What Rats Can Tell Us about Drinking, Diving and DCS

Drinking alcohol before a dive is often cited as a risk factor for decompression sickness (DCS), although it seems that evidence is still lacking, and just how alcohol consumption affects DCS risk in divers is unclear. However, giving alcohol to rabbits after decompressing them has been shown to be beneficial in preventing or treating DCS, but that’s insufficient evidence to suggest it may do the same for humans. Since rats are often used as test subjects before moving on to humans, Peter Buzzacott of the Divers Alert Network led a research team using rats to continue studying what role alcohol may play in DCS.

Fifteen male rats were given 50 milliliters of water, mixed with 12 milliliters of ethanol, every day for four weeks. (That’s the equivalent of a 175-pound man drinking two liters of Foster’s lager, a tough task even for an Aussie.) Fifteen other rats, the control group, were only given water. Both groups were put through staged decompression in a hyperbaric chamber. The test rats usually drank at night, so they probably weren’t under the influence at the time of decompression -- that mimics divers who regularly drink but then sleep, so they have low or no blood alcohol level before diving in the morning.

After decompression, all rats were observed for signs of DCS for an hour. When comparing the bingedrinking rats to the control group, neither their weight nor their alcohol consumption was associated with DCS. The researchers concluded that moderate alcohol consumption prior to compression neither prevented DCS nor caused it in young male rats. (A similar study using older, or female, rats could yield different results.)

There are theories about how ethanol may protect against DCS. It may enhance the solubility of nitrogen in the blood. Perhaps it lowers the surface tension of bubbles, and thus, acts as a de-frothing agent. It may reduce the aggregation and coagulation of platelets, or increase the dilation of blood vessels, thus accelerating gas washout. However, it’s a big leap from rabbits and rats to humans, so forget about slogging down two liters of Foster’s the night before your next dive.

“A Rat Model of Chronic Moderate Alcohol Consumption and Risk of Decompression Sickness,” by P. Buzzacott, A. Mazur, Q. Wang, K. Lambrechts, M Theron and F. Guerrero, Diving and Hyperbaric Medicine, Vol. 45, pgs. 75-78.