Is it safe for me to fly? I really need to get home.

[tursiops]

Understood, but it's essentially the same thing and possible outcome if I interpret the medical professional's (@Duke Dive Medicine) response correctly?

no

 

[duke dive medicine]

Thanks for clarifying - same possible dangerous outcome, correct?

If venous gas emboli (bubbles) cross over into the arterial circulation they have the potential to produce the same severe neurological symptoms as arterial gas embolism, plus some that AGE does not typically produce like spinal cord and inner ear symptoms.

 

[duke dive medicine]

no

The pathophysiology is different, but both AGE and decompression illness caused by arterialized venous gas emboli can produce similar severe neurological symptoms.

Best regards,
DDM

 

[inquis]

you might want to run through the Navy Ascent Table and see where the Excess Nitrogen metric lands after following their guidance on various dives.

@L13 - Here are the Excess Nitrogen (EXN) percentages* after various dives to the Navy NDLs and then waiting for the minimum time they specify before an ascent of 8000 ft in each case:
D (ft) EXN ------ ---- 30 8.1% 40 5.6% 50 4.7% 60 4.6% 70 4.1% 80 4.3% 90 4.1% 100 4.5% 110 4.0% 120 5.2% 130 4.6%

From that, I conclude that flying with EXN = 10% would violate the Navy ascent guidelines.

(*) I don't know exactly how Garmin defines their Excess Nitrogen metric, but I've assumed that 0% is synonymous with the inert equilibrium pressure of 0.79 * (surface pressure - water vapor pressure). I used a vapor pressure of 1.848 fsw or 0.055708 atm, though I've seen slightly different numbers for that floating around.

 

[Pbdiver84]

IIRC, my Terric did show me off gassing, or something, on the plane.

Even though I had no more than sea level, in me.

I'll have to snap a pic next time.

Going to 8000ft pressure altitude from sea level, you should be off gassing

 

[Joneill]

If venous gas emboli (bubbles) cross over into the arterial circulation they have the potential to produce the same severe neurological symptoms as arterial gas embolism, plus some that AGE does not typically produce like spinal cord and inner ear symptoms.

Thanks - I appreciate your expert pov here.

 

[tursiops]

The pathophysiology is different, but both AGE and decompression illness caused by arterialized venous gas emboli can produce similar severe neurological symptoms.

Best regards,
DDM

I'm sorry, you seem to be trying to conflate two different kinds of gas emboli problems....(1) those caused by "lung over expansion" as in holding one's breath, typically called AGE, and (2) those caused by a shunt to get the venous bubbles into the arterial circulation....which I understand is not common, just possible. Is it not confusing -- even misleading -- to simplistically say that everything DCS or AGE, has the same symptoms and outcomes?

 

[L13]

@L13 - Here are the Excess Nitrogen (EXN) percentages* after various dives to the Navy NDLs and then waiting for the minimum time they specify before an ascent of 8000 ft in each case:
D (ft) EXN ------ ---- 30 8.1% 40 5.6% 50 4.7% 60 4.6% 70 4.1% 80 4.3% 90 4.1% 100 4.5% 110 4.0% 120 5.2% 130 4.6%

There are some odd jumps in that table.

From that, I conclude that flying with EXN = 10% would violate the Navy ascent guidelines. That's not something I'd personally do or recommend to anyone.

You have convinced me to look closer. 10% does look high given that. I just did GF's last time, not comparison to the Navy table. I thought GF's in the teens at 8k would be safe enough, now I am questioning that.

At the same time, after a week of diving I have been at 7% after 30+hrs surface interval, which is well beyond the 24 hour conventional recommendation (and I didn't get bent).

(*) I don't know exactly how Garmin defines their Excess Nitrogen metric, but I've assumed that 0% is synonymous with the inert equilibrium pressure of 0.79 * (surface pressure - water vapor pressure). I used a vapor pressure of 1.848 fsw or 0.055708 atm, though I've seen slightly different numbers for that floating around.

I'm not sure either, I haven't been able to find any real documentation. However, calculations of my dives after the fact and comparing to the Garmin % and graph, I came up with the same values you did, or at least close (I think I came up with .056 atm). The displayed value is in whole % (and I think it always rounds up), and graphs have very little resolution so it can't be determined that precisely.

I need to keep a better record of these values in the future, to tease things out better.

 

[Joneill]

I'm sorry, you seem to be trying to conflate two different kinds of gas emboli problems....(1) those caused by "lung over expansion" as in holding one's breath, typically called AGE, and (2) those caused by a shunt to get the venous bubbles into the arterial circulation....which I understand is not common, just possible. Is it not confusing -- even misleading -- to simplistically say that everything DCS or AGE, has the same symptoms and outcomes?

Sorry, but I don't see where he said that at all - he very clearly qualified his responses and answered the questions that I posed.

 

[Sevenrider860]

Look up arterial gas embolism. Yes, permanent injury can happen.

Are you assuming his flight is on a Space X rocket? AGE is not a concern.