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wayne2

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:confused:

All of my formal dive training has preached no flying after diving, for some period of time. Some divers use a dive-computer and many others simply use a rule of thumb like; no flying within 12 to 24 hours after diving. I don't remember any mention of different flight altitudes above sea level being a factor.

Is there any correlation to flying @ low altitudes such as 500'ASL to 1000'ASL and below as apposed to flying commercial aircraft that may have cabin pressures in excess of 5000'ASL.

My question is for any Doctors out there that may be able to clear up some misconceptions with regards to this subject. What are the hard facts and rules on this subject? Would you consider it safe for divers to fly @ lower altitudes within a few hours of diving?


Thanks.
 
Commercial airliners have cabins pressurized to 8000 ft.

The rules for flying after diving apply to flights above 800 ft (almost all flights) or traveling through elevations above 800 ft.
 
You would probably get a more thorough answer in either the Dive Medicine or Dr. Deco parts of the forum.

Walter is right, there is no such thing as a "lower altitude" flight as anything over 1000ft is considered "altitude" and all comercial airliners are pressurized to 8000ft anyway. As for flying at 500-1000', I'm not sure when that would even be a possibility since even small private planes typically fly higher than that. In what context are these flights supposed to be occuring?

The simplest thing is to simply plan your diving so that you have 24hrs surface interval before flying. The reason for this is that 24hrs is the theoretical time after which all the excess N2 should be out of your system. To go up in a plane would lower the outside pressure and would amount to the same as ascending too fast from depth, result in the possibility of taking a DCS hit in the plane.

Welcome to the boards.
 
Other than a few small island hopper flights, airplanes fly at altitudes much higher than 1000ft.

Flying after diving was the subject of a special conference last year. The general gist of the recommendations is that 12 to 18 hour surface interval is recommended following recreational scuba diving. Err toward the longer end of that range when you have done multiple dives over multiple days.

Diving involving staged decompression stops requires longer surface interval.
 
My rule of thumb is a minimum of 18 hours and no deep dives (100 ft.+) the last day.
 
The NOAA manual has tables for flying at varoius altitudes after diving
 
wayne2 once bubbled...
:confused:

All of my formal dive training has preached no flying after diving, for some period of time. Some divers use a dive-computer and many others simply use a rule of thumb like; no flying within 12 to 24 hours after diving. I don't remember any mention of different flight altitudes above sea level being a factor.

Is there any correlation to flying @ low altitudes such as 500'ASL to 1000'ASL and below as apposed to flying commercial aircraft that may have cabin pressures in excess of 5000'ASL.

My question is for any Doctors out there that may be able to clear up some misconceptions with regards to this subject. What are the hard facts and rules on this subject? Would you consider it safe for divers to fly @ lower altitudes within a few hours of diving?


Thanks.

This assumes no formal 02 decompression and diver just does no stop limit, NSL, dives.

Yes, but it depends on the duration and depth of previous dives, and surface interval time, SIT, between previous dives.

A bit more detail in diving training curricula may be helpful to divers as its common to take small non-pressured aircraft to a major airport, and this entails lower altitudes.

Another poster mentioned the FAD table in the NOAA manual. The FAD chart is taken from the 2000 USN Diving Manual and can serve as a more aggressive guide beyond the simple 12h or 24h FAD SIT rule [or its recent compromise, a midpoint of 18 hours]. You must know that bulk of the chart is an extrapolation from very few data points [ a personal communication with DAN researcher who did the table.] It measures your inert gas exposure as inert gas groups in the USN Air tables and gives a SIT before ascent for various altitudes.

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

By 'safe' a certain degree of risk is taken for flying before the 24 hour period: the sooner the ascent after a dive, the higher the ASL altitude, the higher the risk for DCI. Recent data has reduces the FAD SIT to 12 hours, but in multiday dives to maximum exposure on NSL [3-6 dives a day to table limits], a 24 hours SIT is still recommended.

The rule you mention is for flying in commercial planes pressurized at 8000’ ASL ~ 0.7 ATA

The good news is that most divers suffered joint bends after a short FAD interval.

The bad news, is that diver in flight has to suffer with the discomfort until landing, but this can be mitigated if not treated in flight by 100% 02. The longer joint bends are left untreated, the more possible one may suffer from dysbaric osteonecrosis later on in life.

In a diving analogy, a subject at "0' ASL = 1 ATA" taken to higher altitude is like going shallower [flying] after a saturation dive [your surface time without diving], if ascent is rapid and high, inert gases in tissues may go from dissolved to bubble phase and cause DCI even without diving or in bubble theory, feed existing micronuclei into further growth. This is a common problem for pilots ejecting from planes or in sudden cabin depressurization. A solution is to desaturate tissues from inert gases by pre-breathing 100% 02 before flight, and Dr. Deco has excellent discussions on this scattered throughout this website.

After diving, there is an increase in inert gas tension depending on the depth and duration of a dive. NSL tissue surfacing tensions are calculated so that for most people, on surfacing to 1 ATA, tissue gas tensions are low enough to keep gases dissolved rather than in the bubble phase, note people may bubble more than others. If the diver surfaces at a lower ambient pressure, such as commonly taught in diving at altitude without sufficient acclimatization, then different mechanisms are in order, and corrections are needed to the tables.

The recreational FAD SIT is based on few studies, expert judgment and epidemiological review. Because the data is controversial, continued research in refining the optimal interval is ongoing. Its very possible to fly substantially before the 12 hour limit, but there is little data to make such a recommendation to the general diving population.

For those willing to be more aggressive, general guidance can be had from the USN – NOAA FAD table. Most dive computer algorithms take their cue from the UHMS recommendations, the USN FAD table, and proprietary rules of thumb such as in the SUUNTO Vyper, which increase the FAD SIT to past 30 hours.

Aggressive models use Buhlmann's algorithm to set a flight as the end point of a dive: it calculates a SIT based on an inert gas desaturation rate at 1ATA such that a diver can ‘surface’ at 0.5 ATA without troubles [ with 8000' ASL ~ 0.7ATA the differences are margins of safety]. These algorithms are especially aggressive when part of formal 02 decompression, it literally can takes a diver into altitude immediately.


Take Home Message:

Know that a FAD USN table exists to give you the range of FAD SIT possibilities

Single Rule of Thumb:
Target flights ~ 18-24 hours after your last dive. Avoid flying before 12 hours FAD SIT. A > 24 h FAD SIT duration is ideal as possible.
 
I was particularly interested in this as a diver and a pilot. Small planes (Cessna's/Pipers and such) often fly at 500-1000 ft. over water.

I live on an island, with another island 60 miles away. Flying there for the day to dive would be great (I wouldn't as I am the pilot - but my friends would like to).

So - I was wondering - is diving and then flying to an altitude of 1000 ft. not really the same as executing an altitude dive at 1000 ft (where we can find many lakes etc., have tables for and do often???).

Comments very welcome - as I have no idea! :D
 
I was particularly interested in this as a diver and a pilot. Small planes (Cessna's/Pipers and such) often fly at 500-1000 ft. over water.

I live on an island, with another island 60 miles away. Flying there for the day to dive would be great (I wouldn't as I am the pilot - but my friends would like to).

So - I was wondering - is diving and then flying to an altitude of 1000 ft. not really the same as executing an altitude dive at 1000 ft (where we can find many lakes etc., have tables for and do often???).

Comments very welcome - as I have no idea! :D

Yes. At altitude, diving is broken into a diver who is 1, acclimatized and 2, one who is not.

For #1, the reduction in surfacing pressure is compensated by the altitude diving protocols since decompression is based on gradual pressure reduction, not reduced depth.

For #2, in bubble theory, ascends cause offgassing of N2 proportionate to the reduced altitude since diver is saturated with N2 ASL. A large non-gradual ascent can excite bubble seeds to grow, and in this state increases the risk of large bubbles forming sooner by diving, and causing DCI.

When you dive from ASL then ascend to 1000', you are going from N2 saturated at 1 ATA and later to depth. When saturated, whatever bubble seeds that exists are in an unexcited state. Bubbles that potentially form are caused mostly by the dive.

If I surmise what you wish to do, divers from Grand Cayman may wish to dive the sister islands and return. If you maintain the lowest altitude possible and do at least 3 hours SIT before flying to reach a PADI RDP Group A, the risk should be minimal, but there is a risk nevertheless if you fly apart from the FAD protocols described earlier. You could accelerate offgassing by using surface or inwater 02, or reduce N2 loads per dive by using nitrox.
 
Awesome info - thanks! I think a test will be in order with some of my instructor friends at some point - we'll keep it shallow, EAN36 and wait for a good 3 hours before coming backand go from there.
Thanks for the great info!
A.
 
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