Plongée à l'air avec la table de décompression MN 90. Bilan de 12 années d'utilisation par la Marine française : à propos de 61 accidents de désaturation de 1990 à 2002

Abstract

Objective. – Decompression MN 90 Table is used for air diving by military divers and both sports divers in France. In the aim to confirm MN 90 safety, we studied 61 decompression sicknesses observed in the French Navy for 1990–2002. Method. – Each year 1800 divers carry out 150 000 dives ± 10%. Divers are 1600 ship divers (dives less than 35 m-sub-water) and 200 mine clearance divers (dives up to 60 msw max). Each accident must be notified and data are recorded into a database. Results. – The total risk is estimated at 1 accident/30 000 dives. We observed no death and only 2 divers with persistent neurological deficits. We found spinal decompression sickness: 66%, cerebral 23%, inner ear 8% and joint bends 3%. Neurological accidents are purely sensitive for 65%. The evolution was favourable for 97% after early hyperbaric recompression at 400 kPa. One hundred percent respected the MN90 procedure. Water temperature, age, effort during diving, repetitive dive were not found as risk factors. A right-to-left shunt was present for only 30% of type II accident. The main result of the study is that 54% of accidents concerned only 200 mine clearance divers with a risk estimated at 1 accident/3000 dives for 45–60 msw depths. Conclusion. – MN90 decompression procedure is safe for a young population of trained military divers with a low risk of accident. The major risk factor seems to be the depth. Studies are necessary to optimize the decompression for deep air diving.