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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.
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13 Responses
I am confused :S as what exersises to do Pre and Post Diving, as you have posted a comment which says
(C02 or Carbon Dioxide gives us our primary trigger to breathe, we dont have much of a physical response to low oxygen so when we are swimming down in to the blissful embrace of the blue and we start to get that nagging feeling of ‘needing to breathe’ you are not experiencing particularly low oxygen, but are in fact experiencing elevated levels of co2. Hence training to tolerate these elevated levels, will make your dives longer, safer and more comfortable.) but surely if you train ur body to become more tolrent to Co2 ur body has a less accurate reading of co2 levels and oxygen levels as the same way in hyperventilation (I am realy confused)
also i have read prior to a dive to empty your lungs to the point where your spitting out any gasses left in the lungs and take one deep breath in from the bottom of your lungs to under the color bone , which surely has the same effect as hyperventilation becasue the exhail lower the co2 for your current homeostasis and increases the o2 level which makes the blood more alkali giving the bohr effect?
also i have seen a yoga techniquue where you hold one nostril and exhail to the point where you cant anymore and inhail to the point you cant anymore to increase red blood cells is this apropiate ?
If you could get back to me by email it would be highly appreciated and i will look forward to seeing you in Cornwall in the future
Hi, Ill reply by email as well, but for the sake of anyone else who is confused… here we go!
Q: “but surely if you train ur body to become more tolrent to Co2 ur body has a less accurate reading of co2 levels and oxygen levels as the same way in hyperventilation”…
A: Training to tolerate high CO2 levels is a slow and time consuming process,by taking our time over our training and making advances in small steps, we don’t give ourself a less accurate reading, we just push our co2 tolerance closer to our low 02 threshold. So yes, when we get to that point in our training (advanced freediver) we are starting to enter a naturally risky zone. Elite athletes c02 tolerance is at parity with their low 02 tolerance. By this point in your training, you will have a wealth of experience and an understanding of your body and its responses, so the danger is pacified somewhat.
Q: “also i have read prior to a dive to empty your lungs to the point where your spitting out any gasses left in the lungs and take one deep breath in from the bottom of your lungs to under the color bone , which surely has the same effect as hyperventilation because the exhail lower the co2 for your current homeostasis and increases the o2 level which makes the blood more alkali giving the bohr effect?”
A:The exhale which we do prior to a dive… as long as its just ONE exhale… will not expel enough c02 in a single exhale enough to heavily effect the PPC02 in the Alveoli. You are simply removing any latent or stale air in the lungs to give yourself more ‘fresh’ air prior to a dive. As we are not lowering the Arterial PPC02 (by reducing the Alveoli ppco2) we will therefore not fall in the the negative effects of ‘early’ Bohr effect (whereby the oxygen molecules cannot release into the tissues where they are needed).
Q:” also i have seen a yoga techniquue where you hold one nostril and exhail to the point where you cant anymore and inhail to the point you cant anymore to increase red blood cells is this apropiate ?”
A: You cannot increase your red blood cell count significantly with anything but comprehensive treatment. I believe, after speaking to a Dr friend about this some time ago, that it takes weeks(if not months) to increase your red blood cell count. Red blood cells have a lifespan of about 120 days, so the process of creating them isnt quick.
Hope that helps!
Hola! I’ve been following your web site for a long time now and finally got the courage to go ahead and give you a shout out from Houston Texas! Just wanted to mention keep up the great work!
Hyperventilation is both increase in the rate as well as depth of breathing. Why are then the PCO2 levels declining without a concomitant increase in PO2 levels?
It is carbon dioxide that tells hemoglobin to release oxygen to the tissues. If you have a low level of CO2, hemoglobin will hang onto its oxygen molecules (this is called the Bohr effect) and your cells and tissues, including the brain, will suffer from a lack of vital oxygen.
In a healthy person, breathing normally, blood leaving the lungs is close to 100% oxygenated. Hyperventilation can therefore not significantly increase blood oxygenation but it will dramatically reduce your CO2 levels. As stated in the article CO2 levels are the main trigger for breathing, so you remove the trigger to breath without increasing the oxygen supply.
I’m an inexperienced spearo but a recreational scuba/free diver. Biggest problem is location as I’m based in South Wales . I read somewhere that you can increase your breath holding ability (mostly efficiency) through cardio fitness by as much as 25% in as little as one month . Does this hold true?
Thanks for commenting! Thats a bit specific to be honest, everyone is different. For that to work it would mean that perhaps you increased your cardio fitness by 25% in one month!
Certainly working on anaerobic ability could easily increase your breath-hold by 25%, assuming you are new to the sport, as the increases early on can be astonishing. A sensible combination of anaerobic, aerobic and apnea training is what you need to progress.
I run 3x a week, focusing on fartlek runs rather than long distance, and do apnea walks etc whenever i get the chance. In the summer im diving nearly everyday so that helps too.
Hello, I was wondering about if all the negatives still apply if you practice breathing methods like wim hof where you basically hyperventilate
yes, unfortunately the Wim hof method may be beneficial for some in certain areas of life but i consider it exceptionally dangerous for freediving. You cant avoid the basic mechanics of hyperventilation. There have been accidents related to it.
Yes, Wim Hof himself explicity warns people not to use it for diving.
Hi Ian, thanks for your articles!
I’m wondering, have you written anything about the cellular adaptations taking place in the body to low oxygen?
With regards to adaptations from Co2 tables my understanding is it’s just a down regulation of the urge to breath over time.
But regarding 02 adaptations; what is happening at a cellular level for a fully relaxed dry static to cause blackout in a hypothetically Co2 impervious beginner at say 4mins vs after some training for it to take 6mins.
Pure apnea training, no cardio and all other variables considered.
1) Is the primary adaptation with the amount of oxygen the haemoglobin is able to hold?
2) Or is there also significant adaptation taking place at the level of the tissue and its ability to function with low oxygen; whether through becoming more efficient or in some other way more tolerant to low oxygen?
3) Although I suppose tolerating higher Co2 could also create a condition where more oxygen is being squeezed out of the haemoglobin???
Cheers!!
=)
Hello Ian,
A very interesting article and keep up the good work
I’ve been freediving now for a year, and continuously exploring ways to ensure safe return to my family. Having completed proper freediving courses and learned of the dangers of hyperventilation. I was shocked to learn from this article – that I’ve actually been hyperventilating before my dives. I really want to make sure to minimize risk as much as possible
Definition: “Fundamentally, hyperventilation is the process of breathing faster or deeper than you need to, beyond what you require to maintain your current homeostasis.”
1) 3-5 larger than usual, deep breath in & out – ***This is clearly hyperventilation – and what the freediving course taught me to AVOID***
2) Normal breathing, and on the final breath – expel all air in the lungs and DEEP intake of air before diving. *** It seems from your definition “deeper than you need to, beyond what you require to maintain your current homeostasis.” indicates that this constitutes “Hyperventilation”, can you confirm? This was what was taught in my freediving school as the proper way of breathing ***
3) Normal breathing EVEN on the final breath – avoid large inhalation of air beyond the normal breathing that you typically do, kinda feels like a 1/2 to 3/4 full lungs. *** It seems like from the above definition, this is the right technique for breathing ***
Can I understand what is the safe way of breathing prior to diving?