[efattah]

O'boy,

I have found that the lowest oxygen consumption occurs when the urge to breathe comes very early. The sooner the urge to breathe hits you, the sooner your oxygen consumption goes down.

Of course, if the urge to breathe comes early, you might be getting body-buckling contractions later on. Avoid that.

The best breath-hold (I think) should be done with an 'early urge to breathe', but with resisting the contractions and relaxing at the same time.

If you feel no urge to breathe at all, then your O2 consumption will be high. So, delaying the urge to breathe until the very end, by aggressive breathing, is counter-productive... in many ways.

As an example, my highest SaO2 at the 5-minute mark came on a breath-hold in which contractions came around 3'45". I have done several breath holds where I reached the 5-minute mark without contractions, and my oxygen level was way worse at 5-minutes, because the urge to breathe never came, meaning my O2 consumption never dropped.