What is typically the cause of stridor?

Stridor is a high-pitched, wheezing sound that is often associated with breathing difficulties and is typically a result of an obstruction in the air passages. This obstruction can occur anywhere in the respiratory tract, particularly in the upper airway, and can be caused by a variety of factors such as swelling (from anaphylaxis or infection), foreign body aspiration, or structural abnormalities.

When the airways are obstructed, air may struggle to pass through, particularly during inhalation, leading to the characteristic sound of stridor. Understanding this mechanism is crucial for medical professionals, especially in an emergency setting, as it helps in assessing the severity of a patient’s condition and determining the necessary interventions.

The other options do not accurately describe the cause of stridor. Normal airflow through the lungs would not produce stridor, and fluid in the lungs is typically associated with different respiratory sounds, such as crackles. Meanwhile, lung infections might lead to other types of respiratory distress but would usually not present as stridor unless accompanied by upper airway obstruction.