Breathing Volumes and Minute Ventilation

Breathing Volumes

Tidal Volume (TV): The amount of air that enters or leaves the lungs during a normal breath at rest, approximately 500ml in a healthy adult.
Inspiratory Reserve Volume (IRV): The maximum amount of air that can be inhaled forcefully after a normal inhalation, averaging around 3000ml.
Expiratory Reserve Volume (ERV): The maximum amount of air that can be exhaled forcefully after a normal exhale, usually about 1200ml.
Residual Volume (RV): The amount of air that remains in the lungs after a maximal expiration to prevent the lungs from collapsing. This value is typically 1200ml.
Vital Capacity (VC): The sum of the Inspiratory Reserve Volume, the Expiratory Reserve Volume and the Tidal Volume. It represents the total amount of air that can be inspired after a maximal expiration (IRV+TV+ERV).

Minute Ventilation (VE) is the total volume of air entering the lungs in one minute. It is calculated by the product of the Tidal Volume and the respiratory rate (breathing frequency). For example, if Tidal Volume is 500ml and the respiratory rate is 12 breaths per minute, the Minute Ventilation would be 6 litres per minute.
During intense physical activities, the demand for oxygen in the muscles increases, causing the minute ventilation to increase as well. This is achieved by both increasing the depth of each breath (Tidal Volume) and the rate of breathing (respiratory rate).
Understanding Minute Ventilation helps to comprehend how effectively the respiratory system responds to the demands of exercise.

Age: As we age, our lung capacity and elasticity decrease, reducing the overall respiratory volumes and efficiency of gaseous exchange.
Fitness Level: Regular physical exercise can increase the volumes of air inhaled and exhaled and improve the efficiency of the respiratory system, enhancing oxygen and carbon dioxide exchange.
Body Size: Larger individuals generally have larger lungs, and thus larger respiratory volumes.
Altitude: The higher the altitude, the thinner the air, resulting in lower oxygen content. To compensate, your body increases both the rate and depth of breathing.