Shallow - water Blackout
the Freediver’s / Spearfisherman’s worst enemy !
How many times have you heard, “ you are your own worst enemy “ ? With Freediving / Spearfishing this is also true. You might be afraid of the creatures and hazards of the deep Sharks, Giant Grouper, Monster Octopus, Moray Eels, Sea Snakes, Stone Fish, Fire Coral etc, etc - but the thing mostly likely to kill you - is you yourself.
I am talking about Shallow - water Blackout SWB the single biggest cause of death of Freedivers / Spearfishermen.
Have you ever come to the surface after a nice long practise dive, still feeling good, take your first breath, and then get the “ shakes “, black spots appearing before your eyes or battle to think/talk ? You have missed blacking out by the skin of your teeth and are lucky to be alive. If you were still under water even centimetres from the surface you would have blacked out without experiencing any of the above symptoms and probably drowned. SWB occurs fast, without warning and death is painless / mercifully peaceful.
Why SHALLOW - water Blackout ? Even if you are an exceptionally good Freediver / Spearfisherman and can reach depths in excess of 20 m or 30 m or even deeper than 40 metres, most SWB’s occur within metres of the surface. So near and yet so far ! Why ?
Terry Maas, world-class Freediver and Spearfisherman explains the effect by saying, “ Well, it’s here that your expanding, oxygen starved lungs literally suck the life giving air from your blood. Pressure changes in the Freediver’s decent / ascent cycle conspire to rob him of oxygen as he nears the surface by a mechanism I call the ‘vacuum effect’. The re-expanding lungs of the ascending diver increase in volume as the water pressure decreases, and this results in a rapid decrease of oxygen in the body to critical levels. The pressure that forced oxygen into the blood is now reversed. This vacuum effect is really a net flow of oxygen from the body to the lungs. It is most pronounced in the last three to 4,5 metres below the surface, where the greatest relative lung expansion occurs “.
And then you drown. First your protective reflexes cause your vocal chords to close,
preventing water entering your lungs. Death rushes closer and your protective response wanes, your lungs fill with water, and the delicate tissues swell dramatically. After six minutes without oxygen, your brain suffers permanent damage. Rescue and CPR now might revive you to a vegetative state.
Rules to stay alive
1. Don’t practise or dive alone. A dive buddy that knows how to recognise SWB and how to respond if you do blackout must keep an eye on you at all times.
2. Don’t hyperventilate. Overbreathing on the surface huge breaths or fast puffing breaths can’t give you any more oxygen. You don’t use all the oxygen in your lungs anyway. Underwater, when your lungs cry out, it’s not because they need more
oxygen, but it’s because they want to get rid of the carbon dioxide CO2 buildup. Overbreathing on the surface reduces the level of residual CO2 in your body and with it the desire to breath when your bodies oxygen level becomes dangerously low. So as you can see, it is the CO2 level in your body that triggers the brain’s desire to breath and prevent oxygen starvation and blackout. Why then do people that know better, even top Freedivers / Spearfishermen still hyperventilate ? Because it leads to a state of euphoria and well-being, but this leads to overconfidence. It is a fact the more top Freedivers / Spearfishermen drown from hyperventilating than beginners. So make it a rule no more than 5 deep breaths before diving down.
3. Don’t get focused on one thing. Keep an open mind at all times. Know what is happening around you. Monitor your bodies needs. Have you noticed how you forget that you need air when you focus on waiting for that elusive fish to come in closer or when you are determined to swim the whole length of the pool underwater. Give it up - your life is worth more than the prize fish or beating your friends record ! Research has shown that most people who suffer from SWB are young and highly competitive. 4. Don’t only dive to a watch. Think about the amount of energy you are using - not
just the length of time of your dive. Underwater exercise reduces your bottom time, even if you don’t notice it. That stubborn crayfish that you have got your hands on but just wont come out, so you work it and pull and wiggle and pull and pull ……. Or, that hotspot you saw just upstream, full of fish - you will just swim against the powerful current for a short while and you should get there …….
Fist Aid in the event of Shallow - water Blackout
• Watch out for the classic signs of blackout. A dive buddy surfacing will suddenly arch his body like a spasm and then just begin to drift back down. Even a surfaced diver with the shakes, blue lips or glazed eyes can just slip away. Shake them, slap them and ask them to talk sense to you.
• A sinking, unconscious diver must be brought to the surface drop their weights. If their jaw is clenched they will need to have the snorkel yanked from their mouth and forceful mouth-to-mouth administered to overcome the spasmed vocal chords. If you cannot get the snorkel out of their mouth try blowing through the snorkel.
• If you can get the victim to dry land or a boat, turn them on their side with their head lowered to allow the water to drain.
• Oxygen to the brain is most important. Whilst giving mouth-to-mouth, check for a pulse. If the person was unconscious for a short while they should begin breathing for themselves soon. If not begin with full CPR.
• Administer CPR no matter how long the person was underwater. • Persevere; sometimes the person can lapse back into unconsciousness.
• Even when the person has been revived, they need to be admitted to hospital. The swollen lung tissue and secondary drowning is a risk.