Max Altitude after Diving (Scuba)
 

Yes, me again!

I wonder if there is anyone on the forum who can answer a very specific question:

What would be an established altitude maximum for LOW LEVEL flights (500 ft, 1000 ft, 2000 ft,...) after diving. All I can find on the net deals with rest-times before airline travelling, military test, etc.
All these texts deal with cabin pressure alt of 5000 ft and more (8000 ft standard airline cabin pressure). But nothing on safe altitudes for flights IMMEDIATE after diving or few hours (1-4 hrs) rest-time.

Case at hand: I had/have to fly a set of divers to a search mission. Immersion times of 1 hour / 4 X day for a total of about 4 hrs - max depth about 75 ft or 20 m at any time possible.

They requested transport after diving at no more than 500 ft MSL (the search is done at sea level). Problem at hand is that I have to refuel at a location where I might scratch hills if I maintain 500 ft all the way....
Total flight time is about 2hrs.

Anyone flying with rescue-equipments that use divers?

I appreciate your help!

3top

:cool:

PS: As it is a medical question I will post a copy over at "medical", however there may people working with helicopters in exactly this environment.....

2000 ft would be no problem at all.

Huron Topp:

Thanks for the opinion - I though so too (actually I would even go to 3000ft, but for this case 1000 would do fine ...), when I was argueing with the divers (having been a volunteer rescue diver in Austria - cold lakes, at 400 to 1000m elevation, etc.) However they tell me to shut up, they are "professionals". Well I`ll fly them low then.
But I would like to have some proof - any reference from a rescue org. manual or so to show them that helicopter pilots can be "pro" in a different field too, besides you really never know when you have to fly these guys. Any idea?

3top

I'll see if any of my manuals give a "definate" height. This is an excellent link though.
http://www.vnh.org/FSManual/01/09Bub...edDisease.html

Our maximum altitude for a 'bent' diver is 1000' msl and frankly the lower the better en route to the hyperbaric chamber. I can understand why your professional divers want to stay low - any chance of the nitrogen expanding in the tissues (especially brain and nerve tissues) should be minimised. We have a Navy diver on exchange with us so I will ask his opinion and see what the RN position is on it.

Would it help if they were to breathe oxygen en-route if you have to climb?

4 hours total time is one hell of a time to build up Nitrogen in the body.
Ask them how long they plan to take for decompression stops, this should give you an idea about their saturation. The longer the more saturated.

I teach diving for fun, BS-AC, and we recommend no one flies or drives up high hills until at least a tissue code 'B'. That is at least 4 hours from your last dive (surfacing a 'G' with a small deco stop).

When I was in Saudi there were many cases where divers left Jeddah & drove into the mountains, 2-5,000ft, suffered from bad decompression illness and had to be rushed to the hyperbaric chamber.

I fully agree with crab, the lower the better.

Sycamore has a point, oxygen would help draw the Nitrogen out but if they are greatly saturated they could still suffer.

Once you have suffered from Decompression Illness, you are more susceptible to it, I would check to see if any have suffered before.

As you pointed out, they have said they are 'professionals' so tell them your planned height and get them to sign a waiver against any costs or damages resulting from decompression illness.

On the positive side, seeing as you said they were only going to 20m maximum, they might be diving on Nitrox, higher percentages of oxygen, so less Nitrogen to be absorbed, this still puts Nitrogen in the body though.

Good Luck

FB

Thanks guys!

Great info coming. I found finally a table that gives 0 hours waiting times according to requested flight altitude versus Rest Nitrogen Letters. I just have one hell of a problem loading the chart (some trouble with power point here...).

Of course I agree with "as low as possible", but with 20m and 1000 ft there should really be no problem - If I remember right at 1000ft and the highest Letter - L - it was off the total immersion time table as it approached 400 min allowable or so. I will certainly check this out and post it when I am done.

Flying Boat:
They "seem" to be pro´s, on the other hand they are both overweight and at lunchtime they would stuff themselves with greasy chicken and fried rice!
I didn´t dive for a long time, but I do remember that we were urged to "refrain" from heavy food before diving.
They use regular air.

Crab:
As you said your max alt is 1000 for a "bent" diver, so the guy is already in trouble but you still can go to 1000.
My clients are not supposed to get themselves in deco troubles in the first place - the search is nothing for live or death, but scientific.


Keep it coming guys!

3top


:cool:

G'day 3top,

You might be interested in the table below? Although it was first produced in 1989 - shortly before the company in question went bankrupt. The company was the National Safety Council of australia - the NSCA.

They were a very large rescue orginasition in Australia who supplied fixed wing Pararescue, helicopter rescue, and hyperbaric retrivals.

The Parra-Jumpers - PJ's - of the Pararescue teams jumped with LAR-V diving equipment and had to train whilst on immediate standby with SCUBA as well as the LAR-V O2 set. The NSCA medical officers (trained in hyperbaric medcine) prepared the table so that 'on-shift' training could be conducted safely. The table was established using a mixture of Canadian and RN tables.

As an ex-RN Clearance Diver, and PJ, I found the company very proffesional. The fact that they employed diving doctors who were also trained as PJ's, and that the senior diving instructor was an ex RAN chief petty officer Clearance Diver, I believe, sums up the standard they operated to.

NSCA OPERATIONAL PROCEDURE FLYING AND DIVING

1. Allowable diving whilst maintaining immediate availability for operational flying.

a - LAR-V No Limit
b - Air diving 3meters 60minutes
6meters 30minutes
9meters 15minutes

2. Minimum required delay before flying or travelling to altitude after diving.

DIVING ACTIVITY UP TO 1000FT UP TO 3000FT

Up to 50% no deco
< 30m Nil Nil

Up to no deco limit
< 30m Nil 2Hrs

Repetitive dives
Deco diving
< 50m 2hrs 12Hrs

NOTE: Although we followed this table without incident - and indeed, that it extends to greater altitudes and depths, it was reasonably new. Due to the demise of the NSCA a long term study of it's effectivness wasn't undertaken, and should you ellect to use it I would suggest that you seek a current diving doctors opinion.

Crusty Scab! ....what a name!

Thanks for all the advice! Just before the flight I did, I called a divemaster, however as he teaches "tourist"-diving he confirmed the extra careful way and prohibits flying for 12 hours anyway. Period. ....neverminf that coming back to the city they all climb above 500ft. .....but I could not fly there, go and figure.

AFTER the flight (to avoid any "professional"/professional discussions before the flight, I managed to stay below 500ft with a short excursion to 700 - less then 2 minutes...), I gave the divers (who according to them use USNavy tables....) the following list:

http://www.ndc.noaa.gov/pdfs/AscentToAltitudeTable.pdf

As it comes from NOAA it is some "official" table.
The rest of all the advice is very good and for me confirming my own opinion, but as long as it is not official in some way it proofs nothing to "professionals" (besides I do respect their request, as it is them who dive and it is their lives at stake...).
These two guys where out of the water for about 4 hours before getting on the helicopter and according to one off them where at repetetive letter J when completing the dives. The table mentions 1000ft as the first altitude level. I guess below that they will not consider it altitude at all...
This table pretty much confirms all the rest in here!

On the NOAA website one can find everything one needs to know as a pilot about diving+flying.

Thanks again,

3top
:cool:

Deco-chamber evac question
 

Quick question for the medevac types;

When evacuating a diver to a recompression chamber for treatment, what are the altitude restrictions, if any, so as not to aggravate the condition?

Many thanks

I remember a wessex from Chivenor made the news years back with a potential bends case by flying under the Tamar bridge on the way to Bovisands, utter bollocks :=

And before any mil types jump on that.... My info came from the actual doctor from that establishment who assured me that relative low level was preferable, but that meant flight levels :ugh:

I've done it in the past (mil) and was told "as low as possible". I'm no expert so I did what I was told.;)

Max 500 feet if possible, quoted by the BSAC, several years ago..
a diver was flown from Stornoway to the chamber in Aberdeen via the Pentland Firth back in the 1980s by a Lossiemouth helicopter.
Did Bristows work out an overland route through the glens when they started with the CG in SYY?

Coming from that part if the country, I'd love to know where the diver was diving in order to warrant that particular route to Bovisand :suspect:

I was told, as part of a brief by the operators of a decompression chamber somewhere close to the Sulu Sea, that as air pressure decreases with height the lower the better, in an attempt to keep the gas bubbles as small as possible en route to the chamber.

What a load of tosh

Divers dive in water. Helicopters fly in air. Different density. The pressure in water doubles in 33 feet but the pressure in air takes 5500 metres to drop by half.

Depressurisation in a fixed wing to 8000 feet might be an issue but flying at 500 instead of 2000 feet is just inexcusable. Might even be illegal.

What is important is early pressurisation and we now have portable chambers we can use in helicopters so the diver can be pressurised during transfer.

Well I don't know about flying under bridges but unless there's a fuel burn issue with a jet that can pressurize then the maximum altitude is 1000ft.
And homon if the guy is already bent to the point of a medevac flight then use your head, the pressure is already too low on the surface let alone at 2000ft.

Was diving in Micronesia along time ago an an Aussie diver got bent pretty bad and they flew him home in a Learjet at 1000 ft.
Thank god for DAN!

Sorry homonculus you are wrong please check before you say it is a load of tosh.

Not the issue here homonculus, deco-chamber equipped heli units not available, under any circumstance.

This problem involves evacuating live-aboard divers in remote parts of Indonesia, possibly hours away, to a facility that can deal with life-threateneing recompression issues.

Once bent, what pilot guidelines do we follow?

I once talked about this with a Hyperbaric Medicine specialist. He said there were many factors at play and to consider in regard to the bends. However, the broadest rule was to stay low in non-pressurised aircraft.

TK

(edit to correct medical field)