@stuartv no pressure gradient in air so orientation doesn't matter. There is a LOT of venturi effect that happens in the exhaust diaphragm on exhale if it is in the right orientation, and obviously everyone is aware of the venturi on the inhale side if they've ever experienced a freeflow that stopped when the mouthpiece went down.
As to the AI question.
I have not used AI to map my breathing though am curious to do so at some point. The reasoning behind it being unlikely that you would be able to maintain that amount of breathing rate for any extended time unless you regularly do sprint type exercises is that you are in what is considered hyperventilation territory. Even those that do that regularly are rarely able to maintain it for over 1 minute without passing out.
Per CARB who did a big study, a male jogging at 12min/miles will breathe just under 60lpm or about 2cfm. While that is obviously not terribly fast and is certainly something that most people can maintain if you do any cardio work, it is unlikely you'll ever have to do something like that unless you are running away from something.
Walking a 24min mile is about .9cfm fwiw
So let's map to see if 3cfm is reasonable to attain for a while.
Total vital capacity of someone your size who marched brass instruments could be up to about 6 liters or .2cf. This is over twice what the ANSTI machine uses because to get that amount of air, you have to suck in as much as you can, and then forcefully exhale as much as you can. You have to repeat that 15x/minute to hit 3cfm. If you attempt this, do it on the couch because if you force yourself to maintain it for a full minute, you are liable to pass out. If you do it for 3 minutes, I'll be amazed. I have seen people that can do this, but when they did it, they were about to go to BUDS so were training for it.
A more realistic number is about about 3l/breath which is similar to the breath you would take while playing trombone and running around a football field. It is as much as you can reasonably inhale without trying very hard. To do that at 3cfm, you have to take those size breaths 29x/minute. In for 1s, out for 1s. If you do that, you are likely to pass out as well. This would be more analogous to running a 5k or something. Again, not impossible, but the odds that someone has a reason to maintain that underwater for any length of time is unlikely
The USN fwiw defines 2cfm as equivalent to running a 7.5min mile and is under "Heavy Work" and only specs up to 3.5cfm as "Severe Work". Hyperventilating causes O2 levels to drop in the body as it is trying to expel CO2 which is why you pass out. The USN says that their fit divers can maintain a SAC rate of 2.6cfm for about 2 minutes but any more than that is high risk. Anything over 2cfm is considered "extreme conditions" and is to be avoided if at all possible. They spec that anything over 1.4cfm means that the diver needs to slow down. If they are in hard hats the tenders will know their breathing rates and tell them to calm down. Now, this was taken primarily from a hardhat standpoint, but breathing is breathing, so if the USN says that their guys in good shape *which is a complete level if crazy in shape* can do 2.6cfm for 1-2 minutes if they have to, I find it hard that us mere mortals could maintain 20% more than that for 50% longer. If I had AI and I saw that on the graph, I'd definitely know what happened that caused a spike equivalent to what probably feels like trying to catch your breath after sprinting a mile.
Reference for CARB paper
Research Note: # 94-11 How Much Air Do We Breathe?
Good discussion in the KM manual on breathing rates. Obviously scheduled around hard hats, but same principals apply
http://www.kirbymorgan.com/sites/default/files/pdf/manuals/km77/KM77_Complete.pdf
The Deep 6 second is slightly better with my turbo poppet. Look at the ratings it got compared a couple years back compared to the Deep 6 Signature. It simply doesn't make sense. Sample variation doesn't even explain what I am seeing in the review.
