A diving emergency or underwater diving emergency is an emergency that involves an underwater diver. The nature of an emergency requires action to be taken to prevent or avoid death, injury, or serious damage to property or the environment. In the case of diving emergencies, the risk is generally of death or injury to the diver, while diving or in the water before or after diving.
Underwater diving is an activity in which there is a constant risk of an emergency developing. This is a situation common to many human activities. The diver survives in an inherently hostile environment by competence, suitable equipment, vigilance, and attention to detail at a level appropriate to the specific situation. The emergency is the stage of an accident or incident between the causes and the effects, often while it is still possible to take effective action to rectify or mitigate the situation. Like many other classes of emergency, diving emergencies can often be prevented from developing further by appropriate action at an early stage, and by having the appropriate skills and equipment. Professional diving teams are required to have emergence plans in place, and recreational divers are also expected to do so, to the extent appropriate to the dive plan.
An alternative meaning, in the context of medicine, is a medical emergency which was initiated while diving, which may also be described as a diving medical emergency.
A diving emergency is an emergency experienced by a diver during a dive. This includes the time from when the diver enters the water to dive, until the end of all decompression and the diver has exited the water. Surface decompression may legally be part of a dive. It includes but is not restricted to medical emergencies that are a consequence of diving incidents.
See also: Scuba diving fatalities. Many circumstances can lead to a diving emergency. Many events may be considered an emergency under some conditions, but not under other conditions, where wahat would be an emergency to the unprepared diver can be an inconvenience when adequately prepared. Most of them can be mitigated before they become a full emergency,
An out-of-gas emergency occurs when the breathing gas supply is cut off by running out, supply system failure, or supply system interruption. These are the most urgent of the common diving emergencies, and the ones the diver should be equipped and skilled to manage. Many out-of-air emergencies are consequences of other problems that were not effectively managed.
A similar emergency occurs when a scuba diver accumulates more decompression obligation than the available gas endurance for decompression. This can happen either by the diver being unable to ascend in time to avoid the problem, or by using up or losing gas supply due to circumstances or inattention. This form of out-of-gas incident develops with the knowledge of the diver, who has more time available to work on a solution if one exists. It is analogous to the problem of being unable to ascent from under an overhead obstruction, and the decompression obligation is sometimes referred to as a decompression overhead.
See also: Diving air compressor. This is usually a consequence of poor filling procedures and often a problem of contaminated intake air. Bailout to another gas source is the preferred option, but it may be necessary to surface on the gas in use. Consequences depend on the specific contaminant and exposure. Carbon monoxide, carbon dioxide, volatile hydrocarbons, and compressor lubricant are the most commonly encountered contaminants, and there may be legislation requiring compressors used in this service to be periodically tested for these contaminants. It is possible for mixed breathing gas blended using high pressure industrial grade oxygen that is not certified for breathing grade, to contain contaminants not permitted in a breathing gas.
It is possible for the surface gas supply to be contaminated, so there will be an alternative surface supply to the gas distribution panel, which can be switched over with minimal delay, and the diver has a bailout gas supply that can be used in such an emergency. The bailout gas carried by the diver may not be sufficient for long decompression, and if this is expected a diving stage or wet bell will be used which carries a larger supply of emergency breathing gas., as well as providing a relatively secure platform for decompression stops.
The transparent faceplates of most helmets in current use are highly impact resistant and not easily damaged to the extent that they leak dangerously. If this does occur, the free-flow valve can be opened to increase internal pressure to reduce leak flow and purge the helmet of water. Tilting the helmet forward to lower the front will bring the faceplate down and may also reduce leakage and will help purge water from the helmet.
A lost guide line under an overhead where the exit cannot be seen is a life-threatening emergency, as the diver will die if they cannot find the way out before they run out of breathing gas. The guideline is usually the only sure way of finding the exit in a cave or wreck penetration, and if not found, the probable consequence is that the diver will not get out before their breathing gas runs out, and they drown. The threat is very real, and the urgency increases with time as gas is consumed. A related emergency is a lost buddy under an overhead. This implies that the buddy has lost the guide line. An aggravated version is when one or more divers enter an overhead knowingly or unknowingly without laying a guide line, and cannot find the way out.
Severe symptomatic decompression sickness can develop during ascent for a variety of reasons, some poorly understood and therefore not reliably avoided.
Cardiovascular emergency, major trauma, envenomation etc. In many of these situations it is nor practicable to treat thr problem in the water, so it is urgent for the diver to surface and get appropriate first aid as soon as possible without causing more serious injury through haste.
Omitted decompression puts the diver at an increased risk of decompression related to the amount of decompression omitted. There are protocols for managing this type of emergency, depending on severity and whether the diver has developed symptoms. If there is a chamber on site the best approach is to recompress in the chamber, but when there is no chamber, no symptoms, and the diver can be returned to depth in a short time, an in-water procedure for missed stops can be used.
Overwhelming vertigo or nausea underwater can be debilitating. This can be caused by motion sickness, barotrauma of the ears, or inner ear decompression sickness. It is likely to cause vomiting, which can compromise the diver's airway and breathing apparatus. Vomiting through a mouth held demand valve is moderately hazardous, but it can usually be cleared with little effort. A full-face mask is more of a problem, but it can be rinsed and cleared quite easily. Vomiting in a demand helmet is more risky as it is not practicable to rinse to clear, and There is a risk of aspiration of vomit trapped in the helmet air passages, with possibly fatal consequences. This problem is greatest in helmets and full-face masks with internal oro-nasal masks, where it will pass into the demand valve, and that which does not exit through the exhaust ports, will be an aspiration hazard unless flushed out before the next inhalation. A different problem occurs in free-flow helmets - there is less chance of aspiration, but vomit remains in the helmet or drains through into the diving suit, which is unpleasant, but not life-threatening.
Hypothermia developing with a long decompression obligation or long return swim to the exit point. This may be a complication of a loss of thermal protection, or an unexpected change in water temperature, or a failure to use appropriate environmental protection. Clinical hypothermia is rare in divers as the diving suit usually slows heat loss even when damaged or inadequate, but there are situations where it can occur, particularly in deep mixed gas diving where the cold, dense, breathing gas can chill the diver internally without the diver being aware of the reduced core temperature.
The immediate risk for scuba divers is that the airway may be compromised, with a high risk of drowning. There may also be a high risk of asphyxiation due to hypoxua. A contingent risk is of decompression illness if the diver is surfaced to reduce the more immediate probability of drowning.
Debilitating inert gas narcosis can occur if the diver goes to deep the a nitrogen based breathing gas, or can occur if they switch to a nitrogen based gas too deep, which can happen if there is an out-ogf-gas emergency without a better option, or the cylinder is incorrectly identified, or some other diver error.
Severe hypercapnia is more likely to be a problem in rebreather diving. Scrubber failure is the most common cause at moderate to shallow depths. Excessive work of breathing (WoB), when extreme, can exceed the capacity of the diver to eliminate carbon dioxide and eventually cause a hypocapnic blackout, which is likely to be followed by asphyxia or drowning. Several mechanisms may cause high work of breathing WoB,such as high gas density, regulator malfunction, loop flood in a rebreather, or excessive exertion with hypercapnia and the cause must be identified before effective action can be taken, but bailout to open circuit and an immediate termination of the dive is generally an appropriate response where possible. A buddy or standby diver with lower work of breathing may be able to carry out a rescue, depending on the cause of the high WoB.
Buoyancy emergencies can be too much buoyancy, causing an uncontrolled ascent, or too little bouyancy, preventing the diver from ascending, or sinking them to excessive depths.
Entrapment by entanglement, structural collapse, pressure differential, or water flow can prevent the diver from surfacing, and for a scuba diver, may lead to an out-of-gas emergency, or decompression obligation beyond the capacity of the available gas supply. In surface-supplied diving the gas supply is usually secure, the diver is usually in voice contact with the surface, and there is a standby diver available who can follow the diver's umbilical and provide assistance.
A diver may be exposed to high risk environmental contaminants, (chemical, biological, radiation etc) for various reasons. The main ones being that the contaminant was not known or suspected to be present, so precautions were not taken, and failure of protective encapsulation by the diving suit and helmet. In this case the diver is likely to be aware of the problem, and the dive team is likely to be prepared for emergency decontamination procedures.
In oilfield work, crude oil leakage may get into the bell and contaminate the bell atmosphere with volatile hydrocarbons or hydrogen sulfide. These are known hazards of the specific environment, and there should be equipment and procedures in place to detect and manage the problem.
In the event of a suit heating water supply failure that cannot be resolved promptly, the diver will abort the dive. This is a serious problem for divers using helium based breathing gas as heat loss is rapid and the risk of hypothermia is high.
The diver can adjust the flow rate which can help with small deficiencies in the temperature, but if the flow is shut off or the temperature deviates too much the dive must be aborted before the diver is chilled too much.
The bell will be equipped to deal with a bell umbilical failure by switching to onboard emergency gas supply, and the bell will be raised as soon as reasonably possible thereafter. There would be a through-water emergency communications system on a closed bell.
In the event of a dynamic positioning runout, the divers would be recalled to the bell and it would be prepared fo lifting on immediate notice, as a severe runout could snag the bell on an obstacle and it could be lost or stuck.
If the bell lifting winch or cable fails and cannot be restored to function, the bell may be recovered using the clump weight winch (guide wire winch). If this also fails, a wet transfer abandonment may be possible, in which the divers from the damaged bell are transferred to another closed bell through the water.
The bellman would recover an incapacitated diver to the bell. It may be possible to pull the diver back using the umbilical, but it may be necessary for the bellman to lock out to retrieve the diver.
If the bell will not seal at depth, the divers may need to replace the door seal, and check all valves on through-hull penetrations If may be necessary to return the bell to working depth to assess and work on the problem. If a seal cannot be re-established at depth another bell must be sent down to rescue the divers. If the leak starts at the surface, the supervisor would attempt to maintain internal pressure while the bell would be reconnected to the trunking.
A trapped bell may have to be abandoned. In saturation diving the divers would have to be transferred to another bell.
See main article: Panic.
Underwater diving is a activity with a high exposure to inherent hazards, which can be conducted at acceptably safe levels when divers participate within the scope of their technical competence, range of experience, physical, and psychological limits.
Raised levels of physical and psychological stress can develop rapidly due to unexpected events and situations. This may lead to panic in a susceptible diver. Diver safety can depend on the diver recognising the onset of stress and panic and making an effective effort to minimise their impact on the emergent situation.
Many divers have reported panic during a dive, and have survived the experience, but panic is associated strongly with a significant proportion of diving fatalities, though it is not always known if the panic was causative to the outcome.
See also: Dive planning, Diving safety and Diver training. The primary goal of dive planning, diver training and diving skills and procedures is to prevent and avoid diving emergencies. A significant part of diving equipment is also used for this purpose, and designed to further this goal. In general diving emergencies are prevented by:
See also: emergency management. The diver or diving team should be able to manage a reasonably foreseeable diving emergency with significant risk. This is done by using suitable equipment, and by following procedures developed, tested and known to be as effective in those circumstances. When an unforeseen emergency occurs, the diver, and where relevant, the diving team, must make the best of the situation using the skills, knowledge, intelligence and facilities they have available. Many types of emergency are best avoided simply by not diving in circumstances beyond those in which the diver is known to be competent.
Emergency manageent can be describes as comprising a cycle of four phases: Preparation, response, recovery and mitigation.
Preparation includes drawing up standard operating procedures, ensuring that personnel are appropriately trained and competent, identifying the specific hazards, assessing the risk, planning the specific diving project or dive, drawing up an emergency plan, having appropriate checklists, and a dive briefing. Some of these steps may be iterative where the results of one step are input for another.
See also: Hyperbaric evacuation and rescue. Where a hazard cannot be avoided, and the risk is significant, procedures and the relevant skills are developed to manage the problems as they occur, usually at the earliest practicable stage. Where necessary or desirable, equipment which may help manage the foreseen problems may be used, which may require additional skills to operate effectively.
Three levels of skills and procedures are in common use.
See also: Diving team, Buddy diving and Solo diving. In most cases the diver has some level of support.
In occupational diving, the diving supervisor is responsible for management of the diving operation, including emergencies. The diver's attendant assists the working diver and supervisor, and the standby diver is specifically employed to be deployed to assist the working diver in an emergency. There may be other team members with specific responsibilities. The dive team is legally required to be competent. The employer or diving contractor is responsible for ensuring competence of all team members, that the equipment is fit for use and the dive plan and emergency plan are appropriate. Dive team members are required to be trained in first aid.
Recreational divers generally only have a dive buddy who may or may not be competent or may even be a further hazard. buddies are either self-selected, or imposed by a service provider who generally requires the divers to sign a waiver releasing the provider from almost all responsibility. However the service provider is usually required to have some level of emergency plan in place for events which are outside the scope of a buddy diver. An alternative to buddy diving is solo diving, where the diver relies on their own resources and skills in any underwater emergency, and equips themself accordingly.
Technical divers tend to be more extensively trained, more aware of hazards and risk, and make their own arrangements accordingly. They are generally not constrained by legislation, but tend to plan by consensus and are more likely to understand the hazards, risks and consequences of a dive plan. Where appropriate they may organise with voluntary support personnel appropriate to the situation.
In general, there should be plans to deal with reasonably foreseeable emergencies that pose a risk to health and safety wherever there is a duty of care, these may include where relevant:
Some of the action generally taken to prepare for possible medical emergencies will include:
Where a duty of care exists between an employer and employees or a service provider and clients this may include an obligation to plan to deal with reasonably foreseeable emergencies.
The emergency plan, (or emergency action plan), should be specific to the dive plan where applicable, as specific actions should be detailed where possible and depend on the circumstances of the dive plan. As much detail as reasonably practicable can save time during an emergency, when it avoids the need to make detailed plans at the time. The plan should include backup faciities and support for divers remaining in the water.
An underwater emergency can have physical and psychological consequences.
A significant proportion of divers experience relatively long term psychological consequences, such as post traumatic stress disorder after a diving accident.