Suitability of the USN MK 15 (VVAL 18) Decompression Algorithm for Air Diving.

Abstract : A computer algorithm was developed and approved for use breathing a fixed 0.7 ata partial pressure of oxygen in nitrogen gas in 1980 (The MK15 (VVAL18) RTA). The intent was to incorporate this algorithm into a diver carried underwater decompression computer (UDO). This same algorithm was also tested breathing air but approval for Fleet us on air was never sought because at the time b there was no decompression computer suitable for its incorporation. The Navy has recently contracted to have a UDO built raising again the need to have the MK15 (VVALl8) RTA approved for use on air. This report provides an in depth analysis of the risk of decompression sickness (DOS) using the XKl5 (VVALl8) RTA on air and compares that to the risk using the standard air tables. The DOS risk was computed from various dive profiles using a probabilistic decompression algorithm developed at the Naval Medical Research Institute (the NMRI Lal PDA). The NMRI LEl PDA had been calibrated on several thousand air and 0.7 ata constant P02 in N2 dive profiles where the actual outcome (DOS or no DOS) was known and has been shown to give reasonable risk predictions and dives switching between air and constant 0.7 ata Po2 breathing gases were analyzed. Analysis showed that the MK15 (WUALlS) ETA) produced risks not significantly higher and in most cases lower than current USN air procedures. It was recommended that the algorithm be submitted for approval for diving breathing air, constant 0.7 ata PO2 in N2 or switching between the two gases.