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| severe headache, vomiting after surfacing, |
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Mainly just a desire to
breath a lot harder than I should have needed to. No headache. No feeling
of anxiety or panic (but then i don't panic easily). The gas didn't taste
quite right either - 'slightly metallic' is the only way I can describe
it.
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| At 75m depth my first symptom was a serious visual impairment and confusion. These symptoms came on very rapidly with no warning |
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Shortness of breath, mild
headache, slight drowsiness.
Severe shortness of
breath, large increase in breathing rate, feeling of being close to
passing out, twitching of facial muscles around mouth, face felt flushed
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| I became desperately out of breath. I stopped to ensure it was not due to lack of fitness (as I was swimming against a slight current, and was descending to the planned depth of 80m). After about 10 mins the problems started. My hands began to shake and Although I stopped to grab a rock for stability, remained out of breath. I was not able to remove the mouthpiece for a bail out, as I was not able to hold my breath long enough for the swap over... A couple of good dil-flushes had the instantaneous effect of easing my breathing and clarity of thinking. I was also ascending then to 70m, and then 60m. While I was wedged against the rock, I wrote on my slate in capital letters the word 'hypercapnia' so my buddy could understand what I was up to. He watched me closely the whole way up. I stayed on the loop. As I ascended the problem reduced notably. I did the occasional dil-flush through the stops, and on exiting, confirmed the cause was poor packing of Sofnolime due to settling in transit. This is avoidable of course. The symptoms did not include a headache at any time. The sense of urgency to breath is a horrible experience. It is important to discern the difference between poor fitness, (which should be avoided!) and a genuine problem. Dil- flushes are the obvious option, but there is a limit to this at depth! |
| Very rapid breathing rate that was uncontrollable. Felt like I just could not get gas in fast enough and nearly had to hold the mouthpiece in my mouth to make sure I didn't blow it out of my mouth during exhale. Tried slowing breathing rate and forcing very deep breaths but had little success in getting it back under control |
| On the dive when it occurred I had breathlessness, felt stressed, began to feel that the walls were closing in and that I was going to black out. After the dive I had a headache and felt very tired |
| confusion, fear, short of breath, dizzy, vision distortion |
| Panting, Paranoia |
| Breathing getting harder, more resistance, slowly starting headache |
| headache |
| From the above symptoms, it seemed likely that the scrubber was not doing it's job |
| A previous mild hit gave me tunnel vision and a bit of experimenting with CO2 since then shows my sight is the first thing affected. |
| In all cases I was waiting for it to happen |
| I went to Egypt and sneaked a scrubber full of fresh Sofnolime. It got compacted down, and I did not recap it. I was aware of a small amount of rattling from it but disregarded it on a check-out dive to 40 is metres. All was well. The dive was very short. I assumed the Sofnolime would be OK for 1 more go |
| See above! |
| I would say that I only recognised the event as a hypercapnia event as I was ascending and afterwards through analysis of the events. I knew there was something wrong on the dive as there was no real reason to be breathless or to feel stressed |
| did not feel normal |
| From symptoms |
| see above |
| 12m |
| About 25m at the onset of symptoms - on descent phase of dive |
| I was at 75m, 10/52 mix and about 8 mins into the dive with a planned bottom time of 24 mins |
| 6m for underwater event |
| Down to 80m, then immediately up to 70 and then 60m, followed by a full staged ascent with deco completed for dive time. Remained on loop and used occasional dil-flushes which were like miraculous recoveries each time |
| Happened first time (I have experienced this 3 or 4 times since but not quite as bad) during descent. Depth symptoms started was approx 50m |
| It occurred on the descent as I reached 40M. |
| 67m |
| 56m, shortly after descent |
| Don't keep an accurate enough log to say this. The first time I was pushing the unit over the time limits to experience it, the depth was 40-60 feet with the beginning of the dive at maybe 130 feet |
| approx. 60 min |
| Not absolutely sure... maybe 2 minutes |
| 8 mins |
|
Around three hours.
On the surface it took
around five minutes if I remember for the symptoms to start getting bad,
but it was a while ago
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| 10 mins before the problem occurred and then whatever I was supposed to do after that; can't remember but it was all above board |
| Less than 5 mins. |
| Approx 5/6minutes |
| 5 mins |
| 5 min |
| 2 hours |
| 4.5 h |
| About 1 hour |
| The scrubber had done one previous dive to 65m for 20 mins bottom time (60 mins run time) |
| I don't have log books to hand but I think I said how long it was when I filled in the survey if you still have that to hand. About ten hours total is a number that rings a bell (540 mins DiverMole) |
| It had about 20-30 mins. |
| Maybe 10-15 mins at most. Was a new fill before the dive |
| Less than 1 hour |
| New scrubber |
| 75 min |
| 7 hours |
| live duration overstayed (water temp. 28 Celsius) |
| No, No, No and No |
| Exhausted |
| exhausted |
| Dead-space created by settling. or perhaps an amount of channelling as well... |
| I am still not sure but have tried many things to cure problem |
| NO |
| Out breathed, was struggling to get down shot against a tide |
| Possibly out breathed, or channelled |
| exhausted from the bottom and wet from dripping condensation from the
top |
| plane stupidity and stinginess |
| My haste to get into the water resulting in a lack of an effective pre-breathe to get the chemicals warmed up. |
| Me. I overran the scrubber |
| Me I did it on purpose |
| I kind of knew it had settled slightly due to the noise the canister made. The first dive was fine and I was perhaps a little gung-ho or lazy depending on the view you'd like to take! |
| Not sure. There was some slightly exertion due to current which probably caused the rapid increase in CO2 initially |
| It was earlyish days on the unit, the descent had been hard work due to high current to swim against and I believe that I had not been breathing fully, possibly allowing CO2 to be retained. |
| out of breath |
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Strenuous kitting up - RIB in choppy sea, side mounts etc.
Kit problem on surface (counter lung twisted on entry,
hiding diluent injector) - rough water
rushed bubble check, rapid descent
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| staying too long.... |
| standard lime |
| Sofnolime (from APD) |
| Sofnolime fine grain |
| Normal Sofnolime, Empty scrubber on surface events |
| Brand new keg of Sofnolime packed freshly, and not exposed to air prior to use. 797 grade |
| APD supplied Sofnolime |
| Standard AP recc |
| Sofnolime 2.5mm |
| Sodasorb 4-8 grade |
| sodasorb |
| end dive |
| Stopped my descent. Indicated my problem to my buddy. Dil flush, then another about 2' later. All now OK so continued with dive (63m max, 30' bottom time and enough OC gas between us for me to stay o/c to the top if need be) - no further problems |
| It wasn't. It was more managed. Going open circuit had absolutely no effect, even 100% O2 had no effect at 6m. I tried semi closed before going OC with no improvement. I had a very great urge to bolt for the surface throughout the stops and only a strong willpower prevented me from doing this. The difficulty on the stops was communicating my problem to the others in the group. It took a good 12 hours before feeling better and I didn't dive again for 48 hours |
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Part of the exercise was
to see how possible it was to stay on the loop with an exhausted scrubber.
First I did a dill flush to clear my head, then completely drained the
loop and filled with O2 twice and then did pure O2 for about five min to
see how it felt but i ascended to 4m as I did not want the Co2 aiding any
Hyperoxia. Every three breaths through nose and refilled with O2 and every
third one of those I gave it a complete drain and refill. It hen repeated
this process using diluent. For both I felt OK. Though I was expecting the
event to happen I continued as normal beyond when on a normal dive I would
have recognised the symptoms and taken evasive action ( I hope).
On a normal dive I would
do a good dill flush to clear my head and to make sure I was not going to
pass out while changing regs and then just bail out
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| Dil flushes where necessary, and immediate ascent with buddy aware of situation |
| Dil flush, ascend 10-15m. Symptoms re-occurred when tried to descend, so abandoned dive on semi-closed mode |
| I bailed out onto OC, ascended to 15M, felt better, bailed back in to CCR with no subsequent problems. |
| flushed loop with dil twice, deep breaths, relaxed |
| Diluent flush (not entirely successful in removing symptoms), terminated dive |
| initially by slowing down, then by ascending |
| stay within recommended times |
| I learned my lesson... |
| My personal deep dive routine now involves using a fresh scrubber for any 70m + dive. I will use a fill for 2 dives up to 70m. I now have a signal for indicating a hypercapnia event to my regular dive buddy |
| Like i say this was on purpose normally I stay within the recommendations. For trimix its a fresh scrubber for every dive |
| Don't be glib about packing. But then I only sneaked it in as the airline companies area a bunch of bastards with the transport of Sofnolime, as discussed in previous e-mails. I think some admit to being far too over zealous with certain elements of their rebreathers, and particularly packing. I just make sure I pat the canister evenly as it's being filled on the level. Check the final amount and ensure the scrim etc fits correctly. Prebreathe for 2-3 mins, and away |
| Replaced scrim cloth, checked/lubricated O-Rings in scrubber, used high He content gas, added ADV to ensure min lung volume during descent, packed a very loose scrubber (little or no patting), packed a very tight scrubber (lots of tapping). Probably tried other things too such as flushing after even slight exertion to make sure CO2 levels low |
| I am very aware of the quality of my breathing on descent ensuring that I take full inhalation & exhalations |
| won't over-exert myself in future |
| Spend longer on bubble check, & when surface conditions are bad, spend time at 6m to get breathing rate down |
| Limit the scrubber time based on workload and water temp |
| As we all know, the pre-breathe is intended to check the scrubber operation. It is not always made clear that it also serves to 'warm up' the scrubber (CO2 absorption is catalysed by heat). I won't cut the pre-breathe short in future. Additionally, in the early days, I tried to extend the scrubber life and found that 5 or 6 hours was normally OK (only if shallow!). Looking back, I did start to get breakthrough on a couple of dives, in each case, suffering a mild headache after the dive |
| All I heard about hypercapnia before the event was bollocks. The symptoms do not disappear when you go open circuit, they don't even diminish. I have seen many people have mild hits, all have different symptoms. The effects vary from person to person and the only way to find out is to have a hit. The initial symptoms are important as that is the point to get out of the water. I still dive with minimal bailout as this incident shows that breathing OC didn't help |
| I always use the elapsed on time as my scrubber counter |
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have read posts where it is evident a diver has suffered a panic attack, and
NOT a hypercapnia event. Hyperventilation and a sense of your field of
vision and world closing in on you are classics. Divers who won't admit this
would rather say it was hypercapnia. Hypercapnia results in your being
totally unable to hold your breath long enough to bail out O/C off the loop.
The first action MUST be a dil-flush to steady the breathing 1st.. Good cardiovascular and lung fitness are essential. Too many holier than thou's are smokers, and I have no time for them, or really sympathy for what befalls them either! |
| So far none of the above remedies have been proven successful. I have a mix of dives - sometimes the dive is really comfortable and breathing seems incredibly easy. Sometimes I have a terrible time and have even aborted a dive or two due to the problems with what feels like CO2 levels too high. Occurs seemingly at random. This has happened at all sorts of depth ranges from 30m to 75m so I don't think it is depth or stress related |
| None |
| above describes the most severe CO2 hit, I've had 3 or 4 others in my 60 hours experience, none as severe but all caused by over-exertion. I suspect that I am a high CO2 producer and can easily out breath the scrubber when I exert myself. I have learned to take it easier going down the shot and on the bottom - can also recognise symptoms very quickly and know that they will clear quickly with a dil flush |
| Diving too deep too soon. No similar events in following 3-4 years |
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