holding breath while feeling blood system

I have been having quite a struggle getting in to the studio... teaching the Kinesthetic Transference work, warming up with my students and then never having time to do the work myself. I am more than hungry to do the work- but my job administrating the graduate program at York is quite time consuming. I have found myself quite frustrated- but in a way this again clarifies for me what I long for at this time... to simply be able to practice this work and do more serious embodied research. Today I was able to work for 1.5 hrs- nothing really but still better than nothing! And I am able to land inside the work pretty quickly. My ability to juggle sensation through many of the systems seems to not diminish- in fact seems stronger than ever. I am practicing this while I teach it- and I must learn to separate this work in my mind from being 'fit' in the usual sense... as this is more mind/body fitness. I have been experiencing some pain in my diaphragm/lung area and I was able to use that to feel more of my liver/diaphragm than I have ever been able to feel before. I came to a halt however when I had pain in my right foot. It seemed to require a different kind of attention than the 'sensation' elsewhere in my body. I never quite figured it out and I shifted to more mind directed work. I did some breathing work and was feeling my blood system between inhale and exhale as it speaks about in the 'Centering' section of Zen Flesh, Zen Bones - It is astonishing how long I can... I wouldn't even call it hold my breath... but stop breathing as i focus on my blood system. Feeling the blood seems to distract me- as I have heard that free divers for example will distract themselves from breathing by going slowly through the alphabet and thinking of people they know with names that begin with each letter, or sing a song they know over and over and other tools to distract the brain for the desire to breath... as I was doing this I did not time my breath holding- but at the end of the exhale I would go into quite a deep state and it was only at some point where I thought- gee... is this not healthy? I should breath soon... that I would breath. I suspect that this is not so healthy but I am not sure. The place of feeling the blood with gravity sensation is so peaceful and without the breath it takes on an even deeper calm... I feel I must study this more carefully before I continue to practice... I am sure there must be yoga practitioners/meditators/divers who have addressed this