular rings is usually only necessary if the child is experiencing symptoms.

When surgery is necessary, a surgeon will cut the rings to relieve pressure on the windpipe.

Bacterial tracheitis

Bacterial tracheitis is a rare but life-threatening bacterial infection of the windpipe. The average age of diagnosis is 5 years. In addition to biphasic stridor, a child may experience septic shock.

Children with bacterial tracheitis will usually require intravenous antibiotics.

Around 80 percent of children will also require a breathing tube and 94 percent will need to stay in an intensive care unit.


A bacterial infection causing inflammation of the epiglottis, or soft tissue that closes off the windpipe, can be life-threatening.

Though rare now, children between 2 and 6 years of age are most often affected by epiglottitis.

Symptoms of epiglottitis can include:

  • stridor
  • fever
  • bluish skin color
  • drooling
  • difficulty breathing
  • difficulty swallowing
  • hoarse voice

In most cases, a child with epiglottitis will require oxygen and a breathing tube and will need to stay in a hospital.

Doctors may also need to give them antibiotics, anti-inflammatory medications, and intravenous fluids.

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A doctor may recommend a chest X-ray or CT scan to diagnose stridor.

To make a diagnosis, a doctor will begin by performing a physical exam and taking a detailed medical history.

A doctor may ask the following questions:

  • When did the breathing difficulties begin?
  • Did the stridor come on gradually or suddenly?
  • Have there been any other symptoms, such as coughing or wheezing?

Doctors may also use other tests, such as:

  • a chest or neck X-ray
  • a CT scan of the chest
  • laryngoscopy, which allows them to see the voice box
  • bronchoscopy, which uses a bronchoscope to see inside the airways and lungs
  • pulse oximetry, which tests a person’s blood oxygen level
  • arterial blood gas analysis to measure carbon dioxide and oxygen levels

Treatment for stridor involves identifying and treating the underlying cause of the airway obstruction.

After finding the cause, a doctor can recommend the right treatment, such as:

  • oral or injectable medications to reduce airway swelling
  • surgery to remove or repair obstructions
  • surgery to expand the airways

A family doctor may also refer someone to an ear, nose, and throat or ENT specialist for further evaluation.

The outlook for children and adults who experience stridor will depend on the underlying cause.

Some causes of stridor can lead to respiratory failure if treatment is delayed, so it is vital for a person with stridor to visit a doctor quickly for a diagnosis.

In many cases, a doctor can treat an airway obstruction that is responsible for stridor with medication or surgery.