The autonomic nervous system? A cyclic in sympathetic nervous activity should cause respiratory and EDA changes, plus muscle tone changes, etc.

A bit outside my expertise, but I’d start by looking at cyclic changes in arousal. Breathing will likely reflect the same processes.
I think it may be tantamount to asking why breathing rate & depth ever change during rest. Presumably it’s autonomic?

Not sure it’s a wise approach if ASL is available. Then again, lag maps via RapidTide are of their own benefit & return useful values even with v long latency of severely compromised vasculature.

Hm, not sure it's a test of ingenuity. A stress test, maybe. Or a sanity check. Trial by ordeal, something like that. Bloke named Sisyphus on your corporate board by any chance...?

Testing Bluesky reply functionality… Please ignore! Must be a MicroShaft retribution function or something.

Any organization that chooses MS operating systems or software for their critical systems - looking at you, Siemens! - should be dismantled on humanitarian grounds.

What is Outlook?