Accession Number : ADA308010

Title :   Statistically Based Decompression Tables X: Real-Time Decompression Algorithm Using a Probabilistic Model.

Descriptive Note : Technical rept. Jan 91-Dec 93,

Corporate Author : NAVAL MEDICAL RESEARCH INST BETHESDA MD

Personal Author(s) : Survanshi, S. S. ; Weathersby, P. K. ; Thalmann, E. D.

PDF Url : ADA308010

Report Date : MAR 1996

Pagination or Media Count : 44

Abstract : Underwater decompression meters or computers sense a diver's changes of depth in real-time and calculate a decompression schedule for the individual diver's exposure. Currently available devices compare calculated nitrogen tissue tensions to a set of stored 'safe' constants. No explicit quantitative connection between these rules and the risk of decompression sickness has been established. Well calibrated probabilistic models, even though computationally more intense, can be used to specify decompression procedures tailored to control the risk of decompression sickness. Probabilistic models allow conscious choice of the degree of 'safety' or acceptable risk. Previously, the choice required searching up to tens of thousands of possibilities for any given dive. That method cannot be employed in real time without a very fast computer. We describe a quicker search method that depends upon a 'recent optimal' solution so that it can be implemented in real time. The real time algorithm compared favorably with decompression schedules obtained by extensive searches. Timing requirements for updating calculations (important for hardware specification) depends on how fast the 'recent optimal' answer changes. Risk management for repetitive diving is described in terms of conditional probability. The algorithm can be used to permit the acceptable risk level to vary during real time as the dive severity increases, and to include multiple breathing gases.

Descriptors :   *ALGORITHMS, *PROBABILITY, *STATISTICAL DATA, *TABLES(DATA), *DIVERS, *DECOMPRESSION SICKNESS, MATHEMATICAL MODELS, REQUIREMENTS, OPTIMIZATION, RISK, MANAGEMENT, EXPOSURE(GENERAL), REAL TIME, SPECIFICATIONS, COMPUTERS, DEPTH, SOLUTIONS(GENERAL), SCHEDULING, CONSTANTS, MEASURING INSTRUMENTS, SEARCHING, SAFETY, CALIBRATION, DIVING, UNDERWATER, DECOMPRESSION, TIME STUDIES, BREATHING GASES.

Subject Categories : Stress Physiology
      Statistics and Probability

Distribution Statement : APPROVED FOR PUBLIC RELEASE