Health Hazards In SCUBA Diving
The hazards of diving can be categorised as those encountered in the process of descent, those that may occur at any stage under water but usually at the bottom, and those that can be related to ascent. Besides, the hazards in diving can also be categorised into physical , chemical and biological hazards. Both commercial and recreational divers are exposure to these particular health hazards.
Physical Hazards of diving
There is no exception that the general occupational hazards of workplace including fire , electricity shocks and noise hazards during the process of gas tanks filling can occur in the diving industry. However, there are number of specific physical health hazards which are limited to diving and are due to pressure changes. Although increased pressure exerts no mechanical effect on the tissues of the body per se, since liquids and solids are relatively incompressible, a pressure gradient develops when equalization is failed within our body cavities such as the middle ear, paranasal sinuses and the lung.
Dysbarism of ascent (Decompression) and decent (Compression) known as barotrauma are commonly happened to divers.
Five conditions must be present for barotrauma to occur
(1) There must be a gas-filled space. Most of the body is fluid and not compressible. However, any gas-filled space naturally present within the body (sinus) or next to the body (face mask) can damage the body tissues when the gas volume changes as described by Boyle's Law.
(2) The space must have rigid walls. When the walls are elastic like a balloon, there will be no damage done by gas compression or expansion until the volume change surpasses the elasticity of the walls or vessels.
(3) The space must be enclosed. If any substance (with the exception of blood in the vessels lining the space) were allowed to enter or leave the space as the gas volume changes, no damage would occur.
(4) The space must have vascular penetration (arteries and veins) and a membrane lining the space. This allows the blood to be forced into the space and exceed the elasticity of the vessels to compensate for the change in pressure.
(5) There must be a change in ambient pressure.
It is important to note that barotrauma will not normally occur in divers who have normal anatomy and physiology, and who are using properly functioning equipment and correct diving procedures. The predominant symptom of barotrauma is pain. Other symptoms such as vertigo, numbness, or facial paralysis may be produced depending on the specific anatomy.
Common pulmonary barotrauma are mediastinal emphysema, pneumothorax and air embolism. Ear and sinus barotrauma are well known and commonly happened. Rarebarotrauma including mask squeeze, dental barotrauma, suit barotrauma, helmet barotrauma, gastrointestinal barotrauma, pneumoperitoneum and pneumocephalus can occur during the descent and ascent processes of the diving.
Problems of increasing pressure during descent
Aerotitis sinus painˇXAs the diver goes down in water the pressure increases and this may affect his ears or nasal sinuses to cause pain and possibly inflammation of the middle ear and rupture of the ear drum (aerotitis or aural barotrauma). The trouble arises if the eustachian tubes (connection between the throat and middle ear) or the openings of a sinus are blocked thus preventing equalisation of the increasing pressure .
AerodontalgiaˇXAcute pain in a tooth may occur in certain circumstances if a minute pocket of air beneath a filling, inlay or dental cap communicates with the mouth by such a small channel that rapid equalisation of pressure is not possible.
SqueezeˇXThis term is used to describe the effect of generalised pressure upon the diver. In commercial diving, if the commercial diver is using a helmet (ˇĄhard-hatˇ¦ diving) or face mask the pressure of air within must be maintained at the pressure of the water outside by air pumping or by exhaling in the case of the mask. If this is not done the negative pressure will produce a vacuum effect which may cause bleeding of skin and eyes.
Hazards at any stage underwater
DrowningˇXDrowning may occur at any stage if the diver loses his air supply and cannot reach the surface within a very short time. Both equipment failure and out of air supply of any reason can lead to drowning.
Salt-water aspiration syndromeˇXAspiration of small amount of sea-water can cause this syndrome with signs and symptoms of shivering, rigors, fever, nausea, headache and cough with copious sputum, and difficulty in breathing. Sometimes associated with generalized aches which may mimic decompression sickness.
AsphyxiaˇXThis can occur if carbon dioxide is not eliminated by adequate ventilation or properly operating absorbents. The hazard is limited to "hard-hat" divers and scuba divers using special closed circuit devices and prevention again depends on diver training and the correct use of proper equipment.
Nitrogen narcosisˇXNarcosis is a state of stupor or unconsciousness caused by breathing inert gases at pressure while diving. The most common form, nitrogen narcosis, is caused by breathing compressed air at depth. Inert gases vary in their narcotic potency. The effects from nitrogen may first become noticeable at depths exceeding 100 fsw, but become more pronounced at depths greater than 150 fsw. There is a wide range of individual susceptibility and some divers, particularly those experienced in deep operations with air, can often work as deep as 200 fsw without serious difficulty.
Narcosis involves confusion, impaired judgement, and a sense of well-being. Divers find it difficult to concentrate or to reason, and may not be able to remember what they are supposed to do or have already done. Performing even simple tasks is difficult. The signs of narcosis are:
· Loss of judgement or skill
· A false feeling of well-being
· Lack of concern for job or safety
· Apparent stupidity
· Inappropriate laughter
An uncontrollable desire of the diver to laugh, and a tingling and vague numbness of the lips, gums and legs are symptoms reported by divers who have experienced nitrogen narcosis. Divers may display abnormal behaviour such as removing the regulator or swimming to unsafe depths without regard to decompression sickness or air supply. There is no specific treatment for nitrogen narcosis; the diver must be brought to shallower depths where the effects are not felt. Experience, frequent exposure to deep diving, and training may enable divers to perform air dives as deep as 180-200 fsw. The performance or efficiency of divers breathing compressed air will be impaired at depths greater than 180 fsw. The greater the depth the greater the partial pressure of nitrogen and the larger the amount of this gas which will be absorbed by the body. This excessive amount of dissolved nitrogen produces a sense of dizziness like that which follows drinking alcohol. Just like the effect of alcohol there is great individual variation to increasing nitrogen pressure. Prevention of mishap depends on being aware of the danger and recognising early signs (i.e. giddiness and a sense of euphoria) and maintaining communication with the surface and buddy diving.
Oxygen poisoningˇXToo much oxygen in the body which can arise with increasing pressure can also adversely affect the diver. Signs and symptoms of oxygen poisoning are tingling of fingers and toes, visual disturbance, hearing hallucination, abnormal sensations, confusion, muscle twitching, breathing difficulties, nausea, vertigo and convulsions. It is likely to be encountered by diver with closed & semi-closed rebreathing equipment, oxygen therapy for diving disorders and saturation diving.
Hyperthermia and HypothermiaˇXCold is one of the formidable enemies the diver has to face underwater. Immersion in cold water causes a complex response in the diver. If exposures to conditions in which the heat loss from the body is greater than the heat production continues, then body temperature falls and the diver becomes hypothermic. If a diver with no thermal protection is suddenly plunged into very cold water, the effects are immediate and rapidly disabling. The diver gasps, and his respiratory rate and tidal volume increase. His breathing becomes so rapid and uncontrolled that he cannot co-ordinate his breathing and swimming movements. This lack of breathing control makes survival in rough, cold water very unlikely.
A water temperature of approximately 91˘XF (33˘XC) is required to keep an unprotected, resting man at a stable temperature. The unprotected diver will be affected by excessive heat loss and become chilled within a short period of time in water temperatures below 72˘XF (23˘XC). As his body temperature falls, the diver first feels uncomfortable, and then, as his body tries to increase heat production in the muscles, shivering begins. If cooling continues, his ability to perform useful work becomes seriously impaired; his sense of touch is dulled and his hands lose dexterity. As shivering intensifies, it brings on a general lack of co-ordination and a SCUBA diver may experience difficulty keeping his mouthpiece in place. He soon loses his ability to think clearly and finds it increasingly difficult to concentrate. At extremely low temperature or with prolonged immersion, body heat loss will reach a point at which death will occur. Appropriate dress can greatly reduce the effects of heat loss, and a diver with proper dress can work in very cold water for reasonable periods of time.
Inhaled gases are heated in the upper respiratory tract. More energy is required to heat the denser gases encountered at depth. Thus, heat loss through the respiratory tract becomes an increasingly significant factor in deeper diving. In fact, respiratory shock can develop if a diver breaths unheated gas while making deep saturation dives at normal water temperature. The body's ability to tolerate cold environments is due to natural insulation and a built-in means of heat regulation. The automatic, cold-induced vasoconstriction lowers the heat conductance of the superficial layer and acts to maintain the heat of the body core. Unfortunately, vasoconstrictive regulation of heat loss provides only a narrow range of protection. As circulation and heat loss increase, the body temperature falls, and may continue falling, even though heat production is increased by shivering.
Much of the heat loss in the trunk area is transferred over the short distance from the deep organs to the body surface by physical conduction which is not under any physiological control. Most of the heat lost from the body in moderately cold water is from the trunk and not the limbs
Exercise normally increases heat production and body temperature in dry conditions. Paradoxically, exercise in cold water may cause the body temperature to fall more rapidly. Any movement which stirs the water in contact with the skin creates turbulence that carries off heat by convection. Heat loss is not caused only by convection at the limbs but also by increased blood flow into the limbs during exercise. Continual movement causes the limbs to resemble the internal body core rather than the insulating superficial layer. These two conflicting effects result in the core temperature being maintained or increased in warm water and decreased in cold water.
Increased heat production requires an equivalent increase in oxygen consumption. The respiratory minute volume of the lungs must increase by the same magnitude.
All of these factors work against the diver. Even his bodyˇ¦s natural insulation and protective function give way to cold water. The diverˇ¦s thinking ability becomes impaired, and the effect of this impairment on the use of his hands and other motor functions may prevent him from choosing and executing the best procedures to complete a task.
While, under extremely warm water or overheated suit and air supply may possibly result in overheat of the diver. These occur more commons in commercial diving due their extreme working environments. Pre-dive heat exposure may lead to significant dehydration putting the diver at risk once he enters the water. This is especially true if a protective suit has to be worn because of marine life or contaminated water which is warm.
Problems of reducing pressure during ascent
Pulmonary barotrauma(Pulmonary overinflation syndromes)ˇX are a group of barotrauma-related diseases caused by the expansion of gas trapped in the lung during ascent (reverse squeeze) or overpressurization of the lung with subsequent overexpansion and rupture of the alveolar air sacs. The volume of gas varies inversely with the pressure so the air in the lungs expands as pressure is reduced during ascent. If the diver holds his breath the expanding air may cause damage to the lungs the so called "lung burst" or pulmonary barotrauma. The greater the depth of the dive and the more rapid the ascent the greater the liability to lung damage.
The two main causes of alveolar rupture are:
(1) excessive pressure inside the lung caused by positive pressure
(2) failure of expanding gas to escape from the lung during ascent
Pulmonary overinflation from expanding gas failing to escape from the lung during ascent can occur when a diver voluntarily or involuntarily breathholds during ascent. Localized pulmonary obstructions that can cause air trapping, such as asthma, thick secretions from pneumonia, or a severe cold, are other causes. The conditions that bring about these incidents are different from those that produce lung squeeze, and they most frequently occur during free and buoyant ascent training or emergency ascent from dives made with lightweight diving equipment or scuba.
The clinical manifestations of pulmonary overinflation depend on the location at which the free air collects. In all cases, the first step is rupture of the alveolus with a collection of air in the lung tissues with resulting interstitial emphysema. Interstitial emphysema causes no symptoms unless further distribution of the air occurs. Gas may find its way into the chest cavity or arterial circulation.Arterial gas embolism is the most serious potential complication of diving and is caused by an excess pressure inside the lungs that fails to vent during ascent. If this expanding air is not allowed to escape, pressure builds up within the lungs, overexpanding them and rupturing their air sacs and blood vessels. Air is then forced into the pulmonary capillary bed, and bubbles are carried to the left chambers of the heart, where they are then pumped out into the arteries. Any bubble that is too large to go through an artery will lodge and form a plug (embolus) with subsequent tissue or organ ischemia or infarction. The brain is frequently involved and when it is the symptoms are usually extremely serious. Unless the victim is recompressed promptly to reduce the size of the bubble and permit blood to flow again, the effect of ischemia including death may follow.
Occasionally, inhalation of water and fear can also trigger a spasm of the laryngeal muscles (laryngospasm) that seals the main lung passageway, and thus brings about the overexpansion of the lungs. Under these circumstances, death can occurred during ascent from depths of only a few feet.Mediastinal and Subcutaneous Emphysema occurs when gas has been forced through torn lung tissue into the loose mediastinal tissues in the middle of the chest, around the heart, the trachea, and the major blood vessels. Subcutaneous emphysema results from the expansion of gas that has leaked from the mediastinum into the subcutaneous tissues of the neck. These types of emphysema, including interstitial emphysema, should not be confused with the emphysema brought on by the aging process or by smoking. Pneumothorax is the result of air entering the potential space between the lung covering and the lining of the chest wall. In its usual manifestation, called a simple pneumothorax, a one-time leakage of air from the lung into the chest partially collapses the lung, causing varying degrees of respiratory distress. The onset of pneumothorax is accompanied by a sudden, sharp chest pain, followed by difficult, rapid breathing, cessation of normal chest movements on the affected side, tachycardia, a weak pulse and anxiety.
In certain instances, the damaged lung may allow air to enter but not exit the pleural space. Successive breathing gradually enlarges the air pocket. This is called a tension pneumothorax due to the progressively increasing tension or pressure exerted on the lung and heart by the expanding gas. The symptoms become progressively more serious, beginning with rapid breathing and ending in cyanosis, hypotension, shock, and, unless corrected, death.
Middle Ear overpressure (Reverse Middle Ear Squeeze)--Expanding gas in the middle ear space during ascent ordinarily vents out through the eustachian tube. If the tube becomes blocked, pressure in the middle ear relative to the external water pressure increases. To relieve this pressure, the eardrum bows outward causing pain. If the overpressure is significant, the eardrum may rupture and the diver may experience the same symptoms that occur with an eardrum rupture during descent (squeeze).
The increased pressure in the middle ear may also affect nearby structures and produce symptoms of vertigo and inner ear damage. It is extremely important to rule out arterial gas embolism or decompression sickness when these unusual symptoms of reverse middle ear squeeze occur during ascent or upon surfacing.
Sinus overpressure(Reverse Sinus Squeeze)ˇX Overpressure is caused when gas is trapped within the sinus cavity. A fold in the sinus-lining membrane' a cyst. or an outgrowth of the sinus membrane (polyp) may act as a check valve and prevent gas from leaving the sinus during ascent. Sharp pain in the area of the affected sinus results from the increased pressure. The pain will usually be sufficient to stop the diver from ascending. Pain is immediately relieved by descending a few feet. From that point, the diver should slowly ascend until he gradually reaches the surface.
Overexpansion of the Stomach and IntestineˇX While a diver is under pressure, gas may form within his intestines, or gas may be swallowed and trapped in the stomach. On ascent, this trapped gas expands and occasionally causes enough discomfort to require the diver to stop and expel the gas. Continuing ascent in spite of marked discomfort may result in actual harm.
Decompression sicknessˇXAt present under water nitrogen become dissolved in the body fluids, the amount depending on pressure and time. If the pressure is reduced too suddenly bubbles of nitrogen may form in the tissues. These bubbles can produce many different symptoms, known collectively as decompression sickness
According to the ˇ§Health Hazards of Divingˇ¨ published by Labour Department in the protection of workersˇ¦ Health series , the classification of decompression sickness in Hong Kong are as the following sign and symptoms :-
Mild limb pains (ˇ§the nigglesˇ¨)
Severe limb pains (ˇ§the bendsˇ¨)
Skin mottling and irritation (ˇ§the itchesˇ¨)
Vomiting with or without abdominal pain
Vertigo (ˇ§the staggersˇ¨)
Tingling and numbness of limbs
Paralysis or weakness of limbs
Dyspnoea (ˇ§the chokesˇ¨)
Visual effects, flashes of light, double vision, blindness
Angina, heart pain
Irregular pulse Collapse
These symptoms come on during decompression or shortly afterwards, or more rarely delayed for several hours.
Dysbaric osteonecrosisˇXThis is a condition affecting certain bones which may not become apparent on X-ray until several months after exposure. Disability may arise if joints are involved in the bone lesions and shoulders and hips are the most commonly affected.
Rapid ascent on decompression results in a very high incidence of decompression sickness. Prevention depends on controlling the rate of ascent and approved decompression tables should be used. The basic requirement is that the diverˇ¦s ascent should be slow enough to allow him to eliminate dissolved nitrogen from his body without bubble formation.
Chemical & Biological Hazards of diving
Currently, both the surface-supplied and self-contained underwater breathing equipment are being used for commercial diving. Sport divers in Hong Kong are all practising self-contained underwater breathing apparatus (Scuba) of compressed air for majority of their diving. Air compressors are used to provide air to the surface-supplied system and scuba tanks of compressed gases are used to provide air in scuba diving. In the processes of Scuba tank filling ,air around the compressor is used to fill the tank after purification and dehydration. Any defect in the filtering, purification or dehydration processes may affect the quality of the filled gas and there is the possibility of toxic gases contamination due to environmental air changes. A possibility of lead exposure is likely to occur for those divers frequent handle the lead weight.
Dangerous Marine creatures -Sharks, Crocodiles, Caimans and other biting marine animals can create part of the biological hazards of diving. Over two divers and four swimmers probably attack by sharks 1995 in Hong Kong Other marine animal injuries due to fish and urchin stings are common to diver as well. Ciguatera food poisoning with generalized symptoms and skin lesions happened sporadic in most Indo-pacific regions.
Infections -A variety of pathogenic organisms may be encountered through contact with water. Water-borne pathogens may enter the body through intact of damaged skin, or mucous membrane. Portals of entry includes eyes, ears, nose, throat, lung, gastrointestinal or genitourinary tracts. Ingestion of polluted waters been known to pose the risk of hepatitis, typhoid , cholera, dysentery and other gastrointestinal diseases. An increasing problem happens in the closed environments in undersea habitats and hyperbaric facilities of diving operation. Cross-infection of divers through the use of common equipment, diving practices , such as buddy breathing, and the inhabitating of small enclosures, aggravate these problems. Marine creatures sting and bite may result in primary and secondary infection as well.
Hypoglycemia- is an abnormally low blood sugar (glucose) level. It is a condition that is not due to respiratory difficulties, but can complicate or be confused with them. The brain is especially sensitive to lack of glucose. The highly variable symptoms can sometimes closely resemble those of other conditions in which brain function is affected, including carbon dioxide intoxication, hypoxia, carbon monoxide poisoning, oxygen toxicity, and arterial gas embolism. Some of the more common symptoms are unusual hunger, excessive sweating, numbness, chills, headache, trembling, dizziness, confusion, in co-ordination, anxiety, and fainting. In severe cases, loss of consciousness and convulsions may occur. In diving, the possibility of hypoglycemia increases during long, drawn out diving operations and in personnel who have a tendency to skip meals or eat haphazardly during the diving.