In-Water Recompression, Revisited

[DevonDiver]

I'm interested to know current perspectives on the use (and potential future use) of portable recompression chambers.

Putting aside ad-hoc 'self-administered' IWR... surely there's an increasing case for the recommendation for remote technical operations to equip with portable lightweight chambers?

If an operator needs to put in place formal IWR provision, shouldn't they be first looking at out of water options?

Both assume trained medical staff, complex logistics and equivalent gas supply etc.

Dry recompression is much less risk and liability fraught. Portable chambers also permit simultaneous evacuation whilst treatment is provided.

What considerations are organizations like DAN, SPUMS et al giving to the future of providing dry recompression via portable recompression technologies?

 

[Duke Dive Medicine]

For those worried about Ox-Tox seizure potential in IWR might be feel somewhat better with this article:
End tidal CO2 in recreational rebreather divers on surfacing after decompression dives. - PubMed - NCBI

". . .We found no general tendency to CO2 retention during decompression. It is plausible that breaching oxygen exposure limits during resting decompression is less hazardous than equivalent breaches when exercising at deep depths. Mitchell SJ, Mesley P, Hannam JA. End tidal CO2 in recreational rebreather divers on surfacing after decompression dives."

Kevin, that's a great article, thanks for posting. I know you know what end-tidal CO2 is, but for readers who may not, it's the CO2 content in exhaled air. It's noteworthy that the authors measured end-tidal CO2 on surfacing - one significant factor in CO2 retention in divers is gas density; that is, it's depth dependent and increases with increasing depth, so it's likely that divers who are finishing decompression from a shallow stop will have lower readings. The ascent from the last water stop to the surface also gives the diver the opportunity to blow off CO2. It's not surprising that readings taken on the surface approach normal. Also, the correlation between end tidal CO2 and arterial pCO2 (partial pressure of CO2 in the arteries) is notoriously poor. I think the results of the article should be interpreted with both of those considerations in mind.

@DevonDiver, Andy, I'm sure it all comes down to cost, staffing and liability.

Best regards,
DDM

 

[Wookie]

Anyone who takes advice from the same guy who wrote an article in Sport diver magazine about his dive to 400 feet on a single 80 of air after a day of day drinking deserves exactly what they get. The man may be great at testifying against dive operators as an expert witness in court, but as a diver, he leaves a bit to be desired. I'm sorry for dragging this completely off topic, but this doesn't even deserve a response, much less an in depth discussion.

There are excellent resources out there for IWR, including courses offered by Navy divers, ex-navy divers, and front-line training agencies. This "advice and article" is not that.

 

[The Chairman]

I agree with @Wookie. FIGJAMs are not a reliable source of information to base your diving on. Duke Diving Medicine is a far, far, far more reliable source of information.

The best trip to the chamber is the one you prevent by diving cautiously. Personally, I only do one obligated deco dive a day and take a break after two days. Yes, I'm a wimp, but I've never been bent in 48 years of diving. I also don't ride my PDC to max out bottom time by going shallower and shallower. I'm obese, and so I modify my diving to take that into account. Safe diving is no accident.

 

[oldschoolto]

I installed a dive tank to do hyperbaric treatments for my MS.... Using 80% O2 at 20' for 20 minutes and then 5 minutes on air as I come up out of the water... Seems to work well, As I really feel better after a few days of starting treatments.. I don't like 100% O2 for DECO and feel it's not worth the risk VS reward...

60' on 100% O2 sounds very risky....

Jim....

 

[oldschoolto]

You n

I agree with @Wookie. FIGJAMs are not a reliable source of information to base your diving on. Duke Diving Medicine is a far, far, far more reliable source of information.

The best trip to the chamber is the one you prevent by diving cautiously. Personally, I only do one obligated deco dive a day and take a break after two days. Yes, I'm a wimp, but I've never been bent in 48 years of diving. I also don't ride my PDC to max out bottom time by going shallower and shallower. I'm obese, and so I modify my diving to take that into account. Safe diving is no accident.

You need to post this in the EN thread....
Jim.....

 

[Kevrumbo]

. . . It's noteworthy that the authors measured end-tidal CO2 on surfacing - one significant factor in CO2 retention in divers is gas density; that is, it's depth dependent and increases with increasing depth, so it's likely that divers who are finishing decompression from a shallow stop will have lower readings. The ascent from the last water stop to the surface also gives the diver the opportunity to blow off CO2. It's not surprising that readings taken on the surface approach normal. Also, the correlation between end tidal CO2 and arterial pCO2 (partial pressure of CO2 in the arteries) is notoriously poor. I think the results of the article should be interpreted with both of those considerations in mind. . .

Best regards,
DDM

The correlation can be "notoriously poor" between end tidal CO2 and arterial PaCO2 in very critically ill patients. . .

Sorry DDM . . .some other studies & opinions:
. . .
CONCLUSION:
Measurements of end-tidal carbon dioxide concentrations correlate well with PaCO2 values in nonintubated patients presenting with a variety of conditions to EDs [Emergency Dept's]. End-tidal carbon dioxide measurements may be sufficient measures of PaCO2 in selected patients and obviate the need for repeat arterial blood gas determination. Further study is warranted.
Correlation of end-tidal CO2 measurements to arterial PaCO2 in nonintubated patients. - PubMed - NCBI

Clinically, a way to double check correlation of end-tidal CO2 measurement with arterial PaCO2 is with an Arterial Blood Gas Test, especially if a patient happens to be a "CO2 Retainer" (pathologically a "Blue Bloater" as an acute example in a patient with Chronic Obstructive Pulmonary Disease COPD). However, it's obviously impractical to draw a blood sample for an ABG Test in the field unless you just happen to bring a portable clinical lab analysis machine with you (i.e. at a divesite).

From Simon Mitchell ("SJ Mitchell", in the study above):
". . .The way we do it in anesthesiology is measuring the end expiratory CO2. We sample gas, which has supposedly come from the alveolus and measure the CO2 in that gas. That would be one potential way of doing it in a rebreather however we don't have a CO2 monitor that goes on a rebreather yet. In theory, it could help the diver make decisions about slowing down and resting". DAN Technical Diving Conference Proceedings Jan 2008, p.37

 

[Duke Dive Medicine]

Kev, first, there is no need to apologize. I'm speaking from a lot of years of experience in drawing and interpreting arterial blood gases and end-tidal CO2 readings and there are certainly times when arterial pCO2 and end tidal CO2 do correlate; however, I would not draw conclusions about the arterial CO2 content of a diver at 60 feet based on end tidal CO2 readings in divers who've just surfaced from a decompression dive. Also, we're departing from the original point of the thread. There is no doubt that elevated CO2 in divers is a risk factor for O2 toxicity.

Best regards,
DDM

 

[Kevrumbo]

Kev, first, there is no need to apologize. I'm speaking from a lot of years of experience in drawing and interpreting arterial blood gases and end-tidal CO2 readings and there are certainly times when arterial pCO2 and end tidal CO2 do correlate; however, I would not draw conclusions about the arterial CO2 content of a diver at 60 feet based on end tidal CO2 readings in divers who've just surfaced from a decompression dive. Also, we're departing from the original point of the thread. There is no doubt that elevated CO2 in divers is a risk factor for O2 toxicity.

Best regards,
DDM

If you are in some remote location in the world with no immediate access to a Recompression Chamber for HBOT (or no reliable network of supporting Chambers 24/7 for emergency dive casualties like in North Florida Cave Country for example), and you have enough dive cylinders of Oxygen and Air -then a treatment choice regarding IWR would be a draconian and tough last resort decision to make given the risks of Oxygen Toxicity/Convulsions.

Since conventional O2 stop deco profiles are done at 20ft/6m (1.6ATA), by comparison a modified Australian IWR profile with 10min O2:Air Break 5min breathing intervals at a shallower depth of 30ft/9m (2.0ATA) would seem to be not as risky as Bret Gilliam's IWR Protocol of descending all the way down to 60ft/18m (2.8ATA) with 20min O2:Air Break 5min breathing intervals.

And finally @Duke Dive Medicine, the point of the study mentioned below is not for drawing any definite conclusions, but only as a comment mentioned in passing -for whatever it's worth- to anyone having to make the hard choice of undergoing IWR:

End tidal CO2 in recreational rebreather divers on surfacing after decompression dives. - PubMed - NCBI

". . .We found no general tendency to CO2 retention during decompression. It is plausible that breaching oxygen exposure limits during resting decompression is less hazardous than equivalent breaches when exercising at deep depths. Mitchell SJ, Mesley P, Hannam JA. End tidal CO2 in recreational rebreather divers on surfacing after decompression dives."

Don't misinterpret the above conclusion @Duke Dive Medicine, by inappropriately "extrapolating it" as Dr. SJ Mitchell giving license for IWR patients to go beyond 1.6ATA depth breathing Oxygen for any length of time as long as they are not exerting themselves into CO2 retention. . .

 

[Duke Dive Medicine]

There is no need to shout with bold letters, and I don't need to be lectured about what your point is. I get it. Mine is that you seemed from your previous posts (including the unedited version of the above post) to be inappropriately extrapolating (my words which you incorporated into your edits) the conclusions from Dr. Mitchell's study to state that people considering doing IWR at 60 feet can be reassured by it. I appreciate you clarifying. Certainly, divers at rest are less at risk of CO2 retention than divers who are exercising; there are other factors like the diver's physical condition, hypercapnic ventilatory response and breathing resistance that influence CO2 retention.

I also agree with you in that the Australian protocol (or the U.S. Navy's, which is similar) is a safer alternative to the protocol advocated in the article in question.

Note to all: I'm sure that the first, unedited version of THIS post went out to plenty of emails. That post did not meet my own standards of professionalism so I edited it about 30 minutes later, and edited it again this morning in response to the above member's edits of his own post so that it more accurately reflects the reality of the exchange. Apologies for my poorly self-moderated initial response. I am human. The original point of the thread remains; that is, to call attention to a dangerous practice and to invite rational, polite discussion on the topic.

Best regards,
DDM