Diver rescue

Diver rescue, following an accident, is the process of avoiding or limiting further exposure to diving hazards and bringing a SCUBA diver to safety. A safe place is often a place where the diver cannot drown, such as a boat or the shore, from which professional medical treatment can be sought.

Reasons for needing rescue
There are many reasons that divers need rescue, including:
 * running out of breathing gas
 * unconsciousness
 * being unable to see the depth gauge or diving computer to make a safe ascent, generally because the diving mask is lost, keeps flooding or is damaged
 * panic
 * trauma, diving disorder, medical condition
 * becoming lost or trapped underwater
 * being unable to return to the shore or a boat after a dive

Rescuers and training
In recreational diving, the urgency of the rescue and the remoteness of dive sites mean that professional rescuers rarely take part in diver rescues. Other divers at the scene become rescuers.

As the immediate in-water rescuer is often the diver's own buddy, diver training agencies often teach rescue techniques in intermediate-level diver training courses; examples are the PADI Rescue Diver and the BSAC Sport Diver courses.

When the rescue involves a group of people, co-ordination is needed to make it quick and effective. This may be carried out by the skipper of the boat, if diving is taking place from a boat, or by a diver. Some training agencies offer courses to prepare divers for such as role, for example BSAC's Practical Rescue Management course.

Rescue activities
The effort and difficulty of a rescue varies widely and depends on many factors such as the nature of the problem, the underwater conditions and the type and depth of the dive site. A simple rescue could be to tow to safety a diver on the surface who is exhausted or suffering from leg cramps. A complex and high-risk rescue would be to locate, free and bring to the surface a lost diver who is trapped underwater in an enclosed space such as a shipwreck or cave with limited breathing gas supplies.

The sequence of potential activities needed in a generic rescue are:
 * if the casualty's position underwater in unknown, locate the casualty and, if possible, mark the position
 * if the casualty is trapped, free the casualty
 * if the casualty is low on breathing gas, provide more gas
 * if the casualty is submerged, bring the casualty to the surface
 * if the casualty is not buoyant at the surface, make the casualty buoyant
 * if the casualty is not breathing, carry out continuous artificial respiration on the surface
 * if help at the surface is available but not at hand, attract help
 * if the casualty is on the surface in the water and no help is available, tow the casualty to a boat or to land
 * if the casualty is beside a boat or the shore, remove the casualty from the water
 * if necessary, resuscitate, provide first aid and arrange transport to professional medical help

Locating the casualty underwater
It may be difficult to locate the diver underwater where dives take place in low visibility conditions, in currents or in enclosed spaces such as caves and shipwrecks or where the diver uses breathing equipment which releases few bubbles, such as a rebreather.

Diver often use distance lines, surface marker buoys, diving shots, lightsticks and strobe lights to indicate their position to their surface support team. A standard precaution when entering enclosed spaces is to use a distance line; this marks the exit route, which may be need after the diver's fins and bubbles dislodge silt and loose overhead materials such as rust and reduce visibility to zero.

Common search techniques such as the circular search or jackstay search, need preparation and practise if they are to be used effectively and safely.

Searches of enclosed spaces expose the rescuer to danger. The rescuers may need training and experience in Cave diving to minimise the risks of that type of rescuer.

Free the trapped casualty
Divers may become trapped in fishing nets; monofilament is almost invisible underwater. Ropes also are a threat to the diver's safety; normal diving equipment has many inaccessible snag points that can trap the diver. Another problem occurs when divers try to squeeze through small gaps where their bulky equipment become wedged or caught. Also, old ferrous shipwrecks can be structurally unstable; they often retain their shape and therefore have components or cargos that have high potential energy due to gravity, but which have lost their strength through corrosion.

Divers routinely carry a knife, line cutter or scissors or shears to free themselves from ropes, lines and nets. Lifting bags can be used to help move heavy objects underwater.

Provide emergency gas
Running out of gas is a major cause for diving accidents.

The main reasons for running out of gas are:
 * failing to monitor consumption of the gas - not watching the contents pressure gauge
 * under-estimating the amount of gas needed for the ascent and decompression stops
 * consuming gas faster than estimated by going too deep, over-exercising or psychological stress
 * equipment failure, such as a frozen first stage or blown o-ring, in the main breathing set leading to escape of gas

Even when the prime cause of an underwater emergency is not running out of gas, lack of gas can easily become another problem for the rescuers to overcome because more gas is consumed during the accident and its aftermath. This is could be due to the diver remaining at depth for longer than planned or due to increases in the diver's breathing rate, due to exercising or panic.

Common configurations of diving cylinders and diving regulators used for as a backup or reserve for emergencies include:
 * an independent set - a complete, backup set such as a "pony" or one half of a “twinset” worn by a diver or a separate set brought down by the rescuer
 * an "octopus" - a second, backup demand valve or mouthpiece on a scuba set that is already being used by the diver
 * a "spare air" - a small independent set with integrated regulator and mouthpiece

See the diving cylinder and diving regulator articles for more details of the configurations.

There are two main ways of delivering the gas to the out of air diver; provide the casualty with a normal demand valve, preferably on a long hose, or "buddy breathing", the more risky of the two, where the two divers share one mouthpiece.

Clearly the gas capacity the cylinder is important; divers breathing at depth consume more gas because of that gas must be delivered to them at ambient pressure and after a deep dive they will need to breath during the slow ascent to the surface and may need to do decompression stops.

The mixture of the breathing gas is important; hyperoxic gases cannot be breathed safely below their maximum operating depth because of the risk of oxygen toxicity and hypoxic gas cannot be breathed safely in shallow water because the partial pressure of oxygen falls below that needed to sustain consciousness.

Bring the casualty to the surface
If one of the divers is out of gas and is breathing gas from the rescuer, the rescuer and casualty must remain close to one another and ascend together. This ascent is complicated by the casualty's lack of gas to become buoyant at the start of the ascent and at the surface. At the start of the ascent the casualty needs to fin upwards and keep pace with the rescuer until, with the drop in ambient pressure, the gas inside buoyancy devices such as the buoyancy compensator or diving suit, expands and provides buoyancy.

If the casualty is not capable of making an ascent, due to injury or unconsciousness, or the casualty cannot make a safe and controlled ascent, perhaps due to the loss or damage of the diving mask, the rescuer must control the casualty's ascent using the Controlled buoyant lift. As the casualty is totally dependent on the rescuer, it is important if the two were to separate underwater the casualty should continue to ascend to the surface in a failsafe way.

The options, in order of desirability, for making the casualty buoyant include:
 * inflate the casualty's buoyancy compensator to lift off the seabed, then vent it to make a controlled ascent.
 * inflate the casualty's drysuit, if one is worn, to lift off the seabed, then vent it to make a controlled ascent. A drysuit is a less secure buoyancy device than a buoyancy compensator.
 * drop the weights casualty's diving weighting system. This may result is a dangerous and rapid ascent.
 * lift, by fining, the casualty into shallower water where gas in the casualty's buoyancy devices will expand, then vent it to make a controlled ascent.

If the casualty is not breathing, an urgent ascent directly to the surface is needed so that resuscitation can take place there. In this situation and if the rescuer needs to do decompression stops, the rescuer has a dilemma: take the casualty to the surface and increase the risk or severity of the bend, including irreversible injuries or death, or do the stops and kill the casualty.

Make the casualty buoyant on the surface
Having reached the relative safety of the surface, it is important that the casualty does not accidentally re-descend. The usual methods of making the diver positively buoyant are to:
 * inflate the buoyancy compensator. This is a routine surfacing drill in some training schemes.
 * inflate the drysuit, if one is being worn. The gas in a dry suit is not very secure; it can easily escape from seals and vents. Also, excess gas in the suit tends to make the legs buoyant causing the diver mobility problems.
 * drop weights.

Divers who are out of air will probably not be able to inflate their buoyancy compensator or drysuit using the normal and simple technique of pressing the direct feed injection valve. If their equipment allows it, they may be able to inflate these devices orally or use an integrated gas cylinder (if fitted).

Carrying out artificial ventilation in the water
If the casualty is not breathing, it possible to sustain respiration or even restart it by artificial ventilation (AV) at the surface of the water.

Methods of AV vary depending on diver training organization:

The BSAC technique works like this:
 * the casualty and rescuer are buoyant
 * the rescuer is positioned at the side of the casualty's head facing the ear
 * the rescuer extends the casualty's neck and closes the mouth by lifting the chin with one hand
 * the rescuer pushes the casualty's far shoulder upwards with the other hand causing the head the twist towards the rescuer
 * the rescuer makes a seal over the casualty's nose using the rescuer's mouth and exhales to fill the casualty's lungs
 * the rescuer aims to do 10 inflations per minute if stationary, 2 inflations every 15 seconds if towing

Attracting help
At this stage in the rescue immediate help is needed. Very often, the only people that can provide that help are nearby boat users and people on the shore. Unless the emergency services are very close by or the rescue is beyond the capability of the local rescuers, they will not be on the scene quick enough to be able to provide help. Often with a small group of rescuers the emergency services can only be contacted after the highest priority job of getting the casualty is out of the water has taken place.

Often the rescue can be quickened if a boat can come to the casualty rather than a rescuer having to tow the casualty to safety. Once at the surface, using many rescuers becomes feasible; they can communicate and co-operate to make the rescue more efficient.

Methods of attracting help include shouting, waving a straight arm, flag or surface marker buoy, blowing a whistle, flashing or swinging a torch/flashlight at night, or using a strobe at night. Cylinder powered, high-pressure gas whistles may be effective even over the sound of engines.

Towing the casualty
If the casualty is incapacitated or exhausted, help is needed to move the casualty to safety. Towing is time consuming and will exhaust the rescuer, especially in rough water, currents, or if the rescuer is wearing high-drag equipment such as a drysuit or carrying bulky equipment.

It may be possible to avoid a tow by using a boat to pick up the casualty and rescuer. Alternatively, ropes thrown to the rescuer can be used to pull the pair towards safety.

Removing the casualty from the water
Urgently lifting an injured or incapacitated casualty from the water is a significant problem especially where there are few rescuers, the sea is rough sea, the boat has high sides or the rescuers on the shore cannot get in or close to the water to help.

Ropes can be very useful, but some precautions are need:
 * avoid looping the rope so that it goes round the chest, preventing breathing, or the neck, causing asphyxia.
 * when near boats, keep the minimum rope in the water to prevent fouling propellors
 * the minimum safe diameter is 12 mm, 1/2 inch. The rope should be doubled to increase the area of contact and reduce the lifting pressure on the casualty.

"Purbuckling" can be used to lift a casualty from the water up a 1.5 metre / 5 foot vertical surface such as a high sided boat, pontoon or a jetty. For a 1.5 metre lift, a length of rope of at least 4 metres / 13 feet is needed. The casualty is brought horizontally alongside. A rescuer in the water with the casualty takes the loop of rope under the casualty and passes it back to two rescuers on "land". The loop of rope is positioned so that in passes outside the arms between the shoulder and elbow and around the outside of the legs between the knee and the hip. The two rescuers on land secure the end of the loop that they control by standing heavily on it with one foot. They both pull on the central part of the loop rolling the casualty up the surface taking care to co-ordinate the tension so that the casualty remains horizontal and that the rope remains in position on the casualty's arms and thightd. A rescuer should take care of that the casualty's head and neck is not damaged during the lift.

An alternative method of lifting the casualty using a rope is to pass the rope under an arm, around the back and under the other arm. The casualty is lifted vertically. There is a risk of spine damage by bending if the casualty is positioned with his or her back to the vertical surface and the rescuers pull the casualty's shoulders in board before lifting the lower end of the torso over top of the vertical surface.

Resuscitate, provide first aid and arrange transport to professional medical help
If the casualty is not breathing artificial respiration must be provided continuously. It is more likely to succeed if it is started promptly. If the casualty is showing no signs of circulation, chest compression are needed. See main article: cardiopulmonary resuscitation.

If the casualty has injuries the rescuers will need to provide first aid and prepare the casualty to be transported to professional medical help. See main article: first aid.

In the developed world, transporting a diving casualty to hospital or a recompression chamber may be as simple as contacting the marine emergency services, generally by using marine VHF radio, telephone or a distress signal, and arranging a lifeboat or helicopter. In other parts of the world and particularly in remote location, it may be difficult to quickly arrange reliable emergency medical transport and treatment; good insurance and self-reliance are needed. In-water recompression is a high-risk alternative that may be useful in locations where the casualty would not survive the journey to the nearest recompression chamber due to its distance.

Precautions during the rescue
Rescuers should not take unacceptable risks; any rescuers who become casualties themselves may jeopardise the rescue of the original casualty particularly as many of the emergency resources available at dive site, such as rescue manpower, first aid oxygen, underwater time and gas are generally in short supply.

Conscious casualties may panic and put the rescuer's safety at risk particularly when the rescuer approaches a casualty in or under the water. It may be possible to avoid contacting a panicked casualty by throwing a rope or buoyancy aid and encouraging the casualty to help him or herself. If contact must be made, the rescuer should try to approach the casualty from a direction that presents least risk to the rescuer, such as from behind. Alternatively, the rescuer may need to wait until the casualty is incapacitated before approaching.