Lung Volume vs Lung Capacity
Respiration can be stated simply as the process of up taking oxygen and removing carbon dioxide from the cells of the body. The gas exchange and the cellular respiration are the main categories of it. The human respiratory system is well designed to the process of gas exchange. Ventilation and breathing, gas transfer and transport, blood flow to the lungs and control of breathing are the main functions of the human respiratory system. The lungs play an important role with regards to the respiration. The quantity of air in the lungs can be subdivided into several volumes and capacities. The lung capacity is the sum or combination of two or more lung volumes. Measuring lung volume is a key to understand the normal function of the lungs and the disease states. Some of these volumes and capacities can be measured directly by simple spirometry.
What is Lung Volume?
The lung volumes can be classified as Inspiratory Reserve Volume (IRV), Tidal Volume (TV), Expiratory Reserve Volume (ERV), and Residual Volume (RV). Inspiratory Reserve Volume (IRV) is the additional volume of air that can be inhaled with utmost effort after a normal inspiration. Average IRV in men is 3.3 L, and in women it is 1.9 L. Tidal Volume (TV) is the volume of air breathed normally in and out without any effort. This can be increased with exercise or activity. Average TV in men is 0.5 L, and in women, it is 0.5 L. Expiratory Reserve Volume (ERV) is the additional volume of air that can be exhaled forcibly after normal exhalation. Average ERV in men is 1.0 L and for women is 0.7 L. Residual Volume (RV) is the volume of air left in the lungs at the end of maximal expiration (the lungs can never be entirely emptied). Average RV in men is 1.2 L and for women is 1.1 L.
What is Lung Capacity?
Lung capacities can be classified as Inspiratory Capacity (IC), Functional Residual Capacity (FRC), Vital Capacity (VC), and Total Lung Capacity (TLC). Inspiratory Capacity (IC) is the total of Tidal Volume and Inspiratory Reserve Volume (VT + IRV). Average IC in men is 3.8 L, and in women, it is 2.4 L. Functional Residual Capacity (FRC) includes the expiratory reserve volume plus the residual volume (ERV + RV). This is the total volume of air left in the lungs after a normal, resting expiration. Average FRC in men is 2.2 L, and in women, it is 1.8 L. Vital Capacity (VC) means the total utilizable volume of the lungs which is under voluntary control. Average VC in men is 4.8 L, and in women, it is 3.1 L. Total Lung Capacity (TLC) is the total volume of the lungs, and it is the sum of residual volume and vital capacity. Average TLC in men is 6.0 L, and in women, it is 4.2 L.
What is the difference between Lung Volume and Lung Capacity?
• The lung capacity is a combination of two or more lung volumes.
• The value of lung volume is smaller than that of lung capacity.
• Inspiratory Reserve Volume (IRV), Tidal Volume (VT), Expiratory Reserve Volume (ERV), and Residual Volume (RV) are the types of lung volumes, whereas Inspiratory Capacity (IC), Functional Residual Capacity (FRC), Vital Capacity (VC), and Total Lung Capacity (TLC) are the types of lung capacities.
• When considering lung volumes, Residual Volume cannot be measured directly by simple spirometry and, with regard to lung capacities, the Functional Residual Capacity should be measured by using indirect methods.