Comprehensive Respiratory System Disorders Q 65

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Which phrase is used to describe the volume of air inspired and expired with a normal breath?

  

     A. Total lung capacity

     B. Forced vital capacity

     C. Tidal volume

     D. Residual volume

    

    

Correct Answer: C. Tidal volume

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Tidal volume refers to the volume of air inspired and expired with a normal breath. Tidal volume is the amount of air that moves in or out of the lungs with each respiratory cycle. It measures around 500 mL in an average healthy adult male and approximately 400 mL in a healthy female. It is a vital clinical parameter that allows for proper ventilation to take place.

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Option A: Total lung capacity is the maximal amount of air the lungs and respiratory passages can hold after a forced inspiration. Among healthy adults, the average lung capacity is about 6 liters. Age, gender, body composition, and ethnicity are factors affecting the different ranges of lung capacity among individuals. TLC rapid increases from birth to adolescence and plateaus at around 25 years old.

Option B: Forced vital capacity is the vital capacity performed with a maximally forced expiration. Vital capacity may be measured as inspiratory vital capacity (IVC), slow vital capacity (SVC), or forced vital capacity (FVC). The FVC is similar to VC, but it is measured as the patient exhales with maximum speed and effort.

Option D: Residual volume is the maximal amount of air left in the lung after a maximal expiration. In other words, it is the volume of air that cannot be expelled, thus causing the alveoli to remain open at all times. The residual volume remains unchanged regardless of the lung volume at which expiration was started.

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