Diving after flying ?

[blueyoull]

Is there any restriction on the time you have to wait before you can dive after flying? (11 hour flight if that makes any difference):rolleyes:

[Chris Cherrington]

.....

[Rod Bateman]

I always leave it for 12 hours. I believe that flying dehydrates you so you should really leave a gap after flying and make sure you drink plenty of water.

[Chris Cherrington]

...........

[Steve in Sharm]

That is my understanding too and makes the issue complicated.

The DAN study should be completed next year and hopefully this should shed some more light on the subject. Meantime a 12hr or greater gap makes sense.

Chris

So, answer me this.......

Military flight, jump out of plane at high altitude, deploy parachute at very low levels (silly really) to avoid radar, drop into the wet stuff and begin dive.

I believe the "time after flying" delay was about 2 mins 30 seconds........

Steve

[Alison Boler]

AHA Mr Bond, we've been expecting you!

Aren't the people that do this type of thing generally just nipping along in extremely shallow depths though? Not to mention, that a possible bend is the very least of the many likely ways they may get killed or injured on such an occasion ;)

Bit like reminding them to wear their seatbelts whilst driving through Basra!

:)

[Chris Cherrington]

So, answer me this.......

Military flight, jump out of plane at high altitude, deploy parachute at very low levels (silly really) to avoid radar, drop into the wet stuff and begin dive.

I believe the "time after flying" delay was about 2 mins 30 seconds........

Steve

Damn......

You are right and I have misread the OP.......... damn, damn, damn.....:D

No there is no delay after flying its the other way round...

Well spotted sir....

Chris

[Steve Pearson]

This is one I've always contested in my beliefs from what is taught.

BSAC OT4 slide 14 states that you should "recover before diving - 10hrs minimum"

However using the transfer tables:

We start as Table A - level 1 = A1
we fly in a pressurised cabin assumed to be level 4 = C4 (from transfer)
The pressure I think is just under 900mb (I sadly took a VR3 on once to check it)
The C after 90 mins becomes B and after 8hrs becomes A
We then descend to ground level and C4 becomes B1, B4 becomes A1, and A4 becomes A1

Therefore there is no problem diving after this.

Looking at what happens your tissues would offgas during the flight as a result of the pressure gradient difference between your body and the cabin pressure. When you land and start breathing in the normal environment you on-gas until your body is in equilibrium to the atmospheric air pressure.

You would normally expect at least 1-2hrs before you could get into the water in any case with luggage collection, transfer from airport, getting kitted up etc. Therefore I personally believe there is no issue.

That's my take on it anyway....maybe I'm misguided and completely wrong :p

[Woz]

Dear All,

I taught the ST4 lecture last night which covers this. Diving after flying in theory is a Good Idea as you have been offgassing during the flight. However flying dehydrates you, makes you tired and Mr Grumpy Pants. So leave it overnight and drink plenty of fluids.

[Tony Dwyer]

This is one I've always contested in my beliefs from what is taught.

BSAC OT4 slide 14 states that you should "recover before diving - 10hrs minimum"

However using the transfer tables:

We start as Table A - level 1 = A1
we fly in a pressurised cabin assumed to be level 4 = C4 (from transfer)
The pressure I think is just under 900mb (I sadly took a VR3 on once to check it)
The C after 90 mins becomes B and after 8hrs becomes A
We then descend to ground level and C4 becomes B1, B4 becomes A1, and A4 becomes A1

Therefore there is no problem diving after this.

Looking at what happens your tissues would offgas during the flight as a result of the pressure gradient difference between your body and the cabin pressure. When you land and start breathing in the normal environment you on-gas until your body is in equilibrium to the atmospheric air pressure.

You would normally expect at least 1-2hrs before you could get into the water in any case with luggage collection, transfer from airport, getting kitted up etc. Therefore I personally believe there is no issue.

That's my take on it anyway....maybe I'm misguided and completely wrong :p

Steve

Dehydration is potentially significant. Plane cabin air is very dry and moisture is literally pumped out of you. I always carry bottled water and swig it during flights.

In addition ascent to altiude is very rapid and does not model any dive tables as far as I know (open to correction). I have been informed that there is a possibility of micro bubbles forming during cabin pressure drop. These will take time to disipate. Consider that the PO2 at altitude is somewhat lower than at sea level, thus off gassing and dissipation of any micro bubbles is not as efficient.

I always feel somewhat blasted after a long flight and it takes me a day to bounce back. This is not jet lag, but the result of all the stresses of the journey. Due to simple logistics, it has always been somewhat unlikely that I would be able to dive within 10/12 hours of landing anyway.

[Steve Pearson]

Tony, Woz

Whilst I take your points on board they are not definitive reasons for not being able to dive after flying.

Dehydration can be addressed by taking plenty of fluids during the flight.

Tiredness/grumpy...... personal issues not precluding diving.

Microbubbles .... I accept that it is possible due to the change of pressure. These are not perhaps so significant (however could be contributary to Deep Vein Thrombosis in some people) they will be dissipating during the flight, and certainly when diving would be reduced in size if not completely due to the effective compression of them at depth.

It may be foolish to go and do a deep/long deco dive but just a normal dive isn't an issue.

To clarify my point if you look at the BSAC88's page 7, example 6, it shows a dive to 19m, 2hrs after a flight.

You may personally not feel like diving after a flight, but that doesn't mean to say you can't.

Steve

[Dave Sydenham]

Surely the problem with diving after flying is waiting for the airline to find your luggage - usually at least 24 hours.....:p

[tony J]

Surely the problem with diving after flying is waiting for the airline to find your luggage - usually at least 24 hours.....:p
Get your own aircraft, then you don't have such problems ;-)

However my aircraft is rather impractical for most diving trips.

Tony

[Taff Griffiths]

So, answer me this.......

Military flight, jump out of plane at high altitude, deploy parachute at very low levels (silly really) to avoid radar, drop into the wet stuff and begin dive.

I believe the "time after flying" delay was about 2 mins 30 seconds........

Steve

Steve

I think the record for ascension is something like 10mins from the timmy landing to plopping in at English bay!!!!! :o

not by me I hasten to add :mad:

[Steve in Sharm]

Steve

I think the record for ascension is something like 10mins from the timmy landing to plopping in at English bay!!!!! :o

not by me I hasten to add :mad:

Hope your not using the firms computer for this "crabby".........

Me and the lads at Ocean are going to the Thistlegorm on Sunday, laying a wreath and having a short rememberance service at 11 - some bugger stole your poppy. :mad:

[Tristan Green]

Dehydration can be addressed by taking plenty of fluids during the fight.

Steve
LOL

I always put the black eyes down to mask squeeze - now I know better! :p

Cheers,
Tristan

[Steve Pearson]

Thanks Tristan

Iy reely mus gett mi spel chequer sortid owt

Iv amendd it now

[Terry]

All other things being equal.
Dehydration and or impaired circulation and or unusual stress increases the chances of Deco problems.
As in most of us, all three exist as a result of flying. Is it not circumspect to wait for half a day or so prior to diving.

KDS KDS

Terry

[Steve in Sharm]

All other things being equal.
Dehydration and or impaired circulation and or unusual stress increases the chances of Deco problems.
As in most of us, all three exist as a result of flying. Is it not circumspect to wait for half a day or so prior to diving.

KDS KDS

Terry

I think thousands - probably hundreds of thousands of military HALO jumps into the sea followed by a dive would say different, hope DAN takes them into account when they do the math rather than results of holiday divers + supposition.....

My own record is 40 mins at Gibraltar for a 1 hour, 30m dive.......

Steve

[blueyoull]

Just been for my dive med. so I asked the Doc.

His Answer was as with many of your posts, flying makes you dehydrated so you should try and drink plenty of non alcoholic drinks before you do dive but there really is no time limit, on the flip side of that though he did say that you should not dive for around 12hours before flying due to any slight deco problems the might be present.

That'll be the sound of a can of worms then ehh:rolleyes: .

[Thalassamania]

The only reason not to dive right after flying is dehydration. But then you should never let youself dehydrate on a plane for a host of other reasons.

BTW: HALO jumps are (were?) usually made from a C-130 which is pressurized to 1ATA.

[Steve in Sharm]

The only reason not to dive right after flying is dehydration. But then you should never let youself dehydrate on a plane for a host of other reasons.

BTW: HALO jumps are (were?) usually made from a C-130 which is pressurized to 1ATA.

Flying in a C130 is just the same (if not worse) than flying in a commercial, pressurized jet is it not? I doubt very much that the RAF/Government are going to have planes that are better pressurised than those in civvy street.

Pressurised to 1 ATA! Not when that door opens its not - instant drop to 1/2 ata or less?



Steve

[Mike Rowley]

So, answer me this.......

Military flight, jump out of plane at high altitude, deploy parachute at very low levels (silly really) to avoid radar, drop into the wet stuff and begin dive.

I believe the "time after flying" delay was about 2 mins 30 seconds........

Steve

Hi Steve

They are using rebreathers at very shallow depths to swim long distances usually. With A CCR the PN2 can be lower than that in air at atmospheric pressure, depending on set point and depth therefore the diver is actually off-gassing N2 during the dive.:D

If the soldier is on a pure O2 rebreater the PN2 is zero!:cool:

Cheers

Mike

[Steve in Sharm]

Hi Steve

They are using rebreathers at very shallow depths to swim long distances usually. With A CCR the PN2 can be lower than that in air at atmospheric pressure, depending on set point and depth therefore the diver is actually off-gassing N2 during the dive.:D

If the soldier is on a pure O2 rebreater the PN2 is zero!:cool:

Cheers

Mike

Nope, no, no........

Most training jumps/dives are conducted on open circuit, only the serious stuff is conducted on a re-breather (which is actually dropped seperate to the jumper).

Trust me on this, an ex RM friend is sat right next to me as I type.... (and the technical sh!t he is coming out with on this is scaring me :eek: )

RAF Regt do not use rebreathers.......

but both what has been said by you and I both show that you can dive straight away.

Steve

PS. Is this the Mike Rowley who was on my Instr Cse at Bovisand all those years ago?

[Mike Rowley]

PS. Is this the Mike Rowley who was on my Instr Cse at Bovisand all those years ago?[/QUOTE]

Might well be Steve, I don't get involved with the ITS these days but used to be heavily involved at one time. :)

Cheers

Mike

[MattS]

Steve, and er Steve.

This might be a little detailed for the beginners forum...Personally I would refer beginners to the current advice - 12 to 24 hours prior to diving after flying a pressurised aircraft.

DCI is not an exact science...you know that. The tables are a gross approximation of physiology...you know that. There is a well known example on the 88s where an instant ascent from A/1, followed by an instant descent back to A/1 leaves you on B/1, such are the intricacies of rounding errors. So please, the tables are not Gospel and in the case of the 88s, understanding of decompression physiology, both under and above water, has moved on.

As no one can guarantee to tell you exactly what will or will not cause a bend, what is under consideration is the risk of developing DCI. The risk is subject to various factors, of which tables only consider 3 (gas, time and pressure). It is incorrect to say that flying prior to diving is not an issue providing tables are adhered to.

The following AFAIK/AIUI.

From the dissolved gas point of view time at altitude will result in offgassing of PN2. However the reduction in pressure also results in a reduction in PO2. The FAA/CAA limit for pressurised cabins is an ambient equivalent to 8000ft above sea level (about 720mb). Providing my math is correct, that means you could be breathing a PPO as low as 0.15bar - below what is considered the safe surface PPO for trimix!

The body is slowly starved of Oxygen at a cellular level (hypoxia), altering metabolism and blood chemistry (in ways I hardly understand). Circulation is affected by the reduction of pressure on the heart. Immune system and clotting responses are altered adversely - both by the lack of oxygen, and the lack of water which results from breathing conditioned air. Hydrating during the flight is not 100% effective as the bodies ability to absorb water is reduced by the cellular stress that is occurring. Sitting down watching the in-flight movie this will not cause a problem. Try some extended heavy exercise after 10 hours of long haul, and you WILL develop obviously symptomatic altitude sickness (fatigue, nausea, difficulty breathing, hypercapnia).

The physiological stress caused by pressurised flight seeks to overwhelm the safety margin of the decompression model. The longer the flight and the lower the air pressure in the cabin, the more likely an 'unearned' bend becomes. Lack of general fitness no doubt predisposing to problems.

Military HALO jumpers prebreathe 100% oxygen for a fairly lengthy period prior to the jump in order to 'recover' from temporary hypoxia caused by the flight. There are also physical fitness requirements to be met prior to training and for maintaining flight status. It also strikes me that the military are not constrained to the geographical limitations of commercial airports and cheap flights. So can reduce altitude related DCI risk considerably by operating from a location as close as possible to the target zone.

Really not sure whether micro-bubbles are a significant issue. Should they be, a scuba dive is unlikely to crush them into non-existence. You need considerable pressure to break the surface tension holding the bubble together. All bubbles that are present are exposed to the full PPN/PPHe of the breathing gas, and hence subject to growth on ascent. As far as I know DVT is more dependant on the cardiovascular responses that pressurised flight causes. The immune system response that DVT causes are somewhat similar to DCI - make of that what you will.

You may personally not feel like diving after a flight, but that doesn't mean to say you can't.Personally I would regard the stress/fatigue level as an indication of (lack of) fitness to dive. 'Not feeling like diving' indicates a pre-disposition to DCI in a way the decompression models never envisaged.

Perhaps the big danger here is to assume that because you were fine after a brief hop across the Med, you will also be fine after a much longer flight. Reach for the magic coin, heads or tales!

[Steve in Sharm]

Steve, and er Steve.

This might be a little detailed for the beginners forum...Personally I would refer beginners to the current advice - 12 to 24 hours prior to diving after flying a pressurised aircraft.

DCI is not an exact science...you know that. The tables are a gross approximation of physiology...you know that. There is a well known example on the 88s where an instant ascent from A/1, followed by an instant descent back to A/1 leaves you on B/1, such are the intricacies of rounding errors. So please, the tables are not Gospel and in the case of the 88s, understanding of decompression physiology, both under and above water, has moved on.

As no one can guarantee to tell you exactly what will or will not cause a bend, what is under consideration is the risk of developing DCI. The risk is subject to various factors, of which tables only consider 3 (gas, time and pressure). It is incorrect to say that flying prior to diving is not an issue providing tables are adhered to.

The following AFAIK/AIUI.

From the dissolved gas point of view time at altitude will result in offgassing of PN2. However the reduction in pressure also results in a reduction in PO2. The FAA/CAA limit for pressurised cabins is an ambient equivalent to 8000ft above sea level (about 720mb). Providing my math is correct, that means you could be breathing a PPO as low as 0.15bar - below what is considered the safe surface PPO for trimix!

The body is slowly starved of Oxygen at a cellular level (hypoxia), altering metabolism and blood chemistry (in ways I hardly understand). Circulation is affected by the reduction of pressure on the heart. Immune system and clotting responses are altered adversely - both by the lack of oxygen, and the lack of water which results from breathing conditioned air. Hydrating during the flight is not 100% effective as the bodies ability to absorb water is reduced by the cellular stress that is occurring. Sitting down watching the in-flight movie this will not cause a problem. Try some extended heavy exercise after 10 hours of long haul, and you WILL develop obviously symptomatic altitude sickness (fatigue, nausea, difficulty breathing, hypercapnia).

The physiological stress caused by pressurised flight seeks to overwhelm the safety margin of the decompression model. The longer the flight and the lower the air pressure in the cabin, the more likely an 'unearned' bend becomes. Lack of general fitness no doubt predisposing to problems.

Military HALO jumpers prebreathe 100% oxygen for a fairly lengthy period prior to the jump in order to 'recover' from temporary hypoxia caused by the flight. There are also physical fitness requirements to be met prior to training and for maintaining flight status. It also strikes me that the military are not constrained to the geographical limitations of commercial airports and cheap flights. So can reduce altitude related DCI risk considerably by operating from a location as close as possible to the target zone.

Really not sure whether micro-bubbles are a significant issue. Should they be, a scuba dive is unlikely to crush them into non-existence. You need considerable pressure to break the surface tension holding the bubble together. All bubbles that are present are exposed to the full PPN/PPHe of the breathing gas, and hence subject to growth on ascent. As far as I know DVT is more dependant on the cardiovascular responses that pressurised flight causes. The immune system response that DVT causes are somewhat similar to DCI - make of that what you will.

Personally I would regard the stress/fatigue level as an indication of (lack of) fitness to dive. 'Not feeling like diving' indicates a pre-disposition to DCI in a way the decompression models never envisaged.

Perhaps the big danger here is to assume that because you were fine after a brief hop across the Med, you will also be fine after a much longer flight. Reach for the magic coin, heads or tales!

Er, OK,

So Mr BSAC is right, and I'm wrong.....

The fact that I, and a load of my mates have jumped out of hercy birds (sorry, C130 to you) with open circuit scuba etc etc are wrong...

just shut up, is all I can say (unless you can say we have missed each other during our working lives).

I and my friends ( who are all/where ex military) will continue to do what you claim to be impossible!!!!!! If you are correct why, may I ask are PADI now offering some sort of "Helicopter diver" speciality?

see ya!!!!!!!!!!!!!

[Ian@1904]

The only reason not to dive right after flying is dehydration. But then you should never let youself dehydrate on a plane for a host of other reasons.
Yup. Deep vein thombosis is a pain in the belly. That where they injections go in. :eek:

[MattS]

Er, OK,

So Mr BSAC is right, and I'm wrong.....I have no idea who Mr BSAC is Steve. I would expect the BSAC to be quoteing the best advice it could get. DAN currently quote 24 hrs and admit it is conservative.

The fact that I, and a load of my mates have jumped out of hercy birds (sorry, C130 to you) with open circuit scuba etc etc are wrong...

just shut up, is all I can say (unless you can say we have missed each other during our working lives).

I and my friends ( who are all/where ex military) will continue to do what you claim to be impossible!!!!!!Just because you say I claimed it is impossible does not mean I did in fact claim it was impossible. Read it again.

I claimed it was a matter of risk, which it is. I claimed that the military had procedural measures in place to mitigate those risks, which they do. I claimed that civilians may not be subject to such mandatory risk mitigation, which they are not.

If you are correct why, may I ask are PADI now offering some sort of "Helicopter diver" speciality?What is the maximum altitude and duration of a helicopter flight Steve? There is your answer.

see ya!!!!!!!!!!!!!Hopefully not!

[Steve in Sharm]

What is the maximum altitude and duration of a helicopter flight Steve? There is your answer.


Last one I did was 1 1/2 hours! Dont forget that the helicopter is also un-pressurised, unlike commercial jet aircraft - which would make the relevant altitude (see drop in ATA) probably more than the airliner, which, in theory makes it even more risky!!.

Procedures! Mmmm, wear green, smell of beer - sounds about right :rolleyes:


Now this is all getting silly, why dont the "boffins" just admit that there is no hard and fast rule as to flying after diving! Its purely down to:

A. How the diver feels.
B. Did he/she keep themselves hydrated during the flight.
C. Can he/she find his/her luggage fast enough to actually get in the water that day.

If the answers to these are good then there is nothing to stop anyone going for a dive asap, as Steve Pearson and the 88 tables show quite clearly.

Regards

[Janos]

Now this is all getting silly, why dont the "boffins" just admit that there is no hard and fast rule as to flying after diving! Its purely down to:

A. How the diver feels.
B. Did he/she keep themselves hydrated during the flight.
C. Can he/she find his/her luggage fast enough to actually get in the water that day.

Not forgetting:

D. What the acceptable risk of a bend is.

I forget what the incidence of bends is during submarine escape training at the SETT, but certainly my club have hd weekends sessions cancelled because there was a major incident earlier in the week.


If the answers to these are good then there is nothing to stop anyone going for a dive asap, as Steve Pearson and the 88 tables show quite clearly.

Again, I can't remember the details, but weren't BSAC tables originally invented because the military ones then in use were too aggressive?

Personally I would be reasonably happy diving a gentle dive a few hours after landing. However in practice this doesn't happen as normally after a flight I am either:

a) Still drunk
b) Hungover.

Janos

Janos