Lung Volumes and Lung Capacity

Breathing or respiration is the process of two stages, inhaling and exhaling to promote the exchange of gases within the environment. In this process, the required amount of air is taken in and released out with the help of our nose and other respiratory organs. The volume of air involved in breathing process can be evaluated with the help of a spirometer. It is an equipment which is used to examine the total volume of inhaled and exhaled air by the lungs. It is also used in Pulmonary function testing.

Lungs

The Lung’s volumes and capacity refer to the total quantity of air correlated with different stages of the respiratory cycle. The volume of lungs can be directly measured while the lung’s capacities are assumed from lungs volume. The average lung capacity of an adult human male can hold about 6 liters of air, among which only a small amount of this capacity is used during normal breathing mechanism.

Lung’s Volumes and Capacities

Lung's Volumes

TV- The tidal volume is the total amount of air inhaled or exhaled during regular respiration or relaxed breathing. Approximately 500 ml of air is utilized during normal respiration in a healthy man.

IRV- An inspiratory reserve volume is a supplementary volume, approximately ranging between 2500 to 3100 ml of air which could be effectively inhaled after the inspiration of a standard tidal volume.

ERV- An expiratory reserve volume refers to the additional capacity of air which is about 1200 ml are that could be forcibly exhaled out after the expiration of a standard tidal volume.

RV- The residual volume is about the total volume of air around 1100 ml to 1200 ml residing in the lungs after the reserve volume is emitted or breathed out.

By adding up specific lung volumes we can find the values of lung capacities.

TLC- The total lung capacity applies to the total volume of air filled in the lungs after a forced inspiration. The lung capacity of a healthy man is estimated to be 6000 ml.

 TLC = TV + ERV + IRV + RV

VC – The vital capacity: is the total volume of air that can be expired after maximum inhalation approximately 80 percent TLC.

About 4800 ml approximately 80 percent TLC.

VC = TV + ERV + IRV

IC- The inspiratory capacity is the total volume of air that can be inspired which is about 3600 ml.

IC = TV + IRV

FRC – The functional residual capacity is the total volume of air residing within the lungs after an exhalation process and it is about 2400 ml.

FRC = ERV + RV

lung-volumes-and-capacities-graph

The residing air present within the lungs which does not participate in gas exchange is located in the portion of the airways inside the bronchi and bronchioles and outside the alveoli.

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