Captain Terry Clymire NAUI #13529L

We know how important it is that sport divers understand the effects pressure reduction has on our bodies when we ascend in an aircraft after diving. But does flight before we start diving pre-dispose us to DCI?

It is recommended in "Advanced Diving, Technology and Techniques" to wait at least 24 hours after diving and more than 24 hours following any dive that requires decompression. Shorter, deeper dives are preferred when planning to fly soon after because of the fast tissue half-times and their ability to outgas residual nitrogen more quickly than the slow tissue ingassing resulting from long, shallow dives.

Probably 60 percent of divers today are using some sort of dive computer that uses 30-feet-per-minute ascent rate, along with a time-to-fly indicator. DAN reports higher rates of DCI cases among divers relying on computers and flying than those using straight tables and the basic wait-24-hours rule before flying. At the Reef House in the Bay of Roatan, we see many divers from the US and Europe. Some travel a few hours and some for days to reach Central America. What effect does this have? Can it pre-dispose divers to DCI ?

Every training manual contains information about diving and then flying, why not flying and diving?

According to Dr. Peter Bennett at DAN, theoretically some off-gassing of nitrogen does occur, but it is not considered relevant. The most important problem in flying and then diving is the problem of dehydration accompanied by the consumption of alcohol during flight. It is recommended to wait at least 12 hours before diving after using alcohol and at least 20 hours if this is combined with flying. It is widely believed that dehydration increases susceptibility to DCI. D.H.Elliott and R.E.Moon have suggested that fatigue and dehydration from high altitude exposure, possibly combined with the use of alcohol, can result in symptoms associated with DCI. Studies done with caisson workers have shown individuals with higher than normal urine specific gravity levels are more likely to have DCI than other men with the same exposure levels but with low levels of urine specific gravity. Major cases of "hits" tend to "induce a generalized capillary leak syndrome, leading to extravasation of plasma and hypovolemia" Jaminet (1871).

This suggests that dehydration is a facto that predisposes or is the result of DCI. Brunner, conducting tests in 1964, found that in two case studies where the patient plasma and red cells were measured, both had the same hematocrit values of 68%, but their blood plasma levels were at 50% below normal. When they were given plasma, their hematocrit levels returned to normal and the patients were stabilized.

The best rule for flying and diving is to drink plenty of fluids, avoid alcohol, get plenty of rest and upon arrival in the islands of your destination, continue with this routine.