Is Heliox a better field treatment for DCS than 100% Oxygen?

[Thalassamania]

Almost hot off the press, I've not had a chance to read the full article yet. Here's the abstract:

J Appl Physiol 103: 757-762, 2007. 28 June 2007

Effect of hypobaric air, oxygen, heliox (50:50), or heliox (80:20) breathing on air bubbles in adipose tissue

O. Hyldegaard^1,2 and J. Madsen²


1Laboratory of Hyperbaric Medicine, Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet, Copenhagen; and 2Department of Medical Physiology, The Panum Institute, University of Copenhagen, Copenhagen, Denmark


Submitted 6 February 2007 ; accepted in final form 21 June 2007


The fate of bubbles formed in tissues during decompression to altitude after diving or due to accidental loss of cabin pressure during flight has only been indirectly inferred from theoretical modeling and clinical observations with noninvasive bubble-measuring techniques of intravascular bubbles. In this report we visually followed the in vivo resolution of micro-air bubbles injected into adipose tissue of anesthetized rats decompressed from 101.3 kPa to and held at 71 kPa corresponding to 2.750 m above sea level, while the rats breathed air, oxygen, heliox (50:50), or heliox (80:20). During air breathing, bubbles initially grew for 30–80 min, after which they remained stable or began to shrink slowly. Oxygen breathing caused an initial growth of all bubbles for 15–85 min, after which they shrank until they disappeared from view. Bubble growth was significantly greater during breathing of oxygen compared with air and heliox breathing mixtures. During heliox (50:50) breathing, bubbles initially grew for 5–30 min, from which point they shrank until they disappeared from view. After a shift to heliox (80:20) breathing, some bubbles grew slightly for 20–30 min, then shrank until they disappeared from view. Bubble disappearance was significantly faster during breathing of oxygen and heliox mixtures compared with air. In conclusion, the present results show that oxygen breathing at 71 kPa promotes bubble growth in lipid tissue, and it is possible that breathing of heliox may be beneficial in treating decompression sickness during flight.

Address for reprint requests and other correspondence: O. Hyldegaard, Laboratory of Hyperbaric Medicine, Dept. of Anaesthesia 4132, HOC, Copenhagen Univ. Hospital, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen Ø, DK-Denmark (e-mail: ole.hyldegaard@dadlnet.dk)

 

[TSandM]

Interesting . . . This would seem to support the use of high helium mixes for decompression, wouldn't it?

 

[Gilldiver]

I'd be very, very carfull trying to relate an aircraft type of decompression to any diving. The pressure delta is only 4 psi (101 to 71 Kpa).

 

[Thalassamania]

Interesting . . . This would seem to support the use of high helium mixes for decompression, wouldn't it?

It at least points in that direction, but decom is "pre-bubble" (one hopes). It appears to point more directly to the use of heliox for DCS "first aid" rather than oxygen.

 

[MookieMoose]

As Gilldiver mentioned above, you have to be careful comparing DCS from diving to altitude DCS - they seem to behave a little differently. Why is not well understood.

With regards to the Heliox question, I'm currently in the middle of a project which should help sort out this, and some other questions. I'm looking at the same gas mixes described in the abstract above both with and without another therapy - i.v. treatment with perfluorocarbon emulsions (PFC), and looking at things like nitrogen washout and whole-body oxygenation (delivery, consumption, etc.). I haven't completed the study yet, so I don't want to comment too much on the data, but so far 50/50 Heliox looks very good, as does the PFC treatment.

On a similar note, the French comercial diving firm and research company COMEX has published Heliox treatment tables for DCS that, from the little bit I've read, seem to result in better outcomes after treatment than some of the US Navy treatment tables...

Cam

 

[Thalassamania]

As Gilldiver mentioned above, you have to be careful comparing DCS from diving to altitude DCS - they seem to behave a little differently. Why is not well understood.

Clearly, but bubble washout is bubble washout and rats ain't humans. In this case the bubbles were no even caused by decompression. So it really is little more to me than an indicator of the direction we should be looking in.

With regards to the Heliox question, I'm currently in the middle of a project which should help sort out this, and some other questions. I'm looking at the same gas mixes described in the abstract above both with and without another therapy - i.v. treatment with perfluorocarbon emulsions (PFC), and looking at things like nitrogen washout and whole-body oxygenation (delivery, consumption, etc.). I haven't completed the study yet, so I don't want to comment too much on the data, but so far 50/50 Heliox looks very good, as does the PFC treatment.

On a similar note, the French commercial diving firm and research company COMEX has published Heliox treatment tables for DCS that, from the little bit I've read, seem to result in better outcomes after treatment than some of the US Navy treatment tables...

Cam

You'll keep us posted on results as soon as you responsibly can? Please?

 

[MookieMoose]

You'll keep us posted on results as soon as you responsibly can? Please?

Absolutely! I'll report here what I can when the time is right, and I'll post copies of any of the publications as they become available.

Cam

 

[Dr. Doug Ebersole]

As mentioned above, this is interesting but is clearly nothing more than an interesting pilot investigation at present. It does, however, serve the point of suggesting further clinical research into this area is needed. I, too, will look forward to MookieMoose's decompression project. I remember when we used PFCs in the cardiac cath lab many many moons ago. Unftortunately, they didn't really pan out for us. Their use and the heliox question are both very interesting.

 

[MookieMoose]

As mentioned above, this is interesting but is clearly nothing more than an interesting pilot investigation at present. It does, however, serve the point of suggesting further clinical research into this area is needed. I, too, will look forward to MookieMoose's decompression project. I remember when we used PFCs in the cardiac cath lab many many moons ago. Unftortunately, they didn't really pan out for us. Their use and the heliox question are both very interesting.

PFCs have improved in leaps and bounds since the days of Fluosol - the one that was used for myocardial protection in the cath lab. The amount of PFC in the emulsions has increased sbustantially - from 20% in Fluosol to between 60 and 80% in current products. The toxicity has also decreased dramatically. Now all we see is some mild flu-like symptoms (fever, headache, myalgia) and a transient decrease in platelet function. The basic idea is the same in whatever application you are looking at - oxygen delivery to oxygen-starved tissue. In the case of DCS we also have the added benefit of enhancing nitrogen washout. So far the data looks like to most important effect is the delivery of oxygen to tissues which, because of bubbles in circulation, do not have adequite blood flow. The PFC particles in the emulsion I am working with average 0.2 micrometers in diameter, so they are so small that they are able to move past bubbles obstruction blood flow and deliver oxygen to tissue which otherwise might be permanently damages by prolonged hypoxia. The real trick now is to get enough good data to get past the FDA...

 

[gls]

On a similar note, the French comercial diving firm and research company COMEX has published Heliox treatment tables for DCS that, from the little bit I've read, seem to result in better outcomes after treatment than some of the US Navy treatment tables...

Cam

In my understanding, with both US Navy and various commercial tables, Heliox is accepted as a treatment gas. The governing limits are ppO2. For example, on a USN TT6A - a high ppO2 (ppO2 Not to exceed 3.0atm) treatment gas can be administered for the initial :25 min at depth
ie: At 165 fsw 50/50 HeO2 could be used.

Though most commercial tables are proprietary, the USN tables should state as much to anyone with a copy to look at.

intersted in seeing where this thread goes...