Question

Define Vital capacity. What is its significance?

Answer 1

Hint: It’s related to respiration in humans, also known as “Lung Volumes”.

Complete answer:
Vital capacity (VC) is the maximum volume of air expelled from the lungs after maximal inspiration. Vital capacity is calculated using the formula:

VC = Inspiratory reserve volume (IRV) + Expiratory reserve volume (ERV) + Tidal volume (TV)

The IRV and ERV refer to the volume of air inhaled and exhaled above and beyond normal breath. Tidal volume or TV is the standard low volume breath. VC is measured in a cubic centimeter (cc) of air that can be exhaled. Vital capacity depends on sex, height, and age of a person. VC decreases 200 to 250cc per 10 years of age. A normal adult has a Vital capacity of 3 to 5 liters in the whole body at a given point of time. Females have around 50 to 60cc/kg and Males have 70cc/kg of vital capacity. The minimum life-sustaining VC is 15cc/kg.

Additional Information:
- VC is also affected by diseases like in obstructive lung disease there is a mild decrease in VC and in restrictive lung disease, VC is severely decreased, as the lungs cannot expand fully.
- For measuring the average VC for a person following formula can be used, it shows the dependence of VC on sex, age, and height of a person:
- Vital capacity (VC) for female = (21.78 – 0.101*Age)*Height
- Vital Capacity (VC) for male = (27.63 – 0.112*Age)*Height

Note: VC is measured using the instrument called Spirometer that not only gives VC values but also separates and provides the information of IVR, ERV, and TV.