[1][2] Equipment failure is rare in open circuit scuba, and while the cause of death is commonly recorded as drowning, this is mainly the consequence of an uncontrollable series of events taking place in water.
Arterial gas embolism is also frequently cited as a cause of death, and it, too, is the consequence of other factors leading to an uncontrolled and badly managed ascent, possibly aggravated by medical conditions.
[7] The most frequent known root cause for diving fatalities is running out of, or low on, breathing gas, but the reasons for this are not specified, probably due to lack of data.
Other factors cited include buoyancy control, entanglement or entrapment, rough water, equipment misuse or problems and emergency ascent.
The most common injuries and causes of death were drowning or asphyxia due to inhalation of water, air embolism and cardiac events.
Drowning occurs as a consequence of preceding problems, such as cardiac disease, pulmonary barotrauma, unmanageable stress, unconsciousness from any cause, water aspiration, trauma, equipment difficulties, environmental hazards, inappropriate response to an emergency or failure to manage the gas supply.
[14] In many diving destinations, resources are not available for comprehensive investigations or complete autopsies, The 2010 DAN Diving Fatalities workshop noted that listing drowning as a cause of death is ineffective in determining what actually occurred in an incident, and that lack of information is the primary reason for personal injury lawsuits filed in the industry.
[4] The traditional procedure for developing diving safety recommendations is based on the assumption that associations of circumstances with fatalities are causative.
Many of these could be improved by training and practice, some by a change of attitude, but some diving fatalities appear to be unavoidable as the risk is inherent in the activity and depends on factors that are not under the control of the diver.
Divers who died for reasons other than a medical cause were found to be about 7 times more likely to have one or more violations of recommended practice associated with the fatality.
Medical issues are a significant part of the problem, and certified divers are responsible for assessing their own fitness and ability to do any particular dive.
[1] A large percentage (40 to 60%) of deaths in the Edmonds summary were associated with panic, a psychological reaction to stress which is characterized by irrational and unhelpful behaviour, which reduces the chances of survival.
On dives where decompression is planned, competent divers will often carry a bit more weight than strictly necessary to ensure that in a situation where they have lost or used up all their gas and are relying on a supply from a team member, they do not have to struggle to stay down at the correct stop depth.
Some divers may be unaware of the need to adjust weight to suit any change in equipment that may affect buoyancy, due to inadequate training.
The drag caused by a buoyancy compensator inflated to offset the weight belt can contribute to exhaustion in divers attempting to swim to safety on the surface.
The American Academy of Underwater Sciences reported in 1989 that half the cases of decompression sickness were related to loss of buoyancy control.
[3] When twin-bladder buoyancy compensators are used, confusion as to how much gas is in each bladder can lead to a delay in appropriate response, by which time control of the ascent may have already been lost.
The use of a secondary (octopus regulator) second stage or a completely separate emergency air supply (bailout cylinder) would appear to be a safer alternative.
Factors associated with pulmonary barotrauma include panic, rapid buoyant ascent, asthma and regulator failure.
The associated triggers include exercise, drugs, hypoxia from salt water aspiration, cardio-pulmonary reflexes, respiratory abnormalities, restrictive dive suits and harness, and cold exposure.
This opinion was prevalent for a long time, but recent studies by DAN suggest that asthma may be managed successfully in some cases.
The diving environment can provoke or aggravate asthma in several ways, such as salt water aspiration, breathing cold dry air, strenuous exertion, hyperventilation.
[3] Nitrogen narcosis was cited as a contributory or triggering factor in 9% of cases reviewed by Edmonds et al., but was never the sole cause of death.
Subsequent testing of the regulators showed that most of the problems were caused by leaks resulting in inhalation of salt water, but in some cases there was excessive breathing resistance following a mechanical dysfunction.
In less than 5% of fatalities, there were problems due to malfunction or misuse of weight belt (excluding overweighting which is not a failure of the equipment), harness, mask, exposure suit, submersible pressure gauges and entanglement in lines deployed by the diver.
These included current stronger than the diver could manage, rough water, surf, surge from wave movement, and impaired visibility caused by these conditions.
These conditions were frequently encountered when the diver was obliged to surface in an unsuitable place due to earlier problems, and were often exacerbated by overweighting and/or the high drag of an excessively inflated buoyancy compensator, leading to exhaustion or panic which resulted in drowning.
Greater depth can expose a diver to factors such as increased air consumption, impaired judgment caused by nitrogen narcosis, colder water, reduced thermal insulation of a compressed wetsuit, reduced visibility and lighting, slower response of buoyancy compensator inflation, increased work of breathing, greater heat loss when using helium mixtures, higher risk of decompression sickness and a necessarily prolonged ascent time.
No matter how quickly an investigation is launched, in most cases the body will have been recovered and resuscitation attempted, equipment will have been removed and possibly damaged or lost, and the people at the site returned to their homes.
[18] The forensic pathologist also needs to understand the limitations of autopsy findings in diving-related deaths and realize that there are common postmortem artifacts that can be misinterpreted, resulting in erroneous conclusions.Scuba diving fatalities have a major financial impact by way of lost income, lost business, insurance premium increases and high litigation costs.