What do the Events recorded in the PSG annotation file (xml file with stages) using terms CentralApneaFinding, ObstructiveApneaFinding and HypopneaFinding exactly mean? How are they measured/scored? Technician? What are the thresholds and exact definition? Other events recorded are HemoglobinOxygenDesaturationFinding, SleepArousalFinding, ArtifactFinding.
Most of the events in the annotation files were marked by a technician. Each dataset should have an overview of the scoring procedures/rules that should provide the details you mention. For CHAT, that documentation exists here: https://www.sleepdata.org/datasets/chat/pages/manuals/polysomnography-reading-center/6-07-scoring-procedures.md
Let us know if you have further questions. If you want a fuller explanation, I can ask one of our PSG experts to comment. Thanks for using the NSRR!