[hifikuno]

From the littlei know from a breath holding workshop I did awhile ago (for trying to get into freediving) it's the carbon dioxide build up in our blood that gives us the urge to breath, and not the lack of oxygen. If this method allowed for the removal of carbon dioxide from the blood then holding your breath might not even be discomforting.

Edit: goodells explained it better!

[not_a_bot_4sho]

I'm scuba certified.

Now I'm wondering if I should get certified to dive with an anal rebreather too.

[dillydogg]

The acid base balance of the cerebrospinal fluid is the primary driver of the respiratory drive, like allude to with your comment on the CO2. I did want to add that the lack of oxygen can affect respiration, which is detected by the peripheral chemoreceptors, like in the carotid bodies.

Additionally, the thoracic stretch receptors are important for respiratory drive, where the lack of expansion of the chest will promote respiration. When a healthy young person holds their breath for short periods, say 30 seconds or so, their blood CO2 and O2 are not much different, but they still will have to fight the instinct to breathe!