Question

What is Residual volume?

Answer 1

Hint: Lungs are the primary respiratory organs present in most of the higher vertebrates. The capacities and structures of lungs differ among different animals. Lung capacities and volumes help in assessing lung functions.

Complete answer:
Residual volume (RV) refers to the volume of air that still remains within the lungs after a forcible expiration. The average value of residual volume in a normal healthy adult human is between 1100 to 1200 ml. The residual volume of air within the lungs helps in preventing the lungs from collapsing.

There are various factors that determine the residual volume, which is: the strength of the muscles that help in expiration. An improvement in the value of residual volume indicates an increase in lung capacity. Residual volume cannot be measured directly. The Residual Volume measure can be used in the calculation of various lung capacities. Residual volume has many clinical signs such as the measurement of the level of obstruction in various airway diseases such as COPD and asthma.

Note: Pulmonary Function Tests or PFTs are a group of non-invasive tests that are used to determine lung function and capacity. Spirometry is one of the methods by which PFTs can be carried out. The various lung volumes that are measured in PFTs are Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), and Residual Volume (RV). The lung capacities measured are Inspiratory Capacity (IC), Expiratory Capacity (EC), Functional Residual Capacity (FRC), Vital Capacity (VC), and Total Lung Capacity (TLC). And also Peak Expiratory Flow Rate (PEFR).