Which phase of the respiratory cycle can stridor occur during?

• A. Only during expiration
• B. Only during inspiration
• C. Both inspiration and expiration
• D. Only during resting breathing

Answer: (C)

Stridor is a high-pitched, wheezing sound that is typically indicative of obstruction in the upper airway. It can occur during both inspiration and expiration because it signifies turbulence in airflow as the air moves past a narrowed area in the airway.

During inspiration, stridor often arises when the larynx or trachea is compromised, leading to difficulty in drawing air in. Conversely, during expiration, stridor can occur if there is persistent obstruction or turbulence as air is expelled. The possibility of stridor during both phases highlights that the underlying issue affecting airflow can impact respiratory sounds across the entire cycle.

The other options are limited in scope, either suggesting stridor occurs only during one phase or under very specific conditions, which does not align with the nature of stridor as it can arise throughout the respiratory cycle when there's a significant obstruction in the upper airway.