Pneumotachograph

The pneumotachograph is a medical device for performing spirometry and thus for checking lung function . In addition to the function of a classically structured spirometer , a pneumotachograph can also determine dynamic tidal volumes.

function

Schematic of a pneumotachograph

With the pneumotachograph, the patient breathes through a tube in which there are a large number of small lamellae. These fins create a small flow resistance inside the pipe, which creates a minimal pressure difference between point A in front of and point B after the fins. Since this pressure drop A - B with laminar flow is directly proportional to the volume flow according to the Hagen-Poiseuille law, the patient's respiratory flow rate can be measured after the device has been calibrated beforehand.

By integrating the volume flow one can after

${\displaystyle V=\int \left({\frac {\mathrm {d} V}{\mathrm {d} t}}\right)\mathrm {d} t}$

Calculate the time course of the volume and determine all important vital volumes from it .

A device connected to the pneumotachograph for evaluating the measured values ​​(processor) then displays the results as a volume-time curve for the static and as a flow-volume curve for the dynamic tidal volumes.

literature

• Rainer Klinke and Stefan Silbernagl (eds.): Textbook of Physiology . Stuttgart, New York: Thieme , 2005