Diver rescue

Before any attempt to perform a rescue can be made, a person or group of people who are in a position to initiate appropriate procedures must be aware of the need. This may seem an obvious requirement, but many diving fatalities occur without anyone knowing that there is a problem, and in many others the problem is initially the loss of information regarding the current status of the diver. This is common in scuba accidents, where separation of the diving team members is often the first indication of a potential problem, and many emergencies are first recognised when a diver fails to surface at the expected time.

Scuba divers generally have no voice communication and are generally restricted to visual signalling. this is limited by line of sight and visibility, which may be poor. In some cases scuba divers may be connected by a tether, or buddy line, which allows communication by line signals, and professional scuba divers often tow a surface marker buoy, which may be used to transmit a very limited range of signals to surface personnel, mainly location of the diver, and if the diver needs help.

Surface supplied divers are less likely to get lost, as they are initially connected to the surface team by at least an airline, and usually also a lifeline which may be used by the line-attendant to communicate with the diver using line signals. Most 21st century surface supplied divers also have voice communication with the surface team, and this allows constant monitoring of the diver's condition by listening to the breathing sounds. Surface supplied divers are therefore able to indicate distress and need for assistance promptly and effectively in almost all cases, and the simple failure to respond appropriately to communications from the surface is also an effective indication of a problem.

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. Even when open circuit equipment is used it may be difficult to see the bubbles due to surface conditions of wind, waves and spray, fog, or darkness.

Surface supplied divers are usually easy to find, as they are at the far end of the umbilical, and it is extremely rare for the umbilical to be completely severed. The standard procedure for rescue of a surface supplied diver is for the standby diver to follow the umbilical to the diver, reporting back frequently to the supervisor on progress.

Divers often use guidelines, surface marker buoys, diving shots, lightsticks and strobe lights to indicate their position to their surface support team.[3][4] A standard precaution when entering enclosed spaces is to use a guideline; this marks the exit route, which may be needed after the diver's fins, wash, and bubbles dislodge silt and loose overhead materials such as rust which can reduce visibility to near zero.

Common search techniques such as the circular search or jackstay search, need preparation and practice if they are to be used effectively and safely. The spiral box search and compass grid search require less preparation, but probably greater skill, and may be rendered ineffective by currents.

Searches of enclosed spaces expose the rescuer to danger. The rescuers may need training and experience in cave diving, ice diving or wreck diving to minimise the risks of that type of rescue.

Providing emergency gas to a diver who has run out is the highest priority after finding the diver. Without breathing gas the diver will die in minutes. Running out of gas is a major contributor to diving accidents. Many scuba accidents start in some other way and culminate in running out of gas.

The main reasons for running out of scuba gas are:

• failing to monitor consumption of the gas - not watching the contents pressure gauge
• underestimating the amount of gas needed for the return and ascent and decompression stops
• consuming gas faster than estimated by going too deep, over-exercising or psychological stress
• delayed exit or ascent due to other problems, such as getting lost or entrapped
• equipment failure, such as a regulator freeze 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 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 exertion, stress or panic.

Common configurations of diving cylinders and diving regulators used as a backup or reserve for emergencies include:

• An independent set carried by the diver;
  • a complete, backup scuba set such as a "pony" (or bailout cylinder), or
  • the cylinder not currently in use of an independent twin set, or
  • a cylinder not currently in use of a group of side-mounted cylinders, or
  • a separate rescue set brought down by the rescuer, or
  • a "spare air" - a small independent set with integrated regulator and mouthpiece
• A potentially independent pair of twins connected by an isolation manifold and carried by the diver. If the diver can isolate them in time, the remaining gas in the uncompromised side is available.
• Sharing gas with another diver via an "octopus regulator" - a second, backup regulator or second stage on a scuba set that is in use by the buddy or rescue diver

There are two main ways of delivering breathing gas to the out-of-air scuba diver;

• provide the casualty with a separate demand valve, preferably on a long hose or hand-off cylinder, so that rescuer and casualty can breathe simultaneously, and concentrate their efforts on getting to a safer place, or
• share a single demand valve with the casualty by "buddy breathing", which is a more risky procedure, and requires constant attention to breathing and management of the demand valve by both divers. The additional task loading of buddy breathing may reduce the capacity of the divers for other activities required for safe resolution of the emergency.

The gas capacity of the cylinder is important. Divers breathing at depth consume more gas because the gas must be delivered to them at ambient pressure, and volumetric breathing gas consumption is driven by partial pressure of CO₂. At the end of a deep dive they will need more gas to breathe during the longer ascent to the surface and during any 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.

A surface supplied diver can provide breathing gas from their pneumofathometer hose, which can be inserted under the neck seal of the helmet and turned on at the gas panel to provide an adequate but noisy free-flow supply. This is normally sufficient to ventilate the casualty for the return to the surface or bell. In some cases it may be necessary to disconnect the casualty from their umbilical, if it is irretrievably trapped. This requires a few minutes work with spanners, and will lose any voice communications that may have remained. It is possible to connect a replacement umbilical if one is available. This is not usually the case from a bell, as the umbilicals occupy too much space to carry a spare.

Divers may become trapped in fishing nets; monofilament is almost invisible underwater. Loose ropes and lines are also an entanglement hazard; normal diving equipment has many inaccessible snag points that can trap the diver, particularly when components are left to dangle, and when clips are used which can hook onto line without active intervention by the diver (known to technical divers as suicide clips).

Another entrapment risk occurs when divers try to squeeze through small gaps where they or their equipment can become wedged or caught.

Old ferrous shipwrecks can be structurally unstable; they may retain their shape but have lost their strength through corrosion and therefore have components or cargos that have high potential energy due to gravity, and may collapse without warning.

Divers routinely carry a knife, line cutter, scissors or shears to free themselves from ropes, lines and nets. Lifting bags can be used to help move heavy objects underwater, but are not carried as standard equipment by most divers.

The safest place may be the surface, where the supply of breathing gas is unlimited, or if the diver was diving from a bell, the diving bell. where the gas supply is relatively secure, and some first aid is possible. The procedure for retrieving the casualty to the bell is relatively straightforward. The casualty is simply carried there by the rescuer. A rescue tether may be used to aid this process as it allows the rescuer the use of both hands. Once at the bell the casualty will generally be suspended by the harness using a lifting tackle provided tor this purpose.

If a diver is out of gas and is breathing gas supplied by the rescuer, the rescuer and casualty must remain close to one another and ascend together. Starting the ascent may be complicated by the casualty's lack of gas to inflate the buoyancy compensator to become buoyant at the start of the ascent and later, at the surface. At the start of the ascent the casualty may need to fin upwards and keep pace with the rescuer until, with the drop in ambient pressure, the gas already inside buoyancy devices such as the buoyancy compensator or diving suit, expands and provides sufficient 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. This may be done by 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, and more difficult to inflate if the connected hose has no pressure on it.
• drop the weights from the casualty's diving weighting system. This may result in a dangerous and rapid ascent.
• lift, by finning, the casualty into shallower water where gas in the casualty's buoyancy devices will expand, then vent it to make a controlled ascent.
• It is possible to use the rescuer's buoyancy compensator to lift both divers. A technique for this is taught by some agencies, in which the rescuer holds the casualty with his/her legs wrapped round the torso, freeing the hands for buoyancy control. This technique does not allow the rescuer to provide upward thrust by finning, and all lift must be from buoyancy. A further problem is that if the divers are separated, the rescuer will be considerably positively buoyant, and the victim may well be negative, and sink away before the situation can be corrected.

If there is a surface marker buoy available with sufficient buoyancy, the rescuer can clip the casualty to the reel and use the reel to hoist the casualty to the surface.in this case the casualty will not sink back down if released for any reason. Not all diving reels are suitable for this application. The reel needs a ratchet and a winding knob with a good grip. Some reels seize up when wound in under too much tension.

If the casualty is not breathing, an urgent ascent directly to the surface is needed so that resuscitation can take place there.[2] 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 decompression sickness, including irreversible injuries or death, or do the stops and risk leaving the casualty to die by asphyxiation or drowning. In these circumstances the value of a surface backup team becomes obvious, as a message or pre-arranged signal to the surface can bring a standby diver down to take over the recovery of the casualty while the initial rescuer attends to his own safety, or the rescuer can send the casualty to the surface by buoyancy, while remaining at the required depth for decompression. If the rescuer chooses to stop for required decompression, the non-breathing casualty may be made positively buoyant and allowed to surface, where there is at least a possibility of assistance from bystanders or surface team members.[2] This strategy has been successfully used in at least one incident.[2]

Active management of the casualty's airway during the ascent is necessary only as far as avoiding or correcting any position that tends to close the airway, such as extreme flexion of the neck.[2] Expanding gases will generally pass passively out of the airway during rescue from depth, and pulmonary barotrauma is rare. A gradual and natural outflow of expanding air during the ascent may help prevent aspiration of water into the lungs. There is no evidence that compressing the chest to promote exhalation is more effective than simply maintaining an open airway.[2]

Convulsions due to acute oxygen toxicity may render a diver unconscious. A common symptom is convulsions similar in appearance to epileptic seizure.[5]

The US Navy Diving Manual Revision 6 Volume 4 section 17.11.1.4 recommends the following procedure for managing a convulsing casualty at depth. This differs significantly in some details from the procedure recommended by Dr E.D. Thalmann on the DAN website.[5]

• Assume a position behind the convulsing diver.
• Only release the casualty's weights if progress to the surface is significantly impeded. (Thalmann recommends releasing the weights unless the diver is wearing a dry suit,[5] as the dry suit without weights may cause the surfaced diver to take a face down position on the surface.)
• Do not ascend in the water until the convulsion subsides (Thalmann makes no recommendation to delay the ascent.[5])
• Open the victim's airway and leave the mouthpiece in his mouth. If it is not in his mouth, do not attempt to replace it. However ensure that it is switched to "Surface" position in the case of a rebreather, so that the loop does not flood. (Thalman makes no mention of opening the airway, possibly on the assumption that air will escape without this manoeuvre.[5])
• Grasp the victim round the chest above the UBA or between the UBA and his body. If this is difficult, use the best method possible to obtain control.
• Ventilate the UBA with diluent to lower ppO₂ and maintain depth until the convulsion subsides. (This step is significantly omitted by Thalmann.)
• Make a controlled ascent to the first decompression stop, maintaining a slight pressure on the diver's chest to assist exhalation.
  • If the diver regains control, continue with appropriate decompression. (omitted by Thalmann)
  • If the diver remains incapacitated, surface at a moderate rate, establish an airway and treat for symptomatic decompression. (omitted by Thalmann)
• If additional buoyancy is required, activate the victim's life jacket (inflate BC). The rescuer should not release his own weight belt or inflate his life jacket.
• On reaching the surface, inflate the victim's life jacket if not already done.
• Remove the victim's mouthpiece and (in the case of a rebreather) close the switch the valve to "surface" to prevent the rig from flooding and weighing down the victim.
• Signal for emergency pickup. (Recreational divers may not have this option.)
• Ensure the victim is breathing. Initiate rescue ventilation if necessary.
• If an upward excursion occurred during the actual convulsion, transport to the nearest chamber and have the victim evaluated by an individual trained to recognize and treat diving-related illness.

Thalmann further comments that the decision whether to ascend with a diver who is convulsing is tricky,[5] and cites the US Navy Diving Manual again, specifically:

• If a diver convulses, the UBA should be vented immediately with a gas of lower oxygen content, if possible. (This is only appropriate with rebreathers, full-face masks with more than one gas supply connected, or with surface supply.)
• If depth control is possible and gas supply is secure (helmet or full face mask), the diver's depth should be kept constant until the convulsion subsides.
• If an ascent takes place it should be done as slowly as possible. (To some extent this is incompatible with the need to get the victim to a place where treatment is possible.)
• If a diver surfaces unconscious because of an oxygen convulsion or to avoid drowning, the diver must be treated as if suffering from arterial gas embolism.

Thalmann further comments[5] that a full face mask is desirable for use with high oxygen mixes, as it allows the diver to be kept at depth until the convulsion subsides, and that a diver who loses the mouthpiece must be surfaced as he will try to take a breath when the convulsion stops, and on open circuit, that as long as the diver has the mouthpiece in place and is breathing, it should be left until you can get him out of the water, but should be removed on the surface if rescue breathing is necessary and possible. Furthermore, the main goal while the diver is in the water is to prevent drowning and secondarily ensure that the airway is open after the convulsion stops by keeping the neck extended.

Once the casualty has been brought to the relative safety of the surface, it is important that the casualty does not accidentally sink again. 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, and this is almost always the case, they may be able to inflate these devices orally or use an integrated gas cylinder (if fitted).

At this stage in the rescue immediate help is desirable. An immediate call or signal for help may take very little time to get the attention of potential assistance. However, if this fails, the survival of the casualty should be attended to, by artificial ventilation if necessary.

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.[3] Cylinder powered, high-pressure gas whistles may be effective even over the sound of engines.[3]

If the casualty is not breathing, it is possible to sustain respiration or even restart it by artificial ventilation (AV) at the surface of the water.[2]

It may be difficult for the rescuer to assess breathing, but it is more likely that this would fail to indicate shallow breathing than a false positive, and as there is little risk of harm from an attempt to administer rescue breathing when it is not needed, there is no reason to not administer AV if there is any suspicion that the casualty in not breathing.[2]

Methods of in-water 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 to 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

It is not possible to provide effective cardiac compression in the water, and it is also unlikely to reliably identify cardiac arrest in the water.

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.

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

Ropes and webbing 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 propellers
• 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" (or parbuckling) can be used to lift a casualty from the water up a 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 at the top of the vertical face. 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 thighs. A rescuer should take care that the casualty's head and neck are not injured 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.

Commercial divers generally wear a safety harness with lifting points, which simplifies the attachment of equipment for lifting the casualty, and if they are using a lifeline or umbilical, it would be strong enough to lift the diver out of the water.

Recreational and technical diver harnesses are generally unsuited and unsafe for lifting a casualty.

A proper spine board or rescue stretcher is far more suitable, but not often available.

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 is 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. If a diving injury such as decompression sickness is suspected, the success of recompression therapy as well as a decrease in the number of recompression treatments required has been shown if first aid oxygen is given within four hours after surfacing.[6] In other parts of the world and particularly in remote locations, it may be difficult to quickly arrange reliable emergency medical transport and treatment; good insurance and self-reliance are needed.[7] 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.[8][9]