Regardless if we speak about static or dynamic apnea, hyperventilation (at that's exactly what you do according your description), is in freediving generally considered as very dangerous and even counterproductive. Saturation breathing does not necessarily have to be deep - you will find different descriptions and approaches if you look through the forum, but generally it is a rather fast inhalation (i.e. 4 counts), short breath hold (i.e. 3 counts), and then looong slow exhalation (count 12-15). It is the slow exhale that calms down the heart and can even induce bradycardia.
Deep breathing will not help to oxygenate your blood, it only lowers the CO2 level in the lungs and in your blood, which is very dangerous for several reasons:
- higher probability of LMC or blackout due to delayed urge to breath
- low acidity hence high O2 binding of hemoglobin, with consequent reduced oxygenation of brain
- carotid constriction and hence brain hypoxia at the beginning of the apnea with the possibility of blackout in the first phase of apnea
- increased heart rate
- higher O2 consumption
- delaying or suppressing of the diving reflex
Read more information for example in the thread
http://forums.deeperblue.net/static-...-good-bad.html
The revolutionary method of Seb Murat even teaches to ventilate less than normally (and to dive on empty lungs), to kick in the diving reflex as fast as possible - just like seals do. The performances they achieve with this method are amazing. Read more about it for example in the article at
Fridykning.se