End-expiratory lung volume

The end-expiratory lung volume is the volume of the lung space after normal exhalation and corresponds to the sum of the expiratory reserve volume and the residual volume. A healthy person has an average of around 2.7 liters. Various lung diseases can pathologically decrease or increase the volume.

What is the end expiratory lung volume?

The lung volumes are the different volumes of the lungs. The breathing air takes this in in the various steps of breathing. Lung volumes play a role in both inspiration and expiration and are different when you inhale from those when you exhale. Combinations of individual lung volumes are understood as lung capacities.

The end-expiratory lung volume is the volume that the lungs have after normal expiration. It is also called functional residual capacity and thus corresponds to the volume of gas that remains in the lungs after exhaling.

Other lung volumes are the inspiratory reserve volume, the tidal volume, the expiratory reserve volume and the residual volume.

Pneumology is primarily concerned with lung volumes and all lung diseases.

Function & task

The paired lungs are used by air-breathing vertebrates to breathe. The efficiency of the breathing process is called lung volume. The individual lung volumes thus describe the efficiency with which the lungs absorb oxygen and excrete carbon dioxide.

During inspiration, air is drawn into the lungs through active breathing and the associated contraction of the respiratory muscles. When inhaling, only a fraction of the maximum lung volume that can be expanded through exertion is filled.

During expiration, the air exhaled from the lungs causes the diaphragm and chest to relax. During expiration, the lungs are only partially emptied of breathing gas and a volume of gas remains. This volume is the end-expiratory lung volume. This volume is therefore relevant for breathing and primarily plays a role in the form of the functional residual capacity.

The volume results from the sum of the residual volume and the expiratory reserve volume. The residual volume is the volume of gas that remains in the lungs after maximum expiration and that cannot be exhaled due to physical relationships. With a healthy lung, this value is 1.5 liters. The expiratory reserve volume, on the other hand, corresponds to the lung volume that can also be exhaled after normal expiration with forced breathing. The average for a healthy person is 1.2 liters. As the sum of the expiratory reserve volume and the residual volume, the end-expiratory lung volume of a healthy lung is therefore around 2.7 liters.

This functional residual capacity mainly plays a role in the diagnosis of pulmonary function. The value can be determined, for example, using methods such as the helium dilution method. In this test method, the doctor opens a helium gas supply that is supplied to the patient after normal expiration. When he breathes, he mixes the lung volume of the functional residual capacity with the ambient air he inhales. This creates a buffer function that can level fluctuations in the oxygen partial pressure between the breathing steps of inspiration and expiration. Thus, the oxygen partial pressure in the alveoli of the lungs falls. The CO2 partial pressure rises above that of the fresh air.

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Illnesses & ailments

The lung volumes take on pathological values ​​in the context of various diseases. In asthma, for example, the lung volume is severely impaired and requires medicinal agents to increase its efficiency.

The end-expiratory lung volume changes particularly in the case of obstructive pulmonary diseases. Diseases from this group make it difficult to breathe out because the airways are obstructed or narrowed. Breathing is slower as a result and the lungs become inflated.

Too little end-expiratory lung volume causes end-expiratory closure of the small airways. In the worst case, the downstream alveoli can collapse. The breathing loop can be normalized again through positive end-expiratory pressure.

Sometimes, however, the lung volumes are not reduced due to actual loss of function of the lungs, but rather due to curvatures of the spine. An increased end-expiratory lung volume can indicate an obstruction of the lungs. Additional ventilation could be counterproductive in such a circumstance.

Interstitial lung disease has the opposite effect on end-expiratory lung volume. They cause respiratory failure of the lungs and thus reduce the end-expiratory lung volume.

Lung function diagnostics are used in pulmonology to assess pathological lung volumes. Lung volumes also play a role in the intensive care unit, since decisions about possible ventilation steps must be made here. The small and large lung function can be checked using spirometry or body plethysmography. Spirometry measures the lung volume and the speed of breathing activity and can thus be used to assess the entire lung function.

There are various ways of independently testing lung volumes, but these are not particularly accurate. One of these possibilities is the candle test, in which a burning candle is placed about a meter away from the test person. Anyone who can blow out the candle from this distance has an excellent lung volume. A second test option for the private sector is the balloon test, in which the test person blows into a balloon once. The filling level of the balloon provides information on the expiratory vital capacity, which can be an indicator for the individual volumes of the lungs.