Occupation | |
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Names | Physician |
Occupation type | Specialty |
Activity sectors | Medicine |
Description | |
Education required |
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Fields of employment | Hospitals, clinics |
Diving medicine, also called undersea and hyperbaric medicine (UHB), is the diagnosis, treatment and prevention of conditions caused by humans entering the undersea environment. It includes the effects on the body of pressure on gases, the diagnosis and treatment of conditions caused by marine hazards and how relationships of a diver's fitness to dive affect a diver's safety. Diving medical practitioners are also expected to be competent in the examination of divers and potential divers to determine fitness to dive.
Hyperbaric medicine is a corollary field associated with diving, since recompression in a hyperbaric chamber is used as a treatment for two of the most significant diving-related illnesses, decompression sickness and arterial gas embolism.
Diving medicine deals with medical research on issues of diving, the prevention of diving disorders, treatment of diving accidents and diving fitness. The field includes the effect of breathing gases and their contaminants under high pressure on the human body and the relationship between the state of physical and psychological health of the diver and safety.
In diving accidents it is common for multiple disorders to occur together and interact with each other, both causatively and as complications.
Diving medicine is a branch of occupational medicine and sports medicine, and at first aid level, an important part of diver education.
The scope of diving medicine must necessarily include conditions that are specifically connected with the activity of diving, and not found in other contexts, but this categorization excludes almost everything, leaving only deep water blackout, isobaric counterdiffusion and high pressure nervous syndrome. A more useful grouping is conditions that are associated with exposure to variations of ambient pressure. These conditions are largely shared by aviation and space medicine. Further conditions associated with diving and other aquatic and outdoor activities are commonly included in books which are aimed at the diver, rather than the specialist medical practitioner, as they are useful background to diver first aid training.[ citation needed ]
The scope of knowledge necessary for a practitioner of diving medicine includes the medical conditions associated with diving and their treatment, physics and physiology relating to the underwater and pressurised environment, the standard operating procedures and equipment used by divers which can influence the development and management of these conditions, and the specialised equipment used for treatment. [1]
The ECHM-EDTC Educational and Training Standards for Diving and Hyperbaric Medicine (2011) specify the following scope of knowledge for Diving Medicine: [1]
The ECHM-EDTC Educational and Training Standards for Diving and Hyperbaric Medicine (2011) specify the following scope of knowledge for Hyperbaric Medicine additional to that for Diving medicine: [1]
The signs and symptoms of diving disorders may present during a dive, on surfacing, or up to several hours after a dive. Divers have to breathe a gas which is at the same pressure as their surroundings, which can be much greater than on the surface. The ambient pressure underwater increases by 1 standard atmosphere (100 kPa) for every 10 metres (33 ft) of depth. [2]
The principal conditions are: decompression illness (which covers decompression sickness and arterial gas embolism); nitrogen narcosis; high pressure nervous syndrome; oxygen toxicity; and pulmonary barotrauma (burst lung). Although some of these may occur in other settings, they are of particular concern during diving activities. [2]
The disorders are caused by breathing gas at the high pressures encountered at depth, and divers will often breathe a gas mixture different from air to mitigate these effects. Nitrox, which contains more oxygen and less nitrogen is commonly used as a breathing gas to reduce the risk of decompression sickness at recreational depths (up to about 40 metres (130 ft)). Helium may be added to reduce the amount of nitrogen and oxygen in the gas mixture when diving deeper, to reduce the effects of narcosis and to avoid the risk of oxygen toxicity. This is complicated at depths beyond about 150 metres (500 ft), because a helium–oxygen mixture (heliox) then causes high pressure nervous syndrome. [2] More exotic mixtures such as hydreliox, a hydrogen–helium–oxygen mixture, are used at extreme depths to counteract this. [3]
Decompression sickness (DCS) occurs when gas, which has been breathed under high pressure and dissolved into the body tissues, forms bubbles as the pressure is reduced on ascent from a dive. The results may range from pain in the joints where the bubbles form to blockage of an artery leading to damage to the nervous system, paralysis or death. While bubbles can form anywhere in the body, DCS is most frequently observed in the shoulders, elbows, knees, and ankles. Joint pain occurs in about 90% of DCS cases reported to the U.S. Navy, with neurological symptoms and skin manifestations each present in 10% to 15% of cases. Pulmonary DCS is very rare in divers. [4]
If the breathing gas in a diver's lungs cannot freely escape during an ascent, the lungs may be expanded beyond their compliance, and the lung tissues may rupture, causing pulmonary barotrauma (PBT). The gas may then enter the arterial circulation producing arterial gas embolism (AGE), with effects similar to severe decompression sickness. [5] Gas bubbles within the arterial circulation can block the supply of blood to any part of the body, including the brain, and can therefore manifest a vast variety of symptoms.
Nitrogen narcosis is caused by the pressure of dissolved gas in the body and produces temporary impairment to the nervous system. This results in alteration to thought processes and a decrease in the diver's ability to make judgements or calculations. It can also decrease motor skills, and worsen performance in tasks requiring manual dexterity. As depth increases, so does the pressure and hence the severity of the narcosis. The effects may vary widely from individual to individual, and from day to day for the same diver. Because of the perception-altering effects of narcosis, a diver may not be aware of the symptoms, but studies have shown that impairment occurs nevertheless. The narcotic effects dissipate without lasting effect as the pressure decreases during ascent. [6]
Helium is the least narcotic of all gases, and divers may use breathing mixtures containing a proportion of helium for dives exceeding about 40 metres (130 ft) deep. In the 1960s it was expected that helium narcosis would begin to become apparent at depths of 300 metres (1,000 ft). However, it was found that different symptoms, such as tremors, occurred at shallower depths around 150 metres (500 ft). This became known as high-pressure nervous syndrome, and its effects are found to result from both the absolute depth and the speed of descent. Although the effects vary from person to person, they are stable and reproducible for the individual. [7] [ medical citation needed ]
Although oxygen is essential to life, in concentrations significantly greater than normal it becomes toxic, overcoming the body's natural defences (antioxidants), and causing cell death in any part of the body. The lungs and brain are particularly affected by high partial pressures of oxygen, such as are encountered in diving. The body can tolerate partial pressures of oxygen around 0.5 bars (50 kPa; 7.3 psi) indefinitely, and up to 1.4 bars (140 kPa; 20 psi) for many hours, but higher partial pressures rapidly increase the chance of the most dangerous effect of oxygen toxicity, a convulsion resembling an epileptic seizure. [8] Susceptibility to oxygen toxicity varies dramatically from person to person, and to a smaller extent from day to day for the same diver. [9] Prior to convulsion, several symptoms may be present – most distinctly that of an aura.
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, [10] and hyperbaric oxygen therapy, which is the definitive treatment for most conditions of decompression illness. [11] [12]
The administration of oxygen as a medical intervention is common in diving medicine, both for first aid and for longer term treatment. [12] Normobaric oxygen administration at the highest available concentration is frequently used as first aid for any diving injury that may involve inert gas bubble formation in the tissues. There is epidemiological support for its use from a statistical study of cases recorded in a long term database. [13] [14] [15]
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. In the 21st century, it is a highly specialized treatment modality found to be effective for treating many conditions where the administration of oxygen under pressure is beneficial. [16]
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, but in some cases recompression to pressures where oxygen toxicity is unacceptable may be required to eliminate the bubbles in the tissues in severe cases of decompression illness. [12]
Availability of recompression treatment is limited. Some countries have no facilities at all, and in others which have facilities, such as the US, some hospitals do not make them available for emergency treatment. [17]
Fitness to dive, (or medical fitness to dive), is the medical and physical suitability of a person to function safely in the underwater environment using underwater diving equipment and procedures. Depending on the circumstances it may be established by a signed statement by the diver that he or she does not suffer from any of the listed disqualifying conditions and is able to manage the ordinary physical requirements of diving, to a detailed medical examination by a physician registered as a medical examiner of divers following a procedural checklist, and a legal document of fitness to dive issued by the medical examiner.
The most important medical examination is the one before starting diving, as the diver can be screened to prevent exposure when a dangerous condition exists. The other important medicals are after some significant illness, where medical intervention is needed there and has to be done by a doctor who is competent in diving medicine, and can not be done by prescriptive rules. [18]
Psychological factors can affect fitness to dive, particularly where they affect response to emergencies, or risk taking behaviour. The use of medical and recreational drugs, can also influence fitness to dive, both for physiological and behavioural reasons. In some cases prescription drug use may have a net positive effect, when effectively treating an underlying condition, but frequently the side effects of effective medication may have undesirable influences on the fitness of diver, and most cases of recreational drug use result in an impaired fitness to dive, and a significantly increased risk of sub-optimal response to emergencies.
Specialist training in underwater and hyperbaric medicine is available from several institutions, and registration is possible both with professional associations and governmental registries.
Level 2D. Diving Medicine Physician (DMP) minimum 80 teaching hours.
Level 2H. Hyperbaric Medicine Physician (HMP) minimum 120 teaching hours
Level 3. Hyperbaric medicine expert or consultant (hyperbaric and diving medicine) is a physician who has been assessed as competent to:
The American Medical Association recognises the sub-speciality Undersea and Hyperbaric Medicine held by someone who is already Board Certified in some other speciality. [26]
The South African Department of Employment and Labour registers two levels of Diving Medical Practitioner. Level 1 is qualified to conduct annual examinations and certification of medical fitness to dive, on commercial divers (equivalent to ECHM-EDTC Level 1. Medical Examiner of Divers), and Level 2 is qualified to provide medical advice to a diving contractor and hyperbaric treatment for diving injuries [27] (equivalent to ECHM-EDTC Level 2D Diving Medicine Physician)
Australia has a four tier system: In 2007 there was no recognised equivalence with the European standard. [28]
A basic knowledge understanding of the causes, symptoms and first aid treatment of diving related disorders is part of the basic training for most recreational and professional divers, both to help the diver avoid the disorders, and to allow appropriate action in case of an incident resulting in injury. [27]
A recreational diver has the same duty of care to other divers as any ordinary member of the public, and therefore there is no obligation to train recreational divers in first aid or other medical skills. Nevertheless, first aid training is recommended by most, if not all, recreational diver training agencies. [29] [30] [31]
Recreational diving instructors and divemasters, on the other hand, are to a greater or lesser extent responsible for the safety of divers under their guidance, and therefore are generally required to be trained and certified to some level of rescue and first aid competence, as defined in the relevant training standards of the certifying body. In many cases this includes certification in cardiopulmonary resuscitation and first aid oxygen administration for diving accidents.
Professional divers usually operate as members of a team with a duty of care for other members of the team. Divers are expected to act as standby divers for other members of the team and the duties of a standby diver include rescue attempts if the working diver gets into difficulties. Consequently, professional divers are generally required to be trained in rescue procedures appropriate to the modes of diving they are certified in, and to administer first aid in emergencies. The specific training, competence and registration for these skills varies, and may be specified by state or national legislation or by industry codes of practice. [27] [32]
Diving supervisors have a similar duty of care, and as they are responsible for operational planning and safety, generally are also expected to manage emergency procedures, including the first aid that may be required. The level of first aid training, competence and certification will generally take this into account.
A diver medic or diving medical technician is a member of a dive team who is trained in advanced first aid. [33]
A diver medic recognised by IMCA must be capable of administering first aid and emergency treatment, and carrying out the directions of a physician, and be familiar with diving procedures and compression chamber operation. The diver medic must also be able to assist the diving supervisor with decompression procedures, and provide treatment in a hyperbaric chamber in an emergency. The diver medic must hold, at a minimum, a valid certificate of medical fitness to operate in a pressurized environment, and a certificate of medical fitness to dive. [34]
Training standards for diver medic are described in the IMCA Scheme for Recognition of Diver Medic Training. [34]
Experimental work on human subjects is often ethically and/or legally impracticable. Tests where the endpoint is symptomatic decompression sickness are difficult to authorise and this makes the accumulation of adequate and statistically valid data difficult. The precautionary principle may be applied in the absence of information allowing a realistic assessment of risk. Analysis of investigations into accidents is useful when reliable results are available, which is less often than would be desirable, but privacy concerns prevent a large mount of information potentially useful to the general diving population from being made available to researchers.
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The Diving Diseases Research Centre (DDRC) is a British hyperbaric medical organisation located near Derriford Hospital in Plymouth, Devon. It is a registered charity and was established in 1980 to research the effects of diving on human physiology.
The main objective of DDRC is research into diving medicine. The Centre is also an education and training base providing diving medical, clinical and hyperbaric courses.The National Board of Diving and Hyperbaric Medical Technology (NBDHMT), formally known as the National Association of Diving Technicians, is a non-profit organization for the education and certification of qualified personnel in the fields of diving and hyperbaric medicine in the US. [39]
The South Pacific Underwater Medicine Society (SPUMS) is a primary source of information for diving and hyperbaric medicine physiology worldwide. The organisation supports the study of all aspects of underwater and hyperbaric medicine, provides information on underwater and hyperbaric medicine, publishes a medical journal and holds an annual conference. [47] [48]
SPUMS offers a post-graduate Diploma of Diving and Hyperbaric Medicine.Nitrox refers to any gas mixture composed of nitrogen and oxygen. This includes atmospheric air, which is approximately 78% nitrogen, 21% oxygen, and 1% other gases, primarily argon. In the usual application, underwater diving, nitrox is normally distinguished from air and handled differently. The most common use of nitrox mixtures containing oxygen in higher proportions than atmospheric air is in scuba diving, where the reduced partial pressure of nitrogen is advantageous in reducing nitrogen uptake in the body's tissues, thereby extending the practicable underwater dive time by reducing the decompression requirement, or reducing the risk of decompression sickness.
Narcosis while diving is a reversible alteration in consciousness that occurs while diving at depth. It is caused by the anesthetic effect of certain gases at high partial pressure. The Greek word νάρκωσις (narkōsis), "the act of making numb", is derived from νάρκη (narkē), "numbness, torpor", a term used by Homer and Hippocrates. Narcosis produces a state similar to drunkenness, or nitrous oxide inhalation. It can occur during shallow dives, but does not usually become noticeable at depths less than 30 metres (98 ft).
Decompression sickness is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompression. DCS most commonly occurs during or soon after a decompression ascent from underwater diving, but can also result from other causes of depressurisation, such as emerging from a caisson, decompression from saturation, flying in an unpressurised aircraft at high altitude, and extravehicular activity from spacecraft. DCS and arterial gas embolism are collectively referred to as decompression illness.
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats. Oxygen is the essential component for any breathing gas. Breathing gases for hyperbaric use have been developed to improve on the performance of ordinary air by reducing the risk of decompression sickness, reducing the duration of decompression, reducing nitrogen narcosis or allowing safer deep diving.
Saturation diving is diving for periods long enough to bring all tissues into equilibrium with the partial pressures of the inert components of the breathing gas used. It is a diving mode that reduces the number of decompressions divers working at great depths must undergo by only decompressing divers once at the end of the diving operation, which may last days to weeks, having them remain under pressure for the whole period. A diver breathing pressurized gas accumulates dissolved inert gas used in the breathing mixture to dilute the oxygen to a non-toxic level in the tissues, which can cause potentially fatal decompression sickness if permitted to come out of solution within the body tissues; hence, returning to the surface safely requires lengthy decompression so that the inert gases can be eliminated via the lungs. Once the dissolved gases in a diver's tissues reach the saturation point, however, decompression time does not increase with further exposure, as no more inert gas is accumulated.
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.
Diver rescue, usually following an accident, is the process of avoiding or limiting further exposure to diving hazards and bringing a diver to a place of safety. A safe place generally means a place where the diver cannot drown, such as a boat or dry land, where first aid can be administered and from which professional medical treatment can be sought. In the context of surface supplied diving, the place of safety for a diver with a decompression obligation is often the diving bell.
Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well-adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done.
Divers Alert Network (DAN) is a group of not-for-profit organizations dedicated to improving diving safety for all divers. It was founded in Durham, North Carolina, United States, in 1980 at Duke University providing 24/7 telephonic hot-line diving medical assistance. Since then the organization has expanded globally and now has independent regional organizations in North America, Europe, Japan, Asia-Pacific and Southern Africa.
Captain Albert Richard Behnke Jr. USN (ret.) was an American physician, who was principally responsible for developing the U.S. Naval Medical Research Institute. Behnke separated the symptoms of Arterial Gas Embolism (AGE) from those of decompression sickness and suggested the use of oxygen in recompression therapy.
Diver training is the set of processes through which a person learns the necessary and desirable skills to safely dive underwater within the scope of the diver training standard relevant to the specific training programme. Most diver training follows procedures and schedules laid down in the associated training standard, in a formal training programme, and includes relevant foundational knowledge of the underlying theory, including some basic physics, physiology and environmental information, practical skills training in the selection and safe use of the associated equipment in the specified underwater environment, and assessment of the required skills and knowledge deemed necessary by the certification agency to allow the newly certified diver to dive within the specified range of conditions at an acceptable level of risk. Recognition of prior learning is allowed in some training standards.
Robert William Hamilton Jr., known as Bill, was an American physiologist known for his work in hyperbaric physiology.
Fitness to dive, specifically the medical fitness to dive, is the medical and physical suitability of a diver to function safely in the underwater environment using underwater diving equipment and procedures. Depending on the circumstances, it may be established with a signed statement by the diver that they do not have any of the listed disqualifying conditions. The diver must be able to fulfill the ordinary physical requirements of diving as per the detailed medical examination by a physician registered as a medical examiner of divers following a procedural checklist. A legal document of fitness to dive issued by the medical examiner is also necessary.
Human physiology of underwater diving is the physiological influences of the underwater environment on the human diver, and adaptations to operating underwater, both during breath-hold dives and while breathing at ambient pressure from a suitable breathing gas supply. It, therefore, includes the range of physiological effects generally limited to human ambient pressure divers either freediving or using underwater breathing apparatus. Several factors influence the diver, including immersion, exposure to the water, the limitations of breath-hold endurance, variations in ambient pressure, the effects of breathing gases at raised ambient pressure, effects caused by the use of breathing apparatus, and sensory impairment. All of these may affect diver performance and safety.
The following outline is provided as an overview of and topical guide to underwater diving:
The following index is provided as an overview of and topical guide to underwater diving:
The following index is provided as an overview of and topical guide to underwater diving:
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