How late is relapse possible on a flight after DCI?

[BA3]

Thanks so much, I have actually spoken to them already, and they've been great. It can just be difficult to get everything clear over the phone.

I was actually going to ask about supplementary oxygen. From what I gather it seems like there's perhaps 2 mechanisms by which flying can cause symptoms to worsen. One being bubbles expanding and causing blockages and other problems, and the other being what you've said:

There shouldn't be any bubbles after appropriate hyperbaric treatment, but with significant inflammatory damage and possible circulatory compromise, the hypoxia of altitude can lead to a recurrence of symptoms

I would guess that supplemental oxygen could maybe protect somewhat against the second mechanism, by combating that hypoxia of altitude?

For the first mechanism, would you say that 6 weeks after DCI, even if it went untreated, that the chance of any bubbles still being present would be pretty much zero?

How long bubbles hang around again seems to be a source of differing opinions, as I spoke to someone from DAN who said that after 24 hours any bubbles will be gone, and it's only the damage that remains, but also read this paper which says:

"Hills and Le Messurier (unpublished observations) followed up a diver in Adelaide using X-rays, and found that asymptomatic tissue bubbles could still be identified 22 days after his bends-provoking dive."

 

[Hoag]

As others have said, it tends to be an individual thing. A buddy of mine had a "hit" while flying after time spent in a chamber.

He was an "Aerospace Controller" in the RCAF who was being prepped for a flying assignment in the E3 AWACS. Part of his High Altitude Indoctrination (HAI) course included 2 chamber runs, but whereas divers think of chamber runs as going back down to depth, these profiles took them up to altitude. The first profile is typically from surface to the equivalent of 30,000 feet, at which point, half of the students disconnect their mask from the O2 supply. Their "buddy" holds the hose and acts as a safety monitor. the trainee them performs a questionnaire and some motor skills tests so that if/when they ever become hypoxic, they will recognize the symptoms. Once they recognize their symptoms, they reconnect and go on 100% O2 for a couple minutes to rebalance their O2 levels in their bodies. Then the ones who were "buddies" on the first run disconnect and run the tests.

The second profile takes the class from the surface to 25,000 in under 1/2 second. This is to simulate "explosive decompression".

After the training is over, you spend an additional two days at the school so that the Aero Medical Techs (AMTs) can make sure you are OK. This is where my buddy first ran into trouble. The night after he did his two "Chamber Rides", be started to show signs of DCS. He notified the on call AMT and he got to do another chamber ride, this one to treat the DCS. Everything looked good, and after a couple days he was clear to fly home. On the flight home from Winnepeg, he got bent again and they had to divert the plane and do an emergency landing. He was met at the airport by an air ambulance and they flew him at tree top level to the closest chamber which was in Toronto for another ride. Eventually, he made a full recovery and was cleared to go on to his AWACS assignment and has had no incidents since.

 

[Duke Dive Medicine]

Thanks so much, I have actually spoken to them already, and they've been great. It can just be difficult to get everything clear over the phone.

I was actually going to ask about supplementary oxygen. From what I gather it seems like there's perhaps 2 mechanisms by which flying can cause symptoms to worsen. One being bubbles expanding and causing blockages and other problems, and the other being what you've said:



I would guess that supplemental oxygen could maybe protect somewhat against the second mechanism, by combating that hypoxia of altitude?

For the first mechanism, would you say that 6 weeks after DCI, even if it went untreated, that the chance of any bubbles still being present would be pretty much zero?

How long bubbles hang around again seems to be a source of differing opinions, as I spoke to someone from DAN who said that after 24 hours any bubbles will be gone, and it's only the damage that remains, but also read this paper which says:

"Hills and Le Messurier (unpublished observations) followed up a diver in Adelaide using X-rays, and found that asymptomatic tissue bubbles could still be identified 22 days after his bends-provoking dive."

Yes, I would say the chances are pretty much zero that any bubbles are in your body at this point. Radiology is not diagnostic for DCS, though frank air/gas bubbles have been found radiographically in severe DCS. The reference in the Butler paper you linked makes mention of x-ray streaking in periarticular (joint) tissue; joints are poorly perfused so maybe that's a component, and I also think that that case is an outlier. I'd be interested to hear @Dr Simon Mitchell 's opinion.

Best regards,
DDM

 

[BA3]

I expect this question might be difficult to answer, but I’m just wondering again on the difference between the two mechanisms of flying based problems, and if there’s perhaps a distinction between the type of damage that they may do.

If the worsening of symptoms is due to hypoxia of damaged tissues, as opposed to bubbles expanding and causing blockages etc, would you say it's perhaps more likely to be a temporary worsening, and less likely to cause damage that might lead to worse long-term outcomes? Or would it be much the same?

Thanks so much for all the replies, beyond the information, which is invaluable, they also really help with feeling a bit less alone!

 

[Duke Dive Medicine]

I expect this question might be difficult to answer, but I’m just wondering again on the difference between the two mechanisms of flying based problems, and if there’s perhaps a distinction between the type of damage that they may do.

If the worsening of symptoms is due to hypoxia of damaged tissues, as opposed to bubbles expanding and causing blockages etc, would you say it's perhaps more likely to be a temporary worsening, and less likely to cause damage that might lead to worse long-term outcomes? Or would it be much the same?

Thanks so much for all the replies, beyond the information, which is invaluable, they also really help with feeling a bit less alone!

I think that would be highly individual and dependent on a variety of circumstances; a clear answer in your case would be impossible, especially via the internet. Sorry.

Best regards,
DDM

 

[BA3]

No problem at all, I thought as much!

I guess breathing supplemental oxygen should hopefully at least protect against the hypoxia of altitude, or just slightly lessen it

 

[tursiops]

PPO2 at 8000 ft is about 0.16.
Breathing 1 liter/min from a nasal cannula would bring this up to about 0.20.
At 2 liters/min (typical), you'll go up to about 24%.
The usual small ambulatory tank might last 4-6h.
On an airplane you can't use an oxygen tank, you need a portable oxygen concentrator.
UpToDate
Good luck.

 

[BA3]

Great, thanks so much. Is there also any difference with things like how tissues will uptake the oxygen at pressure? Or is it literally just down to the partial pressure that you're breathing?

 

[Dr Simon Mitchell]

I'd be interested to hear @Dr Simon Mitchell 's opinion

Sorry, I am a bit late.

Interesting story with a slightly unusual constellation of post-treatment symptoms (but I've long since stopped being surprised by just about anything in DCS).

Let's assume that nothing bizarre (like being recompressed on air rather than oxygen) has happened here.

The chances of a significant relapse in DCS after multiple recompressions and a 6 week wait after the initial event are slim to none. By "significant relapse" I mean the emergence of new serious symptoms or re-emergence of older serious symptoms that are refractory to further treatment. If it was me I would get on with it and travel home.

However, there is one caveat, and BA3, please do not be offended by what I am about to say. You have spent 6 weeks ruminating on this issue, and (quite understandably) focusing intently on the state of your body. You are in a state of high alertness for abnormality and it is going to be very difficult for you to be rational about any deviation from normal that arises during your travel; and there are many such deviations that can occur in anyone on a long haul flight (headache, sore back, fatigue, difficulty concentrating etc etc). It would be entirely possible for you to undertake this flight and form a strong belief that it has provoked new or old symptoms of DCS even if it hasn't. I have seen examples of such illness-belief around DCS turn into a significant psychological problems in the medium term. That is one reason why anyone you talk to is going to be very cautious in the way they frame their advice to you, and why I have to say to you that there are no guarantees, and that the choice to travel is yours to make as an informed risk acceptor. I do believe the real risk is extremely low, but the risk of perceived problems is much higher.

Under your circumstances I personally would not bother with supplemental oxygen. It may create a lot of issues with the airline in terms of your fitness for flying and I would be extremely skeptical that it will lower your real risk in any material way.

I would arrange to go and be checked by the hyperbaric medicine team you have been in contact with after arrival home, as much for your peace of mind as anything else.

Simon M

 

[cbfunky]

I know I'm a bit late to this post, but I specifically signed up to this board to say a big thank you to @Dr Simon Mitchell for the in-depth answer that I came across on Google.

I have a similar situation as OP where I got hit with DCS last February, and received a few seasons hbot, obviously also scared to death to get on a plane afterwards (and I absolutely agree on your statement about hyper awareness).

It's been a year now and I still have symptoms like OP describes (tingling in arms/legs, arms falling asleep or even going numb almost every single night, some muscle twitches - but also clear head/neck mris). So it really helped me hearing you say that it can't really be any more nitrogen. I want to go hiking at high altitude this spring and the possibility of remaining nitrogen was a big worry for me.

Can I hijack this question and ask your experience with these long term symptoms? Is there a chance they'll ever go away?

Thanks again, I'm sure your answer will put more than one mind at ease.