Diving disorders, or diving related medical conditions, are conditions associated with underwater diving, and include both conditions unique to underwater diving, and those that also occur during other activities. This second group further divides into conditions caused by exposure to ambient pressures significantly different from surface atmospheric pressure, and a range of conditions caused by general environment and equipment associated with diving activities.
Effects of variation in ambient pressure
Many diving accidents or illnesses are related to the effect of pressure on gases in the body;
Barotrauma is physical injury to body tissues caused by a difference in pressure between a gas space inside or in contact with the body, and the surroundings .
Barotrauma occurs when the difference in pressure between the surroundings and the gas space makes the gas expand in volume, distorting adjacent tissues enough to rupture cells or damage tissue by deformation. A special case, where pressure in tissue is reduced to the level that causes dissolved gas to come out of solution as bubbles, is called decompression sickness, the bends, or caisson disease.
Several organs are susceptible to barotrauma, however the cause is well understood and procedures for avoidance are clear. Nevertheless, barotrauma occurs and can be life-threatening, and procedures for first aid and further treatment are an important part of diving medicine.
- Barotraumas of descent (squeezes)
- Ear squeeze (also alternobaric vertigo)
- Sinus squeeze (aerosinusitis)
- Tooth squeeze (dental barotrauma, barodontalgia)
- Mask squeeze
- Helmet squeeze
- Suit squeeze
- Barotraumas of ascent (overexpansion injuries)
- Lung overexpansion injury (pulmonary barotrauma) - rupture of lung tissue allowing air to enter tissues, blood vessels, or spaces between or surrounding organs:
- Pneumothorax: Free air in the pleural cavity, leading to collapsed lung.
- Interstitial emphysema: Gas trapped in the spaces between tissues.
- Mediastinal emphysema: Gas trapped around the heart.
- Subcutaneous emphysema: Free gas under the skin.
- Arterial gas embolism: Air or other breathing gas in the blood stream, causing blockage of small blood vessels.
- Intestinal gas overexpansion
- Middle ear overpressure (reversed ear) (also alternobaric vertigo)
- Sinus overpressure (aerosinusitis)
- Tooth overpressure (dental barotrauma, barodontalgia)
Decompression sickness is a condition caused by dissolved gases coming out of solution as bubbles in the tissues and fluids of the body during and directly after depressurisation. DCS is best known as a hazard of underwater diving but may occur in other decompression events such as caisson work, flying in unpressurised aircraft, and extra-vehicular activity from spacecraft.Since bubbles can form in any part of the body,or migrate via the bloodsteam to any part of the body, DCS can produce a wide range of symptoms, and its effects may vary from joint pain and skin rashes to paralysis and death.
Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen (O
2) partial pressures significantly greater than found in atmosperic air at sea level. Severe cases can result in cell damage and death, with effects most often seen in the central nervous system, lungs and eyes.
Divers are exposed to raised partial pressures of oxygen in normal diving activities, where the partial pressure of oxygen in the breating gas is increased in proportion to the ambient pressure at depth, and by using gas mixtures in which oxygen is substituted for inert gases to reduce decompression obligations, to accelerate decompression, or reduce the risk of decompression sickness.They are also exposed to raised partial pressures of oxygen if given oxygen as first aid, which is a standard protocol for most acute diving related disorders, and when undergoing hyperbaric oxygen therapy in the case of decompression sickness or arterial gas embolism.
Non-dysbaric disorders associated with diving
Hypoxia is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise. A mismatch between oxygen supply and its demand at the cellular level may result in a hypoxic condition.
Generalized hypoxia occurs when breathing mixtures of gases with a low oxygen content, e.g. while diving underwater especially when using closed-circuit rebreather systems that control the amount of oxygen in the supplied air, or when breathing gas mixtures blended to prevent oxygen toxicity at depths below about 60 m near or at the surface. This condition may lead to a loss if consciousness underwater and consequent death either directly by cerebral hypoxia, ir indirectly by drowning.
Latent hypoxia may occur when a breathhold diver surfaces. This is also known as deep water blackout. The consequence is likely to be drowning.Tissue hypoxia occurs when arterial gas emboli due to either lung overexpansion injury or decompression sickness block systemic capillaries and shut off the supply of oxygenated blood to the tissues downstream. If untreated, this leads to tissue damage or death, with consequences that depend on the site and extent of the injury.
Immersion diuresis is a type of diuresis caused by immersion of the body in water (or equivalent liquid). It is mainly caused by lower temperature and by pressure.
The temperature effect is caused by vasoconstriction of the cutaneous blood vessels within the body to conserve heat. The body detects an increase in the blood pressure and inhibits the release of vasopressin, causing an increase in the production of urine.
The pressure effect is caused by the hydrostatic pressure of the water directly increasing blood pressure. Its significance is indicated by the fact that the temperature of the water doesn't substantially affect the rate of diuresis. Partial immersion of only the limbs does not cause increased urination.Diuresis is significant in diving medicine as the consequent mild dehydration may be a contributing factor in the onset of decompression sickness.
Hypercapnia is a condition where there is too much carbon dioxide (CO2) in the blood.
Divers may develop this condition for several possible reasons:
- Increased work of breathing due to increased density of the breathing das with depth.
- Inadequate ventilatory response to exertion.
- Dead space of the breathing apparatus.
- Higher inspired CO2 due to failure of the carbon dioxide scrubber in the diver's rebreather to remove sufficient carbon dioxide from the loop.
- Over-exertion, producing excess carbon dioxide due to elevated metabolic activity.
- Deliberate hypoventilation, known as "skip breathing".
- Shallow breathing, due to stress or other reasons.
- Contamination of the breathing gas supply.
Carbon monoxide poisoning occurs by inhalation of carbon monoxide (CO). Carbon monoxide is a toxic gas, but, being colorless, odorless, tasteless, and initially non-irritating, it is very difficult for people to detect. Carbon monoxide is a product of incomplete combustion of organic matter due to insufficient oxygen supply to enable complete oxidation to carbon dioxide (CO2). Breathing gas for diving may be contaminated either by intake of contaminated atmospheric air, usually from internal combustion exhaust gases, or, more rarely, by carbon monoxide produced in the compressor by partial combustion of lubricants.The effects of carbon monoxide in breathing gas are increased in proportion to the depth, as the partial pressure of the contaminant is increased in proportion to the depth for a given gas fraction. The permitted levels of carbon monoxide in breathing gas for diving is lower than for at atmospheric pressure due to the concentratng effect of raised ambient pressure.
Hazards in the underwater environment that can affect divers include marine life, marine infections, polluted water, ocean currents, waves and surges and man-made hazards such as boats, fishing lines and underwater construction. Diving medical personnel need to be able to recognize and treat accidents from large and small predators and poisonous creatures, appropriately diagnose and treat marine infections and illnesses from pollution as well as diverse maladies such as sea sickness, traveler's diarrhea and malaria.
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions (which is defined as 35.0 °C (95.0 °F)). Body temperature is usually maintained near a constant level of 36.5–37.5 °C (97.7–99.5 °F) through biological homeostasis or thermoregulation. If exposed to cold and the internal mechanisms are unable to replenish the heat that is being lost, a drop in core temperature occurs. As body temperature decreases, characteristic symptoms occur such as shivering and mental confusion.Hypothermia usually occurs from exposure to low temperatures, but any condition that decreases heat production, increases heat loss, or impairs thermoregulation may contribute. Heat is lost more quickly in water than on land, and also more quickly in proportion to wind speed. Water temperatures that would be quite reasonable as outdoor air temperatures can lead to hypothermia. Divers are often exposed to low water temperatures and wind chill, which may be aggravated by evaporative cooling of wet dive suits, and mild hypothermia is not uncommon in both recreational and professional divers, while moderate to severe hypothermia remains a significant risk.
Seasickness is a form of motion sickness, a condition in which a disagreement exists between visually perceived movement and the vestibular system's sense of movement characterized by a feeling of nausea and, in extreme cases, vertigo, experienced after spending time on a craft on water, floating at the surface of a rough sea, and in strong surge near the bottom.Seasickness can significantly reduce the ability of a diver to effectively complete a task or manage a contingency, and may predispose the diver to hypothermia and decompression sickness.
Injury caused by marine animals
Treatment of diving disorders depends on the specific disorder or combination of disorders, but two treatments are commonly associated with first aid and definitive treatment where diving is involved. These are first aid oxygen administration at high concentration, which is seldom contraindicated, and generally recommended as a default option in diving accidents where there is any significant probability of hypoxia, and hyperbaric oxygen therapy, which is the definitive treatment for most incidences of decompression illness. Hyperbaric treatment on other breathing gases is also used for treatment of decompression sickness if HBO is inadequate.
The administration of oxygen as a medical intervention is common in diving medicine, both for first aid and for longer term treatment.
Recompression treatment in a hyperbaric chamber was initially used as a life-saving tool to treat decompression sickness in caisson workers and divers who stayed too long at depth and developed decompression sickness. Now, it is a highly specialized treatment modality that has been found to be effective in the treatment of many conditions where the administration of oxygen under pressure has been found to be beneficial. Studies have shown it to be quite effective in some 13 indications approved by the Undersea and Hyperbaric Medical Society.
Hyperbaric oxygen treatment is generally preferred when effective, as it is usually a more efficient and lower risk method of reducing symptoms of decompression illness, However, in some cases recompression to pressures where oxygen toxicity is unacceptable may be required to eliminate the bubbles in the tissues that cause the symptoms.
Fitness to dive
All divers should be free of conditions and illnesses that would negatively impact their safety and well-being underwater. The diving medical physician should be able to identify, treat and advise divers about illnesses and conditions that would cause them to be at increased risk for a diving accident.
Some reasons why a person should not be allowed to dive are as follows:
- Disorders that lead to altered consciousness: conditions that produce reduced awareness or sedation from medication, drugs, marijuana or alcohol; fainting, heart problems and seizure activity.
- Disorders that substantially increase the risk of barotrauma injury conditions or diseases that are associated with air trapping in closed spaces, such as sinuses, middle ear, lungs and gastrointestinal tract. Severe asthma is an example.
- Disorders that may lead to erratic and irresponsible behavior: included here would be immaturity, psychiatric disorders, diving while under the influence of medications, drugs and alcohol or any medical disorder that results in cognitive defects.
Conditions that may increase risk of diving disorders:
- Patent foramen ovale
- Diabetes mellitus — No serious problems should be expected during dives due to hypoglycaemia in divers with well-controlled diabetes. Long-term complications of diabetes should be considered and may be a contrindication.
Conditions considered temporary reasons to suspend diving activities:
- Pregnancy—It is unlikely that literature research can establish the effect of scuba diving on the unborn human fetus as there is insufficient data, and women tend to comply with the diving industry recommendation not to dive while pregnant.
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