Flying After Diving: History, Research & Guidelines November 2002 Flying After Diving: History, Research & Guidelines Richard Vann, Ph.D. Research Director Divers Alert Network DEMA 2002 Las Vegas The first evidence that altitude exposure after diving increased the DCS risk was in a 1960 Navy study to see if altitude exposure was useful as a test of the adequacy of decompression after diving. There was a great deal of DCS, but the test never caught on. DEMA

1961 – 1st Report Cabin altitude 8-10,000 ft Flying After Diving November 2002 1961 – 1st Report Cabin altitude 8-10,000 ft Pilot & copilot were incapacitated Flew <4 hrs after diving to <30 fsw Flight engineer was less severely affected and landed the aircraft Flew ~12 hrs after diving - Miner (1961) Flight Safety Foundation J - Blumkin (1991) FSFJ 38(5):1-5 The first report of DCS associated with flying after diving was in 1961 when the pilot and co-pilot were incapacitated at a cabin altitude of 8-10,000 ft less than four hours after diving to less than 30 fsw. The flight engineer had also been diving but was less severely affected and landed the aircraft. He had been diving about 12 hrs earlier. DEMA

1967 – 1st Animal Study Dives: 53-88 fsw for 7 hrs Flying After Diving November 2002 1967 – 1st Animal Study Dives: 53-88 fsw for 7 hrs PFSI: 1, 3, 6, or 12 hr Altitude: 10K ft for 2 hrs Results: 93% DCS with 1 hr surface interval No DCS with 12 hr surface interval - Furry et al. (1967) Aerosp Med 1967;38(8):825-28 The first animal study of FAD was published in 1967 for naval aviation by a man named Furry (see picutre). He exposed dogs for 7 hrs at 53-88 fsw and then taken to 10,000 ft for 2 hrs after PFSIs of 1 to 12 hrs. The DCS incidence was high after a 1 hr surface interval but there was no DCS after a 12 hr interval. DEMA

1969 – 1st Human Study Dives: 40 fsw/200 min; 120 fsw/15 min Flying After Diving November 2002 1969 – 1st Human Study Dives: 40 fsw/200 min; 120 fsw/15 min SI: 5 min, 30 min, 1 hr, 2 hrs, or 3 hrs Altitude: 8K ft/112 min & 16K ft/5 min Results: in 41 exposures at 2 hrs, 1 DCS at 8,000 ft & 9 DCS at 16,000 ft Application: basis of 2 hr USN FAD rule for single no-D dives from ‘85-99 - Edel et al. Aerosp Med 1969;40(10):1105-10 The first human FAD study was by Peter Edel in 1969. He investigated dives to the USN no-stop limits at 40 and 120 fsw. These were followed by surface intervals ranging from 5 min to 3 hrs and altitude exposure at 8,000 and 16,000 ft. There was only one bend at 8,000 ft. Edel’s study became the basis for the 2 hr FAD guideline used by the Navy from 1985-99. DEMA

1982 - Direct Ascent Study Altitude: 10K/4h-16K/1h; 8.5K/4h-14K/1h Flying After Diving November 2002 1982 - Direct Ascent Study Altitude: 10K/4h-16K/1h; 8.5K/4h-14K/1h D (fsw) T (min) DCS Exposures USN RG 11 1440 1@16K 20 H 40 34 1@16K 20 E 60 20 2@14K,16K 36 D 80 14 1@10K 35 D 100 10 1@16K 38 D 130 7 0 20 D - Bassett (1982) USAF SAM Report The only other really relevant and significant study was by Bruce Bassett of the Air Force, but the results were only published as an Air Force report. Bassett investigated dives for which immediate ascent to altitude was possible with a 1 min surface interval. There were no bends at 8,500 ft. A 34 min dive was possible at 40 fsw with direct ascent, etc…… The USN Repetitive Group Designator was D or E for most of the dives. Keep this in the back of your mind as it will come up again when we review the new USN FAD guidelines. There was one significant flaw in the study as nine subject exposures were terminated due to excessive Doppler VGE. DEMA

FAD Situation in 1970s-80s Sparse data from manned testing Flying After Diving November 2002 FAD Situation in 1970s-80s Sparse data from manned testing >30 guidelines published since 1980 0 - 24 hr range for PFSI Controversy between advocates of Maximum dive time & PFSI = 0-4 hrs Zero DCS & PFSI  24 hrs Despite there being very little human data, FAD guidelines were published by many agencies. According to Paul Sheffield’s account, there were more than 30 guidelines by 1989, and these covered a range of surface intervals from 0-24 hrs. In 1976, a tug-of-war began between those who wanted very short surface intervals and maximum dive time and those who recommended long surface intervals and no bends. What do you do when you don’t know what to do? Hold a workshop. DEMA

UHMS FAD Workshop 24 Feb 89 Literature review Flying After Diving November 2002 UHMS FAD Workshop 24 Feb 89 Literature review Fundamental issues of decompression FAD research Expert opinion Paul Sheffield organize a UHMS workshop to review what was known about FAD and to develop FAD guidelines. DEMA

UHMS FAD Workshop Recreational Diving Guidelines Flying After Diving November 2002 UHMS FAD Workshop Recreational Diving Guidelines Type of Diving No-D diving (<2 hr/48 hrs) No-D multi-day diving D-stop diving PFSI 12 hrs 24 hrs 24-48 hrs The guidelines were based more upon expert opinion that on fact since there was so little data. The recommended PFSI was 12 hrs for less than 2 hrs of No-D diving in a 48 hr period. For multi-day diving, 24 hrs was recommended, and 24-48 hrs for decompression diving. DEMA

Flying After Diving November 2002 More Controversy DAN & certifying agencies revised all guidelines to 24 hrs Skin Diver Magazine took exception arguing 24 hrs was not justified by the low incidence and hotels and dive operators would lose money DAN and the training agencies revised the guidelines, but Bill Gleason, editor of Skin Diver Magazine, took a dim view of a 24 hr guideline when there was no supporting data and the best non-evidence available indicated the bends incidence due to FAD was very low. They argued that this would cut short divers vacations and cost dive operators money. DEMA

1991 Resolution Jun 91 UHMS, DAN, certifying agencies met Flying After Diving November 2002 1991 Resolution Jun 91 UHMS, DAN, certifying agencies met 1991 DAN revised recommendations Type of Diving SI (hrs) No-D diving 12 hr minimum No-D multi-day diving or D-stop diving >12 hr The issue was resolved in a 1991 meeting where the 24 hr recommendation was changed to >12 hrs. -------------------------------------------------------------- These have been the guidelines since 1991. I am going to review for you what we have learned since then and bring you up to date with the revised FAD guidelines that were agreed to in a workshop this past May. DEMA

Proportion of Divers Who Fly Flying After Diving November 2002 Proportion of Divers Who Fly Project Dive Exploration 379 369 232 759 268 434 566 591 451 591 465 508 269 391 459 483 430 Diving Injuries One of the first questions one thinks of is what fraction of divers fly after a dive trip. There really is no right answer to this question as it depends on where you are diving: not many people fly to a quarry but most people fly to an island or a liveaboard. Here are two independent measures of the overall proportion by year. One comes from injured divers beginning in 1987, and the other from Project Dive Exploration since 1998. As about 75% of all diving injuries generally occur within 12 hrs, the diving injuries may be underestimated. PDE may be biased to a higher level as many PDE dives were from the islands or liveaboards. Based upon these data, approximately 20% of divers may fly after diving. 729 DEMA

Divers with Symptoms Before Flying Flying After Diving November 2002 Divers with Symptoms Before Flying From 1998 to 2000, 278 injured divers were involved with flying after diving Of these, 55% had symptoms before they flew This is an educational problem: divers are not recognizing their symptoms We tend to focus on how long to wait after diving before flying in order to avoid bends. It turns out that this question is irrelevant for about half of the injured divers because they have symptoms before they fly. “How can that be?” you ask, “They should know better than to fly when they are bent.” There may be a number of explanations for this: they’re in denial; they don’t recognize the possibility of bends; or they need to get home and the symptoms are not serious enough to keep them on the ground. In any event, it’s an educational problem. Tell your students to call DAN if they feel anything unusual after diving. DEMA

FAD Affects DCS Severity Flying After Diving November 2002 FAD Affects DCS Severity p<0.0001 We should ask if flying with symptoms has any consequences for case severity. As a measure of severity, we used the fraction of cases with any form of residual symptom after all recompressions were complete. (If these numbers seem high, injured divers continue to improve with time and nearly all but the most serious are symptom-free after one year.) We divided 6,165 injured divers from 1989 to 2000 into three groups: those who had symptoms before flying, those who developed symptoms during or after flying, and all others some of who may not have reported flying. It turned out that there was no difference in the incidence of residual symptoms between divers who flew with symptoms (49%) and divers who developed symptoms during or after flight (43%). Of divers who did not fly, however, only 32% had residual symptoms, a statistically significant difference. The take-home message would appear to be, avoid flying with symptoms and wait long enough after diving before flying to avoid getting symptoms. The incidence of any residual symptoms after all treatments was 14-17% greater for divers who flew than for divers who did not fly DEMA

PFSI & Recreational Diving Flying After Diving November 2002 PFSI & Recreational Diving Does PFSI affect DCS risk after repetitive, multi-day diving? We don’t know the PFSIs for the entire population, but we have data for 382 injured divers (no preflight Sx) 245 injury-free controls from Project Dive Exploration Well, how long should one wait after diving before flying? What can we learn from divers who developed symptoms during or after flight and from PDE divers who flew and were injury-free? We have data for 382 FAD injury cases and for 245 injury-free controls. DEMA

Flying After Diving November 2002 Case-Control Study Can’t estimate absolute injury rates without the entire population Can estimate the relative risk of one condition compared with another Is the relative risk at short surface intervals greater than at longer surface intervals? - Freiberger et al., ASEM 2002; 73:980. Case-control studies can tell you what variables may be significant but not how important they are. Without knowledge of the entire population at risk, we can’t estimate the absolute injury rates. We can, however, estimate the relative risk of, say, one surface interval compared to another. This is known as a case-control study. It’s like asking if there are more short surface intervals in the cases than in the controls. DEMA

Flying After Diving November 2002 Average PFSI If we simply compare the mean surface intervals, there is a statistically significant difference between cases and controls. The mean for cases was only 21 hrs while for controls, it was 27 hrs. DEMA

Flying After Diving November 2002 PFSI Distribution If we look at the distributions of cases and controls over 12 hr time intervals, the differences in PFSI become clearer. 53% of the cases waited less than 24 hrs while 76% of the controls waited more than 24 hrs. DEMA

Relative Risks Increased relative risk of DCS for Flying After Diving November 2002 Relative Risks Increased relative risk of DCS for shorter surface intervals gradual increase for SIs from 2412 hrs steep increase for SIs from 120 hrs deeper dives on the last day of diving Define Relative Risk = 1 for 24 hr surface interval 60 fsw maximum depth on last dive day With the help of statistics, we can show that the relative risk increases as the PFSI decreases and the maximum dive depth on the last day of diving increases. Unfortunately, our knowledge of the dive profiles for injured divers is minimal. The risk increases gradually from 24 to 12 hrs and steeply at less than 12 hrs. Let’s define the relative risk as 1 for a 24 hr PFSI and a 60 fsw maximum depth on the last day of diving. DEMA

Flying After Diving November 2002 PFSI & Relative Risk Here is a graphical description of the relationship of PFSI and relative DCS risk. The surface interval is on the x-axis, and the relative risk is on the y-axis. Each line represents the relative risk for a different maximum depth on the last dive day: 30, 60, 100, and 130 fsw. The deeper the dive on the last day, the higher the risk. Note that the increase in relative risk is gradual for long surface intervals and steep at short surface intervals. Our reference point of 24 hrs and 60 fsw was defined with a relative risk of one. By comparison, a PFSI of 12 hrs after maximum depth of 130 fsw on the last day has a relative risk 7 times greater than at 24 hrs and 60 fsw. DEMA

In-Flight Pain & Neuro Sx at 26 Hrs After Diving Flying After Diving November 2002 In-Flight Pain & Neuro Sx at 26 Hrs After Diving 5-8,000' estimated flight altitude Here is an actual FAD case from PDE in which the entire 10 dive profile over three days of diving was recorded. The diver was the wife of a DAN physician and despite waiting 26 hrs before flying, she developed pain and neurological symptoms during the flight. The message here is that you can still get bent if your wait longer than 24 hrs. The 140 fsw dive on the third day that may have contributed to her risk. DEMA

Flying After Diving November 2002 PFSI & Absolute Risk Estimate PFSIs that have low DCS risk after no-decompression dives near the recreational exposure limits Chamber study 1993 to 1999 The relative risk studies suggest that there are significant differences in DCS risk between long and short preflight surface intervals and that deep dives may require longer surface intervals. Relative risk studies are not completely satisfying, however, since a large relative risk may still be fairly small if the baseline risk is very small. To estimate the effects of PFSI on absolute risk, we conducted a laboratory study where the experimental conditions measured and closely controlled. The study objective was to estimate the duration of PFSI for which the DCS risk would be small after exposures near the limits of recreational no-decompression diving. The study began in 1993 and finished in 1999. DEMA

Experimental Design Flight Decrease the PFSI and observe the change Flying After Diving November 2002 Experimental Design Flight 8,000 feet for 4 hours Dive Decrease the PFSI and observe the change in DCS incidence PFSI (3-17 hrs) The basic experiment is a dive (or dives) followed a 4 hr simulated flight to 8,000 feet after a predetermined surface interval of 3-17 hrs. The experimental subjects were are dry and at rest during both the dives and flights. 8,000 feet was chosen for the flight as it is the maximum commercial airline cabin altitude permitted by the FAA even though the aircraft may be at an altitude in excess of 30,000 feet. In airline flights, the average cabin altitude is 5,000-5,500 feet. DEMA 3 3 3 3 3 3

DCS Severity Mild DCS Moderate DCS Serious DCS Flying After Diving November 2002 DCS Severity Mild DCS limb pain, localized abnormal sensation Moderate DCS sensory deficit, weakness Serious DCS paralysis, difficulty breathing, fainting, cerebral dysfunction, death For the study to provide useful information, some subjects must develop decompression sickness, but the risk of injury must be acceptably small and the injuries easily reversible. For the purposes of the FAD study, we classify DCS as Mild, Moderate, or Serious according to the definitions shown here. DEMA 5 5 6 6 6 5

Flying After Diving November 2002 Sequential Design Accept a surface interval if only a “few” mild DCS incidents occur. Test a shorter interval. Reject a surface interval if “too many” mild DCS incidents occur or if DCS is moderate or serious. Test a longer surface interval. We used a sequential experimental design for efficiency and to limit the risk to subjects. The sequential design was based on Acceptance and Rejection rules such that a preflight surface interval would be accepted if there were only "a few mild" DCS incidents but rejected if there were "too many" mild incidents or moderate DCS. When a surface interval was accepted, a shorter surface interval was tested. When a surface interval was rejected, a longer surface interval was tested. DEMA 4 4 5 5 5 4

Recreational Dive Planner (RDP) -start-up funding provided by PADI Flying After Diving November 2002 Recreational Dive Planner (RDP) -start-up funding provided by PADI We used the Recreational Dive Planner to select dive times and generally tested dives near the limits of the table. PADI had provided start-up funding for the project. The red circles show the single dives that were tested. Most were near the limits of the RDP. DEMA

RDP FAD Procedures Wait 4 hrs after one no-D dive of less than 60 min Flying After Diving November 2002 RDP FAD Procedures Wait 4 hrs after one no-D dive of less than 60 min Wait 12 hrs after one no-D dive of more than 60 min or after repetitive dives Wait 24 hrs after emergency decompression The RDP FAD procedures required 4 hrs after a single short no-D dive, 12 hrs after a longer no-D dive or repetitive dives, and 24 hrs after decompression dives. DEMA

Single Dive Profiles 40' for 60 min 40' for 120 min 60' for 55 min* Flying After Diving November 2002 Single Dive Profiles 40' for 60 min 40' for 120 min 60' for 55 min* 100' for 20 min* * Recreational Dive Planner (RDP) limit Here are the single dive profiles we tested. The 60 and 100 fsw dives were at the no-D limits. The 40 fsw limit is 140 min. DEMA

Repetitive Dive Profiles Flying After Diving November 2002 Repetitive Dive Profiles 40'/60 min -1 hr SI- 40'/60 min 60'/55 min -1 hr SI- 60'/20 min* 60'/55 min -1 hr SI- 60'/20 min -1 hr SI- 60'/20 min* 100'/15 min -1 hr SI- 60'/35 min* * Near RDP limits We tested repetitive profiles with two or three dives at 40, 60, or 100 fsw. Except for the 40 fsw dives, the bottom times were near the RDP limits. The surface interval between dives was one hour which we believed would be more stressful than a longer surface interval. DEMA

Results 802 FAD exposures 40 DCS incidents (5%) 21 Moderate DCS Flying After Diving November 2002 Results 802 FAD exposures 40 DCS incidents (5%) 21 Moderate DCS 18 Mild DCS 1 Serious DCS There were a total of 802 subject exposures with 40 DCS incidents of which 21 were Moderate, 18 were Mild, and 1 was Serious. DEMA

Single Dives (n=344) 40'/60min 40'/120min 60'/55min 100'/20min DAN RDP Flying After Diving November 2002 Single Dives (n=344) 40'/60min 40'/120min 60'/55min 100'/20min DAN RDP USAF There were 334 exposures of the four single dive profiles. The preflight surface interval is shown here on the x-axis and the DCS incidence on the y-axis. The single dive results are compared here with several FAD guidelines: the 2 hr Navy rule, the 4 hr RDP rule, the 12 hr DAN rule, and the 24 hr Air Force rule. Both 2 and 4 hrs appear to be too short. Twelve hours appears satisfactory except, perhaps, for the long dives such as 120 min at 40 fsw. The 24 hr rule seems quite conservative for single dives. USN DEMA 17 10 14 14

Repetitive Dives (n=458) 100'+60' 60'+60' 60'+60' +60' 40'+40' Flying After Diving November 2002 Repetitive Dives (n=458) 60'+60' 60'+60' +60' 100'+60' 40'+40' PADI=12 hrs DAN “>12 hrs” USAF For repetitive dives, bends occurred at surface intervals of 13 to 16 hrs. There were 52 exposures at 17 hrs without DCS. The “greater than 12 hr” rule appears clearly inadequate for repetitive diving while 24 hrs remains conservative. DEMA 12 18 12 13 15 12 15

Flying After Diving November 2002 FAD Trials Summary No DCS for single dives less than 60 min at PFSIs of 11 hrs or more No DCS for repetitive dives at a 17 hr PFSI Results apply only to the dive profiles tested with dry, resting divers Here’s a simple summary of the FAD trials. There were no bends for single dives with less than 60 min of bottom time at PFSIs of 11 hrs or longer. There were no bends for repetitive dives at a PFSI of 17 hrs. Bear in mind that these results apply directly only to the dives we tested with dry, resting subjects. There is no guarantee that the requirements might not be different for open water, multi-day, repetitive recreational diving. DEMA 27 20 24

1999 USN FAD Rules Why change? Flying After Diving November 2002 1999 USN FAD Rules Why change? Duke studies indicated that a 2 hour PFSI was too short Need to perform low level flights as soon as possible after a dive Need procedures to allow further ascent to altitude after performing a dive at altitude The Navy changed its flying after diving guidelines in 1999, in part because the DAN studies indicated that 2 hrs was too short but also because they wanted greater operational flexibility. DEMA

Flying After Diving November 2002 1999 USN Dive Manual These are the new rules which are published in all Navy Diving Manuals since 1999 and also the NOAA Diving Manual. DEMA

1999 USN FAD Rules SI Before Ascent to Altitude Flying After Diving November 2002 1999 USN FAD Rules SI Before Ascent to Altitude RG 1,000' 4,000' 8,000' 10,000' C 0:00 0:00 0:00 8:26 F 0:00 0:00 9:43* 19:07 I 0:00 5:15 15:58* 24:00 K 3:00 8:20 19:03* 24:00 Z 8:17 13:37 24:00 24:00 * based on DAN trials This is a partial table to illustrate how the new rules are used. The preflight surface intervals (in hh:mm) are given as a function of the Navy Repetitive Group Designators (RG) and the flight altitude. The underlined RGs represent profiles tested by DAN. The Navy adjusted the corresponding surface intervals empirically according to the DAN results. The surface intervals for untested altitudes and repetitive groups were extrapolated using the Cross corrections and a Haldane decompression model. DEMA

Flying After Diving November 2002 USN Guidelines at 8,000' Here we see a comparison of the DAN trials and the Navy guidelines. The blue line represents the Navy PFSIs as a function of the Repetitive Group Designator. The red squares are the tests for which DCS occurred in the DAN trials. The green circles are tests for which DCS did not occur. The two yellow triangles on the x-axis represent Bruce Bassett’s trials of direct ascent to altitude. In general, the Navy PFSI guidelines are longer than the surface intervals for which we had bends. DEMA

Fleet Feedback Procedure is too complex Procedure is too restrictive Flying After Diving November 2002 Fleet Feedback Procedure is too complex Prefer simple 12 or 24 hour rule Procedure is too restrictive Prevent some working on waterfront from going home to mountains after work Desire to return to 2300 foot unlimited ascent rule While the Navy procedure is reasonably flexible, some low-level grumbling has been reported. Some say it’s too complex, some say it’s too restrictive. You can’t please everyone. DEMA

May 2002 Workshop: Revised Recreational FAD Guidelines Flying After Diving November 2002 May 2002 Workshop: Revised Recreational FAD Guidelines Are any FAD guidelines needed at all? Are current FAD guidelines acceptable? What is the longest PFSI needed after multi-day, repetitive diving at the limits of the recreational dive tables? The current recreational FAD guidelines were agreed upon in 1991. With the availability of the DAN data, it seemed reasonable to consider whether the existing guidelines should be revised. This was done during a workshop last May with representatives of the recreational diving industry. These were some of the questions that were considered. As Ed Thalmann, a representative from DAN, remarked, revising the guidelines was probably very similar to writing the Declaration of Independence. DEMA

2002 FAD Workshop: Consensus Recommendations (1) Flying After Diving November 2002 2002 FAD Workshop: Consensus Recommendations (1) Apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet for divers who do not have symptoms of DCS Recommendations should reduce DCS risk but do not guarantee avoidance Longer preflight surface intervals will further reduce DCS risk Here are the consensus guidelines which will be published this winter in the Workshop Proceedings. DEMA

2002 FAD Workshop: Consensus Recommendations (2) Flying After Diving November 2002 2002 FAD Workshop: Consensus Recommendations (2) Dives within the No-D Limits Single No-D Dive: a minimum preflight surface interval of 12 hours is suggested Multiple Dives per Day or Days of Diving: a minimum preflight surface interval of 18 hours is suggested Dives Requiring Decompression Stops Little experimental or published evidence A preflight surface interval substantially longer than 18 hrs appears prudent The revised guidelines of 2002 have a better empirical basis than the 1991 guidelines and should be safer. The practical problem remains of having to stop diving 18 hrs before flight. DEMA

NASA O2 FAD Tables NBL dive profile – 40 fsw for 240-390 min Flying After Diving November 2002 NASA O2 FAD Tables NBL dive profile – 40 fsw for 240-390 min Breathing gas – nitrox (46% O2) Dry suit (EMU) – pressurized to 4.0 psid Equivalent Air Depth – 23.9 fsw NASA has a similar problem in that the astronauts need to fly at a cabin altitude of up to 10,000 ft after training for space walks in the Neutral Buoyancy Lab for up to 6.5 hrs at a depth equivalent to air at about 25 fsw. *NBL - Neutral Buoyancy Laboratory, Johnson Space Center, Houston *EMU - Extravehicular Mobility Unit (standard U.S. 'space suit') DEMA

FAD Limits (Nitrox) - EAD=25 fsw Flying After Diving November 2002 FAD Limits (Nitrox) - EAD=25 fsw Duration (min) Air PFSI (hr) (USN PFSI) Oxygen PFSI (hr) 1-45 3 (8:26) 0.33 46-80 5 (16:18) 0.67 81-290 14 (24:00) 2 291-400 24 (24:00) 3 To allow the astronauts to fly as soon as possible after NBL training, NASA offers oxygen breathing that reduces the preflight surface interval by a factor of 7-8. How safe are the NASA procedures? Comparison with the Navy procedures indicates that the NASA air surface intervals are a much as three times shorter. Cabin altitude <10,000 ft MSL No flight restrictions > 24 hr post-dive DEMA

Operational Experience Flying After Diving November 2002 Operational Experience Anecdotal – no database Average 3-5 individuals annually PFSI of 4-18 hours No cases of DCI The bottom line is that we don’t know how well the NASA oxygen procedures work, and we cannot recommend specific FAD guidelines without empirical data. DEMA

Flying After Diving November 2002 On-Going USN FAD Study Evaluate untested USN FAD guidelines including decompression dives Evaluate effectiveness of post-dive O2 breathing in reduce PFSI Use echocardiography to search for arterial bubbles in the heart Three year project with 500-700 subjects Work has recently started on a 3-year Navy-supported human study of flying after diving to provide additional data, including the effects of oxygen breathing in the surface interval. DEMA

Come Dive and Fly with Us Flying After Diving November 2002 Come Dive and Fly with Us We need subjects for this study, so if any of you are interested and will be in or visiting the Durham, NC area over the next three years, come see us. You can visit the DAN web site for information on the project. ---------------------------------------------------------------------- The take-home message is that slow and steady progress is possible with continued effort. You can expect to see further revised FAD guidelines over the next 3-5 years. DEMA