Emergency ascent (diving)
The emergency ascent is a quick and direct ascent to the water surface resulting from an emergency situation. The recommended ascent speeds and decompression stops may be disregarded. An emergency ascent from a great depth is always the last option to save your own life and / or that of your buddy . There are emergency ascent procedures for professional divers , research divers , recreational divers or entire submarines and their crew. A distinction can be made between five different methods, which are considered in the following subsections.
Floating emergency ascent
From a water depth of less than about 10 meters, a diver can reach the surface of the water relatively safely by swimming straight up, without dropping lead and without inflating the buoyancy compensator . During this ascent, the (device) diver has to exhale continuously over the entire ascent to the surface of the water. According to Boyle-Mariotte's law , the air in the diver's lungs expands by a factor of 2.2 when climbing from 12 meters . Even after exhaling completely before starting the emergency ascent, the remaining air in the lungs can expand due to the decrease in ambient pressure to such an extent that the lungs can tear during the last few meters before the surface of the water. This type of Notaufstiegs is often (CESA English Controlled Emergency Swimming Ascent ; German: "controlled, emergency swimming ascent") called. In the Open Water Diver course of the diving organization PADI , the CESA is practiced and tested from a depth of 6 to 9 meters.
Controlled emergency ascent
By carefully inflating the buoyancy compensator, an experienced diver can maintain an ascent speed of less than 10 m / min. The ascent is done without hitting the fins and to keep the ascent speed constant, air must be deflated from the buoyancy compensator every 2 to 3 meters. As the ambient pressure drops, the air expands and creates more buoyancy. Even with this type of emergency ascent, it is important that the diver can exhale constantly during the entire ascent or at least inhale and exhale strongly. Due to the decreasing ambient pressure, an ascent of 60 centimeters is sufficient to cause a ruptured lung. You must stop at a depth of 3 meters and, if the emergency permits, a safety or decompression stop of 3 minutes must be carried out. Afterwards a slow and safe ascent is possible. For deep dives , it is recommended to ascend to 10 to 15 meters as quickly as possible, stop there and tare properly. The ascent can then be done with max. 10 m / min up to 3 meters. The further ascent after a decompression stop of 3 minutes and a slow ascent is usually considered safe. However, this procedure can lead to decompression sickness of varying degrees of severity . This can make it necessary to stay in a decompression chamber . In contrast to an uncontrolled ascent , however, a controlled emergency ascent can often prevent permanent damage. Nevertheless, a medical check-up is urgently recommended after every controlled emergency ascent, as symptoms can only appear up to 48 hours later.
A diver whose buddy panics , injures himself or if the equipment fails can save him with a controlled emergency ascent. To do this, he grips the carrier of the buoyancy compensator of the buddy with his right hand and operates both his own equipment and that of the buddy with his left hand. The unimpaired diver leads the emergency ascent. If the compressed air diving devices of both buddies are working normally, the emergency ascent is relatively easy. However, if one of the devices is defective, the affected diver can get air from his buddy from the second regulator , the so-called octopus . Alternatively, the two divers can switch to alternating breathing .
In advanced recreational diving training (PADI Rescue Diver or CMAS **), controlled emergency ascent is practiced. To do this, you descend to 20 to 30 meters and immediately begin a controlled emergency ascent. Due to the almost non-existent bottom time , the risk of a decompression sickness is relatively low. In diving circles, this exercise is often also called a retirement lift , because the diver should get to the surface of the water safely without physical exertion.
Solo divers usually try to avoid an emergency ascent. They therefore usually have a redundant breathing gas supply . This also applies to divers who are in an environment from which emergency ascent is not possible, e.g. B. cave divers or wreck divers.
Uncontrolled emergency ascent
An uncontrolled (emergency) ascent , i.e. surfacing without control or the required reduction in ascent speed, must be avoided at all costs. An uncontrolled emergency ascent usually results from a panic or panic inflation of the buoyancy compensator , often as a result of a middle ear barotrauma with perforation or rupture of the eardrum or due to obstruction (so-called diver shortness of breath). Likewise, the loss or, for example, in no-air situations (empty compressed air cylinder), the dropping of the lead can lead to an uncontrolled emergency ascent.
A diver ascending in an uncontrolled manner, who has fully inflated his buoyancy compensator at a depth of 30 meters and has not reduced the buoyancy during the ascent, breaks through the surface of the water within about 15 seconds. This corresponds to roughly 12 times the recommended ascent speed of less than 10 m / min and more than 6 times the maximum ascent speed of 18 m / min.
The risk of a ruptured lung and severe decompression sickness is very high on uncontrolled ascent. These risks already exist in the event of an uncontrolled emergency ascent from shallow depths. Depending on the diving depth and previous bottom time, there is an acute danger to life due to the formation of nitrogen bubbles in organs or the circulation . From a diving medical point of view, first aid must be provided immediately after every uncontrolled emergency ascent and an emergency medical examination or treatment initiated (see decompression sickness # life-saving immediate measures and first aid ). Even if an affected diver initially seems to be in good shape after an emergency ascent, this can change quickly and the accident victim may only show symptoms and die hours later.
Emergency ascent with a diving rescuer
If a submerged submarine is unable to maneuver or if a major water ingress has occurred, the crew can rescue themselves to the surface of the water with a diving rescuer if other life-saving appliances are not available or fail. The crew leaves the submarine through a lock or after the pressure has been equalized with the surrounding water and the pressure hull flooded. By inflating the diving rescuer, the wearer then drifts to the surface of the water. Usually the inflation is done by a small compressed air cartridge . The breathing air is chemically generated by a lime cartridge for a period of around 15 to 45 minutes. The emergency ascent with a diving reserve corresponds to an uncontrolled emergency ascent when scuba diving. Therefore, there are basically the same diving medical risks. Since a submarine crew - unlike divers - usually has not previously accumulated nitrogen in the body, the risk of decompression sickness is much lower.
Emergency ascent of an entire submarine
If a submarine can no longer be tared or if there is no more energy available to blow out the diving cells , an emergency ascent can be carried out on many submarines. The gas required for the emergency blowing out of the diving cells is generated by chemical gas generators .
Individual evidence
- ↑ Breaking down a CESA. during your PADI Instructor training. Oceans Unlimited Scuba Diving, accessed July 18, 2017 .
- ↑ Note does not apply or applies less strictly to apnea divers , snorkel divers , i.e. those who have not inhaled from a diving device underwater.
- ↑ a b c d emergency ascent , divezone.ch, accessed: 27 July 2010
- ↑ CESA (English), knows-dive.com, accessed: July 27, 2010
- ↑ a b c d e Jürgen Eichhorn: Diving - The emergency ascent . 1978, ever.ch, accessed on July 18, 2017.
- ^ Albert A. Bühlmann (founder), Ernst B. Völlm, Peter Nussberger: Tauchmedizin . 5th edition. Springer, Berlin / Heidelberg 2002/2012, ISBN 978-3-642-62753-8 , chap. 3: Incidents while diving , p. 29 ff.
- ↑ Cf. Peter König, Andreas Lipp: Textbook for research divers . 5th edition. Institute for Oceanography of the University of Hamburg, June 2007, chap. 4: The effects of pressure on diving ( PDF ).
- ^ The "Steel Coffins": Rescue from a Submerged Submarine , KBismarck.com, accessed: July 28, 2010