What is the approximate anatomical dead air space in milliliters?

• A. 50 mL
• B. 150 mL
• C. 250 mL
• D. 350 mL

Answer: (B)

The approximate anatomical dead air space in a normal adult human is about 150 milliliters. This volume refers to the portion of the respiratory system that does not participate in gas exchange but remains within the conducting airways, such as the trachea and bronchi.

Understanding the concept of anatomical dead space is crucial because it emphasizes the volume of air that is inhaled but does not reach the alveoli where gas exchange occurs. This volume remains constant in individuals, highlighting how much lung volume is effectively "wasted" in terms of participating in oxygen and carbon dioxide exchange during respiration. Factors such as age or body size may cause slight variations, but the 150 mL estimate is commonly accepted in physiological studies.

This foundational knowledge is key in assessing ventilation efficiency and evaluating respiratory health, especially in clinical settings.