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. Providing first aid 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. 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. 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. Rescue involving a decompression obligation The rescuer is primarily responsible for their own safety, and is expected to complete all personal decompression obligations. This may in some cases involve sending an unresponsive victim to the surface by making them positively buoyant while the rescuer completes their decompression. Where a decompression chamber is available on site, it may be deemed appropriate to surface the divers and recompress following surface decompression schedules, which can be extended to a treatment schedule if symptoms of decompression sickness manifest. This decision should be made by a diving medical practitioner qualified to advise on hyperbaric treatment. Sometimes this is not practicable and the diving supervisor will make the call guided by the operations manual and relevant code of practice. Saturation divers cannot be decompressed to surface at acceptable risk, and must remain under pressure during first aid and further medical treatment. Rescue of divers from a disabled bell If a closed bell cannot be