Decompression chamber question

[Blastman4444]

I have a question when I got treatment in the chamber they used 100% o2 at a depth of 60 feet from what I am reading that exceeds the max 1.6 atm limit how is that done without oxygen becoming toxic? I know they switched to air breaks so I'm assuming that's how but it must push the limits. The first time they turned on the 02 I felt little light headed for a few minutes.

 

[knotical]

A seizure in the chamber does not have the drowning implications that seizing underwater does.

 

[Akimbo]

A lot of factors increase the probability of an oxygen toxicity hit including stress, physical exertion, and cold. These factors are dramatically minimized in a treatment chamber. Also, it is very unusual that severe reactions like convulsions are the first recognizable symptoms, especially to a trained chamber attendant who is not suffering from narcosis as a deep diver might. The attendant or dive super will yank you off O2 at their first suspicion.

As knotical implied, the worse thing likely to happen if you did convulse is a bitten lip and tongue, maybe a bump in your head, and an attendant looking for a new job. It is possible, but the benefits far out-weigh the risks.

I have treated and been onboard for dozens of table five and six treatments and have never witnessed an O2 hit. The same for hundreds of Sur-D-O2 (Surface Decompression using Oxygen) dives — a prevalent procedure in military and commercial surface diving. This is also true for most of the US Navy Master Divers and diving supervisors I have known. I have heard of a few hits in my career, but most were hyperbaric medical patients whose physical condition was compromised in many different ways.

I saw some French commercial divers running Sur-D-O2 at [-]almost 3[/-] 4 ATA/30 Meters in the early 1970s. I wasn’t around enough to know if they had toxicity hits, but that is too rich for my peace of mind.

 

[Dr Deco]

Hello kell490:

Oxygen toxicity controlled by the partial pressure of oxygen in the brain. The time to convulsion in turn is modified by the partial pressure of carbon dioxide, a vasodilator. When a diver is in the water and breathing elevated oxygen pressures, the activity of the diver is contributing to the production of CO₂. An accumulation of CO₂ has been found to influence the time to convulsion. Since patients in a hyperbaric chamber are remaining quiet, the CO₂ problem is minimized.

In addition, as mentioned by others, an oxygen ”hit” in a chamber will not lead to drowning.

Dr Deco :doctor:

 

[Blastman4444]

So the 19 feet on 100% o2 1.6 atm just is a safety margin. Do divers ever use 100% while doing safety stops to flush out more nitrogen?

 

[Thalassamania]

Yes, divers do ... and I have heard of hits on pure O2 at 30 foot stops (see the Andrea Doria TV special from some years back), either Peter or Al were hit, I can't remember who.

 

[Akimbo]

So the 19 feet on 100% o2 1.6 atm just is a safety margin….

Sure, and to compensate for higher physical activity levels required in the water compared to reclining in the barrel with BIBs mask and reading book. Like decompression tables, there are huge variations between individuals, their physical condition, age, and hundreds of other factors that can influence DCS. Barotrauma is about the only diving illness that is highly predictable and has virtually no individual variability.

 

[Duke Dive Medicine]

We routinely treat clinical patients at 2 ATA. Divers get up to 2.8 ATA, and a severe clostridial myonecrosis (gas gangrene) patient will get 3 ATA. The difference, as the others have noted, is that chamber patients are at rest, warm, dry, and have relatively normal CO2 levels. The only thing I'd differ with is Akimbo's statement that seizures are not usually the first symptom to appear. Seizures can and do occur without warning, although I've personally only seen a handful in 20+ years.

 

[Akimbo]

… Also, it is very unusual that severe reactions like convulsions are the first recognizable symptoms, especially to a trained chamber attendant who is not suffering from narcosis as a deep diver might....

… The only thing I'd differ with is Akimbo's statement that seizures are not usually the first symptom to appear. Seizures can and do occur without warning, although I've personally only seen a handful in 20+ years.

Sounds like we are saying the same thing. Convulsions can be the first recognizable symptom, just very rarely. A factor that may put a little space between our experiences is I have only dealt with healthy commercial and military divers who are acutely aware of oxygen toxicity symptoms and have lots of time on a BIBs mask. They are usually the first to raise the red flag, even when caused by too much Tabasco on their corn flakes.

After re-reading, it would have been clearer by writing “I have never witnessed a confirmed or likely O2 hit”. Maybe 1 out of 50-75 runs a symptom was suspected by the diver or super and the mask removed. In every case, the diver went back on the mask after 10-15 minutes and completed the run without further incident. Sorry if there was any confusion.

 

[redacted]

An interesting article on the subject: Oxygen Toxicity Signs and Symptoms