1

Flying After Diving:Flying After Diving:History, Research & GuidelinesHistory, Research & Guidelines

Richard Vann, Ph.D.Richard Vann, Ph.D.Research DirectorResearch Director

Divers Alert NetworkDivers Alert NetworkDEMA 2002DEMA 2002Las VegasLas Vegas

21961 – 11961 – 1stst Report Report

Cabin altitude 8-10,000 ftCabin altitude 8-10,000 ftPilot & copilot were incapacitated Pilot & copilot were incapacitated

Flew <4 hrs after diving to <30 fswFlew <4 hrs after diving to <30 fswFlight engineer was less severely Flight engineer was less severely

affected and landed the aircraftaffected and landed the aircraftFlew ~12 hrs after divingFlew ~12 hrs after diving

- Miner (1961) Flight Safety Foundation J - Miner (1961) Flight Safety Foundation J - Blumkin (1991) FSFJ 38(5):1-5- Blumkin (1991) FSFJ 38(5):1-5

31967 – 11967 – 1stst Animal Study Animal Study

DivesDives: 53-88 fsw for 7 hrs : 53-88 fsw for 7 hrs PFSIPFSI: 1, 3, 6, or 12 hr: 1, 3, 6, or 12 hrAltitudeAltitude: 10K ft for 2 hrs : 10K ft for 2 hrs ResultsResults::

93% DCS with 1 hr surface interval 93% DCS with 1 hr surface interval No DCS with 12 hr surface intervalNo DCS with 12 hr surface interval

- Furry et al. (1967) - Furry et al. (1967) Aerosp Med 1967;38(8):825-Aerosp Med 1967;38(8):825-

2828

4

1969 – 11969 – 1stst Human Study Human StudyDivesDives: 40 fsw/200 min; 120 fsw/15 min: 40 fsw/200 min; 120 fsw/15 minSISI: 5 min, 30 min, 1 hr, 2 hrs, or 3 hrs : 5 min, 30 min, 1 hr, 2 hrs, or 3 hrs AltitudeAltitude: 8K ft/112 min & 16K ft/5 min: 8K ft/112 min & 16K ft/5 minResultsResults: in 41 exposures at : in 41 exposures at 2 hrs, 1 2 hrs, 1

DCS at 8,000 ft & 9 DCS at 16,000 ft DCS at 8,000 ft & 9 DCS at 16,000 ft ApplicationApplication: basis of 2 hr USN FAD rule : basis of 2 hr USN FAD rule

for single no-D dives from ‘85-99for single no-D dives from ‘85-99- Edel et al. Aerosp Med 1969;40(10):1105-10- Edel et al. Aerosp Med 1969;40(10):1105-10

51982 - Direct Ascent Study1982 - Direct Ascent Study

AltitudeAltitude: 10K/4h-16K/1h; 8.5K/4h-14K/1h: 10K/4h-16K/1h; 8.5K/4h-14K/1hD (fsw)D (fsw) T (min)T (min) DCSDCS ExposuresExposures USN RGUSN RG 1111 1440 1440 11@16K@16K 2020 HH 4040 34 34 11@16K@16K 2020 EE 6060 20 20 22@14K,16K@14K,16K 3636 DD 8080 14 14 11@10K@10K 3535 DD100100 10 10 11@16K@16K 3838 DD130130 7 7 00 2020 DD

- Bassett (1982) USAF SAM Report- Bassett (1982) USAF SAM Report

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FAD Situation in 1970s-80sFAD Situation in 1970s-80sSparse data from manned testingSparse data from manned testing>30 guidelines published since 1980>30 guidelines published since 19800 - 24 hr range for PFSI0 - 24 hr range for PFSIControversy between advocates ofControversy between advocates of

Maximum dive time & PFSI = 0-4 hrsMaximum dive time & PFSI = 0-4 hrs Zero DCS & PFSI Zero DCS & PFSI 24 hrs 24 hrs

7

UHMS FAD WorkshopUHMS FAD Workshop24 Feb 8924 Feb 89

Literature reviewLiterature reviewFundamental issues of Fundamental issues of

decompressiondecompressionFAD researchFAD researchExpert opinionExpert opinion

8UHMS FAD WorkshopUHMS FAD Workshop Recreational Diving GuidelinesRecreational Diving Guidelines

Type of DivingType of Diving No-D diving (<2 hr/48 hrs)No-D diving (<2 hr/48 hrs) No-D multi-day divingNo-D multi-day diving D-stop divingD-stop diving

PFSIPFSI12 hrs 12 hrs 24 hrs 24 hrs 24-48 hrs 24-48 hrs

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More ControversyMore ControversyDAN & certifying agencies DAN & certifying agencies

revised all guidelines to 24 hrsrevised all guidelines to 24 hrsSkin Diver Magazine Skin Diver Magazine took took

exception arguing 24 hrs was not exception arguing 24 hrs was not justified by the low incidence and justified by the low incidence and hotels and dive operators would hotels and dive operators would lose moneylose money

101991 Resolution1991 Resolution

Jun 91 UHMS, DAN, certifying Jun 91 UHMS, DAN, certifying agencies metagencies met

1991 DAN revised recommendations1991 DAN revised recommendationsType of DivingType of Diving SI (hrs)SI (hrs)No-D diving No-D diving 12 hr minimum12 hr minimumNo-D multi-day divingNo-D multi-day diving

or D-stop diving or D-stop diving >12 hr>12 hr

11Proportion of Divers Who FlyProportion of Divers Who Fly

0%

10%

20%

30%

40%

1986 1988 1990 1992 1994 1996 1998 2000 2002

Year

% Who Flew Unpressurized

or by Commercial Air

Project DiveProject DiveExplorationExploration

DivingDivingInjuriesInjuries

269269

268268

391391 459459

434434

465465 508508

566566 591591

483483

451451

430430

729729

232232

591591

759759

379379

369369

12Divers with Symptoms Divers with Symptoms

Before FlyingBefore FlyingFrom 1998 to 2000, 278 injured divers From 1998 to 2000, 278 injured divers

were involved with flying after divingwere involved with flying after divingOf these, 55% had symptoms before Of these, 55% had symptoms before

they flewthey flewThis is an educational problem: divers This is an educational problem: divers

are not recognizing their symptomsare not recognizing their symptoms

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FAD Affects DCS SeverityFAD Affects DCS Severity49%

46%

32%

0%

10%

20%

30%

40%

50%

Flew with Sx Sx In-Flight All Others

% of Divers with

Residual Symptoms

after All Treatments from 1989-

2000

The incidence of any residual symptoms after all treatments was 14-17% greater for divers who flew than for divers who did not fly

p<0.0001p<0.0001

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PFSI & Recreational DivingPFSI & Recreational DivingDoes PFSI affect DCS risk after Does PFSI affect DCS risk after

repetitive, multi-day diving?repetitive, multi-day diving?We don’t know the PFSIs for the We don’t know the PFSIs for the

entire population, but we have entire population, but we have data for data for 382 injured divers (no preflight Sx)382 injured divers (no preflight Sx) 245 injury-free controls from Project 245 injury-free controls from Project

Dive ExplorationDive Exploration

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Case-Control StudyCase-Control StudyCan’t estimate absolute injury rates Can’t estimate absolute injury rates

without the entire populationwithout the entire populationCan estimate the Can estimate the relative riskrelative risk of one of one

condition compared with anothercondition compared with another Is the relative risk at short surface Is the relative risk at short surface

intervals greater than at longer intervals greater than at longer surface intervals?surface intervals?

- Freiberger et al., ASEM 2002; 73:980.- Freiberger et al., ASEM 2002; 73:980.

16Average PFSIAverage PFSI

27.1

20.7

0

5

10

15

20

25

30

Injury Free Controls Injury Cases

Preflight Surface Interval

(hrs)

17PFSI DistributionPFSI Distribution

0%10%20%30%40%50%60%

<12 12-24 24-36 36-48 >48Surface Interval (Hrs)

Inju

red

or P

DE

Div

ers

382 Injured Divers245 PDE Divers

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Relative RisksRelative Risks Increased relative risk of DCS forIncreased relative risk of DCS for

shorter surface intervalsshorter surface intervals–gradual increase for SIs from 24gradual increase for SIs from 2412 hrs 12 hrs –steep increase for SIs from 12steep increase for SIs from 120 hrs0 hrs

deeper dives on the last day of divingdeeper dives on the last day of diving Define Relative Risk = 1 forDefine Relative Risk = 1 for

24 hr surface interval24 hr surface interval 60 fsw maximum depth on last dive day60 fsw maximum depth on last dive day

19PFSI & Relative RiskPFSI & Relative Risk

0

3

6

9

12

15

0 10 20 30 40 50Surface Interval (hrs)

Rel

ativ

e R

isk

30'

60'

100'

130' max depth on last dive day

Relative Risk = 7

Relative Risk = 1

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In-Flight Pain & Neuro Sx at In-Flight Pain & Neuro Sx at 26 Hrs After Diving26 Hrs After Diving

Depth 0 (fsw)

50

100

150

0 24 48 72 96

Time (hrs)

5-8,000' estimated5-8,000' estimatedflight altitudeflight altitude

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PFSI & Absolute RiskPFSI & Absolute RiskEstimate PFSIs that have low DCS Estimate PFSIs that have low DCS risk after no-decompression dives risk after no-decompression dives near the recreational exposure near the recreational exposure limits limits Chamber studyChamber study1993 to 19991993 to 1999

22Experimental Experimental

DesignDesign

FlightFlight

8,000 feet8,000 feetfor 4 hoursfor 4 hours

DiveDive

Decrease the PFSI and Decrease the PFSI and observe the change observe the change

in DCS incidencein DCS incidence

PFSI (3-17 hrs)PFSI (3-17 hrs)

23DCS SeverityDCS SeverityMild DCSMild DCS

limb pain, localized abnormal limb pain, localized abnormal sensationsensation

Moderate DCSModerate DCSsensory deficit, weakness sensory deficit, weakness

Serious DCSSerious DCSparalysis, difficulty breathing, paralysis, difficulty breathing,

fainting, cerebral dysfunction, deathfainting, cerebral dysfunction, death

24Sequential DesignSequential Design

AcceptAccept a surface interval if only a a surface interval if only a “few” mild DCS incidents occur. “few” mild DCS incidents occur. Test a shorter interval.Test a shorter interval.

RejectReject a surface interval if “too a surface interval if “too many”many” mildmild DCS incidents occur DCS incidents occur or if DCS is moderateor if DCS is moderate oror serious. serious. Test a longer surface interval. Test a longer surface interval.

25Recreational Dive Planner (RDP)Recreational Dive Planner (RDP)

-start-up funding provided by PADI-start-up funding provided by PADI

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RDP FAD ProceduresRDP FAD ProceduresWait Wait 4 hrs4 hrs after one no-D dive of less after one no-D dive of less

than 60 minthan 60 minWait Wait 12 hrs12 hrs after one no-D dive of after one no-D dive of

more than 60 min or after repetitive more than 60 min or after repetitive divesdives

Wait Wait 24 hrs24 hrs after emergency after emergency decompressiondecompression

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Single Dive ProfilesSingle Dive Profiles40' for 60 min40' for 60 min40' for 120 min40' for 120 min60' for 55 min*60' for 55 min*100' for 20 min*100' for 20 min*

* Recreational Dive Planner (RDP) limit* Recreational Dive Planner (RDP) limit

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Repetitive Dive ProfilesRepetitive Dive Profiles40'/60 min 40'/60 min -1 hr SI--1 hr SI- 40'/60 min 40'/60 min60'/55 min 60'/55 min -1 hr SI--1 hr SI- 60'/20 min* 60'/20 min*60'/55 min 60'/55 min -1 hr SI--1 hr SI- 60'/20 min 60'/20 min -1 hr -1 hr

SI-SI- 60'/20 min* 60'/20 min*100'/15 min 100'/15 min -1 hr SI--1 hr SI- 60'/35 min* 60'/35 min*

* Near RDP limits* Near RDP limits

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ResultsResults

802 FAD exposures802 FAD exposures40 DCS incidents (5%)40 DCS incidents (5%)

21 Moderate DCS21 Moderate DCS18 Mild DCS18 Mild DCS1 Serious DCS1 Serious DCS

30

0

5

10

15

20

2 4 6 8 10 12 14 16 18 20 22 24Preflight Surface Interval (hours)

% D

CS

Single Dives (n=344)Single Dives (n=344)

40'/60min40'/60min40'/120min40'/120min60'/55min60'/55min100'/20min100'/20min

USNUSN

RDPRDP

DANDAN

USAFUSAF

31

0

5

10

15

20

2 4 6 8 10 12 14 16 18 20 22 24Preflight Surface Interval (hours)

% D

CS

Repetitive Dives (n=458)Repetitive Dives (n=458)

60'+60'60'+60'60'+60' +60'60'+60' +60'

100'+60'100'+60'

40'+40'40'+40'

DANDAN““>12 hrs”>12 hrs” USAFUSAF

PADI=12 hrsPADI=12 hrs

32FAD Trials SummaryFAD Trials Summary

No DCS for single dives less than 60 No DCS for single dives less than 60 min at PFSIs of 11 hrs or moremin at PFSIs of 11 hrs or more

No DCS for repetitive dives at a 17 hr No DCS for repetitive dives at a 17 hr PFSIPFSI

Results apply only to the dive profiles Results apply only to the dive profiles tested with dry, resting diverstested with dry, resting divers

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1999 USN FAD Rules1999 USN FAD RulesWhy change? Why change?

Duke studies indicated that a 2 hour PFSI Duke studies indicated that a 2 hour PFSI was too shortwas too short

Need to perform low level flights as soon Need to perform low level flights as soon as possible after a diveas possible after a dive

Need procedures to allow further ascent Need procedures to allow further ascent to altitude after performing a dive at to altitude after performing a dive at altitudealtitude

341999 USN Dive Manual1999 USN Dive Manual

35

1999 USN FAD Rules1999 USN FAD Rules SI Before Ascent to AltitudeSI Before Ascent to Altitude RGRG 1,000'1,000' 4,000'4,000' 8,000'8,000' 10,000'10,000' CC 0:00 0:00 0:00 0:00 0:00 0:00 8:26 8:26 FF 0:00 0:00 0:00 0:00 9:439:43** 19:07 19:07 II 0:00 0:00 5:15 5:15 15:5815:58** 24:00 24:00 KK 3:00 3:00 8:20 8:20 19:0319:03** 24:00 24:00 ZZ 8:17 8:17 13:3713:37 24:0024:00 24:00 24:00

* * based on DAN trialsbased on DAN trials

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USN Guidelines at 8,000'USN Guidelines at 8,000'

0

5

10

15

20

25

A B C D E F G H I J K L M N O Z

USN Repetitive Group Designator

PFSI

(hrs

)

1999 USN GuidelinesDCSNo DCSBassett (direct ascent)

37Fleet FeedbackFleet Feedback

Procedure is too complexProcedure is too complex Prefer simple 12 or 24 hour rulePrefer simple 12 or 24 hour rule

Procedure is too restrictiveProcedure is too restrictive Prevent some working on waterfront from Prevent some working on waterfront from

going home to mountains after workgoing home to mountains after work Desire to return to 2300 foot unlimited Desire to return to 2300 foot unlimited

ascent ruleascent rule

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May 2002 Workshop:May 2002 Workshop:Revised Recreational FAD GuidelinesRevised Recreational FAD Guidelines

Are any FAD guidelines needed at all?Are any FAD guidelines needed at all? Are current FAD guidelines acceptable?Are current FAD guidelines acceptable? What is the longest PFSI needed after What is the longest PFSI needed after

multi-day, repetitive diving at the limits multi-day, repetitive diving at the limits of the recreational dive tables?of the recreational dive tables?

392002 FAD Workshop:2002 FAD Workshop: Consensus Recommendations (1) Consensus Recommendations (1)

Apply to air dives followed by flights Apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 at cabin altitudes of 2,000 to 8,000 feet for divers who do not have feet for divers who do not have symptoms of DCSsymptoms of DCS

Recommendations should reduce Recommendations should reduce DCS risk but do not guarantee DCS risk but do not guarantee avoidanceavoidance

Longer preflight surface intervals will Longer preflight surface intervals will further reduce DCS riskfurther reduce DCS risk

402002 FAD Workshop:2002 FAD Workshop: Consensus Recommendations (2) Consensus Recommendations (2)

Dives within the No-D LimitsDives within the No-D Limits Single No-D DiveSingle No-D Dive: a minimum preflight : a minimum preflight

surface interval of surface interval of 12 hours12 hours is suggested is suggested Multiple Dives per Day or Days of DivingMultiple Dives per Day or Days of Diving: a : a

minimum preflight surface interval of minimum preflight surface interval of 18 18 hourshours is suggested is suggested

Dives Requiring Dives Requiring Decompression StopsDecompression Stops Little experimental or published evidence Little experimental or published evidence A preflight surface interval A preflight surface interval substantially substantially

longer than 18 hrslonger than 18 hrs appears prudent appears prudent

41NASA ONASA O22 FAD Tables FAD Tables NBL dive profile – 40 fsw for 240-390 minNBL dive profile – 40 fsw for 240-390 min Breathing gas – nitrox (46% OBreathing gas – nitrox (46% O22)) Dry suit (EMU) – pressurized to 4.0 psidDry suit (EMU) – pressurized to 4.0 psid Equivalent Air Depth – 23.9 fswEquivalent Air Depth – 23.9 fsw

*NBL - Neutral Buoyancy Laboratory, Johnson Space Center, Houston*NBL - Neutral Buoyancy Laboratory, Johnson Space Center, Houston*EMU - Extravehicular Mobility Unit (standard U.S. 'space suit')*EMU - Extravehicular Mobility Unit (standard U.S. 'space suit')

42FAD Limits (Nitrox) - EAD=25 fswFAD Limits (Nitrox) - EAD=25 fsw

Duration Duration (min)(min)

Air PFSI (hr)Air PFSI (hr)(USN PFSI)(USN PFSI)

Oxygen PFSI Oxygen PFSI (hr)(hr)

1-451-45 3 (8:26)3 (8:26) 0.330.33

46-8046-80 5 (16:18)5 (16:18) 0.670.67

81-29081-290 14 (24:00)14 (24:00) 22

291-400291-400 24 (24:00)24 (24:00) 33

Cabin altitude <10,000 ft MSLNo flight restrictions > 24 hr post-dive

43Operational ExperienceOperational Experience

Anecdotal – no databaseAnecdotal – no databaseAverage 3-5 individuals annuallyAverage 3-5 individuals annuallyPFSI of 4-18 hoursPFSI of 4-18 hoursNo cases of DCINo cases of DCI

44

On-Going USN FAD StudyOn-Going USN FAD StudyEvaluate untested USN FAD guidelines Evaluate untested USN FAD guidelines

including decompression divesincluding decompression divesEvaluate effectiveness of post-dive OEvaluate effectiveness of post-dive O22

breathing in reduce PFSIbreathing in reduce PFSIUse echocardiography to search for Use echocardiography to search for

arterial bubbles in the heartarterial bubbles in the heartThree year project with 500-700 subjectsThree year project with 500-700 subjects

45Come Dive and Fly with UsCome Dive and Fly with Us