Diving Decompression Model With A Conception On The Algorithm For Heliox Diving

After a decompression dive,decompression is compulsory a nd in accordance with the appropriate decompression profile with which a diver surfaces.The decompression profiles are usually presented as tables which are determined with decompression software based on a specific decompression algorithm.In 1908,Halda ne for the first time proposed a decompression model with which he determined the decompression algorithm and for the first time calculated different decompression profiles for air diving.However,the diving practice indicates that the incidence of DCS is at a high level if decompression profiles based on the Haldone model are used for diving.Thus,the safety of decompression tables is required to be improved.With the rapid development of marine resources,application of military diving in deep sea,increasingly popular recreational diving,increase in the depth of commercial diving and application of repetitive diving,reverse diving,multi-day diving and post-dive flying,the available decompression tables fail to meet above requirements.Thus,it is imperative to develop new decompression theory and algorithm.With the deepening of studies on decompression after a dive,some new decompression theories and decompression models have been proposed,and great advance has been achieved in the decompression model.Not only the available decompression tables are improved and enriched,but some software has been developed on the basis of different decompression models for the calculation of decompression profiles.First,we analyzed and summarized the progressio n of decompression models for diving and combed available theories related to decompression.The current decompression tables were determined according to the classic Haldone model in 1970 s.With the development of decompression theory,M value was proposed for the establishment of decompression model on the basis of prior supersaturation ratio.Generally,the M values vary between tissues and between different depths.C urrently,M values have been widely used in some decompression models.However,modern models are more accurate to mimic the gas dissolution and free gases and concern both the safe number of bubbles and the critical volume.Second,we briefly introduced the important decompression models in the prior century.The available models can be divided into traditional dissolved gas model and modern free gas model.The main difference between them lies on the method used for the calculation of decompression load.In the dissolution phase model,the decompression load was calculated based on the exte nt of inert gas supersaturation;in the free bubble model,the decompression load is calculated based on the number or volume of bubbles formed due to supersaturation.Thus,there is significant difference in the decompression profiles determined according to two decompression models.Generally,the first stop determined according to the dissolution phase model is shallower,but in free bubble model,the calculated first stop is deeper to restrict the growth and production of bubbles in the body.In recent years,probabilistic models and deterministic models have been proposed with the development of decompression theories and the establishment of diving related databases.Most of available models are deterministic models,but the US navy employs probabilist ic model for the calculation of decompression tables which have been present in the US navy diving manual(Revision 6).O f note,probabilistic models and deterministic models have their own advantages and disadvantages in the mimic of gas dissolution,formation,movement and washout.Finally,on the basis of analysis and summary of available decompression models and decompression theories,we proposed our considerations on the calculation of decompression tables: the %M values gradient are reduced to reduce the distance between bottom and first stop,which may prolong the time consuming in deep depth;the increased time will be added to the last two stops;the profiles will be tested by ultrasound detection of bubbles in divers.We expect that this algorithm will be more efficient and safe to calculate decompression profiles for deep diving with a long bottom time as compared to that based on traditional decompression models and is more convenient for the calculation of decompression profiles as compared to that based on modern decompression models.