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You learn something on every dive
ScottPadipro - 9/16/2007 10:38 PM
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Category: Personal
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Here is an edited for space excerpt from a post made by my dive buddy about a dive we attempted to do last week. I was sitting right next to him prior to our entering the water but I suffered no ill effects during the dive even though I too went on and off the loop several times before we splashed. The only reason I can come up with for this is the fact that each time I would go on the loop to pre-breath I would exhale completely and allow the ADV to open when I inhaled and replenish the loop volume so there was nothing in the loop but clean gas from my tanks. "The dive was a simple 140 fsw MOD decompression dive with a 1.2 bottom set point. We planned the dive with 21/35 diluent and off board bailout, with my dive buddy carrying a 40 cf of ean50 and myself a 40 cf of O2. The day prior to the dive, we emptied, filled, and analyzed our diluent and bailout bottles at our local tech shop. The gas analyzed correctly, and this was confirmed on a personal analyzer. My Megalodon was assembled that evening including the air point and O2 calibrations. The morning of the dive the winds were light, but the surface conditions were broken by moderate rollers. The surface current was north and light, but the current strengthened down to about 100 fsw where it then let up again. This came into play during the descent. Another diver set the hook on the wreck, but it seemed the down line was too long for the depth. Due to the long scope of the line and the light current, it took the captain a very long time to determine whether the line was set on the wreck or if the ball was just drifting away. My buddy and I were already kitted up and agonizing over the long delay to get in the water. My Movie Meg is short enough that I can’t sit comfortably while fully geared, as there is no way to support the weight of the unit. This lengthy delay caused some stress. I also happened to be sitting on the starboard side of the boat, which is where the exhaust is ported. I had done my pre-breath, and since I was uncomfortable and didn’t know how long the wait to splash would be, I closed the DSV and took (the loop) out of my mouth. This happened probably no less than 3 or 4 times before the splash. I wonder if I inhaled CO and other hydrocarbons from the diesel exhaust and introduced them into the loop? The descent would be made with a .4 set point. I was somewhat stressed when we splashed. I drifted to the ball as I sank beneath the surface. As I started down, the current seemed to pick up. The down line was not the proper weight rope, but of thinner nylon line. With the drag of the gear against the current, the lengthy scope and thin rope made for a long and somewhat difficult trip to the wreck. Upon reaching the wreck, I reset to 1.2 and manually injected O2 to bring the PO2 up to about 1.0, and then let the solenoid and automation to make the final correction. This took about 1 minute and gave me a bit of a breather, which I definitely needed. We gave the OK signals to continue the dive, so we descended another 20 feet to about 140. I looked around for about a minute before we started to move down the cargo hold. This is when it became evident something was wrong. At first, there was a sense of paranoia. I have felt this before when flying in uncomfortable conditions, so I was definitely aware of it. As we finned away from the structure, I started to feel very strange inside. When I looked away from the bottom and forward, I experienced vertigo. The environment spun around me and I felt very ill. I gave my buddy a shake of the light in his field of vision and when he turned toward me, I headed back toward the structure and ascended the 20 feet back to where I had just done my set point change. I grabbed the railing and closed my eyes to try and overcome the nausea. My vision settled down and while staying planted on the rail, I gave my buddy the OK signal. Not really smart, as I should have given him the something not-right hand signal, but he knew something was wrong. He watched me as I tried to overcome the urge to vomit. I was about to bail out to OC so I could puke through my regulator when the imminent urge to hurl faded. I decided to stay on the loop, and thumbed the dive. My buddy unhooked the line, as the other diver on OC was already above us, and we started up to fulfill our short decompression obligation. We made stops at 80, 50 (where I switched my set point to 1.4 and get some more O2), and 20 feet. I felt terrible all the way up, but not as nauseated as I had on the bottom. At the surface, I struggled to get back in the boat, feeling weak and a bit out of control. I put myself on O2 after getting out of my gear, which did little to help the situation. After about an hour on the surface and a dip back in the water for a surface float to cool off, I started to snap out of it. When I got home that evening I felt very tired, and slept very hard on and off until the next day. Here’s what I think happened: 1. 6 weeks of fatigue prior to dive with only a few days recovery 2. 2 weeks of upper respiratory virus gone 1-week prior to dive 3. Elevated stress prior to splash 4. Diesel exhaust fumes inhaled while off loop 5. Increased workload during descent But after post dive analysis, I think I suffered from carbon monoxide poisoning. Did I inhale CO and hydro carbons while breathing at the back of the boat and then introduce them to the loop? Remember, I went on and off the loop 3 to 4 times for several minutes each while waiting to splash. The exhaust outlet was behind me and the smell of fumes was very noticeable as we trolled for the wreck at slow speed with occasional bursts of throttle. If I exhaled these CO fumes into the loop where they would remain present for the entire dive, then what would the effect be under pressure? CO at 1 ATA is obviously no good for the human body but what about at over 5 ATA?" My buddy has recovered completely and we made two dives just the other day with no probelms. The moral of this story is watch out for those exhaust fumes especially if you`re on a rebreather where they can be introduced into the breathing loop and because there is no overboard exhause like on open circuit they remain during the entire dive. Dive safe, Scott