Spirometry
Spirometry is also called the “small lung function test”. Spirometry enables the doctor to determine the vital capacity (i.e. the maximum amount of air that a person can breathe in and out) and the one-second capacity (how many liters of air are moved in one second during a strong exhalation). The measuring device, the spirometer consists of a tube system with a mouthpiece and is connected to a recorder.
This recorder displays the amount of air breathed as a curve, similar to how the heart currents are recorded on an ECG. The patient encloses the mouthpiece with his lips and is also given a nose clip. This is intended to prevent air from escaping through the nose and thus not being registered during the measurement.
The patient is then told how to breathe during the examination. Usually, the normal inhalation and exhalation (i.e. the breathing volume) is measured first. Then the patient should exhale as deeply as possible, and immediately afterwards inhale as deeply as possible and then exhale again strenuously and quickly.
Then normal breathing is recorded again. As a rule, the procedure is repeated several times to obtain several meaningful curves. During this lung function test it is immensely important that the patient cooperates well and understands the breathing instructions.
The examiners should motivate him to really do the exercises at full strength. Certainly, this is especially difficult with children, because they are not easily excited about the test in the somewhat frightening environment and with the uncomfortable nose clip. The lung function test is free of risks and also not painful. In some patients, however, the heavy breathing can lead to a brief feeling of dizziness.
Full-body plethysmography
This examination is mainly performed by specialized internists, i.e. lung specialists. The patient is placed in an airtight cabin, similar to a telephone booth. He is given a mouthpiece and breathes in and out through the so-called pneumotachograph, first normally and then, if necessary, accelerated or particularly deeply.
The resulting pressure differences in the chamber are then measured. In most cases, the doctor also carries out a closure pressure measurement. The mouthpiece is blocked and the patient exhales briefly against the resistance.
With the whole body plethysmography or body plethysmography the lung volume and also the resistance of the bronchi can be measured. The main advantage of this lung function test is that the patient does not have to actively participate. Normal breaths are sufficient to obtain meaningful values.
Plethysmography is absolutely harmless. There is neither pressure nor radiation exposure and the door of the chamber can of course be opened at any time. Only for patients with claustrophobia the examination could be a problem, because the chamber is relatively small and must be closed for a successful measurement.
