What is the amount of air that normally reaches the alveoli in an adult?

In adults, the average tidal volume, which is the amount of air exchanged during normal breathing, is about 500 mL. However, not all of this air reaches the alveoli for gas exchange. In fact, approximately 150 mL of this air fills the anatomical dead space—the areas of the respiratory system that do not participate in gas exchange, such as the trachea and bronchi.

Therefore, the amount of air that actually reaches the alveoli for effective gas exchange is calculated by subtracting the volume of dead space from the tidal volume. This results in an estimated volume of about 350 mL that contributes to oxygenation and carbon dioxide removal in the lungs. This is a critical factor in understanding respiratory physiology and the efficiency of breathing in adults.