What is a functional residual capacity?
Functional residual capacity, or FRC, is the volume of air that remains inside the lungs after normal expiration or breathing. FRC represents the volume of air inside smaller respiratory passages and alveoli or air bags that form the lungs. In conditions such as emphysema, where the lungs become less elastic, there may be greater than normal FRC. Factors such as obesity can lead to reduced functional residual capacity. FRC is used along with other measurements known as lung function tests, to assess the condition of the lungs.
When a person breathes normally, the volume of air remains inside the lungs. This air consists of a volume of exhalation reserve or ERV and residual volume or RV. If, after normal expiry, one continues to breathe with as much effort, the ERV is an extra amount of exhaled air. The residual volume or RV is a small amount of air that remains inside the alveolůpoté, which was excluded from the lungs. Together ERV and RV form a functional residual capacity.
functional residual capacity can be useful because, when combined with other lung measurements, it can provide a value for total pulmonary capacity or TLC, which represents the total air volume that the lungs contain when they are full. As people age, while the total lung capacity remains the same, it is normal for functional residual capacity to increase. This is due to the natural loss of elastic backward nature in the lungs, which occurs as part of the aging process.
Increased functional residual capacity can be caused by any conditions that lead to excessive lung inflation. Such conditions may include emphysema and asthma. Reduced inflation and lower FRC occur when people lie or have been soothed and for those who are obese.
respiratory physiological laboratories can use different methods to measure functional residual capacity, including what is called the techniques of gas dilutionsmography of the whole body. The dilution of gas may include breathing in the known amount of helium in a closed system until the state of balance is achieved where the helium concentration in the lungs and the rest of the system is the same. The amount that Helium was diluted could be used to calculate the volume of functional residual capacity. Throughout the body of the knitness is performed by a person's breathing exercises inside the sealed box. Changes in the pressure inside the box can be measured and used to calculate the air volume in the lungs that represent FC.