Skydiving after diving

Question:
Could you please let me know about what guidelines, if any, that DAN can give me about Skydiving after diving.My main concern is that commercial airliner cabin pressure is approximately equal to 8000ft. Skydiving is from heights of 12,500 - 14,000 ft.

I intend to skydive on days when I may have been doing open water training with students that morning. Typically my Aladdin AirX O2 computer will give me a "no fly" time of between 2 and 4 hours. As a rough rule of thumb I am intending to double this time before I skydive to allow a margin of extra safety and to allow for the increased altitude.

Answer:
Skydiving should be considered at the same risk level than flying.
The current position is: wait AT LEAST 12 hours after a single No Decompression Dive and 24 hors after repetitive, multiple day or decompression diving.
DAN's recent results suggest that in the second case an interval of 17 hours will probably be safe, but the study is still going on and the official recommendation has not changed yet.
For your further information here are some abstracts from our previous articles.

From Alert Diver European Edition IV / 98
DAN Research Reports
DAN reviews Flying After Diving guidelines from the past, present and future
BY RICHARD D. VANN, PH.D.

There is a very small risk of decompression sickness (DCS) after diving with dive computers or using dive tables. Mountain- or air travel can increase this risk significantly as a result of exposure to reduced atmospheric pressure. Flying after diving guidelines are the surface intervals that are recommended before flying after scuba diving is considered safe.

The History
The 1989 Undersea and Hyperbaric Medical Society workshop expert consensus recommended:
- a 12-hour wait after up to two hours of no-stop dive time within the previous 48 hours;
- a 24-hour wait after multiday, unlimited (repetitive) no-stop diving; and - a 24- to 48-hour wait after dives that required decompression stops.
The 1991 revised DAN guidelines recommended waiting at least 12 hours after a single no-stop dive and longer than 12 hours after repetitive dives, decompression dives or multiple days of diving. These are DAN's current guidelines.
In 1993 DAN began a human study with the goal to provide data upon which to base more objective guidelines. The test dive profiles have been single no-stop dives or two and three repetitive no-stop dives, all separated by one-hour surface intervals. Dive profiles were followed by surface intervals of three to 17 hours, with a four-hour flight at an altitude of 2,438 meters.
102 to 192 individual exposures have been conducted per year.

Pre-defined rules specified how much testing was needed before a surface interval could be accepted. After acceptance, the surface interval was then reduced by one hour, and the shorter interval was tested until it was accepted or until sufficient DCS occurred to violate pre-defined rejection rules. DAN has conducted more than 700 exposures, with 29 DCS incidents. The signs and symptoms were generally mild pain, with occasional local paresthesias (tingling and numbness). The overall DCS incidence was about 4 percent, but long preflight surface intervals had a 0 percent incidence, and short surface intervals had an incidence approaching 15 percent. For single no-stop dives, DCS occurred after preflight surface intervals of 12 hours or less. For repetitive dives, DCS occurred after surface intervals of 16 hours or less.

The Future
Based on data DAN has accumulated thus far, the simplest approach would be:
- To wait for at least 13 hours after a single no-stop dive; and - To wait for at least 17 hours after repetitive no-stop dives before flying in pressurized commercial aircraft.
While this strategy would cover much flying after diving activity, it does not address short, shallow dives, low-altitude air- or mountain travel, or multiday repetitive diving.
We cannot test every possible combination of dives and altitude exposures in the laboratory. To address the problems of short dives and low-altitude exposures, DAN will attempt to develop a decompression model that predicts the DCS incidence based upon data from the current trials.

From Alert Diver III/99
about the other side of the coin....but useful information anyway Low Living, High Diving
By Guy de Lisle Dear

Q: One young diver is now living in a Jordan village on the Dead Sea, at approximately 365 meters below sea level.

1. What are the long-term side effects of living for a prolonged period of time (two years) at approximately 1,200 feet below sea level?
2. Would this person need to take any precautions before diving in the Red Sea in Aqaba?
3. If he would need to be transported via medevac for any reason from Jordan, would he not be able to fly within a specific time period?

A: There is no evidence that living at depth, at least at such a small water-equivalent depth, has any deleterious effects. The barometric pressure at the surface of the Dead Sea is about 800mmHg (normal atmospheric pressure is 760mmHg). Theoretically, the diver should consider himself to be diving at altitude in the Red Sea in Aqaba , when coming from his subsea home. The Theoretical Ocean Depth (TOD), converted for the Dead Sea would add about one meter to any given dive. This means he should count each dive as being one stop deeper. The U.S. Navy tables recommend, in fact, that no alteration be made for dives at altitudes lower than 701 meters. DAN's preliminary research findings indicate that waiting to fly or go to elevation after diving requires at least a 13-hour wait after a single no-stop dive and a 17-hour wait after multiple dives before flying. If the diver developed symptoms of decompression illness and required a medical evacuation, there should be no problem if the plane could pressurize the cabin to 800mmHg. In a dire situation in which the diver requires transportation over a mountain pass or other elevation to reach a medevac aircraft, then he should breathe 100 percent oxygen during the trip to prevent or lessen any effect that altitude may have on symptoms of decompression illness.