What effect do constricted airways have on velocity when the volume of air remains constant?

When the volume of air remains constant and the airways become constricted, the velocity of airflow increases. This relationship is explained by the principle of continuity in fluid dynamics, which states that for an incompressible fluid (like air in many situations), the product of the cross-sectional area and the velocity of flow must remain constant.

As the cross-sectional area of the airway decreases due to constriction, in order to maintain a constant volume of air flowing through, the velocity of the air must increase. This relationship is often described mathematically as velocity being inversely proportional to the area: as the area decreases, the velocity must increase to keep the product of area and velocity consistent at a constant volume.

This principle is crucial in respiratory physiology and understanding how conditions like asthma or bronchitis can affect airflow in the lungs. In these conditions, constricted airways lead to increased resistance and consequently, higher velocities of air attempting to pass through the narrowed passages, which can affect breathing and overall respiratory function.