Ease of deco from He based gases...

[Braunbehrens]

Dr Deco once bubbled...
Dear Readers:

Long Halftimes and Desaturation

As indicated by ?fins wake,? the desaturation times are different from recreational and commercial or military divers, or even technical divers.

It is my [I opinion], but shared by others, [/I] that ?tissues? with halftimes of 400 to 700 minutes do not in reality exist. Rather, when such is needed to calculate a DCS-free decompression, what is really being done is to allow free gas to exit from a true tissue gas bubble. Val Hempleman (a British researcher) in the 1950s referred to this as a ?tissue-bubble complex.?

This will definitely persist. I am aware of a diver from Ocean Systems (in the 1960s) who sustained a case of joint pain DCS during a chamber dive, was successfully treated, and then took an airplane flight three days later. The pain developed in the same place (probably Boyle?s Law expansion). This tissue gas phase can persist, and it is a part of the thorny question of flying after diving.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

Yes, this is very interesting. While Trey and the WKPP are basically saying to dive helium as if it wasn't there, they also advocacte lots of deep stops .... more even than the more recent algorithms that use deep stops.

I think this probably serves to eliminate very small bubbles that would normally form in tissue, and then cause problems later.

I know of at least one GUE instructor who routinely fly's on the last day of the classes he teaches, and these often include decompression diving. His point is that if you are not bent at the end of the dive, then 3 hours later (or more) when your plane takes off you should have no trouble handling that minor change in pressure.

From what I've read I think that he is basically right, if you have managed to dive in such a way as to not produce any bubbles in the deeper deco phase, then you should be fine.

Of course it's one thing to say that, another one to get on that plane. I certainly wouldn't advise anyone to do this....after all, deco is still poorly understood, and this is all theory.

 

[fins wake]

I know of at least one GUE instructor who routinely fly's on the last day of the classes he teaches, and these often include decompression diving. His point is that if you are not bent at the end of the dive, then 3 hours later (or more) when your plane takes off you should have no trouble handling that minor change in pressure.

Appaling practice. I know GUE instructors are supremely fit 'survivors' with low body fat content and good vascularization, and extremely good decompression technique (i.e. as in not overshooting deco stops, having steady ascent rates etc) so the risk is arguably less than for 'the average recreational diver', but there can be no inference drawn for the recreational community. And in fact, as I believe this instructor's hypothesis is completely wrong, he might well find himself struggling with that 'minor change in pressure' (to 2400 metres of altitude!) himself one day ...

From what I've read I think that he is basically right, if you have managed to dive in such a way as to not produce any bubbles in the deeper deco phase, then you should be fine.

How does one know one isn't bubbling? How does one know there aren't micronuclei which might yet form large bubbles upon stress (to borrow a pet theory on these pages which I also subscribe to), e.g. in the air at 2400 metres?

I certainly wouldn't advise anyone to do this

No, me neither.

after all, deco is still poorly understood, and this is all theory.

Not as poorly understood as certain people make out on the Internet. Nor is it all theory. Some is, usually proposed by leading hyperbaric specialists and verified to greater or lesser extent by scientific experiments in the field or in the laboratory. Some is merely opinion, usually "corroborated" by anecdotal evidence which is not subject to third-party peer review.

I know which decompression data I put my trust in. :banging: :bah:

 

[Braunbehrens]

fins wake once bubbled...
Appaling practice. I know GUE instructors are supremely fit 'survivors' with low body fat content and good vascularization, and extremely good decompression technique (i.e. as in not overshooting deco stops, having steady ascent rates etc) so the risk is arguably less than for 'the average recreational diver', but there can be no inference drawn for the recreational community. And in fact, as I believe this instructor's hypothesis is completely wrong, he might well find himself struggling with that 'minor change in pressure' (to 2400 metres of altitude!) himself one day ...

Either that or you're wrong and they're right.

 

[BigJetDriver]

Braunbehrens once bubbled...


Either that or you're wrong and they're right.

This in response to Fins Wake:

fins wake once bubbled...
Appalling practice. I know GUE instructors are supremely fit 'survivors' with low body fat content and good vascularization, and extremely good decompression technique (i.e. as in not overshooting deco stops, having steady ascent rates etc) so the risk is arguably less than for 'the average recreational diver', but there can be no inference drawn for the recreational community. And in fact, as I believe this instructor's hypothesis is completely wrong, he might well find himself struggling with that 'minor change in pressure' (to 2400 metres of altitude!) himself one day ...

I feel compelled to add:

While you are free to take as much risk personally as you choose, I would literally beg all of you NOT to do deco dives, and then climb on my airplane (or any other for that matter).

The physics of the problem are immutable. When (not if) you get bent at altitude, we may (if you are lucky) or may not have a doctor on board. If we do not, no one will be able to use the Extended Medical Kit to help you. (While I am a certified DMT and could do so, the new rules prevent me from leaving the cockpit to help you.)

We will divert, but since we will be a long way, in all probability, from a large enough airport, it will be a long time before you get competent medical help.

Unfortunately, my company will charge you, or your insurance company a very large bill for the diversion costs. Almost as a side-note, you'll have seriously altered the plans and schedules of 282 other folks!

 

[Braunbehrens]

Maybe then we'll finally get to see if those oxygen masks really work.

Speaking of which, I took my O2 analyser on a plane once. Fascinating. Read 16% the whole way. No wonder people get sick on long plane rides. Of course this is a PO2 reading, really, not a percentage reading, since it was calibrated at ground level.

 

[BIGJC]

Does anyone have any links to the articles on diving helium as if it was not there???


why would someone risk flying after diving? it is unnecesssary...

 

[Dr Deco]

Dear Readers:

A Mini Editorial :doctor:

Flying After Diving

If the truth were known, it would be trivial if all there were to flying after diving was, “Are you bent now?” There would not be much need for further study. It is not really that simple, but if it works for him, that is fine – for him.

There is also the saying in barophysiology, “When it works it works well, but when it fails, it fails catastrophically.” :nono:

DCS – What Do We Know?

Actually, quite a bit is known about decompression, but not all is suitable to be placed into service for recreational divers at the moment. In addition, there still are some differences of option between scientists. Divers read into this that it is a free for all out there.

While many concepts are straightforward, many are still at the experimental stage. The careful reader will note allusions to differences between my decompression concepts and those of Dr Wienke. These are more separable, however, since his tables concern the underwater portion of the dive and I concentrate on what would be (for recreational divers, anyway) the surface portion of the dive. This only illustrates what was said above; today’s individuals are more informed than those of the past. Diver’s read more and can use this website to garner much-needed information. :book2:

There are in actuality many disorders and conditions that involve a gas phase in the body. Is decompression theory in any worse shape then studies of these other problems? Not realty.

• Air embolism following surgical procedures. This is a serious problem and considerable money is invested here by the government for study; there is a need for medical treatment that can combat gas embolism in the brain. Current work is investigating the interaction of surfactant with gas bubbles in small tubes. Work is far from complete and involves topic such as bubble “break off” and “stick-slip dynamics.” Recompression is still the only solid answer despite the several drug interventions that have been tested. Barophysiology does not have drug therapy but we are not behind anyone else;
• Echo Visualization of Tissues by Microbubbles. Much work has been devoted over the past three decades to visualize of tissues by air-filled “microballoons” capable of passing through the pulmonary filter and yet having a usable half life. The results are moderate. Better bilayer membranes and the free gas switch for sulfur hexafluoride have proved useful;
• Surfactants These are of interest in eliminating embolization of capillaries. Useful information, some of which might be applied to diving some day, is being found. Here we have various silicone and fluorocarbon compounds. None of these are leaving barophysiology “in the dust.”
• Ultrasound imaging devices Here we see considerable improvement. Some could be used to visualize free gas in tissue. The resolution of the instruments can be improved. We at NASA are currently testing such a device.
• Encapsulated Drug Delivery Systems These are the microencapsulating of medicines in bilayer coats. They are being studied with the goal of delivery to specific regions of the body. Possibly, with ultrasound resonance, the capsules might be opened and the medication delivered in a dose that exceeds what could be put directly into the whole of the circulatory system.

New for Barophysiology

Much experimental information exists in recent on the relationship between exercise and the change of tissue perfusion. Divers do not yet directly utilize this on the whole, but it is a topic that has been discussed numerous times on this FORUM for a several years.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[DivingDoc]

Braunbehrens once bubbled...
Maybe then we'll finally get to see if those oxygen masks really work.

Speaking of which, I took my O2 analyser on a plane once. Fascinating. Read 16% the whole way. No wonder people get sick on long plane rides. Of course this is a PO2 reading, really, not a percentage reading, since it was calibrated at ground level.

I think (don't quote me on this) that most planes pressurize to an altitude of 6000 feet.

ET

 

[DivingDoc]

Thanks, Dr Deco for an informative post.

Dr Deco once bubbled...
Dear Readers:

A Mini Editorial :doctor:
DCS – What Do We Know?

Visualization of Tissues by Microbubbles.[/u] Much work has been devoted over the past three decades to visualize of tissues by air-filled “microballoons” capable of passing through the pulmonary filter and yet having a usable half life. The results are moderate. Better bilayer membranes and the free gas switch for sulfur hexafluoride have proved useful; [*] Surfactants These are of interest in eliminating embolization of capillaries. Useful information, some of which might be applied to diving some day, is being found. Here we have various silicone and fluorocarbon compounds. None of these are leaving barophysiology “in the dust.”

[*]Ultrasound imaging devices Here we see considerable improvement. Some could be used to visualize free gas in tissue. The resolution of the instruments can be improved. We at NASA are currently testing such a device. [*] Encapsulated Drug Delivery Systems These are the microencapsulating of medicines in bilayer coats. They are being studied with the goal of delivery to specific regions of the body. Possibly, with ultrasound resonance, the capsules might be opened and the medication delivered in a dose that exceeds what could be put directly into the whole of the circulatory system. [/list] New for Barophysiology

How would these meds be delivered? Obviously, for the lung, an inhaled drug would work. Multiple joint pains? Are you really going to inject each joint? Obviously, the drug would have to be coupled to a compound which "homes" to certain tissues, like gadolinium homes to places of inflammation or how technicium homes to the thyroid or places where tissues are actively metabolizing.

I also wonder about the possible utility of a technique being developed by Thomas Platts-Mills, Director of the Allergy Immunology training program at U. of Virginia. He has used rapid MRI imaging following a single breath of polarized helium, which shows non-ventilated areas of the lungs very well. He has used it to look at the difference in lung ventolation following exercise.

Not sure if it would show gas bubbles in tissues or not, but it would seem to me to be worth considering.

ET

 

[DivingDoc]

Here are some abstracts on polarized helium (attached).