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Updated: May 11, 2026

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics
Published on: August 27, 2013
Low frequency filtering of nasal pressure channel causes loss of flow limitation
Robert N Walter1, Bradley V Vaughn
1Department of Neurology - Sleep Division, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. robreganw@gmail.com
Study Objectives:
The objective of this clinical vignette is to explore whether changes in low filter settings for respiratory waveforms have a clinically significant effect on patient management of obstructive sleep apnea (OSA).
Design:
This is a case report.
Methods:
We collected data from a continuous positive airway pressure (CPAP) titration polysomnogram (PSG) performed in our university based sleep laboratory. We reviewed the flow signal using low frequency filter settings of 0.0, 0.1, 0.3, and 0.5 Hz.
Results:
We noted that a change in the low frequency filter for respiratory flow caused a change in the appearance of an otherwise flattened waveform indicating flow limitation to no longer appear flat.
Conclusion:
We noted that indiscriminate use of the low frequency filter for nasal pressure and flow estimate channels may lead to greater difficulty recognizing respiratory flow limitation.
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