When people started to try and plumb the depths of the oceans on a single breath they were confronted, rather quickly, with the desire to breathe, thereby curtailing their efforts and rendering their dives shallower than they may have wanted. In the past, when freediving was purely a method of fishing or gathering, this limitation would have had direct financial and survival implications to those using it. This gave the practicing divers a pretty strong reason to find a way to overcome the need to breathe. At some point, someone discovered that if they hyperventilate before a dive, they wouldn’t feel the need to breathe for quite some time, seemingly making the dive easier and allowing them to carry out their underwater mission.
Hyperventilation, continued as a technique for apneists for countless years. You can even pick up relatively recently published books about spearfishing and freediving which will offhandedly refer to hyperventilating divers, and many of the older generation of ‘un-trained’ freedivers and spearos still continue to hyperventilate before they dive.
Its only relatively recently, that research and testing has allowed us to see the very real dangers of hyperventilating prior to freediving.
Before I continue let me define what Hyperventilation really is. Fundamentally, hyperventilation is the process of breathing faster or deeper than you need to, beyond what you require to maintain your current homeostasis. So if you are sitting on a sofa, chilling out and you start to breathe deeper than normal and perhaps a bit faster than normal, you are hyperventilating. However if you are running, your breathing rate will increase, but this is not hyperventilation as your body requires you to do so.
So why shouldn’t we hyperventilate? I mean if it allows us to feel more comfortable when underwater then surely its a good thing?
The main result of hyperventilation is a rapid decrease of C02 in our bloodstream. C02 is the gas which causes us to want to breathe, so by removing this gas from our bloodstream we start the dive with a very low c02 content, this then tricks us in to thinking that we don’t really need to breathe. However, the hyperventilation hasn’t increased our 02 levels to compensate and our 02 levels are decreasing just as quickly as normal, but without the safety mechanism of the high c02 ‘need to breathe’ reflex. So this leaves the diver in a very dangerous position, as they continue their dive but without any strong desire to return to the surface. Its a bit like driving along with a broken fuel gauge, it may say the tank is half full but the reality is that its a lot lower!
There are additional reasons why hyperventilation is dangerous for freediving. Beyond tricking the body in to thinking it has more oxygen than it does, hyperventilation will actually reduce the amount of available oxygen to your muscles and organs. Alkalosis is an increase in the Alkaline levels of the blood through the loss of dissolved C02, this causes the Hemoglobin to bond too strongly with the oxygen molecules in the blood and thereby not allowing the oxygen molecules to release in to the muscles and organs. So by hyperventilating you are essentially lowering the amount of 02 available to you during your dive.
Very intense hyperventilation will also reduce your blood pressure, when combined with the Alkalosis (sometimes refered to as the Bohr effect) and can take the diver to the point of feinting. They may suffer less extreme initial effects, such as tingling fingers and toes, tunnel vision, loss of hearing and nausea.
Lets assume that you have ignored all the facts up to this point, and continue to dive nonetheless, what could happen to you when you dive in such a state, other than passing out at depth?
You have probably heard of shallow water blackout. A very sudden blackout which occurs during the final phases of ascent from a deep dive. This occurs due to several factors; overexertion, panic, ignoring the warning signs of low 02, poor dive technique and hyperventilation. Hyperventilation will cause you to dive for longer than your oxygen reserves will allow and will make you more susceptible to blackout during ascent. This is due to a rapid reduction in the partial pressure of oxygen in you bloodstream as you pass through the pressure gradients. Shallow water blackouts occur with little to no warning and can only be avoided by sticking to the rules and training.
So what do we do to prolong our dives rather than hyperventilate?
The answer is simple… Training! Lots of training…. Using dive tables and increasing your c02 tolerance will (in best AIDA instructor voice) ‘ultimately result in longer and safer dives’.
Lets leave hyperventilation in the past guys and girls, train hard and enjoy our diving with safety in mind.
You can of course learn all about this, and more on one of our freediving courses, where we will teach you all of the techniques need to be safe and confident freediver. We have put lots of information on this site, so have a look through the blog and you will find a very basic description of correct breathing here.