How is vital capacity defined?

• A. The total air volume the lungs can hold
• B. The maximum air exhaled after maximum inhalation
• C. The minimum air needed for survival
• D. The average air inhaled at rest

Answer: (B)

Vital capacity is defined as the maximum amount of air that can be exhaled after a maximum inhalation. This measurement is significant because it reflects the capacity of the lungs to exchange air and can indicate respiratory health. Vital capacity includes several components of lung volume: tidal volume (the amount of air inhaled or exhaled during normal breathing), inspiratory reserve volume (the maximum amount of air that can be inhaled above the tidal volume), and expiratory reserve volume (the maximum amount of air that can be exhaled after a normal expiration).

By assessing vital capacity, healthcare providers can gain insights into a person's lung function and detect any potential respiratory issues. It is important to differentiate vital capacity from the total lung capacity, which includes residual volume, the air that remains in the lungs after maximal exhalation, and is not involved in the vital capacity measurement. Thus, understanding vital capacity helps in evaluating how effectively the lungs can move air in and out, which is critical for proper gas exchange.