Question

Volume of air breathed in or out during normal breathing is called as
A. Vital capacity
B. Inspiratory reserve volume
C. Expiratory reserve volume
D. Tidal volume

Answer 1

Lung volume refers to the volume of gas in the lungs at a given time during the respiratory cycle, also known as respiratory volume. By summation of different lung volumes, lung capacities can be derived. The four types of volume in the lungs are as the follows: tidal volume, expiratory reserve volume, inspiratory reserve volume, and residual volume.

Complete answer:
Option A Vital capacity: The air that can be moved into or out of the lungs in a single respiratory cycle is the highest level. Vital capacity can be equated to Expiratory reserve volume $+$Tidal volume $+$Inspiratory reserve volume.
Option A is not correct.
Option B Inspiratory reserve volume: It can be defined as the amount of air that can be further inhaled after a normal inhalation. For a normal adult person, inspiratory reserve volume is about $3.1$ liters.
Hence option B is also not correct.
Option C Expiratory reserve volume: It can be defined as the amount of air that can be exhaled after a normal exhalation. For an average adult person, expiratory reserve volume is about $1.2$ liters.
Hence option C is not correct.
Option D Tidal volume: It measures the amount of air that is inhaled and exhaled during a normal breath. On an average adult person, this volume is around one-half liter.
Hence the correct option is D.

Hence, Option D. Tidal volume is the correct answer.

Note:
The technique by which lung volumes are measured is called spirometry. During spirometry, one of the important measurements taken is m forced expiratory volume (FEV), which basically measures the amount of air that can be forced out of the lung over a specific period, which is usually one second (FEV$1$). In addition to this, the forced vital capacity (FVC), is also measured. The ratio between these values i.e., $\dfrac{{FEV1}}{{FVC}}$ ratio is used to diagnose serious lung diseases which includes asthma, emphysema, and fibrosis.