For a doctor to determine the most accurate diagnosis of diseases of the respiratory tract, it must be as accurate as possible insight into the problem. Imaging technology allows to look into the body, unfortunately for example lung is an organ, where without contrast agent does not buy the picture. Furthermore, the methods that can be used are whole body plethysmography or, a better option, spirometry. A measurement of spirometry is performed by the pneumotachograph or the spirometry. Spirometer measures lung volumes and lung capacity. Pneumotachograph is the flow rate measuring device, but can also be used for indirect measurement of lung volumes and capacities. Spirogram is the result of spirometry measurements.