As we breathe, air enters the respiratory tract from the nose and traverses through the nasal passages into the pharynx. Pharynx is the area that is common to the passage of air and food. After the pharynx, air enters the larynx or the voice box and then enters the trachea (windpipe). In the larynx, a leaf-like structure called the epiglottis, forms a trapdoor on the trachea. The epiglottis closes the larynx while we swallow food to prevent its entry into the airway system. Trachea divides into the left and right bronchus at the carina and these bronchi supply air in the deeper parts of the lungs.

Any partial or complete blockage in this air pathway can be ominous and lead to breathing difficulty and abnormal breathing sounds.

STRIDOR

Loud, harsh, high pitched sound heard when the baby breathes in. This is produced due to partial blockage of the upper respiratory tract i.e from the pharynx to the carina. Often it is low pitched in calm babies and it becomes louder when the baby is agitated.

It may be accompanied by sinking of skin in the neck and tightening of neck muscles.

Stridor is a symptom and the cause of stridor must be eliminated in order to treat it.

More often than not, stridor is a medical emergency. It is most commonly heard in children with upper respiratory tract infections like:

• Laryngotracheobronchitis or croup
• Epiglottitis
• Bacterial tracheitis

However, non-infectious causes of stridor are not uncommon and need proper evaluation. These can be congential (babies are born with it) or acquired (children develop it after birth):

Congenital causes:

• Laryngomalacia
• Laryngeal muscle weakness – neurologically disabled children
• Anatomical malformations like laryngeal web, subglottic stenosis, tracheal narrowing
• Vocal cord paralysis

Acquired causes:

• Upper respiratory tract infections
• Foreign body aspiration
• Abscesses: retropharyngeal, peritonsillar
• Anaphylaxis
• Laryngeal webs
• Acquired subglottic stenosis
• Vocal cord palsy
• Tracheal mass

What can we do if our baby has stridor?

If the baby is born with a stridor or stridor is heard in the first few days of life, baby should be evaluated by a pediatric pulmonologist before the baby is discharged home.

Baby should be brought to the hospital for evaluation of airway in case he develops a stridor at home.

How is evaluation of stridor done?

Doctor examines the baby to ensure airway maintenance by checking oxygen saturation of the baby and sometimes arterial blood gases may be done to find out if this problem is acute or long standing.

Infectious causes of stridor can generally be diagnosed by physical examination and presence of other indicators like fever, drooling of saliva, congestion etc. Some blood test scan also be done to diagnose viral infections.

For other causes, airway visualization may be necessary which can be done by:

• Xray neck – Xrays give valuable information to the treating doctor about the cause, location of block and degree of blockage
• Laryngoscopy – This procedure is done to look for causes of obstruction in the pharynx and larynx. It gives direct visualization of these structures.
• Flexible bronchoscopy– This procedure offers complete evaluation of the entire respiratory tract from the nose till the bronchus. It also gives information of moving structures that can cause obstruction occasionally only while the baby cries.