Presentation of Acute Stridor
Stridor is a harsh, vibratory sound produced from turbulent airflow through the respiratory passages. It is normally heard on inspiration but can be heard on expiration and sometimes can be biphasic. Click here to listen to an example of a child with croup.
Stridor is a symptom, not a diagnosis, and the underlying cause must be determined. It may be inspiratory (most common), expiratory, or biphasic, depending on its timing in the respiratory cycle, and the three forms each suggest different causes, as follows:
- Inspiratory stridor suggests a laryngeal obstruction
- Expiratory stridor implies tracheobronchial obstruction
- Biphasic stridor suggests a subglottic or glottic anomaly
Causes of acute onset of stridor. Please add the following to the start of this section.
The acute causes of new on set stridor include
- Infections such as croup, epiglottitis, peritonsillar abscesses, and retropharyngeal abscesses
- Ingestion of foreign objects or food
- Ingestion of toxic chemicals
- Airway burns
- Injuries to the jaw or neck
The volume of stridor does not correlate with the degree of obstruction.
Poiseuille’s Law
The underlying pathology is inflammation of the pharanx, larynx, trachea or bronchi. Poiseuille’s Law states that if the radius of the airway is halved then the resistance in the airflow increases by 16-fold.[3] It is the subglottic inflammation and swelling that compromises the airway in croup.
Learning bite
A small reduction in the diameter of the airway dramatically reduces the airflow and the child can rapidly deteriorate.