It's a great example of education being aimed at the lowest common denominator and like much of healthcare gender based in the extreme.

I would ABSOLUTELY do abdominal thrusts if needed - for all the great reasons shared above.

The giveaway is the superimposed frequency is too regular in its waveform morphology both from f and amp perspective.

I haven't bothered to research why this happens but i had assumed it's a lack of EM shielding on very sensitive transducers / electronics?