Flying @ 1500 ft after shallow dives

[DandyDon]

Years ago I did two 20 foot dives in a spring-fed lake then flew home at 8,000 feet, with my Deco Instructor's blessings. Honestly, you can't load much extra nitrogen at 20 feet - impossible to reach saturation, isn't it? I did buy nitrox for the dives, but that doubtfully made any difference at 20 feet. Two key factors...

1. How long after the last dive before you board the plane? It was a few hours for me.
2. A lung injury on a dive would cancel everything.

I don't know how low Coast Guard helicopters fly when they pick up an injured diver at sea, but they do it with Oxygen and a medic so that's totally different.

 

[Altamira]

I have posted this similar comment on other threads covering the same question. As a retired AF and commercial airline pilot, I would say your success very much depends on how lucky you are on your flight's ability to stay at very low altitude. I will also tell you that if an inflight emergency occurs while enroute, in most circumstances, the pilot is going to exchange airspeed for additional altitude as quickly as possible to provide more separation from the ground, and more time to resolve the emergency. Should that occur, the pilot is going to do whatever is required to save himself, the airplane, and passengers. Your lack of adequate time between diving and flying is going to be at the bottom of the pilot's list of priorities.

 

[DogDiver]

Well, I guess you will find out first hand.

 

[wnissen]

If you were treating the dive as an altitude dive at 2,000 ft., the adjusted depth would be different by at most 10 ft.

 

[bubblemonkey2]

if an inflight emergency occurs while enroute, in most circumstances, the pilot is going to exchange airspeed for additional altitude as quickly as possible

That's true and (but?) in any aircraft that lowers (e.g. ~"7000ft" / ~0.77atm) or loses (<0.77atm) cabin pressure, the ascent results in supersaturation all tissues, in all people--even those who haven't even been diving!

The atm at 30,000' is reported as ~0.3. How many non-divers have experienced DCS during rapid aircraft de-pressurization incidents?

I presume this leads to a ceiling on safe ascent rates and cabin pressures, and/or experimental pilots pre-breathing pure oxygen pre-flight to eliminate ground-level inert gas loads (correct me if I'm wrong)
Killer at 70,000 Feet | Military Aviation | Air & Space Magazine

For divers the question is: how much extra nitrogen is stuck in the body from diving, and what are its dynamics of release over time?

Buhlmann models suggest much shorter waiting periods than 24 or even 12hrs, for most types of recreational diving. The premise is that all of the "fast tissues" off-gas sooner than you can check into a public airport, and that the "slow tissues" didn't absorb enough nitrogen during recreational dive schedules to be significantly more supersaturated at flight altitudes than someone who didn't dive at all.

However if someone were to spend 24 hours straight in a saturation environment with no surface intervals, even a "shallow" one (e.g. a habitat at 10 to 20 metres, or a pressurized work shaft), then it's problems.

Nobody wants to say "3 hours" and be responsible (or sued) for DCS injuries though.

Are there any publicly available experimental studies that measured DCS incidence for divers and non-divers at various flight profiles and durations?

 

[KevinNM]

Scuba classes don’t talk about this but DCS happens in airplanes with no scuba involved. A lot of the core research was done by the Army Air Corps in WW2, because pilots and crew of bombers were getting bent.

 

[Raphus]

Scuba classes don’t talk about this but DCS happens in airplanes with no scuba involved. A lot of the core research was done by the Army Air Corps in WW2, because pilots and crew of bombers were getting bent.

This is true. Skin dcs is nearly always a problem if cabin pressure drops.
And there are mild cases of dcs even when the cabin is pressurized and the patient is a non diver.

I think there are a lot of undetected mild skin dcs cases, where the patient just thinks he has a allergic reaction or sth. Because he doenst know about dcs.

 

[Altamira]

Scuba classes don’t talk about this but DCS happens in airplanes with no scuba involved. A lot of the core research was done by the Army Air Corps in WW2, because pilots and crew of bombers were getting bent.

Most WWII fighters and bombers were not pressurized. The first U.S. aircraft in WWII to be pressurized was the B-29. My father was a P-51 pilot based in England in WWII, and told me about frequently not feeling too great after repetitive days of high altitude bomber escort missions, interspersed with rapid altitude changes during air-to-air combat, and strafing German ground targets on the return leg when fuel and ammunition permitted. I doubt he or fellow pilots had a clue about DCS or its symptoms during those missions, but they could probably check off quite a few symptoms if they had our current information about DCS. They were a tough breed of men!

 

[broncobowsher]

Well it was yesterday he was going to do it, so we should hear how it turned out. Looking back at it, they were only planned as 25' dives. He would be hard pressed to have any issues if the dives lasted 24 hours each.

 

[gajahduduk]

Well it was yesterday he was going to do it, so we should hear how it turned out. Looking back at it, they were only planned as 25' dives….

Haha. OP here, not wanting to keep y’all in suspense, but still on the road here.

I feel perfectly fine and normal.

Details: 2 freshwater Lake Michigan wreck dives. first in like 3 meters, < 30 min dive, not much to see. SI about 30 minutes. Second, about 8 meters, 45 minutes. Again limited just by what there was to see on the wreck.

15 min flight began about 2.5 hours after end of second dive. Pilot aware of situation and promised to keep altitude < 2000 feet, and didn’t let me know otherwise afterwards, but I didn’t press him for actual max.

I’ll review this thread in detail later and probably have more to say in reply. But thanks in advance for all the input.