Bodyplethysmography

Bodyplethysmography, also known as whole-body plethysmography, is a procedure used to test the function of the lungs. It is used primarily to determine two important parameters of lung function: intrathoracic gas volume during resting breathing (volume of air in lungs at the end of a normal exhalation) and resistance (airway resistance).

Indications (areas of application)

• Complaints such as dyspnea (shortness of breath) or cough both at rest and on exertion
• Bronchial asthma
• Chronic obstructive pulmonary disease (COPD) resulting from years of smoking or chronic bronchitis (inflammation of the bronchial tubes)
• Pulmonary emphysema – overinflation of the lungs as a result of obstruction, which manifests itself in the destruction of the alveoli, difficult exhalation and a decrease in lung performance
• Pulmonary fibrosis – connective tissue, scarring remodeling of the lung skeleton, which severely impedes the elasticity of the lungs and thus the inhalation; this is a restrictive lung disease
• Follow-up of bronchopulmonary diseases.
• Therapy control of bronchopulmonary diseases
• Allergy diagnostics

The procedure

During the measurement, the patient sits in an airtight chamber of about 1 m², which is similar to a closed telephone booth. The patient is connected to a separate room via a mouthpiece through which he can breathe freely. The mouthpiece is also a so-called pneumotachograph, which measures the respiratory flow rate (volume moved by breathing per unit time) during inspiration (inhalation) and expiration (exhalation). The chamber is also equipped with pressure sensors. The aim of the examination is to measure lung volumes that cannot be ventilated (volumes that cannot be actively moved by respiration), this includes, for example, the residual volume (volume that remains in the lung after maximum expiration so that it does not collapse).The principle of the bodyplethysmograph is based on the Boyle-Mariotte law. This law states that the product of volume and pressure is constant in a closed space. When the patient breathes, the pressure in the chamber changes due to the thoracic movements (movement of the chest) and is registered by the sensors. To calculate the intrathoracic gas volume, the mouthpiece is closed at the end of a normal exhalation. As a result, the patient inhales and exhales against a resistance. The air trapped in the lungs is compressed and decompressed. This results in the measurable pressure changes in the plethysmograph, from which the quantities sought are calculated. The calculated intrathoracic volume corresponds to the functional residual capacity (volume in the lung after normal expiration). From it, the residual volume can now be determined. The quantities have the following meaning:

• Residual volume (RV): the residual volume is often increased in the obstructive lung diseases (diseases that make exhalation difficult). The patient cannot completely exhale the inhaled volume because swelling or secretions due to inflammation constrict the airway. Obstructive lung diseases include bronchial asthma, chronic obstructive pulmonary disease (COPD) or emphysema.
• Resistance: the resistance results from the respiratory flow strength measured at the mouthpiece and the registered pressure changes. It represents the force opposing the gas flow and is mainly dependent on the diameter of the airway. Airway resistance is also a measure for detecting obstructive lung disease, as it is elevated in this case.

Bodyplethysmography is used to accurately quantify obstructive and restrictive lung disease (disease that decreases the elasticity of the lungs and makes it difficult to breathe in), measure lung hyperinflation (by increasing residual capacity), perform bronchospasmolysis tests (test to characterize increased airway resistance due to administration of drugs that dilate the bronchi, for example, only in asthma), and perform provocation tests. Bodyplethysmography is a proven method of pulmonary function diagnostics and enables accurate measurement of all clinically relevant parameters.Results