BREATH HOLD DIVING
The following is a brief description of the physical changes that actually occurred to Francisco Pipin Ferreras during his World Record Breaking breathold dive... this amazing man went down to 127.5 metres in 95 seconds on one breath of air (Key Largo, Florida, 1994). His training for this dive took 22 years and he had logged 550 free dives...
Because of the increased pressure on the body underwater, the diaphragm does not have the same range of movement as it does on land and thus the lungs cannot fully expand. Because of bouyancy underwater, blood which collects in the lower body due to gravity now floats into the chest causing the right side of the heart to fill with more blood than usual... which in turn forces the heart to work a bit harder and this reduces the volume of air in the lungs. Divers must be sure to breathe slowly and evenly to prevent breathing resistance problems which can lead to panic.
The first symptoms of too much carbon dioxide is an increased rate of respiration, then respiratory discomfort, and very high levels will cause dizziness, stupor and unconsciousness. This occurs when the diver changes from his normal regular breathing pattern (carbon dioxide gets flushed from the lungs when breathing in oxygen) to one of shallow, inefficient breathing (perhaps from stress and anxiety) or skip breathing (to make his air last longer)... or sometimes poor breathing equipment. This condition can be very dangerous as the diver could lose consciousness and drown.
Carbon monoxide poisoning is extremely dangerous... this pollutant combines very easily with blood hemoglobin, making the hemoglobin incapable of transporting enough oxygen to the body tissues. Hemoglobin combines with carbon monoxide about 200 times as readily as with oxygen. Because of the lessened oxygen-carrying capability of carbon-monoxide-poisoned blood, hypoxia develops even though there is enough oxygen going to the lungs.
A fairly safe amount of carbon monoxide above water can become lethal when breathed under pressure at depth. Symptons include headache, dizziness, nausea, weakness and confusion. Signs include failure to responds, clumsiness and bad judgment, although frequently no signs or symptoms are displayed. A diver may simply lose consciousness without warning, and breathing may cease.
Tanks may get contaminated with carbon monoxide when the fumes of an internal combustion engine are drawn into the air intake of a compressor or from the partial combustion of lubricating oil within a compressor.
A victim requires medical care which includes treatment with oxygen in a recompression chamber.
Lengthy exposure to above normal oxygen partial pressures causes a number of toxic effects, collectively called Oxygen Poisoning. The warning symptoms are muscular twitching, nausea, abnormal vision and hearing, breathing difficulties, anxiety and confusion, fatigue, lack of co-ordination, and convulsions. While these effects are not permanent, they are dangerous underwater as they can lead to air embolism and drowning.
Sport divers breathing compressed air should never experience problems with oxygen poisoning if they stick with the rules and stay above 35m. Attempts by untrained divers to use rebreathers, cryogenic scuba units, oxygen-enriched gas mixtures, or oxygen filled scuba cylinders can result in oxygen poisoning. Training courses are available for learning how to dive with enriched-air Nitrox.
Near drowning is the term used to describe the condition that follows suffocation in water after which there are at least 24 hours of survival. Symptoms will include the victim's skin turning blue, unconsciousness, froth in the mouth and the victim will stop breathing. Near-drowning victims must be given immediate CPR if they are not breathing, and must receive hospital treatment as soon as possible, as brain tissue will be permanently damaged after 4 to 5 minutes of hypoxia. The victim must also be kept under observation, for if they have swallowed water, this can damage alveolar tissue which in turn leads to body fluids from the blood stream seeping into the lungs, causing a condition known as "Secondary Drowning". This condition can occur several hours after the initial drowning.
This is more common among breath hold divers (including spearfishermen) and occurs when the diver takes a lot of deep, rapid breaths before diving. This form of breathing lowers the carbon dioxide level to below normal and is called "Hyperventilation". As carbon dioxide is what triggers the urge to breathe, lowering the level interferes with the breathing control mechanism and the oxygen level in the body can fall to below that needed to maintain consciousness. If this happens underwater, you may be too far down by the time you realise you need to return to the surface to breathe. The exertion required to swim back to the surface further uses oxygen and as you rise to the surface, the drop in partial pressure of oxygen in the lungs may be enough to stop further use of oxygen completely. At the same time, the partial pressure of carbon dioxide in the lungs also drops, creating the false impression that you do not need to breathe. Shallow water blackout is so named as it occurs in shallow wa er when coming up from a free dive.
The effects of nitrogen narcosis can be compared to that of being drunk or on drugs... lightheadedness, impaired motor skills, the inability to think clearly or behave rationally. There is a famous story of a diver who, suffering from nitrogen narcosis, took the dv out his mouth and was offering air to passing fish. As with alchohol, the diver may not remember what happened afterwards. Nitrogen narcosis is not permanent, but can be lethal should the diver not be able to monitor his air supply, depth or time. Another reason why it is so important to dive with a buddy.
Decompression Sickness is the term applied to the condition that occurs when a diver, after having absorbed nitrogen into his tissues during descent, ascends too rapidly for the nitrogen in his tissues to diffuse into the bloodstream properly. This leads to the nitrogen coming out of the tissues and into the blood in the form of small bubbles, which can then block circulation. This condition is more commonly called "The Bends", and displays the following symptoms: mottled, itchy skin; pain in the elbow and shoulder joints, back and abdomen pain similar to that of a strained muscle; pins-and-needles in the legs and even paralysis. If not treated promptly in a decompression chamber, this condition can be fatal.
There have been cases of divers dying during a dive due to heart attacks.. it is very important to be physically fit when diving as this sport increases the workload of the heart. This condition has occured mostly in unfit male smokers over 30 who had minor heart ailments.
This is an interesting condition, whereby the body reacts to cold water splashed on the face or body by slowing the heart rate and decreasing blood flow to the limbs. Because of this, divers with even minor heart problems must be aware that this relex could cause them problems.
Physical damage to the body caused by changes in pressure is called Barotrauma. When descending, it is important to keep equalising; if this is not done, pressure can cause the ear drums to rupture, or lead to nosebleeds and headaches. Even a badly-filled tooth can cause problems, as the air space will cause a pressure differential leading to pain, swelling and bleeding. Of all Barotrauma conditions, an Air Embolism is the most serious. This is caused by compressed air in the bloodstream being carried to the heart, brain and other arteries. As the diver ascends, the release of pressure causes the air bubbles to expand thus causing blockages where ever they are situated. These blockages can cause heart-attacks when the blood flow to the heart is cut off, or paralysis, convulsions, unconciousness and death if blood is cut off from the brain. DO NOT ATTEMPT TO RECOMPRESS A VICTIM IN THE WATER. The victim must be treated in a hyperbaric chamber as soon as possible.
This is the condition where a diver gets so cold he is unable to function properly. Symptoms start with an increase of heart rate, shivering and muscular incoordination, and the most severe symptoms will include coma. Hypothermia does not necessarily just occur in cold water... long periods underwater even in warm water can leech the body's heat and bring on shivering and fatigue.
Hyperthermia is when the diver overheats... normally because the body-generated heat which usually evaporates from the skin cannot do so. The reasons for this could be many, including a diver working under the hot sun with a full wetsuit on. Symptoms range from mere cramp to coma and death in severe cases. Brain damage has been known to occur in survivors.
Many divers suffer from sea-sickness, either while on a boat or in the water during a dive. Should nausea occur while underwater, the diver can vomit through his regulator; his buddy must, howAver, be alert for any signs of panic.
Divers must be aware that excessive moisture loss (vomiting, sweating etc) can bring about dehydration which in turn can lead to decompression sickness. Divers must make sure they take in enough fluids to compensated for sweating, sea-sickness and urinating.