November 23, 2021

Adaptive Leak-Flow Compensation for Volume Measurement in Gas Flow Analyzers

As described here, manual adjustment of a baseflow might be a cumbersome process. It requires multiple steps which must be repeated every time if the intentional leak or the ventilator settings are changed. To simplify daily work, the FlowAnalyser PRO offers adaptive baseflow adjustment to compensate for leakage automatically. But how does it work?

The baseflow (or the leak flow) is not directly estimated based on pressure and flow. Instead, as a first step, the algorithm estimates the leak size which is assumed to be constant. It has a time constant τ of 30 seconds which results in an adaption time of 30 … 40 seconds typically. Therefore, it takes some time, until the algorithm is adapted to a new intended leak size. However, the leak flow is calculated based on the leak size and the actual pressure. This means that pressures changes take immediately effect to the calculated leak flow and needs no time to adapt.

How to activate?
The automatic leak flow compensation can be activated in the FlowAnalyser PRO device by marking the checkbox “Automatic” where the baseflow can be set. This setting is available on the user interface of the device and in the PC-tool FlowLab (Options -> Trigger). Note, that the automatic leakage compensation affects not only the inspiratory and expiratory tidal volume but also the minute volume and the volume curve.


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