What is the Reid index used to measure?

• A. Airway resistance
• B. Submucosal layer thickness
• C. Lung capacity
• D. Recovery time from asthma

Answer: (B)

The Reid index is a specific measurement used to evaluate the thickness of the mucosal layer in the airways, particularly referring to the ratio of the mucous gland layer to the thickness of the wall of the airway (the total wall thickness). It is calculated by dividing the width of the mucous gland layer by the width of the airway wall itself. An increased Reid index is often associated with chronic bronchitis, as it reflects increased mucus production and gland enlargement in response to chronic irritation, typically from smoking or environmental pollutants.

While airway resistance, lung capacity, and recovery time from asthma are important parameters in pulmonary physiology, they are not directly measured by the Reid index. Airway resistance is more related to the dimensions of the airways and airflow dynamics, lung capacity pertains to the volume of air the lungs can hold, and recovery times in asthma involve assessment of clinical symptoms and bronchodilator responses rather than structural changes measured by the Reid index. Thus, the focus of the Reid index is specifically on the characteristics of the airway structure related to mucus production.