In the article, "How to Improve Your Air Consumption," by Ted Harty, Ted states that he has more techniques now that he teaches free diving. (1) I am saying, don't worry about your breathing right now, just breathe.
Free diving and scuba do not mix. There are probably some of you that will do one or the other, but probably not that will do both. With scuba, our goal is really to spend as much time underwater as possible. The treasured 60 minute marker on the average scuba cylinder is what I shoot for. I can admit that holding one's breath for 5 minutes is impressive. With that said, what do you get to see on a 5 minute dive?
When the new diver learns about the physics and physiology of scuba diving, it is regularly drilled into their head that one should never hold their breath. I really believe that this extends to not messing with breathing techniques as well. Outside of the photographer who might be sitting on the bottom and holds their breath for a fraction of a second while depressing the shutter release, air consumption should be natural. I also encourage divers to not start their dive until they, and everyone they are diving with are ready. If anyone is anxious, that anxiety is not likely to go away and very likely to continue with the diver throughout the entire time underwater.
Relaxation and being at peace starts before the dive and is a state of mind. I became cave certified in 2007 and air consumption rates with an overhead environment are crucial. One cannot become nervous, start breathing heavy and use up more air as they are required to return to the cave entrance to exit. Cave divers as well as technical divers use the "rule of thirds" to determine their turn around time. One third in, one third back, and one third for reserve. Increasing air consumption rates means ending the dive sooner or having to not do a dive that will require greater than two-thirds of the gas volume the diver is carrying.
I do agree that relaxation techniques on dry land can benefit air consumption rates, but while diving, several factors change when manipulating the regular inhalation and exhalation we normally do. Carbon dioxide buildup, over-expansion injuries, and decompression sickness are the big ones that divers want to avoid. Carbon dioxide build up in diving usually occurs from the diver not fully exhaling. That doesn't mean exhaling to the point we could call our lungs "empty" but surely to the point where the diaphragm cannot push anymore air out of the lungs. Carbon dioxide buildup can manifest itself from, "inadequate breathing, a tight wetsuit, overexertion, regulator malfunction, deep diving, and contamination of the air supply with exhaled gases. Carbon dioxide levels in the blood can increase, causing shortness of breath and sedation, resulting in carbon dioxide toxicity. Carbon dioxide toxicity symptoms include: nausea, vomiting, dizziness, headache, rapid breathing, rapid heart rate, flushing, and severe cases can progress to confusion, convulsions, and loss of consciousness." (2)
Assuming that failures of scuba diving equipment are rare, if the diver attempted to take a breath from their regulator and nothing came out, those few moments that it takes to decide on an emergency swimming or emergency buoyant ascent are only exacerbated by having less air in the space of the volume of the lungs from which the alveoli can continue to pickup oxygen that still remains in that space. Additionally, without the ability to exhale, carbon dioxide cannot be exhaled and will build up. I was not able to find scientific evidence as to what happens to the diver breathing compressed air and emphasizes a greater exhalation than an equal inhalation. If we assume that dive tables are already conservative, we should also assume that it is based upon regular breaths in and out!
While there is not enough evidence showing that an increase in the possibility of decompression sickness by doing a free dive after scuba diving, as with all risks associated with scuba diving, our goal is to minimize the risks and not add another, minimal though it could be. Especially when the diver is new and still mastering the use of all the equipment, having anyone increase their task loading is counterproductive. NAUI says it best, "Just Dive." (3)
So, if you want to do longer dives and you are having to turn around, what options do you have? If you are using dive tables on air, use a dive computer. A dive computer will average the depth you are at any given time. While the computer won't decrease air consumption, it can help to manage your dive specifics, how long you are at a depth, and by diving shallower you will not use as much air. It may also help with anxiety about the dive itself especially since using tables are not easy. Consider diving with Nitrox. Nitrox will increase bottom time and decrease nitrogen absorption, all things being equal on air. While many report feeling better and more refreshed after diving on Nitrox, there is no evidence to substantiate this effect. Placebo or not, feeling better after a dive means you are becoming more relaxed as a diver. Dive with a larger tank. For divers that use a lot of air, diving with a larger tank may extend bottom time. Consider that the "air hogs" that buy bigger tanks eventually sell them for smaller sizes as their air consumption rate increases. Choose a well breathing and well maintained regulator appropriate for the dive, depth, and conditions of the diving you are doing. An unbalanced 1st and 2nd stage regulator system will be harder to breath on at 100 feet especially as the pressure in the tank decreases. Breathing harder and faster uses more air.
Evaluate your dive buddy. Are you nervous or anxious when you dive with them? How did you feel when you dove or when you dive with an instructor or more experienced diver? Dive shallower. Diving at a shallower depth or an average shallower depth will extend your dive time, all things being equal. Slow down and don't dive in currents or heavy tidal exchanges. I practice taking one's time and slowing down as the first and best thing for a new diver to do! Diving at slack tide or doing a drift dive means you are exerting less energy. Less energy used means less air consumption. Make sure you have efficient dive equipment. Regulators are not the only thing that can increase air consumption. The type of kicking can effect many things, but try the modified frog kick. Get in trim. That's not just lose some weight, but also lose the dangling things that stick out and create resistance in the water. Make sure you are properly weighted too. Having too much weight on your belt will increase air consumption. Consider doing a surface descent, too. If you get to your dive site quicker, you won't use as much air.
Most of these things that I mentioned are things, like everyone seems to say, "will come as you do more diving," but some of them may be happening because of improper training or rushing. Consider having an experienced diver give you some feedback and evaluate how you are doing. I've seen divers exhausted at the surface even before their dive began. Don't forget your snorkel! If you don't have a snorkel, that means you will have to swim on your back or use the gas in your tank. The biggest factor in air consumption is buoyancy. A diver with good buoyancy will use less air. This happens because they are not only putting less air in the BCD and or drysuit, but because they are not flailing! Yes, keep those arms in and stop flailing. A perfect buoyancy or underwater ironing specialty can help with buoyancy issues.
All this leads us back to the reasons for this post, how to increase your air consumption buy using free diving techniques. Sorry, but the risks outweigh any if little benefit. There are other factors that a diver looking to improve air consumption must consider. If you use a lot of air, so be it. Accept it and have fun diving. In the long run, you may drop your air consumption a little bit by using some of these ideas. If not, just dive!
(1)
http://scubadiverlife.com/2015/04/29/how-to-improve-your-air-consumption/
(2)
http://www.emedicinehealth.com/wilderness_carbon_dioxide_toxicity/article_em.htm
(3)
http://www.alertdiver.com/Could_Breath-Hold_Diving_after_Scuba_Cause_Decompression_Sickness_
