About Lung Capacity

By Dr. Rachel Levine

Lung capacity is a measurement of the total volume of air that the lungs can hold, usually estimated at around 6,000 mL. This amount is influenced by a number of things including gender and position relative to sea level. Increased lung capacity is a measure of greater cardiovascular fitness.

Total Lung Capacity

Total lung capacity is the maximum amount of air the lungs can hold at a given time. It is determined by adding together the total amount of air already in the lungs prior to inhalation (the expiratory resolve volume, the residual volume and the tidal volume) to the total amount of additional air inhaled or the inspiratory reserve volume (IRV). Usually, people do not inhale or exhale their total lung capacity but rather breathe a shallow amount in and out of their lungs, known as tidal volume (Vt). Furthermore, there is always a residual amount of air in the lungs that can not be expired, known as residual volume (RV). The air left in the lungs that can be expired after an expiration is known as the expiratory reserve volume (ERV).

Tests

A series of pulmonary function tests can be used to measure the effectiveness of the lungs. The most common test is spirometry, which entails breathing into a mouthpiece attached to a spirometer. Measurements that can be taken include the amount of air that can be exhaled after a deep inhale (forced vital capacity), the speed of the exhale (peak expiratory flow), the greatest amount of air taken in during one minute (maximum voluntary ventilation), the total lung capacity, the amount of air remaining in the lungs after an exhale (functional residual capacity) and other measurements. Other types of tests include body plethysmography, inhalation challenge tests and exercise stress tests.

Factors Affecting Lung Capacity

Lung capacity can be increased as well as decreased. Athletes in particular show increased lung capacity, which corresponds with increased cardiovascular function. Lung capacity is increased for people who are tall, nonsmokers, athletes, and those who live at high altitudes. Lung capacity is smaller for people who are shorter in stature, smokers, non-athletes, and those who live at lower altitudes.

Increasing Lung Capacity

Breathing exercises that emphasize slow, deep breathing or holding the breath gradually expand lung capacity. Running and other cardiovascular exercises increase lung capacity as well. Increasing lung capacity can also be done by playing a wind instrument or signing with correct diaphragmatic breathing. Breathing under water through a tube will also increase lung capacity because the pressure on the chest makes it harder to breathe.

Cardiovascular Fitness

Cardiovascular fitness is improved by increased lung capacity. Basically, cardiovascular fitness is the body's ability to deliver oxygen to the working muscles and remove waste products. If the lungs take in more oxygen with each breath, the body receives its oxygen supply and gets rid of its waste supply without putting extra stress on the heart to work faster. If a person maintains lung capacity, the heart must beat more frequently to increase circulation in order to get more oxygen to the working muscles.

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