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Diagnosing Stridor

Stridor, or noisy breathing, is caused by a narrowed or partially blocked airway, the passage that connects the mouth to the lungs. This results in wheezing or whistling sounds that may be high-pitched and audible when a person inhales, exhales, or both.

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NYU Langone otolaryngology specialists—also known as ear, nose, and throat doctors, or ENTs—often diagnose the cause of stridor during a physical exam. If further diagnostic testing is necessary, doctors use advanced imaging techniques to get a clear look at the airway.

The condition also affects children. Because their airways are narrower, even a small blockage can interfere with breathing.

Causes of Stridor in Adults

Bilateral vocal cord paralysis is a common cause of stridor in adults. It results from a disruption in nerve function in both of the vocal cords—the two small structures in the throat that vibrate and collide to produce sound—leading to vocal cord tissues blocking the airway. This causes biphasic stridor, which means the symptoms of noisy breathing occur when a person inhales and exhales.

Bilateral vocal cord paralysis can result from having thyroid, chest, or esophageal surgery, or from being intubated—having a breathing tube inserted. These procedures can cause scar tissue that interferes with breathing.

Subglottic stenosis, or an unusual narrowing of the airway below the vocal cords, can also cause noisy breathing during inhalation and exhalation.

Other causes of stridor in adults include a narrowing of the windpipe called tracheal stenosis, certain types of tumors that invade the airway, trauma, or an inhaled piece of food or small object that gets stuck in the airway.

Medical History

Your NYU Langone doctor may ask you to describe when you first noticed the noisy breathing, whether the sound comes and goes or is consistent, and whether it’s disrupting your everyday activities, such as eating and sleeping.

Physical Exam

Your doctor may examine your face, neck, and throat for signs of a blocked airway. The doctor may also listen to your breathing with a stethoscope, an instrument used to magnify sounds in the lungs and airway. He or she may also look for signs of infection, which may cause swelling in the throat.

Flexible Laryngoscopy

Flexible laryngoscopy helps a doctor examine the airway and vocal cords. Doctors use the procedure to determine whether the airway is narrow and, if so, identify the cause. This exam takes place in the doctor’s office and lasts for about five minutes.

To perform the procedure, your doctor first uses a local anesthetic spray to numb the nose and throat. Then he or she inserts an endoscope—a very thin, flexible instrument with a high-definition video camera and light at the end—into a nostril and down the airway. The camera helps identify any narrowing, obstruction, or other abnormalities.


If your doctor thinks the cause of the stridor is a foreign object, such as a piece of food that you’ve ingested or inhaled, he or she may recommend a chest X-ray. X-ray creates detailed pictures of structures inside the body and may show an object lodged in the airway or lungs.

CT Scans

A CT scan is a type of X-ray that produces detailed, three-dimensional, cross-sectional images of tissues and organs, which are displayed on a computer monitor. These scans can help a doctor determine if a tumor, vocal cord paralysis, or subglottic or tracheal stenosis is the cause of the stridor.


Bronchoscopy is an examination of the airway and lungs using a bronchoscope, a long, thin instrument with a camera on the tip. A doctor may recommend a bronchoscopy if an X-ray shows an ingested or inhaled object. Specialists use general anesthesia for this test to lessen any discomfort.

To perform this exam, your doctor inserts the bronchoscope through the nose or mouth and into the lungs. The scope sends a clear image of the airway and lungs to a monitor and helps doctors determine whether an object is blocking airflow.

If the bronchoscope reveals that an object is present, the doctor may pass small surgical instruments through the bronchoscope to remove it.


Electromyography, or EMG, measures the electrical impulses that travel along nerves, nerve roots, and muscles, testing how well the nerves and muscles work together. Your doctor may perform EMG to determine whether there is some dysfunction of the nerves or muscles in the larynx, or voice box.

To perform this test, the doctor inserts a tiny needle, called an electrode, into a muscle in the throat. This allows your doctor to measure the amount of electricity muscle cells generate when they are activated by a nerve impulse. In people who have stridor, the muscle fibers may not respond as well as normally functioning muscles do.

Our Research and Education in Stridor

Learn more about our research and professional education opportunities.