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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 2002

Las VegasLas Vegas

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1961 – 11961 – 1stst Report ReportCabin 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 - Miner (1961) Flight Safety Foundation J Foundation J

- Blumkin (1991) FSFJ - Blumkin (1991) FSFJ 38(5):1-538(5):1-5

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1967 – 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 hr

AltitudeAltitude: 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

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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

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1982 - Direct Ascent Study1982 - Direct Ascent StudyAltitudeAltitude: 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 DD

100100 10 10 11@16K@16K 3838 DD

130130 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 1980

0 - 24 hr range for PFSI0 - 24 hr range for PFSI

Controversy 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

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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

PFSIPFSI

12 hrs 12 hrs

24 hrs 24 hrs

24-48 hrs 24-48 hrs

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More ControversyMore Controversy

DAN & certifying agencies DAN & certifying agencies revised all guidelines to 24 hrsrevised all guidelines to 24 hrs

Skin 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

DAN & certifying agencies DAN & certifying agencies revised all guidelines to 24 hrsrevised all guidelines to 24 hrs

Skin 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

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1991 Resolution1991 ResolutionJun 91 UHMS, DAN, certifying Jun 91 UHMS, DAN, certifying

agencies metagencies met1991 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

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Proportion 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

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

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Divers with Symptoms Divers with Symptoms Before FlyingBefore Flying

From 1998 to 2000, 278 injured divers From 1998 to 2000, 278 injured divers

were involved with flying after divingwere involved with flying after diving

Of these, 55% had symptoms before Of these, 55% had symptoms before

they flewthey flew

This 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

49%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

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 Study

Can’t estimate absolute injury rates Can’t estimate absolute injury rates without the entire populationwithout the entire population

Can 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.

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Average PFSIAverage PFSI

27.1

20.7

0

5

10

15

20

25

30

Injury Free Controls Injury Cases

Preflight Surface Interval

(hrs)

27.1

20.7

0

5

10

15

20

25

30

Injury Free Controls Injury Cases

Preflight Surface Interval

(hrs)

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PFSI DistributionPFSI Distribution

0%

10%

20%

30%

40%

50%

60%

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

Inju

red

or

PD

E D

iver

s

382 Injured Divers

245 PDE Divers

0%

10%

20%

30%

40%

50%

60%

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

Inju

red

or

PD

E D

iver

s

382 Injured Divers

245 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)

Re

lati

ve

Ris

k

30'

60'

100'

130' max depth on last dive day

Relative Risk = 7

Relative Risk = 1

0

3

6

9

12

15

0 10 20 30 40 50Surface Interval (hrs)

Re

lati

ve

Ris

k

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)

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 Risk

Estimate 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 study

1993 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 Severity

Mild DCSMild DCSlimb pain, localized abnormal limb pain, localized abnormal

sensationsensationModerate DCSModerate DCS

sensory deficit, weakness sensory deficit, weakness Serious DCSSerious DCS

paralysis, difficulty breathing, paralysis, difficulty breathing, fainting, cerebral dysfunction, deathfainting, cerebral dysfunction, death

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Sequential DesignSequential DesignAcceptAccept 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.

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Recreational 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 Procedures

Wait Wait 4 hrs4 hrs after one no-D dive of less after one no-D dive of less than 60 minthan 60 min

Wait 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 Profiles

40' for 60 min40' for 60 min

40' for 120 min40' for 120 min

60' 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 Profiles

40'/60 min 40'/60 min -1 hr SI--1 hr SI- 40'/60 min 40'/60 min

60'/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

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0

5

10

15

20

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

% D

CS

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

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0

5

10

15

20

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

% D

CS

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

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FAD Trials SummaryFAD Trials SummaryNo 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 moreNo DCS for repetitive dives at a 17 hr No DCS for repetitive dives at a 17 hr

PFSIPFSIResults 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

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1999 USN Dive Manual1999 USN Dive Manual

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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

PF

SI

(hrs

)

1999 USN GuidelinesDCSNo DCSBassett (direct ascent)

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

PF

SI

(hrs

)

1999 USN GuidelinesDCSNo DCSBassett (direct ascent)

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Fleet FeedbackFleet FeedbackProcedure 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')

42

FAD 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

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

43

Operational 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 dives

Evaluate 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

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Come Dive and Fly with UsCome Dive and Fly with Us