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 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.
Disorders particularly associated with diving include those caused by variations in ambient pressure, such as barotraumas of descent and ascent, decompression sickness and those caused by exposure to elevated ambient pressure, such as some types of gas toxicity. There are also non-dysbaric disorders associated with diving, which include the effects of the aquatic environment, such as drowning, which also are common to other water users, and disorders caused by the equipment or associated factors, such as carbon dioxide and carbon monoxide poisoning. General environmental conditions can lead to another group of disorders, which include hypothermia and motion sickness, injuries by marine and aquatic organisms, contaminated waters, man-made hazards, and ergonomic problems with equipment. Finally there are pre-existing medical and psychological conditions which increase the risk of being affected by a diving disorder, which may be aggravated by adverse side effects of medications and other drug use.
Treatment depends on the specific disorder, but often includes oxygen therapy, which is standard first aid for most diving accidents, and is hardly ever contra-indicated for a person medically fit to dive, and hyperbaric therapy is the definitive treatment for decompression sickness. Screening for medical fitness to dive can reduce some of the risk for some of the disorders.
Effects of variation in ambient pressure
Many diving accidents or illnesses are related to the effect of pressure on gases in the body.
Barotrauma
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 change 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)
Compression arthralgia
Compression arthralgia is pain in the joints caused by exposure to high ambient pressure at a relatively high rate of compression, experienced by underwater divers. Also referred to in the US Navy Diving Manual as compression pains. Fast compression (descent) may produce symptoms as shallow as 30 msw. At depths beyond 180m even very slow compression may produce symptoms. The pain may be sufficiently severe to limit the diver's capacity for work, and may also limit travel rate and depth of downward excursions by saturation divers. The symptoms generally resolve during decompression and require no further treatment.
Decompression sickness
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 bloodstream 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.
Symptoms: Loss of bowel or bladder function Collapse or unconsciousness Coughing spasms or shortness of breath Dizziness Unusual fatigue Itching Joint aches or pain Mottling or marbling of skin Numbness or tingling Paralysis Personality changes Staggering, loss of coordination, or tremors Weakness
Dysbaric osteonecrosis
Dysbaric osteonecrosis, also known as aseptic bone necrosis, is generally a longer term effect on the bones and joints of divers caused by decompression bubbles and may occur even if no clinical decompression sickness has been diagnosed.
High pressure nervous syndrome
High-pressure nervous syndrome (HPNS) is a neurological and physiological diving disorder that results when a diver descends below about while breathing a helium–oxygen mixture. The effects depend on the rate of descent and the depth. The effects of HPNS comprise trembling, myoclonic jerks, drowsiness, alterations in EEG patterns, visual disruptions, queasiness, vertigo, and diminished cognitive function.
Nitrogen narcosis
Nitrogen narcosis is a reversible alteration in consciousness that occurs while breathing gas with a high partial pressure of nitrogen. The effect is similar to alcohol intoxication or nitrous oxide inhalation and does not usually become noticeable at nitrogen partial pressures less than about 3 bar, equivalent to a depth of about 30 meters (100 ft) on air. As depth increases, the mental impairment may become hazardous. Divers can learn to cope with some of the effects of narcosis, but it is impossible to develop a tolerance. Narcosis affects all divers breathing gas mixtures containing nitrogen, although susceptibility varies widely from dive to dive, and between individuals. One of the risks of Nitrogen narcosis is that divers may remove their regulator or fail to follow proper safety procedures.
Oxygen toxicity
Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen () partial pressures significantly greater than found in atmospheric 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 breathing 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
Drowning
"Drowning is the process of experiencing respiratory impairment from submersion/immersion in liquid".
Near drowning is the survival of a drowning event involving unconsciousness or water inhalation and can lead to serious secondary complications, including death, after the event. Drowning is usually the culmination of a deteriorating sequence of events in a diving accident, and is seldom a satisfactory explanation for a fatality, as it fails to explain the underlying causes and complications that led to the final consequence. Generally, a diver is well prepared for the environment, and well trained and equipped to deal with it. A diver should not drown merely as a result of being in the water.
Salt water aspiration syndrome
Salt water aspiration syndrome is a rare diving disorder experienced by divers who inhale a mist of seawater from a faulty demand valve causing irritation of the lungs. It can usually be treated by rest for several hours. If severe, medical assessment is required.
Hypoxia
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 of consciousness underwater and consequent death either directly by cerebral hypoxia, or 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.
Swimming-induced pulmonary edema
Swimming-induced pulmonary edema (SIPE) occurs when fluids from the blood leak abnormally from the small vessels of the lung (pulmonary capillaries) into the airspaces (alveoli).
SIPE usually occurs during heavy exertion in conditions of water immersion, such as swimming and diving. It has been reported in scuba divers, apnea (breath hold) free-diving competitors, combat swimmers, and triathletes. The causes are incompletely understood at the present time.
Immersion diuresis
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
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.