Stridor – Causes, Symptoms, Treatment

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Stridor is a variable, high-pitched respiratory sound that can be assessed during breathing. Typically, stridor is produced by the abnormal flow of air in the airways, usually the upper airways, and most prominently heard during inspiration. However, it can also be present during both inspiration and expiration. Stridor can be due to congenital malformations and anomalies as well as in the acute phase from life-threatening obstruction or infection. The diagnostic approach may include x-rays or bronchoscopy by a trained specialist to ascertain the etiology when there is diagnostic uncertainty. It should be noted that in infants and young children, a small amount of inflammation can result in significant and rapid airway obstruction.

Stridor is the audible sound of turbulent airflow through a narrowed portion of the airway. Stridor may be inspiratory, expiratory, or biphasic in nature. Stridor is not a diagnosis or disease; rather, it is a symptom of airway pathology. Stridor is a common manifestation of airway obstruction. Stridor can be present in a variety of conditions ranging from benign, self-limiting disease processes, to progressive airway compromise.

Types of Stridor

The timing and the sound of your child’s noisy breathing provides clues to the type of airway disorder:

  • Inspiratory stridor – occurs when your child breathes in and it indicates a collapse of tissue above the vocal cords.
  • Expiratory stridor – occurs when your child breathes out and it indicates a problem further down the windpipe.
  • Biphasic stridor – occurs when your child breathes in and out, and it indicates a narrowing of the subglottis, the cartilage right below the vocal cords.


The pathophysiology of stridor is based upon the anatomic location involved as well as the underlying disease process. Narrowowing of the supraglottic areas can occur rapidly because there is no cartilage in these areas. The subglottic area is of most concern in infants in which minimal airway narrowing here can result in dramatic increases in airway resistance.

Inspiratory Stridor

An obstruction in the extrathoracic region causes inspiratory stridor. During inspiration, the intratracheal pressure falls below the atmospheric pressure, causing a collapse of the airway.

Expiratory Stridor

An obstruction in the intrathoracic region causes expiratory stridor. During expiration, the increased pleural pressure compresses the airway causing a decrease in the airway size at the site of the intrathoracic obstruction. Both inspiratory and expiratory stridor occur because of bacterial tracheitis and foreign bodies. Laryngeal webs and vocal cord paralysis occur due to a fixed airway obstruction, which does not change with respiration.

Causes of Stridor

The etiologies for stridor differ depending on whether the patient is pediatric or an adult. For pediatrics, the most common causes of acute stridor include croup, foreign body aspiration. However, there are many other causes. The cause of stridor can further be differentiated based on acuity and based on congenital versus noncongenital causes.

Congenital Causes of Stridor in Pediatrics
  • Nasal deformities such as choanal atresia, choanal atresia, septum deformities, turbinate hypertrophy, vestibular atresia, or vestibular stenosis
  • Craniofacial anomalies such as Pierre Robin or Apert syndromes, or conditions causing macroglossia
  • Laryngeal anomalies such as laryngomalacia, laryngeal webs, laryngeal cysts, laryngeal clefts, subglottic stenosis, vocal cord paralysis, tracheal stenosis, tracheomalacia
Noncongenital Causes of Stridor in Pediatrics
  • Acute – Foreign body aspiration, airway burns, bacterial tracheitis, epiglottitis, anaphylaxis, croup.
  • Subacute – Peritonsillar abscess, a retropharyngeal abscess.
  • Chronic – Vocal cord dysfunction, laryngeal spasm, neoplasm.
The most common cause of chronic stridor in infants is laryngomalacia.
  • Laryngomalacia – Parts of the larynx are floppy and collapse causing partial airway obstruction. The child will usually outgrow this condition by the time he or she is 18 months old. This is the most common congenital cause of stridor. Very rarely children may need surgery.
  • Subglottic stenosis – The larynx (voice box) may become too narrow below the vocal cords. Children with subglottic stenosis are usually not diagnosed at birth, but more often, a few months after, particularly if the child’s airway becomes stressed by a cold or other virus. The child may eventually outgrow this problem without intervention. Most children will need a surgical procedure if the obstruction is severe.
  • Subglottic hemangioma – A type of mass that consists mostly of blood vessels. Subglottic hemangioma grows quickly in the child’s first few months of life. Some children may outgrow this problem, as the hemangioma will begin to get smaller after the first year of life. Most children will need surgery if the obstruction is severe. This condition is very rare.
  • Vascular rings – The trachea, or windpipe, may be compressed by another structure (an artery or vein) around the outside. Surgery may be required to alleviate this condition.

Infectious causes

  • Croup – Croup is an infection caused by a virus that leads to swelling in the airways and causes breathing problems. Croup is caused by a variety of different viruses, most commonly the parainfluenza virus.
  • Epiglottitis – Epiglottitis is an acute life-threatening bacterial infection that results in swelling and inflammation of the epiglottis. (The epiglottis is an elastic cartilage structure at the root of the tongue that prevents food from entering the windpipe when swallowing.) This causes breathing problems that can progressively worsen which may ultimately lead to airway obstruction. There is so much swelling that air cannot get in or out of the lungs, resulting in a medical emergency. Epiglottitis is usually caused by the bacteria Haemophilus influenzae, and now is rare because infants are routinely vaccinated against this bacteria. The vaccine is recommended for all infants.
  • Bronchitis – Bronchitis is an inflammation of the breathing tubes (airways), called bronchi, which causes increased production of mucus and other changes. Acute bronchitis is usually caused by infectious agents such as bacteria or viruses. It may also be caused by physical or chemical agents — dusts, allergens, strong fumes — and those from chemical cleaning compounds or tobacco smoke.
  • Severe tonsillitis – The tonsils are small, round pieces of tissue that are located in the back of the mouth on the side of the throat. Tonsils are thought to help fight infections by producing antibodies. The tonsils can usually be seen in the throat of your child by using a light. Tonsillitis is defined as inflammation of the tonsils from infection.
  • Abscess in the back of the throat (retropharyngeal abscess) – An abscess in the throat is a collection of pus surrounded by inflamed tissue. If the abscess is large enough, it may narrow the airway to a critically small opening.
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Traumatic causes

  • Foreign bodies in the ear, nose and breathing tract may cause symptoms to occur. Foreign bodies are any objects placed in the ear, nose or mouth that do not belong there. For example, a coin in the trachea (windpipe) may close off breathing passages and result in suffocation and death.
  • Fractures in the neck.
  • Swallowing a harmful substance that may cause damage to the airways.
Other conditions that may cause stridor in infants and children include
  • croup, which is a viral respiratory infection
  • subglottic stenosis, which occurs when the voice box is too narrow; many children outgrow this condition, though surgery may be necessary in severe cases
  • subglottic hemangioma, which occurs when a mass of blood vessels forms and obstructs the airway; this condition is rare and may require surgery
  • vascular rings, which occur when an outer artery or vein compresses the windpipe; surgery may release the compression.
Stridor may occur as a result of
  • foreign bodies (e.g., aspirated foreign body, aspirated food bolus);
  • infections (e.g., epiglottitis, retropharyngeal abscess, croup);
  • subglottic stenosis (e.g., following prolonged intubation or congenital);
  • airway edema (e.g., following instrumentation of the airway, tracheal intubation, drug side effect, allergic reaction);
  • laryngospasm (from aspiration, GERD, or complication of anesthesia)
  • subglottic hemangioma (rare);
  • vascular rings compressing the trachea;
  • thyroiditis such as Riedel’s thyroiditis;
  • vocal cord palsy;
  • tracheomalacia or tracheobronchomalacia (e.g., collapsed trachea).
  • congenital anomalies of the airway are present in 87% of all cases of stridor in infants and children.[1]
  • vasculitis.
  • infectious mononucleosis
  • peritonsillar abscess
  • Laryngeal edema is a common cause of stridor post extubation (occurring from pressure of the endotracheal tube on the mucosa as a result of endotracheal tube that is too large (e.g. pediatrics), cuff over inflation, and prolonged intubation times.)[rx];
  • tumor (e.g., laryngeal papillomatosis, squamous cell carcinoma of larynx, trachea or esophagus);
  • ALL (T-cell ALL can present with mediastinal mass that compresses the trachea and causes inspiratory stridor)

Diagnosis of Stridor

  • Neonates: Congenital abnormalities present within the first month of life, with some presenting later in life.
  • Infants to toddlers: The most common cause in this age group is croup or foreign body aspiration.
  • Young adolescents: Vocal cord dysfunction, peritonsillar abscess
  • Acute: Epiglottitis, bacterial tracheitis will present with severe respiratory distress and secretions, and fever, if fever is not present then suspect foreign body aspiration or anaphylaxis
  • Subacute: Croup will present with intermittent stridor
Physical Exam
  • General appearance – Assess for any swelling of soft tissues of the neck and oropharynx, and rashes or hives, or any clubbing of digits.
  • HEENT – Assess tongue size, pharyngeal edema, or peritonsillar abscess. Be cautious in manipulating the oropharynx of a suspected epiglottitis patient, and consider doing this in a controlled setting such as the operating room.
  • Lungs – Asses rate and depth of breathing, auscultate for inspiratory and expiratory stridor. Auscultate over the anterior neck to best hear stridor.
  • Initial evaluation – should begin with a rapid assessment of the patient’s airway and effort of breathing. First, ensure that the airway maintains patent and can move air in and out of the lungs. Asses the patient’s rate and depth of breathing, and evaluate for hypoxia or cyanosis and if the patient looks like they are decompensating secondary to fatigue.
  • If the patient is hemodynamic stable with stridor – obtain a thorough history of present illness, review of systems, and medical history. Keys to the correct diagnosis can be delineated based on patient age, acuity of onset, history of exposures to allergens or infectious sources.  In the stable patient with stridor, additional testing including imaging, radiography, and endoscopy may be performed.
  • In the patient is unstable – there may be signs of respiratory distress, gasping, drooling, fatigue, cyanosis, and these signs prompt a more rapid evaluation and rapid management to ensure airway patency. This can include endotracheal intubation or emergency surgical airway.
  • Laboratory testing – may include a complete blood count (CBC), if an infectious source is suspected, however, this is usually not necessary for diagnosis. A rapid viral panel may be obtained to assess for parainfluenza viruses in the pediatric patient.
  • Bronchoscopy – Congenital, chronic or severe stridor may require direct visualization of the airways with a flexible fiberoptic bronchoscope. This procedure is under sedation and local anesthesia and may be performed on an outpatient, as well as an inpatient basis.
  • Pulse oximetry – An oximeter is a small machine that measures the amount of oxygen in the blood. To obtain this measurement, a small sensor (like a Band-Aid) is taped onto a finger or toe. When the machine is on, a small red light can be seen in the sensor. The sensor is painless and the red light does not get hot.
  • Sputum culture – A diagnostic test performed on the material that is coughed up from the lungs and into the mouth. A sputum culture is often performed to determine if an infection is present.
  • Radiography including – a lateral plain film may be obtained to assess for the size of the retropharyngeal space, in which a widened space may indicate a retropharyngeal abscess. A mnemonic can be used “6 at C2, and 22 at C6” to remember that the normal retropharyngeal space should not be greater than 6mm at the level of C2 and not more than 22 mm at the level of C6. This view may also aid in visualizing of an enlarged epiglottis. An anteroposterior view to assessing for subglottic narrowing such as the “steeple” sign in croup.  A chest radiograph can be obtained in suspected foreign body aspiration. However, a negative chest radiograph does not rule this out.
  • Computed tomography (CT) – can be considered when there is diagnostic uncertainty in the stable patient with stridor. CT of the chest and neck can evaluate for an infectious source such as cellulitis as well as stenotic lesions, or foreign bodies. Magnetic resonance imaging (MRI) can help discern tracheal stenosis in pediatric patients.
  • Laryngoscopy and bronchoscopy – can help visualize the airways to establish a definitive diagnosis. If the patient appears critically ill, then endotracheal intubation should be performed if the cause of stridor is thought to be from epiglottitis or bacterial tracheitis.
  • Electromyography (EMG). Your doctor puts a tiny needle into a muscle in your throat and measures the electrical current going through your nerves and muscles.
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Treatment of Stridor

Management of stridor should be undertaken from the time of initial assessment in the critically ill-appearing patient. Specific treatment should be tailored to the underlying diagnosis. In general, the following precautions should be maintained when managing/treating stridor.

  • Avoid agitating child with stridor
  • Monitor for rapid deterioration due to respiratory failure
  • Avoid direct examination or manipulation of the pharynx (if epiglottitis is suspected). In such situations, securing the airway takes precedence over diagnostic evaluation.
  • Skilled personnel in airway management should accompany the patient at all times. Further evaluation should be performed where definitive airway management can be achieved in a controlled environment such as the operating room.
  • Consider foreign body aspirations if symptoms develop acutely such as sudden coughing and choking in a previously healthy child.
  • Avoid beta-agonists in croup; they are a possible risk of worsening upper airway obstruction.

The first issue of clinical concern in the setting of stridor is whether or not tracheal intubation or tracheostomy is immediately necessary. A reduction in oxygen saturation is considered a late sign of airway obstruction, particularly in a child with healthy lungs and normal gas exchange. Some patients will need immediate tracheal intubation. If intubation can be delayed for a period, a number of other potential options can be considered, depending on the severity of the situation and other clinical details. These include:

  • Expectant management with full monitoring, oxygen by face mask, and positioning the head on the bed for optimum conditions (e.g., 45 – 90 degrees).
  • Use of nebulized racemic adrenaline epinephrine (0.5 to 0.75 ml of 2.25% racemic epinephrine added to 2.5 to 3 ml of normal saline) in cases where airway edema may be the cause of the stridor. (Nebulized Codeine in a dose not exceeding 3 mg/kg may also be used, but not together with racemic adrenaline [because of the risk of ventricular arrhythmias].)
  • Use of dexamethasone (Decadron) 4–8 mg IV q 8 – 12 h in cases where airway edema may be the cause of the stridor; note that some time (in the range of hours) may be needed for dexamethasone to work fully.
  • Use of inhaled Heliox (70% helium, 30% oxygen); the effect is almost instantaneous. Helium, being a less dense gas than nitrogen, reduces turbulent flow through the airways. Always ensure an open airway.

Management of the child with cough or difficult breathing

Treat pneumonia

The child with SEVERE PNEUMONIA needs urgent care.

  • If possible, refer the child with SEVERE PNEUMONIA to a hospital for care.
  • Administer antibiotics for a total of 10 days.
    • intramuscular gentamicin and ampicillin or
    • intramuscular chloramphenicol or
    • intramuscular benzylpenicillin or ampicillin or
    • change to oral chloramphenicol when child improves.
  • Administer oxygen if possible.
  • Give a bronchodilator (salbutamol) if the child is wheezing.
  • Give paracetamol every 6 hours if the child has fever (axillary temperature of 38.5°C or above).
  • Manage the airway by clearing a blocked nose with a plastic syringe (without the needle) to gently suck secretions from the nose.
  • If the child can drink, give fluids by mouth, but cautiously to avoid fluid overload.
  • Encourage the mother to continue breastfeeding if the child is not in respiratory distress.
    • If the child is too ill to breastfeed but can swallow, have the mother express milk into a cup and slowly feed the child the breast milk with a spoon.
  • If the child is not able to drink, either use a dropper to give the child fluid very slowly or drip fluid from a cup or a syringe without a needle. Avoid using a nasogastric (NG) tube if the child is in respiratory distress.
  • Keep the infant warm. Keep the sick infant dry and well wrapped. If possible, have the mother keep her infant next to her body, ideally between her breasts. A hat or bonnet will prevent heat loss from the head.
The child with non-severe PNEUMONIA needs antibiotics but can be managed at home.
  • Administer an oral antibiotic.
    • The preferred treatment is oral amoxicillin (25 mg/kg/dose) 2 times a day for 3 days.
    • An alternative treatment is oral chloramphenicol (50 mg/kg) in 3 divided doses per day.
    • The duration of treatment should be extended to 5 days in high HIV prevalence settings.
  • Show the mother how to give the antibiotic.
  • Encourage the child to eat and drink.
  • Encourage the mother to continue breastfeeding the child.
  • Advise the mother to return with the child immediately if the child’s breathing worsens or the child develops any danger sign.
  • Follow up in 2 days.
The child with COUGH or COLD (no pneumonia) does not need antibiotics.
  • Teach the mother to soothe the throat and relieve the cough with a safe remedy such as warm tea with sugar.
  • Advise the mother to watch for fast or difficult breathing and to return if either one develops.
  • Follow up in 5 days if there is no improvement.

Treat wheezing

Give inhaled bronchodilator using a spacer.

  • A spacer is a way of delivering the bronchodilator drugs effectively into the lungs. No child under 5 years should be given an inhaler without a spacer. A spacer works as well as a nebuliser if correctly used.
  • From salbutamol metered dose inhaler (100ug/puff) give 2 puffs.
    • Repeat up to 3 times every 15 minutes before classifying pneumonia.
Spacers can be made in the following way
  • Use a 500ml drink bottle or similar.
  • Cut a hole in the bottle base in the same shape as the mouthpiece of the inhaler. This can be done using a sharp knife.
  • Cut the bottle between the upper quarter and the lower 3/4 and discard the upper quarter of the bottle.
  • Cut a small V in the border of the large open part of the bottle to fit to the child’s nose and be used as a mask.
  • Flame the edge of the cut bottle with a candle or a lighter to soften it.

In a small baby, a mask can be made by making a similar hole in a plastic (not polystyrene) cup. Alternatively commercial spacers can be used if available.

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To use an inhaler with a spacer
  • Remove the inhaler cap. Shake the inhaler well.
  • Insert mouthpiece of the inhaler through the hole in the bottle or plastic cup.
  • The child should put the opening of the bottle into his mouth and breathe in and out through the mouth.
  • A carer then presses down the inhaler and sprays into the bottle while the child continues to breathe normally.
  • Wait for three to four breaths and repeat for total of five sprays.
  • For younger children place the cup over the child’s mouth and use as a spacer in the same way.

N.B. If a spacer is being used for the first time, it should be primed by 4-5 extra puffs from the inhaler.

Treat stridor

  • Give oxygen if possible
  • Give one dose of oral corticosteroid
  • If diphtheria: give procaine penicillin and diphtheria antitoxin IM
Treat STRIDOR as severe
  • If stridor is present when the child is breathing quietly (not crying)
  • Give oxygen using nasal prongs if possible. Continue oxygen therapy until the lower chest wall indrawing is no longer present.
  • Steroid treatment: give one dose of oral dexamethasone (0.6 mg/kg).
  • If the child has severe chest indrawing, refer the child.
If DIPHTHERIA is the cause of stridor
  • Give IM procaine penicillin (50 000 units/kg) daily for 7 days.
  • Give 40 000 units of diphtheria antitoxin IM immediately. As there is risk for a serious allergic reaction, an initial intradermal test should be done to check for hypersensitivity.
  • If the child is in severe distress, consider referral if possible as the child might need a tracheotomy (a hole in the front of the neck into the windpipe to allow air entry to lungs).
  • Check on the child every few hours. Anyone caring for the child should have been immunized against diphtheria.
  • Give all unimmunized household contacts of the child one IM dose of benzathine penicillin (600 000 units if 5 years or younger; 1 200 000 units to persons over age 5 years) and immunize them with diphtheria toxoid.
  • Give all immunized household contacts a diphtheria toxoid booster.
  • A child who has had diphtheria may have complications of the heart (myocarditis) or paralysis 2–7 weeks after the initial infection.
  • Manage the child as MILD STRIDOR if child has a hoarse voice and stridor is only heard when the child is agitated or crying. Manage child at home with supportive care, encouraging oral fluids, breastfeeding or feeding. Give paracetamol if child has a fever. Advise the mother to return immediately with the child if the child’s breathing worsens or the child develops any danger sign.

Treat the child with cough or difficult breathing for more than 2 weeks

The child with COUGH for more than 2 weeks needs evaluation for possible asthma or tuberculosis.

Managing the child with cough for more than 2 weeks:

  • Evaluate for asthma and TB
  • Give first-line antibiotic for pneumonia for 5 days if child was not recently treated with antibiotics for pneumonia
  • Give salbutamol for 14 days if child is wheezing or coughing at night
  • Weigh child to assess for weight loss
  • Ask about TB or chronic cough in the family
  • See the child in 2 weeks
  • If there is no response to above treatment or child is losing weight, obtain an X-ray of the chest to check for signs of TB.
  • If an X-Ray is not available, a clinician can make the decision to begin treatment for TB based on high index of suspicion (see below)
Approach to diagnosis of TB in children
  • The commonest type of TB in children is extrapulmonary TB, mainly intrathoracic. Other forms include TB lymphadenopathy, TB meningitis, TB effusions (pleural, pericardial, peritoneal) and spinal TB.
  • The diagnosis of pulmonary TB in children is difficult. Most children with pulmonary TB are too young to produce sputum for smear microscopy.
  • Important features of pulmonary TB include:
    • Contact with a smear-positive pulmonary case;
    • Respiratory symptoms for more than 2 weeks, not responding to broad-spectrum antibiotics;
    • Weight loss or failure to thrive especially when not response to therapeutic feeding programme.
  • Positive test to the standard dose of tuberculin (2 units tuberculin (TU) or RT23 or 5 TU of PPD-S: 10 mm or more in unvaccinated children, 15mm or more in BCG-vaccinated children. However, with severe TB and/or advanced immunosuppression, the TST may be negative.
  • Chest X-ray findings are often not specific, however become more valuable if there has been a history of close contact with a diagnosed pulmonary TB case.


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