Stupidest question ever

[junior diver]

I don't think I've posted this in the right place but this seemed the best place to put it. If we have to do deco coming up from a long and/or deep dive. We have to do this the first time we go on a plane? A couple of years and a couple of thousand feet down from where the plane is going to go must count as a really deep, long dive.

 

[Wendy]

I don't understand your question?

 

[Don Burke]

I don't think I've posted this in the right place but this seemed the best place to put it. If we have to do deco coming up from a long and/or deep dive. We have to do this the first time we go on a plane? A couple of years and a couple of thousand feet down from where the plane is going to go must count as a really deep, long dive.

Actually, going from sea level to complete vacuum is the same change in ATM as going from fully saturated at 33 feet to the surface.

Since commercial planes generally do not go above 40,000 feet, oxygen deprivation is a bigger issue. Planes are pressurized to something around eight to ten thousand feet to prevent all of this. Aircrews expecting to be in an unpressurized portion of a plane will usually prebreathe oxygen for a few hours before a flight.

Now, if you are talking about coming off a dive with significant amounts of gas dissolved in your tissues and jumping on a plane, some steps are in order.

 

[Uncle Pug]

The whole air column only weighs as much as 33 feet of sea water.

When you go from the 1 atmosphere pressure of sea level to 8000' (cabin pressurize in a commercial airliner) you are not reducing your ambient pressure as much as ascending from 33fsw to the surface.

Even if you were riding your lawn chair attached to multiple helium weather balloons to flightlevel 33 you would still only experience a portion of the depressurization that a diver experiences in going from 33fsw to the surface.

So... even though you may spend a long time at *depth* here on the surface of the earth... your *decompression obligation* is not so great that you can't hook up the old lawn chair and go for a ride.

 

[junior diver]

K, thanks.

 

[Seabear70]

Ok, think of it this way...

You have something like 300 miles of atmosphere over you...

All of that combined produces a pressure of roughly 14.7psia on your body.

However, each cubic foot of seawater weighs in at 64 pounds Or, .444 psig.

If we look at 300 miles however, we get 9.280303030303030303030303030303e-6 psig per foot of change. Not much at all.

So, yes, there is a change in pressure in a plane at 20-30,000 feet, and it can affect you, but it's not as extreme as with water

 

[Seabear70]

Another thing to consider is that when dealing with pressure, the percentage of change is as important as the psi.

 

[Mako Mark]

I think something to consider is tha rate at which the pressure changes.

We know that a rapid ascent from depths as little as 33 ft can cause type 3 decompression (shock decompression illness). The possibility of a plane going through explosive decompression such as when a door blows out, or a fighter pilot ejects could potentially induce symptoms.

I heard (a possible urban legend) that dcs is in fact a common injury to pilots that eject at high altitude, perhaps some of the flyboys on the board could cinfirm this.

 

[Seabear70]

I think something to consider is tha rate at which the pressure changes.

We know that a rapid ascent from depths as little as 33 ft can cause type 3 decompression (shock decompression illness). The possibility of a plane going through explosive decompression such as when a door blows out, or a fighter pilot ejects could potentially induce symptoms.

I heard (a possible urban legend) that dcs is in fact a common injury to pilots that eject at high altitude, perhaps some of the flyboys on the board could cinfirm this.

This was discussed at my dive school, and yes, it can and does happen.

One extreeme example was the original space walks, One of my instructors was commenting on the fact that the news claimed they were getting "space sickness" he then proceded to tell us that no, "Those ****ers was bent!"

The owner of the dive school then approached NASA and a deal was worked out to develop the first deco tables for space walks at The Ocean Coporation in Houston, Texas.

 

[Seabear70]

BTW : it's not a stupid question, it should have been covered in your OW course though I would think. Did they talk to you about no fly times?