Bubble incidence after staged decompression from 50 or 60 msw: effect of adding deep stops.
OBJECTIVE
The French Navy uses the Marine Nationale 90 (MN90) decompression tables for air dives as deep as 60 msw. The resulting incidence of decompression sickness (DCS) for deep dives (45-60 msw) is one case per 3000 dives.


METHODS
Three protocols with experimental ascent profiles (EAPs) were tested in the wet compartment of a hyperbaric chamber. For each protocol, eight subjects dove to 50 or 60 msw and ascended according to the standard MN90 table or an EAP. Precordial bubbles were monitored with Doppler sensors at 30-min intervals after surfacing. Protocol I went to 60 msw and used deep stops beginning at 27 msw. Protocol II was a repetitive dive to 50 msw with a 3-h surface interval; the EAP made the first deep stop at 18 msw. Protocol III again went to 60 msw, but the EAP used a single, shorter deep stop at 25 msw.


RESULTS
For Protocol I, all divers developed bubbles at Spencer grade 2-3 and still had bubbles 120 min after surfacing; there was no statistical difference between bubbling for the MN90 and EAP, but one diver presented a case of DCS after the EAP. For Protocol II, the EAP produced severe bubbling for the eight divers. Those findings led to stopping the EAPs with the longer deep stops used in Protocols I and II. Protocol III again showed no difference between the standard and modified profiles.


CONCLUSIONS
The addition of deep stops requires careful consideration. Two of our EAPs made no difference and one produced increased bubbling.
Blatteau
Jean-Eric
JE
CEMPP, Toulon Naval, France. je.blatteau@infonie.fr
Hugon
Michel
M
Gardette
Bernard
B
Sainty
Jean-Marie
JM
Galland
François-Michel
FM
D000328:Adult; D018771:Arthralgia / Q000209:etiology; D002985:Clinical Protocols; D003664:Decompression / Q000009:adverse effects / Q000379:methods* / Q000592:standards; D003665:Decompression Sickness / Q000517:prevention & control*; D004242:Diving / Q000009:adverse effects / Q000502:physiology*; D004618:Embolism, Air / Q000145:classification* / Q000209:etiology / Q000503:physiopathology; D005221:Fatigue / Q000209:etiology; D006801:Humans