Ultrasonic Spirometry

TrueFlow measurement technology

Ultrasonic Spirometry is a quick measurement method for direct and precise flow determination.

This ultrasound transit-time flow measurement method (TrueFlowTM)works with a high resolution of 1,000 measurement points per second, so that no substitute parameters for flow (e.g. differential pressure, temperature or turbine) are necessary.

Within the breathing tube ScoutTube, two diagonally opposing piezo-elements send and receive alternatively ultrasonic waves. Without any flow the transit time of the ultrasound waves is the same in both directions. Flow, moving the air inside the tube, will accelerate the waves in one direction, and slow them down in the other. The higher the difference between go and return, the higher the flow. All other factors (gas properties, humidity, temperature) are the same for both directions and cancel each other out.


  • Easy and quick changing of the disposable breathing tube ScoutTubeTM without the assembly of several pieces.
  • The high resolution of 1,000 measurement points per second is a substantial condition for reliability
  • No fluctuation of measurement values due to changing ambient conditions or breathing humidity.
  • Calibration free during running operation
  • No erroneous measurements due to wrongly or non calibrated pneumotachs
  • Determination of flow and all derived parameters as volume or also the resistance during the Bodyplethysmography measurement.


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