In-water recompression to decompress - what are your thoughts?

[Akimbo]

@drbill

There is a LOT of precedence here. The most common decompression procedures used in the US Navy and commercial diving industry employs a short surface interval and completing decompression in a chamber -- functionally a similar situation. It is commonly called Sur-D-O2 (Surface Decompression using Oxygen). If you haven't looked a Navy Tables recently, they have incorporated Sur-D-O2 into the standard air tables as an option to all in-water decompression.

The procedure may include some in-water decompression or not, depending on the time/depth profile. The diver is yanked out of the water, tenders help strip him/her down to a bathing suit (if they're wearing one), escort them a short distance to the chamber, and recompress them to complete decompression on pure O2 -- but there are Sur-D-Air tables that are rarely used. The maximum allowable time between leaving the last stop and reaching your chamber stop is 5 minutes. They strip their suit and anything else off because it probably is not clean enough for Oxygen/fire safety in the chamber.

Edit: Caution, a little "adult" language
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You might notice that the diver is put in the outerlock of a double-lock chamber and signaled to enter the larger innerlock once depth is reached. This is because the outer lock is much smaller so it can be pressurized much more rapidly off the large LP air compressor(s) supplying it. The rush is to get them back to depth. There is plenty of time to get them on BIBS (Built-In Breathing System -- basically the Oxygen mask).

 

[Kevrumbo]

The procedure may include some in-water decompression or not, depending on the time/depth profile. The diver is janked out of the water, tenders help strip him/her down to a bathing suit (if they're wearing one), escort them a short distance to the chamber, and recompress them to complete decompression on pure O2

Talk about a physical post-dive stimulus for VGE: That was excruciating to watch that fast hard climb up the ladder out of the water (a big no-no for us sport technical divers), for the already deco compromised commercial diver in the video undergoing mandatory O2 Sur-D procedure, and tactically he should've been hoisted up on a small lift platform to the deck level if possible. These guys make great money, but no wonder they have relatively short careers -body cannot take that kind of repeated decompression stress let alone the physical strain year-after-year. . .

This is a more fun video to watch @Akimbo, @drbill: A chamber training run to 5ata for a Volunteer Crew at the Catalina Recompression Chamber outlining the inside procedure in speed time lapse videography. . .

 

[Akimbo]

Talk about a physical post-dive stimulus for VGE: That was excruciating to watch that fast hard climb up the ladder out of the water (a big no-no for us sport technical divers), for the already deco compromised commercial diver in the video undergoing mandatory O2 Sur-D procedure, and tactically he should've been hoisted up on a small lift platform to the deck level if possible.

In theory that is true but in practice there are far fewer (DCS) hits. Hoisting divers on deeper HeO2 surface dives (non-saturation) has become common practice in most parts of the world where it is still allowed. The reason is not because of VGE but because many jurisdictions and/or companies require an open-bottom bell.

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Granted, the probable reasons for far fewer DCS cases with Sur-D is the diver is more relaxed, warmer, and in no big rush to complete decompression. Normally you don't put the next diver in the water until the all divers are on deck due to logistics and personnel limitations. They can also safely decompress on pure Oxygen much deeper in a chamber than in the water.

Most of the company-proprietary (non-US Navy) Sur-D tables I have seen look more like a treatment Table 5 than USN Sur-D tables. Recompressing to 60' (18.3M or 2.8 PPO2) instead of 40', spending several 20 minute periods on BIBS, and followed by a continuous ascent in the 1'/minute range is pretty common. Here is Table 5 so other readers can compare.

 

[Kevrumbo]

Looking at Treatment Table 5 in comparison above, and getting back to IWR, has anyone here resorted to the controversial Hawaiian or Pyle Deep IWR Tables below?

 

[Searcaigh]

I have a lot of experience with habitats. There are a lot more logistics problems with them than most people can imagine. By the time everything is considered it is easier, more effective, and less expensive to just have a chamber like this onboard.

View attachment 456967​

In an ideal world of course, but in reality most boats I dive from are smaller than this chamber

Whilst we don't deny that a chamber is the preferred choice for treatment they don't exactly exist at every dive destination.

As per London Diving Chamber website which lists chamber locations worldwide. I am not sure how up to date this is but if you are planning to go diving in Raja Ampat, it might be worth checking how much O2 your boat is carrying!

In my own particular area (UAE) two chambers are listed, but from practical experience the only one available for Joe Public surprisingly is at the military hospital in Abu Dhabi at minimum a 4 hour drive from the east coast of UAE where most of us dive.

We had an incident a couple of years ago when one of our team took a hit on a 70m dive off the east coast of UAE diving a wreck (Ines). He was put on surface O2 and some pain relief was obtained. As we still had divers down, we had to wait for them to surface 90 minutes later, followed by a 20 min boat ride back to port.

The 4 hour drive from Fujairah to Abu Dhabi involves an ascent to 500m and during this phase the victim had a return of the pain despite having been on breathing O2 for over 2 hours prior to the road trip as well as breathing it during the car journey. Fortunately we had stacks of O2 between us and a tech dive op exists in Fujairah, so no shortage of O2 and we had spare tanks in the car for the trip.

Would an IWR have been of benefit? Most of our team assume so, but we are not under any assumption that this replaces a chamber ride once one is available.

We all want to go diving in places that are remote in order to dive on virgin reefs and get away from the mass diving ops, but given the lack of chambers in these areas some option to treat DCS must be considered.

 

[Akimbo]

In an ideal world of course, but in reality most boats I dive from are smaller than this chamber

Whilst we don't deny that a chamber is the preferred choice for treatment they don't exactly exist at every dive destination.

I couldn't agree more. I was really addressing the comment about habitats.

(comment for other readers since you already know this stuff)
I have always thought that preparation for IWR needs to be made when chambers are not available. Habitats for decompression, or to conduct saturation dives, have proven to practical only in extremely limited situations. Unfortunately, if your vessel and budget can't support a chamber it is very unlikely it will support a habitat or open-bottom bell. An IWR kit using FFMs provides about 60% of the advantage of a chamber at less than 0.1% of the all-in cost -- which includes the larger vessel, compressors to run it, plus mobilization and demobilization. A couple of large LP compressors and a chamber are in the 7 ton range.

 

[Russell Bowyer]

Thank you everyone for your input on this subject

 

[Russell Bowyer]

Out of interest has anyone experienced In water re-compression themselves or been involved with helping someone that required IWR?

 

[rjack321]

Out of interest has anyone experienced In water re-compression themselves or been involved with helping someone that required IWR?

Yes to both questions. And I have been in a chamber too.

IWR is never required btw, its a choice among alternatives (some better than others)

 

[Russell Bowyer]

Yes to both questions. And I have been in a chamber too.

IWR is never required btw, its a choice among alternatives (some better than others)

When you say IWR is never required, what do you mean by that?