It's appropriate that a discussion regarding the usefulness of "Emergency Breathing Techniques" at high altitude should have drifted into the realm of science fiction, because that's what it is - PURE FICTION.
To LEM's question - "Does the second case make the blood boil, at least for a few seconds?", the answer is YES. And the end result of a few seconds of blood boiling is about the same as the micro-second that it takes for a bullet to pass through your heart - You're Dead!
Emergency / Rapid breathing techniques at Medium altitude will lead to hyperventilation, unconsciousness, and death.
Regards,
Old Smokey