Study On Novel Diving Decompression Algorithm

Decompression sickness is a core issue in diving and hyperbaric medicine.Certain decompression rules should be followed to prevent decompression sickness before astronaut spacewalk,ascent during diving and decompression in cabin.The decompression algorithm is a mathematical model constructed using the principles of physiology and physics.This type of model can simulate the movement of biological inert gas in human body,and calculate corresponding decompression plan through certain rules set by the human to guide safe decompression.The first decompression algorithm was created by Haldane in the year of 1908,with5 kind of theoretical compartments.Since the creation of decompression algorithm,the decompression theories has been continuously innovated as well as decompression methods,resulting in new scientific and more efficient decompression algorithms.At present,the theoretical basis of the decompression table used in our country still stays in Haldane’s algorithm.Studying to absorbing the advantages of the new decompression theory and decompression algorithm would help to improve the safety and efficiency of decompression.This requires starting from the source algorithm,analyzing the current mainstream decompression algorithm.And then optimize the algorithm on this basis,so as to calculate the new decompression schedules to meet the needs of diving practice.In this study,the calculation steps of decompression algorithm were used as clues.The ZH-L₁₆,the Varying Permeability Model and the Thalmann algorithm in the current mainstream decompression algorithms were deeply analyzed,and absorption fusion was performed according to their characteristics.First of all,the process of the simulation of the inert gas motion process were analyzed,and the calculation process and characteristics of the physiological inert gas kinetic exponential equation and the linear-exponential equation were studied.Combined with the characteristic that the desaturation rate of physiological inert gas is slower than the saturation rate,the simplification and optimization of the formula were performed.By introducing the asymmetrical half-saturation ratio,the asymmetry of physiological inert gas movement was simulated.At the same time,taking into account the influence of the respiratory quotient on the partial pressure of the physiologically inert gas in the inhalation gas made the simulation more accurate.Secondly,this study demonstrates the rationality of the basic framework of the parallel theoretical tissues and the physiological principles behind it,and determined the applicability of the parallel theoretical tissues to the new algorithm.At the same time,by analyzing and comparing the characteristics of parallel theoretical distribution in several different decompression algorithms,several rules of the half-time setting and distribution of parallel theoretical tissues were summarized.Theses rules were used to determine 11types of theoretical tissues and their half-time.Thirdly,on the basis of the analysis of the decompression ceiling calculation process of ZH-L₁₆,the Varying Permeability Model and the Thalmann algorithm,this study summarized the methods of calculating the decompression ceiling as a ratio method,a linear method and a difference method.After absorbing the characteristics of the linear method and the difference method,they were merged to form the nonlinear decompression upper limit calculation process.The combination of the reduced bubble generation by the difference method and long time on the shallow stop of the proportional method were combined to produce a new decompression algorithm ANL.The ANL algorithm used some of the basic parameters of ZH-L₁₆A.The number of parallel theoretical tissues sets were set to 11.The simulation of the tension of physiological inert gas was performed by using an asymmetric saturation-desaturation process.The nonlinear method was used to optimize the calculation of the decompression ceiling.In order to evaluate the ANL,an algorithm test platform software were developed independently,and it was used in the subsequent algorithm operation and optimization.In this study,the real-time decompression algorithms that can be used on dive computers were also studyed.By using the real-time calculation of physiological inert gas motion as a clue,it has been initially analyzed and designed,so as to build a basis for the development of future dive computers.Finally,by analyzing and comparing the decompression rules of several existing decompression tables,the rules of ANL algorithm in several aspects such as distance between stops,ascent or descent rate,gas switching and stop time were defined.Using the decompression algorithm test platform software,a decompression schedule for conventional air and helium-oxygen diving based on the ANL algorithm was generated,and some of the decompression schemes were compared with the existing air and helium oxygen conventional diving decompression tables.The results showed that for different types of dive,ANL algorithm can calculate the decompression plan similar to the current decompression table by correcting the half-saturation time ratio according to certain rules.The preliminary demonstration of its theoretical level of security and feasibility,the new algorithm has potential practical value.