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Show The same logic applies to probing for an avalanche victim. If the initial use of the coarse probe gives the highest probability of finding the victim alive, then the coarse probe should be repeated over and over again until the victim is found. If repeated use of the coarse probe fails to locate the victim after a time interval which leaves him a very slight chance of survival, the situation is altered. The probability of live recovery has now been replaced by a very strong probability that the victim is dead. Fine probing is then in order as a measure to locate the victim. His survival chances are still not zero, of course- a few victims have lived for many hours under avalanche snow. The accident site commander has to make a decision at some point in the rescue to switch to fine probing if the coarse probing is repeatedly unsuccessful. Just when this should be done will be governed by many such factors as the size of the avalanche, time since the victim's burial, number and conditions of the rescuers and the prevailing weather and avalanche hazard. The man on the scene has to make the ultimate decision. Table I casts some light on the site commander's dilemma. It shows the increased probability of live rescue with repetition of the coarse probe. The increases are significant for smaller avalanches. They are less significant for larger avalanches and the site commander may then be justified in resorting early to the fine probe. ( Reference No. 8.) What is the optimum depth for probing? Should depth be decreased to increase speed? The answers are determined by three complex factors: 1. The probable burial depth of the victim as indicated by available clues. In Section 2.2 guidelines were given for establishing possible burial depth. Unfortunately, the overall accident picture is often unclear. The victim then is assigned equal chances of being buried at any depth up to the maximum thickness of deposited avalanche debris. 2. The probability at various burial depths of the victim being alive. This factor is dependent on the density of the snow. Under wet, dense spring snow, the victim suffocates quickly even at shallow depths. The less dense and colder the snow, the better will be his chances for survival at all depths. In general, for all types of snow, the dependence of survival time on burial depth is given in Figure 17. 3. The speed of probing to various possible depths. Steepness of the terrain and hardness of the snow both influence the rate of probing to a fixed depth. Obviously, the shallower the probing depth the more rapid the probing rate. 41 |