What Is Stridor?

  • Farwah Alam BS(Hons)in Microbiology and Molecular genetics, University of the Punjab, Pakistan
  • Jason Ha Bachelor of Medicine, Bachelor of Surgery - MBBS, University of Bristol

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Ever heard your breath sing? A bold, high-pitched sound that grabs your attention and refuses to be ignored? If you have not, consider yourself lucky. If you have, then this is not your typical lullaby sound, it’s something known as stridor that turns every inhale and exhale into attention-grabbing performance. So, let's discover what this mysterious sound is, dissecting what stridor is, why it happens, and why, once you've heard it, you won't easily forget it. 


Stridor is an abnormal, high-pitched turbulent noisy breathing that occurs due to obstruction in airflow through narrowed airways. Stridor is not just a sound, this wheezing sound is the symptom, an expression of potential distress in respiratory airways. Till now you have become familiar with this medical jargon that might sound like a puzzle. Fear not, let's break it down into bite-sized pieces. Stridor is the body's way of expressing that something is up with the breathing tract. It occurs more frequently in children than in adults. 

Types of stridor

It's crucial to know where the noisy breathing and breathy hiccups are coming from. Knowing from where the stridor is coming helps doctors figure out what's the cause of it, leading to a more precise diagnosis and treatment. The timing of the sound can help determine the origin and nature of the abnormality, hence determining the location of the airway disorder. Is the disorder from within the chest cavity (intrathoracic) or from outside of it (extrathoracic)? Is the trouble occurring during breathing in or breathing out? 

Classification based on location:

Stridor is classified into two types based on the location:  

  1. Intrathoracic stridor (inside the chest cavity)
  2. Extrathoracic stridor (outside the chest cavity)

Classification based on timing:

Stridor is classified into three types on the timing of the disorder:

  1. Inspiratory stridor (happens during inhale)
  2. Expiratory stridor (happens during exhale) 
  3. Biphasic stridor (happens during both inhale and exhale processes).

Outside the chest: inspiratory stridor

Specifically, the extrathoracic region includes the larynx and the voice box. The voice box is further segmented into three parts: supraglottic (tippy top of your breathing pipe), glottic (middle part of the voice box) and subglottic (last part of the voice box). Collapse of tissue in the extrathoracic region, which is the region outside of the chest cavity, causes an inspiratory stridor. This happens when you breathe in, and the air pressure inside your breathing tube drops below the atmospheric pressure outside. It looks like the air is sucked out, and if you have a collapse of tissue in these voice box areas, you get that distinct sound – the breathy melody of inspiratory stridor. The common causes of inspiratory stridor in the extrathoracic region are:

  • Laryngomalacia (a birth defect in the voice box causing the partial blockage of the airway opening)
  • Croup (disease that causes swelling of airways)
  • Retropharyngeal abscess (infection that happens behind the back wall of the throat)
  • Craniofacial malformations (fusion of skull bone or facial bones in an abnormal way) are the common causes of inspiratory stridor in the extrathoracic region.

Inside the chest: expiratory stridor

On the other hand, the intrathoracic region includes the trachea, the tube in the chest and the mainstem bronchi. Here, the culprits of the squeeze or the collapse of the tissue causing narrowing of airways are the congenital issues. But this time, intrathoracic stridor occurs during the exhalation or breathing out process. This happens when elevated pleural pressure (pressure surrounding the lungs) compresses the airway, leading to a reduction in airway size at the site of the intrathoracic obstruction.

Biphasic stridor

This kind of stridor occurs during breathing in and out, causing narrowing at the glottis level. This specific airway segment undergoes minimal changes during respiration, resulting in the dual-phase nature of the sound. Foreign objects and tight airways are the main culprits leading to biphasic stridor.

Causes of stridor

Stridors can be caused by any process that causes the narrowing of airways. So stridor can be short-term (acute) or hang around for a while (chronic). Let's delveinto what might be playing this breathing melody.

Acute stridor

An onset of acute stridor is a sudden symphony that may happen in minutes to hours or may develop over days. Patients with acute stridor may experience rapid progression of their symptoms. The culprits behind the curtain of acute stridor are: 

  • Croup
  • Bacterial tracheitis 
  • Epiglottitis
  • Retropharyngeal abscess 
  • Foreign body aspiration 
  • Peritonsillar abscess 
  • Airway burns 
  • Anaphylaxis
  • Therapeutic hypothermia 
  • Post-extubation complications

Chronic stridor

On the other hand, chronic stridor is like a long-term player, persisting for weeks. Sometimes, it's there from the start of life shadowing congenital issues, or it might appear later in childhood. It's like a subtle hum in the background, and the reasons behind it are diverse. Chronic players of stridor include conditions such as: 

  • Craniofacial anomalies like Pierre Robin or Apert syndromes 
  • Macroglossia-inducing disorders: a big tongue disorder
  • Larynx and airway issues like laryngomalacia, laryngeal webs, laryngeal cysts, laryngeal clefts, subglottic stenosis, vocal cord paralysis 
  • Tracheal troubles like tracheal stenosis, tracheomalacia
  • Vascular and growth issues like vascular ring, bronchogenic cysts, infantile hemangiomas, tumours, respiratory papillomatosis, hypocalcemic laryngeal spasm

Symptoms and presentation

So, you have covered the basics of stridor, but what about stridor’s sidekicks: symptoms that may appear along this noisy breathing journey? These symptoms are like reading the body's language to decipher the nature of stridor.

  • Hives: notice itchiness and raised bumps on the skin; it's like an allergic alert and can be a sign of anaphylaxis
  • Cough: if your cough is like a barking dog's sound, not like a usual cough's sound, then it may be due to croup
  • Drooling:
    • If the sound is a bit off with drooling, then it indicates this may be at the  supraglottic, such as a retropharyngeal abscess or epiglottitis 
    • If there's drooling with difficulty in swallowing, then the body is signalling the presence of foreign objects or maybe something pressing on the oesophagus.
  • Mental status: feeling off with mental state when coupled with increased or harder breathing? It's like the body showing a warning of losing airways. 
  • Stridor during feeding: if a stridor occurs during feeding, this may be because of tracheoesophageal fistula(an abnormal condition between the food tube and breathing tube), reflux issues, or trouble swallowing 
  • Fever: fever can be due to croup, epiglottitis, bacterial tracheitis, or a retropharyngeal abscess. It's like a body’s red flag, signalling that there may be bacterial intruders in the body. 

Testing and diagnosing

So you make unusual sounds and you are curious about what could be behind the scenes. Now it's turn to crack the code by doing detective work of testing and diagnosing.

Getting the scoop

The first doctor asked about the patient's history, such as when the noisy breathing tunes started or if they had any other symptoms like fever or hives.

Checking for distress signs

Next, the doctor may check for the signs of distress that are causing stridor like flaring of nostrils and colour changes.

Examining the breathing sounds

The next doctor listens to the breathing sounds. Is it a breath in, a breath out, or a bit of both? And how's the voice doing? 

Detective tools

The next doctor advises special tests that act as a detective tool and uncover the mystery behind this harsh sound.

  • Flexible laryngoscopy: in this, a tube with a camera is introduced into the body through the body, giving a sneak peak of the airway.
  • Plain X-ray, airway fluoroscopy, barium swallow, and CT scan of the chest: tests that create snaps of breathing rhythm to evaluate the problems.
  • Magnetic resonance imaging or magnetic resonance angiography: when a doctor wants to examine the soft tissues in detail, this test is advised. 

Treatment and management

Now it's time to figure out how to manage the stridor.

  • For bacterial tracheitis and epiglottis, antibiotics are the superheroes.
  • Both steroids and racemic epinephrine know how to calm the croup chaos.
  • Retropharyngeal and peritonsillar abscesses require surgical drainage.
  • Some severe cases of laryngomalacia, laryngeal stenosis, critical tracheal stenosis, laryngeal and tracheal tumours, and foreign body aspiration require surgical correction.


As a wrap up, remember stridor is not just a medical term, it's the way our body communicates with us. It's an invitation to listen, understand diagnose and treat the ongoing problem. 


  1. Sicari, Vincent, and Christopher P. Zabbo. “Stridor in Children.” StatPearls, StatPearls Publishing, 2023. PubMed, http://www.ncbi.nlm.nih.gov/books/NBK525995/.
  2. Philadelphia, The Children’s Hospital of. Stridor (Noisy Breathing). 30 Mar. 2014, https://www.chop.edu/conditions-diseases/stridor-noisy-breathing.
  3. Croup. 31 Jan. 2022, https://www.hopkinsmedicine.org/health/conditions-and-diseases/croup.

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Farwah Alam

BS(Hons)in Microbiology and Molecular genetics, University of the Punjab, Pakistan

Farwah, a research scholar in microbiology and molecular genetics, is a passionate science communicator. She simplifies complex concepts, expressing her love for science and aspiring to contribute meaningfully to health research.

my.klarity.health presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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