In 2005 when I started getting my first DCS problems, there was debate among the doctors as to whether it was DCS or not. Although most agreed that the pain in the joints was likely DCS, the tingling and numbness in fingers and toes was considered less conclusive. Also the skin sparking that I get after more severe cases has not (to my knowledge) routinely been reported by scuba divers. The skin sparking feels like small pin-pricks under the skin, happening at random times and at random places around the body. I believe it is caused by bubbles forcing themselves through small capillaries under the skin but I don't know for certain.
The finger/toe numbness is strange. What happens to me is that the left half or the right half of my finger goes numb, but not the other half. If it were caused by cold, the entire finger would go numb.
Also coldness is not a possible explanation because it often happens when I'm warm. I get out of the water, warm up, and by then my hands and feet are very warm. Then, suddenly and instantaneously, half of one finger or one toe goes numb/tingly. Then seconds later another half of another toe/finger goes numb, and this proceeds in sequence until several finger or toes have the problem. Further this never ever happens at any other time in my life.
In 2005 to gain further confidence about this symptom, I tried doing similar dive profiles, except modified the depth. I kept the same approximate dive time, same approximate surface interval, and this resulted in the same time in the water and same 'coldness' factor. Except for one thing; the finger/toe numb/tingling effect never ever happened on the shallow profiles, only on the deep ones. I would rule out expectation or placebo since
A) the problem first occurred without expectation
B) I doubt that belief that you will not get DCS can protect you from DCS
When I went into the recompression chamber in 2005, the skin sparking stopped immediately when the chamber was pressurized. The pain in my joints and knuckles persisted after the chamber session and it took many days for that to go away (presumably there was micro-damage that was semi permanent and needed healing).
In fact when the tingling/numbness first hit me in 2005, it was familiar. At that moment my first thought was that I had not felt that feeling since July 2001, when it happened after two consecutive dives to 71m with 12 minutes in between. Back then when I got the feeling I had no idea it was DCS.
Using these minor symptoms as a guide is what allowed me to analyze my own data and develop rules which now completely prevent me from ever getting any symptoms. If I ignored those symptoms and treated them as an unrelated effect, I would not have made any progress.
I have a high degree of confidence in the algorithm running in the Xen computer and I strongly believe that anyone following the computer will not get freediving DCS. However it could be 40 years until that fact is proven scientifically. In the mean time countless people will suffer crippling paralysis from DCS.
Even now, as Pipin is planning a dive to 183-220m, it is his choice whether he does a deco stop at 10m like Herbert did. Given Musimu's severe DCS from 209m with no deco, and Coste's severe DCS from 183m with no deco, it is obvious to me that deco is critical for such a dive. We can only hope and pray that Pipin does deco.
In fact, prior to Herbert's 214m dive, we both had experienced DCS several times and Herbert asked me what sort of deco strategy I thought would be sufficient on this dive. After discussion we both agreed that a 1 minute stop at 10m would be (intuitively) enough, followed by O2 at depth after-- and it seemed to work for him, unlike Musimu and Coste who got bent.
