Stridor is a panting, usually high-pitched sound produced by a rapid, turbulent flow of air through a narrowed segment of the upper airways. Most often inspiratory, it is almost always audible without a stethoscope. Present in children, can it also be present in adults? What are the causes ? And the consequences? How to treat it?

Stridor is an abnormal, panting, more or less shrill noise emitted by breathing. Usually, it is loud enough to be heard from a distance. This is a symptom, not a diagnosis, and finding the underlying causes is very important as stridor is usually a medical emergency. 

Of laryngotracheal origin, stridor is caused by a rapid, turbulent flow of air flow through a narrowed, or partially obstructed, upper respiratory tract. He can be :

• high-pitched and musical, close to a song;
• severe, such as a croaking or snoring;
• hoarse with a horny type, like a croak.

Stridor can be:

• inspiratory: it is audible on inspiration during a pathological narrowing of the diameter of the upper extra-thoracic airways (pharynx, epiglottis, larynx, extra-thoracic trachea);
• biphasic: in the event of severe obstruction, it is biphasic, that is to say present at both stages of respiration;
• or expiratory: in the event of an obstruction located in the intrathoracic airways, stridor is generally expiratory.

Stridor is the frequent manifestation in children of a pathology of the respiratory tract. Its incidence is not known in the general pediatric population. However, a higher frequency was observed in boys.

It should be noted that although it is much less common, stridor also exists in adults.

Children have small, narrow airways and are more prone to noisy breathing. Stridor is caused by pathologies involving the larynx and the trachea. Wheezing is typical of bronchial pathology. When noisy breathing is increased during sleep, the cause is in the oropharynx. When the breathing is louder when the child is awake, the cause is in the larynx or trachea.

In children, the most common causes include congenital causes and acquired causes.

Congenital causes of stridor in children

• Laryngomalacia, that is to say a soft larynx: it is the most common cause of congenital stridor and represents 60 to 70% of congenital laryngeal anomalies;
• Paralysis of the vocal cords;
• A stenosis, that is to say a narrowing, congenital subglottis;
• A tracheomalacia, that is to say a soft and flexible trachea;
• A subglottic hemangioma;
• A laryngeal web, that is to say a membrane connecting two vocal cords due to a congenital malformation;
• A laryngeal diastema, that is to say a malformation that makes the larynx communicate with the digestive tract.

Acquired causes of stridor in children 

• Acquired subglottic stenosis;
• Croup, which is inflammation of the trachea and vocal cords, most often caused by a contagious viral infection;
• An inhaled foreign body;
• A shrill laryngitis;
• Epiglottitis, which is an infection of the epiglottis caused by the bacteria Haemophilus influenzae type b (Hib). A frequent cause of stridor in children, its incidence has decreased since the introduction of the vaccine against Haemophilus influenzae type B;
• tracheitis, etc.

Common causes in adults

• Head and neck tumors, such as laryngeal cancer, can cause stridor if they partially obstruct the upper airways;
• An abscess;
• Edema, i.e. swelling, of the upper respiratory tract which may occur as a result of extubation;
• Vocal cord dysfunction, also called paradoxical vocal cord mobility;
• Paralysis of the vocal cords, following surgery or intubation in particular: when the two vocal cords are paralyzed, the space between them is very narrow and the airways become insufficient;
• An inhaled foreign body such as a food particle or a little water inhaled into the lungs causing the larynx to contract;
• Epiglottitis;
• Allergic reactions.

The causes of stridor can also be classified according to its tone:

• Acute: laryngomalacia or paralysis of the vocal cords;
• Severe: laryngomalacia or subglottic pathology;
• Hoarseness: laryngitis, stenosis or subglottic or high tracheal angioma.

Stridor may coincide with respiratory or food repercussions, accompanied by signs of severity such as:

• difficulty in food intake;
• episodes of suffocation during feeding;
• retarded weight growth;
• dyspnea, which is difficulty in breathing;
• episodes of respiratory distress;
• episodes of cyanosis (bluish discoloration of the skin and mucous membranes);
• obstructive sleep apnea;
• an intensity of the signs of respiratory struggle: flapping of the wings of the nose, intercostal and suprasternal retraction.
  

Before any stridor, an ENT examination with performing a nasofibroscopy should be proposed. A biopsy, CT scan, and MRI are also done if a tumor is suspected.

Stridor causing shortness of breath while the person is at rest is a medical emergency. Assessment of vital signs and degree of respiratory distress is the first step in management. In some cases, securing the airways may be necessary before or in conjunction with the clinical examination.

Treatment options for stridor vary depending on the cause of the symptom.

In case of laryngomalacia

Without criteria of seriousness, nor associated symptom, an observation period can be proposed, subject to the implementation of an anti-reflux treatment (antacids, thickening of the milk). Follow-up should be regular in order to ensure the gradual regression of symptoms and then their disappearance within the expected timeframe.

Symptoms of laryngomalacia are mostly mild and go away on their own before the age of two. However, almost 20% of patients with laryngomalacia have severe symptoms (severe stridor, feeding difficulties, and growth retardation) requiring treatment with endoscopic surgery (supraglottoplasty).

In the event of an inhaled foreign body

If the person is outside a hospital, another person can, if trained, help them expel the foreign body by performing the Heimlich maneuver.

If the person is in a hospital or emergency room, a tube may be inserted through the person’s nose or mouth (tracheal intubation) or directly into the trachea after a small surgical incision (tracheostomy) , to allow air to pass through the obstacle and prevent suffocation.

In case of edema of the respiratory tract

Nebulized racemic adrenaline and dexamethasone may be recommended in patients in whom airway edema is involved.

In case of severe respiratory distress

As a temporary measure, the mixture of helium and oxygen (heliox) improves air circulation and reduces stridor in large airway disorders such as post-extubation laryngeal edema, stridular laryngitis and tumors of the larynx. Heliox allows a reduction in flow turbulence due to a lower density of helium compared to oxygen and nitrogen.