Stridor

Stridor is a high-pitched vibratory sound that occurs during breathing due to narrowing or blockage of the larynx or pharynx.

Symptoms and Causes

Stridor is a high-pitched respiratory sound that occurs abnormally as a consequence of narrowing of the upper airway. It may result from an acute disorder, such as the presence of a foreign body, or from a chronic condition.

The abnormal sound is produced as a result of turbulent airflow passing through partially obstructed airways. According to its pathophysiology, it may be classified into three types:

Inspiratory stridor: caused by obstruction of an extrathoracic airway that reduces the diameter of one of the organs involved in inspiration.
- Larynx: laryngeal stridor is the most common type. It affects the phonatory organ, which is involved in breathing, swallowing, and speech and is located between the pharynx and the trachea.
- Pharynx: this is the area commonly known as the throat. It connects the nasal cavities, the Eustachian tube, the larynx, and the esophagus, which extends to the stomach.
- Epiglottis: this is the cartilage located at the back of the throat, between the larynx and the tongue, which closes access to the larynx during swallowing to prevent liquids or food from entering the lungs.
Expiratory stridor: the narrowing occurs in an intrathoracic airway, so airflow obstruction takes place during expiration.
- Trachea: this is the airway that connects the larynx with the bronchi located in the lungs. Stridor usually occurs in the upper part of this organ.
Biphasic stridor: the abnormal sound is heard both during inspiration and expiration. It is the most severe type, as it implies a fixed obstruction in the trachea or the subglottic area, the part of the larynx located below the vocal cords.

The prognosis of stridor varies depending on the underlying cause and its severity. Early diagnosis is essential to provide appropriate treatment and ensure unobstructed airflow.

Symptoms

Stridor produces a high-pitched, squeaking sound during breathing. Along with this highly characteristic sign, other symptoms may occur, such as:

Difficulty breathing.
Voice changes: hoarseness, aphonia, weakness of voice tone.
Difficulty swallowing with episodes of choking.

In infants, stridor is often associated with:

Nasal flaring.
Noises during feeding.
Unusual sounds during sleep.
Difficulty gaining weight.

Warning signs requiring immediate medical attention include:

Cyanosis: bluish or grayish discoloration of the face, lips, or nails.
In children, stridor at rest: the abnormal sound is not associated with crying or feeding.
Very rapid breathing.
Apnea: temporary interruption of breathing, which may last between 10 and 60 seconds.

Causes

The most common causes of stridor are:

Aspiration of a foreign body.
Smoke inhalation.
Phlegm or sputum.
Anaphylaxis: a severe allergic reaction affecting the entire body. Stridor results from throat inflammation and breathing difficulty.
Laryngitis: inflammation of the larynx.
Tonsillitis: inflammation of the tonsils, usually caused by a viral or bacterial infection.
Adenoiditis: inflammation and infection of the adenoids.
Adenotonsillar hypertrophy: enlargement of the tonsils and adenoids as a result of allergies or recurrent infections.
Laryngomalacia: flaccidity of the laryngeal tissues located above the vocal cords, which collapse over the airway during inhalation. It is common in infants and usually resolves spontaneously.
Tracheomalacia: weakness of the tracheal cartilages that impairs breathing. It is a common congenital condition in newborns that usually resolves spontaneously by approximately 24 months of age.
Bronchomalacia: weakening of the bronchial cartilage, causing collapse during expiration.
Epiglottitis: rapid inflammation of the epiglottis due to bacterial infection. It is a medical emergency because of the risk of death.
Viral croup: a viral respiratory infection causing inflammation of the larynx and trachea. It is common in children between 6 months and 3 years of age.
Laryngeal hematoma, usually resulting from trauma.
Vocal cord paralysis.
Tracheal stenosis: narrowing of the trachea.
Gastroesophageal reflux: stomach acid rises into the esophagus, causing irritation.
Airway injury.
Bronchogenic cysts: benign congenital malformations occurring during embryonic development of the tracheobronchial tree and causing mucus- or fluid-filled tissue structures.
Laryngeal cyst: tissue sacs filled with glandular secretions located in the laryngeal mucosa.
Congenital subglottic stenosis.
Tracheal narrowing.
Inflammation of the face or neck.
Lymphangioma: a rare benign tumor caused by congenital malformation of the lymphatic vessels.
Subglottic hemangioma: a benign vascular tumor characterized by proliferation of blood vessels below the vocal cords.
Vocal cord cancer.
External compression: vascular rings, lymphadenopathy, mediastinal masses, lobar emphysema.
Recurrent respiratory papillomatosis: formation of benign tumors in the larynx caused by the human papillomavirus.
Macroglossia: abnormally large tongue size in relation to the oral cavity.
Pierre Robin syndrome: congenital malformation characterized by cleft palate, an abnormally small jaw, and posterior displacement of the tongue.
Metabolic disorders, such as hypocalcemia or hypomagnesemia.
Neurological disorders affecting swallowing.
Diagnostic procedures, such as bronchoscopy or laryngoscopy.
Neck surgery.
Prolonged use of a breathing tube.

Risk factors

The risk of stridor increases in the following cases:

Age: although it can occur in anyone, it is more common in infants and children under 5 years of age.
Prematurity: infants requiring respiratory support at birth are more prone to stridor.
Living in overcrowded conditions, as the likelihood of infections is higher.
Having any of the conditions described in the previous section.

Complications

The main complications of stridor, which derive from the underlying cause rather than the sound itself, are:

Airway obstruction preventing complete airflow passage.
Aspiration pneumonia: more common in children with tracheomalacia because they have greater difficulty clearing secretions, promoting the passage of liquids and food into the lungs.
Respiratory failure: gas exchange in the lungs does not occur adequately.
Hypoxia: reduced oxygen levels in the blood, resulting in decreased oxygen supply to tissues.
Difficulty swallowing, leading to poor weight gain and possible nutritional deficiencies. This is one of the consequences of chronic laryngomalacia.
Chronic tracheal injury.
Cardiorespiratory arrest: a medical emergency caused by lack of oxygen that may result in death.

What specialist treats stridor?

Stridor is diagnosed and treated within the specialty of Otorhinolaryngology.

Diagnosis

Diagnosis of stridor and its underlying cause begins with anamnesis, during which the patient’s medical history is completed. Family and personal history, the nature of symptoms (acute or chronic), and the most significant signs of disease are evaluated.

Once the medical history has been completed, several procedures are performed:

Physical examination:
- Height, weight, and body mass index (BMI).
- Skin coloration and possible skin lesions.
- Cervical edema (fluid accumulation in the neck) or labial angioedema (lip swelling).
- Breathing at rest.
- Pulmonary auscultation.
- Pulse oximetry to assess oxygen levels.
Blood tests: provide information about the patient’s general health status and help detect inflammatory or infectious processes.
Examination of the airway interior: minimally invasive studies providing images of the respiratory system.
- Nasopharyngoscopy: an endoscope (a flexible tube with a camera at the tip) is inserted through one of the nostrils and gently advanced to examine the nose, throat, adenoids, tonsils, and vocal cords.
- Laryngoscopy: the scope is inserted through the mouth to capture images of the throat, vocal cords, and larynx.
- Bronchoscopy: an endoscope is introduced from the mouth into the lungs, allowing visualization of the pharynx, trachea, and bronchi.
X-rays: X-rays are used to obtain images of the neck and chest that help identify malformations, abscesses, neoplasms, foreign bodies, or vascular rings.
Chest computed tomography (CT): X-rays from multiple angles are used to generate three-dimensional and more detailed images.

The gold standard test for diagnosing stridor and identifying its underlying cause is fiberoptic bronchoscopy.

Treatment

Treatment of stridor focuses on the underlying disease causing it. The main approaches include:

Removal of the foreign body trapped in the airway.
Inhaled corticosteroids, anti-inflammatory drugs, or nebulized adrenaline to reduce inflammation.
Antibiotics to treat bacterial infection.
Surgical intervention to remove excess tissue caused by laryngomalacia if it does not resolve spontaneously after two years.
Corticosteroids, beta-blockers, or surgery to reduce subglottic hemangioma.
Management approaches for tracheal stenosis:
- Balloon dilation: a deflated balloon is introduced into the narrowed area with the aid of an endoscope. Once in place, it is inflated to push the airway walls outward and reopen the passage.
- Endoscopic laser therapy: laser treatment is performed through the mouth to remove tissue obstructing the airway.
- Surgery: if the previous procedures are unsuccessful or cannot be performed, an incision is made in the neck to repair the trachea through conventional surgery.
Endotracheal intubation: if the patient presents advanced respiratory distress, decreased consciousness, and complete airway obstruction, a tube is inserted through the nose or throat into the trachea. Oxygenation is maintained using mechanical ventilation (a machine that delivers air into the lungs).
Tracheostomy: when intubation is difficult, an artificial opening is created to connect the trachea directly to the outside and attach the mechanical ventilation device.