Low Altitude Flying after diving (same day)

[DandyDon]

Thanks, Bruce. Need to look for that book.

BTW, you clicked the Female designator on your Profile, which is fine. Just wondered if you were really Lady Bruce...?

 

[KLD]

Hi Dandy Don,

Got emails to check in on SB, and with a few days off,
picked up on some script.

No, I didn't have a sex change, just picked up SB using
my girlfriend's monicker. Yea, too lazy to change the cookies
in my computer for SB.

Good to hear from an Amarillo/Lubbock "local" and maybe
catch you out at Santa Rosa later on low altitude prolonged
tests with C & C Team -- 150 fsw exposures on heliox RBs.

Very best to you Texans (have 5 on C & C) who
dive the high desert, whether 1st or 6th generation,
or transplants (like me, since we also operate out of Corpus
Christi Naval Air Station, I have a condo down there, plus
do a bunch of tech training for NAUI down at American
Diving/Salvage on South Padre Island). Plus Houston
too.

Take care,

BW

Thanks, Bruce. Need to look for that book.

BTW, you clicked the Female designator on your Profile, which is fine. Just wondered if you were really Lady Bruce...?

 

[chrisch]

The British Sub Aqua Club (BSAC) tables include an altitude calculator that lets you work out how high you can travel after the various dive profiles. I've never used them but the principle suggests to me that you can go to altitude after diving subject to gas loading. This is pretty much as per BW et al have said.
My computer manual suggests 12 hrs min and 24 if performing staged deco. The computer itself says I can fly after 24 hrs. I dived at the weekend but as yet, remain unable to fly. Perhaps I should ask for a refund?
Chris.

 

[DennisW]

As Don said, the NOAA dive manual has some very good information on flying after diving. The problem with an airliner is the cabin altitude which is normally set to 8000 ft.

I can tell you that a loss of pressure at above 30,000 ft can cause anyone in the plane to have a problem with DCS, not just someone who has been diving. The differential in pressure if it is a severe loss in pressure is great enough that anyone on the plane may need to get a chamber ride.

 

[miketsp]

There's a nice semi-fictional story of an explosive decompression in an airliner on:
http://home.comcast.net/~skydrifter/horror.htm

Really interesting reading....

 

[fdog]

It's not flying on the same day, but...the next day...

While in college I worked as a scuba Instructor. The University I worked at also had a chamber with all the toys.

There were quite a few weekends when I would dive several intermediate depth dives on Saturday, and go skydiving on Sunday morning. Altitudes for the skydives were 12,000'. Depths for the dives were around 50-60 fsw.

Not a single niggle. Actually, we did a few scans with the doppler, and found nothing. Not conclusive by any means, but it's data.

All the best, James

 

[mempilot]

As Don said, the NOAA dive manual has some very good information on flying after diving. The problem with an airliner is the cabin altitude which is normally set to 8000 ft.

I can tell you that a loss of pressure at above 30,000 ft can cause anyone in the plane to have a problem with DCS, not just someone who has been diving. The differential in pressure if it is a severe loss in pressure is great enough that anyone on the plane may need to get a chamber ride.

I'm assuming you mean't anyone that absorbed an inert gas under pressure prior to flying would need a chamber ride after a flight that experienced rapid decompression. Under normal 1ATA or less, inert gasses aren't forced into the blood stream. A 'pressurized' cabin is still less than 1ATA. The only way to get more than 1ATA in an a/c is to pressurize it while it's still on the ground and since the outflow valves are open by squat switches on the gear, this is impossible unless you override them by putting the system in a water 'ditch' mode. Upon sudden decompression of the cabin, there is trauma, but not in the form of DCS based on what I've been taught and experienced. You'll have ruptured capillaries in the sinus areas which will cause bleeding from the nose, ears, and bloodshot eyes. Short of a structural failure, most decompression of an a/c cabin happens relatively slowly via leakage after the air packs fail to provide positive pressure or the controller fails. Outflow valves fail closed and there are multiple valves. The pressure equalizes through through door seals at this point and can take a while.

Commercial aircraft restrict maximum cabin altitude to 8000. Effects of hypoxia show themselves after short periods of time above 10000. Depending on the the maximum differential pressure the pressurization system can hold and the cruise altitude the aircraft is flying at, the actual cabin pressure can often be quite a bit less than 8000. I often note cabin pressure altitudes in the 4000 to 6000 range in the upper 20k cruise altitudes. On longer flights at higher altitudes, the cabin pressure will peak at 8000.

That all being said, a small unpressurized airplane flying at low level (<3000) doesn't have much a pressure differential from sea level. That doesn't mean DCS isn't a factor. It would depend on RN left in your system. Someone experiencing problems after waiting even 6 hours with a flight to 1700' would indicate they where at the edge of DCS hit anyway. I often fly my personal a/c within 12 hours after diving but keep the altitude low (<3000). But I didn't dive the edge of the tables either. I never fly after a decompression dive until my PG is C or less.

 

[flw]

I've often flown after about 16 hours from multi-day deep diving weeks, never had a hint of a problem, however I do stick to high He gas mixes in a RB, and if there was any sign of trouble before I'd wait for the (14 hour long) ferry home instead. The flights to here are all Logan air/British Airways, so the chances of them actually taking off when scheduled are slim anyway, and I'm likely trapped at the airport for an extra couple of hours increasing the time, and the flights are short
I got a bit 'niggled' at the weekend, and definitely woudn't have chanced it then. The problem really comes is that if you are bent before you get on the flight, and it becomes more apparant during it, requiring an unscheduled landing, because you're outside the acccepted guidelines, it's unilkely your insurance would cover you for the costs involved

 

[Charlie99]

Under normal 1ATA or less, inert gasses aren't forced into the blood stream. .

Wrong! There is nothing magic about 1ata in regards to dissolved gases in the blood. Given sufficient time, your blood and tissues will saturate to the ambient inert gas partial pressure. At sea level, this is about 0.75ata (the approx 0.06ata water vapor in your lungs makes it less than 0.79ata ppN2)

Altitude DCS in people not exposed to more than 1ata has been observed ever since planes (such as WWII bombers) have been able to achieve high altitudes.

 

[mempilot]

Wrong! There is nothing magic about 1ata in regards to dissolved gases in the blood. Given sufficient time, your blood and tissues will saturate to the ambient inert gas partial pressure. At sea level, this is about 0.75ata (the approx 0.06ata water vapor in your lungs makes it less than 0.79ata ppN2)

Altitude DCS in people not exposed to more than 1ata has been observed ever since planes (such as WWII bombers) have been able to achieve high altitudes.

I'll give you that, but commercial and private planes aren't subjected to the altitudes required to cause the problems described. I've been through high altitude training with the Air Force and various other agencies. There is no mention of DCS caused by decompression of the cabin in a way comparible to diving. A decompression at cruise altitude isn't going to cause DCS in an acute way that surfacing from even 33' would. No argument on your example and flying at extreme altitudes where pressure suits are required.