1. 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

2. 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

3. 1967 – 1st Animal Study Dives: 53-88 fsw for 7 hrs
Flying After Diving
November 2002
1967 – 1st Animal Study
Dives: 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 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

4. 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):
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
DEMA

5. 1982 - Direct Ascent Study Altitude: 10K/4h-16K/1h; 8.5K/4h-14K/1h
Flying After Diving
November 2002
Direct Ascent Study
Altitude: 10K/4h-16K/1h; 8.5K/4h-14K/1h
D (fsw) T (min) DCS Exposures USN RG H E D D D 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

6. 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
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

7. 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

8. 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 hrs for decompression diving.
DEMA

9. 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

10. 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 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. 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

33. 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

34. 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

35. 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: :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

36. 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

37. 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

38. 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

39. 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

40. 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

41. 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 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

42. 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
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

43. 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

44. 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 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

45. 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