I'm posting this in hope that some will learn from my mistake (and there was one terrible mistake) and also to hear any comments that could help me with figuring why it had happen or any other conclusions that might be drawn from this.
There are going to be a lot of details here as I'm trying to analyze this incident, so this is going to be long, and maybe boring.
My first blackout. Atleast I think it was a BO and not an LMC, I think the distinction in this case is not important as it should be threated the same.
It was on the 7th of October, my last diving day in Dahab (out of a week or so of diving). We were diving on a rope near the lighthouse, bottom is sandy at about 17m, with a slope of maybe 40 degrees down (guessing).
I was using plastic bi-fins and 3mm Elios with 3kg on the weight belt (nuetral buoyancy at around 11m on full inhale).
I'll try to describe the diving session and some parts from the previous day.
Terms I use:
TLC: full inhale, no packing.
Contrlled exhale: I'm comfertable diving only shallow (10m~) with FRC (or close to FRC) so if I dive deeper and don't want to dive with full lungs I exhale a number of short "puffs" of air that seem to leave me with relatively consistant volume.
Static on the bottom: Not a "real" static as I will move around a little if there is something interesting to see or grab something/borrow my hands in the sand if I'm gliding down because of the slope.
Dynamic on the bottom: not a "real" dynamic as I will not try to cover as much distance but just swim around close to the bottom with a few fin thrusts and/or pushing with my hands from the bottom.
Numbers are: (Time of day), (Depth), (Dive time), (Approximate Interval)
12:22 10.0m 0:28 Recovered a weightbelt with about 8-10 kilos on the way to the rope, struggled back to shore and then went on to the rope, there was moderate excertion as I was very negative.
12:33 10.3m 1:18 TLC. Just a warmup dive, clearing air out of the suit and such. Don't remember if it was FI (pull down) or CW (fins).
3~ minutes rest
12:37 17.3m 2:34 TLC, FI, static
3:30~
12:43 16.7m 2:06 Controlled exhale (3 "puffs"), CW, static
5~
12:50 17.3m 2:00 Controlled exhale (4 "puffs"), CW, static
4~
12:56 27.1m 1:44 TLC, CW, dynamic, BO
5:30~
13:03 10.3m 1:16 TLC, just to check that I am ok and "regain confidence".
End of session.
This is how I remember the dive with the blackout:
I started gliding around 13m I think, at the bottom of the rope I pushed myself down the slope, kept gliding parallel to the slope, with a few fin strokes or hand pushes from the bottom here and there, I gathered some distance on the bottom that way till I heard my alarm (26m) and stopped on the bottom (27m) for a few seconds, turned around and started finnig leisurely back to the rope. I could see the rope from where I turned so the distance wasn't more than 30m probably, my estimation is 15-20m. Already when I neared the rope (18m~ depth) I started feeling hypoxic, which should've rang some bell as it doesn't happen to me very often and never at those depths. It wasn't a strong sensation and it didn't occur to me at that time that I may be at risk. I remember getting to the surface, I recall the image of the bottle (buoy) at the end of the line, I remember taking a breath (which might have been a bigger breath than I intended), I remember taking the snorkel in my hand as in to put it back into my mouth - I guess that wasn't a conscious decision, it's just what I did in the few previous dives after 1-3 breaths. But I didn't put it in my mouth. I remember feeling one twich on the right side of my body (but that might have been Greg who caught me) but I have no visual recollection to connect with the second that twitch occured. I asked Greg if I had a samba and I don't recall now what exactly he answered but it was positive about me screwing it up. I concluded at that moment that it was a samba. Since I just recalled the twitch I said jestuflly that it would've probably been ok in a competition and he laughed. I felt fine, as if nothing strange had happened. After he dove I told him what I remember from the dive and he said that after I inhaled I bounced down underwater and he grabbed me. So there was half a second or so that my head was underwater which was missing from my memory - I don't remember the visuals of it nor the sensation of water on my face. He said I came right out of it.
I dove one more slow dive to 10 meters, just incase I'll need it later as a psychological anchor, also to see if there are any strange sensations. I felt totally normal after that dive session, except the idea of a blackout that shoock me a little.
Canceled the afternoon dive session but went on a night dive (well, more like a night frolic) in which most dives didn't exceed 1 minute or 10 meters, with maybe 2 dives to 15m and 1:30 (where my alarms were set).
Considerations/suspected reasons:
Time I spent active (dynamic) - I've done a few very comfertable slow dynamics (finning, not gliding off the floor) to and fro dive sites and all of them ended at 1:00-1:05 range (with me checking the numbers only after the dive). On this dive I was active in some way almost the entire duration, but I've done the same dive profile just to 25m a few times the previous days (more than once per session) on the same location with no signs of hypoxia. Probably with a longer stay at 25m. So I don't think that I exceeded my dynamic time limit on that dive, I might be wrong though.
Breath-up, Hyperventilations and contractions - My breath-up in the last months is something like this:
Breathe normal for most of the duration of the interval (try control my breathing).
About one minute before starting the dive: Inhale to the max, Exhale to the max (moderate speed), take a few normal breaths again, inhale to the max and dive. I do that to prepare for a full inhale for the dive - I feel that my heartrate doesn't rise as much on the second inhale. (I'm considering now doing the first inhale ealier in my breathup).
About contractions... well, when I'm in the 'zone' my contractions (while diving, not static) are small tensing of the diaphragm, not full blown body rippling contracions (as I don't appriciate those underwater and like to have only easy dives). I guess there were a few of those but I didn't really take notice them. (Maybe I should work on being more aware of them.)
Not doing a proper recovery breath - may prevent a BO/LMC if I'm on the edge.
The settings of this dive session (more reasones):
I Didn't feel excerted when I started diving on the rope.
I felt pulmonary blood shift on both of the controlled exhale dives, a very pronounced one on the second dive. On the other hand I don't recall ever in my life feeling peripheral vasoconstriction so I don't know if I had any that day. Same for lactic acid buildup in the legs.
I usually try to make my surface interval twice my dive time (for anything below 30m), this time I didn't as I was intrigued by this issue and wanted to try shorter surface intervals, figuring that DCS is not really an issue at such depths/times and that I am supposed to "reoxygenate" fast enough (what might have been a mistake).
I recall not "wetting" my suit that dive session which was different from most of the dive sessions in the previous days. Maybe excertion before the session weakend my dive response?
I doubt I was dehydrated.
The day before I was in the blue hole, the jeep that took us had a TERRIBLE exhaust issue... all of us that sat in the back kept complaining about how much exhaust we inhaled. At the end of the ride back my head was a little dizzy and a I felt a slight headache and nausea, the feeling faded in less than an hour.
I suspect carbon monoxide poisoning as one of the factors in this BO incident (though I can't really tell). I think that I might have abosrbed more of it on the way back because of pulmonary blood shift as my last dive before rushing to gather equipment and to the jeep was a forced exhale one to 4-5 meters (which felt a lot for me as I don't do much depth/pressure training and even then only FRC).
I didn't find any real info on the web as to how long it takes to get clean from CO (maximum 48 hours except nurological symptomes), I saw claims that carboxyhaemoglobin's half-life period is 5 hours. The dive session was 19-20 hours after the last jeep ride which MIGHT leave me with 6.25% CO of the amount I abosrbed. I have no idea how much influence that could have had.
Food: I don't recall what I ate but it couldn't be noticeably different from what I ate any other day in Dahab.
Sleep: I did wake up a couple of times in the middle of the night (including the moque at 2:30am due to Ramadan), but it wasn't the first night it happened and it's not that uncommon for me. I didn't feel any fatique in the morning.
Blood pressure: I usually have normal BP, inclining to high if anything. I don't see a reason to think it was different that day.
Pre-dive preparation: I did my normal (very few) diaphragmatic and ribcage stretches (with a few packs).
[To be continured on the next post]
There are going to be a lot of details here as I'm trying to analyze this incident, so this is going to be long, and maybe boring.
My first blackout. Atleast I think it was a BO and not an LMC, I think the distinction in this case is not important as it should be threated the same.
It was on the 7th of October, my last diving day in Dahab (out of a week or so of diving). We were diving on a rope near the lighthouse, bottom is sandy at about 17m, with a slope of maybe 40 degrees down (guessing).
I was using plastic bi-fins and 3mm Elios with 3kg on the weight belt (nuetral buoyancy at around 11m on full inhale).
I'll try to describe the diving session and some parts from the previous day.
Terms I use:
TLC: full inhale, no packing.
Contrlled exhale: I'm comfertable diving only shallow (10m~) with FRC (or close to FRC) so if I dive deeper and don't want to dive with full lungs I exhale a number of short "puffs" of air that seem to leave me with relatively consistant volume.
Static on the bottom: Not a "real" static as I will move around a little if there is something interesting to see or grab something/borrow my hands in the sand if I'm gliding down because of the slope.
Dynamic on the bottom: not a "real" dynamic as I will not try to cover as much distance but just swim around close to the bottom with a few fin thrusts and/or pushing with my hands from the bottom.
Numbers are: (Time of day), (Depth), (Dive time), (Approximate Interval)
12:22 10.0m 0:28 Recovered a weightbelt with about 8-10 kilos on the way to the rope, struggled back to shore and then went on to the rope, there was moderate excertion as I was very negative.
12:33 10.3m 1:18 TLC. Just a warmup dive, clearing air out of the suit and such. Don't remember if it was FI (pull down) or CW (fins).
3~ minutes rest
12:37 17.3m 2:34 TLC, FI, static
3:30~
12:43 16.7m 2:06 Controlled exhale (3 "puffs"), CW, static
5~
12:50 17.3m 2:00 Controlled exhale (4 "puffs"), CW, static
4~
12:56 27.1m 1:44 TLC, CW, dynamic, BO
5:30~
13:03 10.3m 1:16 TLC, just to check that I am ok and "regain confidence".
End of session.
This is how I remember the dive with the blackout:
I started gliding around 13m I think, at the bottom of the rope I pushed myself down the slope, kept gliding parallel to the slope, with a few fin strokes or hand pushes from the bottom here and there, I gathered some distance on the bottom that way till I heard my alarm (26m) and stopped on the bottom (27m) for a few seconds, turned around and started finnig leisurely back to the rope. I could see the rope from where I turned so the distance wasn't more than 30m probably, my estimation is 15-20m. Already when I neared the rope (18m~ depth) I started feeling hypoxic, which should've rang some bell as it doesn't happen to me very often and never at those depths. It wasn't a strong sensation and it didn't occur to me at that time that I may be at risk. I remember getting to the surface, I recall the image of the bottle (buoy) at the end of the line, I remember taking a breath (which might have been a bigger breath than I intended), I remember taking the snorkel in my hand as in to put it back into my mouth - I guess that wasn't a conscious decision, it's just what I did in the few previous dives after 1-3 breaths. But I didn't put it in my mouth. I remember feeling one twich on the right side of my body (but that might have been Greg who caught me) but I have no visual recollection to connect with the second that twitch occured. I asked Greg if I had a samba and I don't recall now what exactly he answered but it was positive about me screwing it up. I concluded at that moment that it was a samba. Since I just recalled the twitch I said jestuflly that it would've probably been ok in a competition and he laughed. I felt fine, as if nothing strange had happened. After he dove I told him what I remember from the dive and he said that after I inhaled I bounced down underwater and he grabbed me. So there was half a second or so that my head was underwater which was missing from my memory - I don't remember the visuals of it nor the sensation of water on my face. He said I came right out of it.
I dove one more slow dive to 10 meters, just incase I'll need it later as a psychological anchor, also to see if there are any strange sensations. I felt totally normal after that dive session, except the idea of a blackout that shoock me a little.
Canceled the afternoon dive session but went on a night dive (well, more like a night frolic) in which most dives didn't exceed 1 minute or 10 meters, with maybe 2 dives to 15m and 1:30 (where my alarms were set).
Considerations/suspected reasons:
Time I spent active (dynamic) - I've done a few very comfertable slow dynamics (finning, not gliding off the floor) to and fro dive sites and all of them ended at 1:00-1:05 range (with me checking the numbers only after the dive). On this dive I was active in some way almost the entire duration, but I've done the same dive profile just to 25m a few times the previous days (more than once per session) on the same location with no signs of hypoxia. Probably with a longer stay at 25m. So I don't think that I exceeded my dynamic time limit on that dive, I might be wrong though.
Breath-up, Hyperventilations and contractions - My breath-up in the last months is something like this:
Breathe normal for most of the duration of the interval (try control my breathing).
About one minute before starting the dive: Inhale to the max, Exhale to the max (moderate speed), take a few normal breaths again, inhale to the max and dive. I do that to prepare for a full inhale for the dive - I feel that my heartrate doesn't rise as much on the second inhale. (I'm considering now doing the first inhale ealier in my breathup).
About contractions... well, when I'm in the 'zone' my contractions (while diving, not static) are small tensing of the diaphragm, not full blown body rippling contracions (as I don't appriciate those underwater and like to have only easy dives). I guess there were a few of those but I didn't really take notice them. (Maybe I should work on being more aware of them.)
Not doing a proper recovery breath - may prevent a BO/LMC if I'm on the edge.
The settings of this dive session (more reasones):
I Didn't feel excerted when I started diving on the rope.
I felt pulmonary blood shift on both of the controlled exhale dives, a very pronounced one on the second dive. On the other hand I don't recall ever in my life feeling peripheral vasoconstriction so I don't know if I had any that day. Same for lactic acid buildup in the legs.
I usually try to make my surface interval twice my dive time (for anything below 30m), this time I didn't as I was intrigued by this issue and wanted to try shorter surface intervals, figuring that DCS is not really an issue at such depths/times and that I am supposed to "reoxygenate" fast enough (what might have been a mistake).
I recall not "wetting" my suit that dive session which was different from most of the dive sessions in the previous days. Maybe excertion before the session weakend my dive response?
I doubt I was dehydrated.
The day before I was in the blue hole, the jeep that took us had a TERRIBLE exhaust issue... all of us that sat in the back kept complaining about how much exhaust we inhaled. At the end of the ride back my head was a little dizzy and a I felt a slight headache and nausea, the feeling faded in less than an hour.
I suspect carbon monoxide poisoning as one of the factors in this BO incident (though I can't really tell). I think that I might have abosrbed more of it on the way back because of pulmonary blood shift as my last dive before rushing to gather equipment and to the jeep was a forced exhale one to 4-5 meters (which felt a lot for me as I don't do much depth/pressure training and even then only FRC).
I didn't find any real info on the web as to how long it takes to get clean from CO (maximum 48 hours except nurological symptomes), I saw claims that carboxyhaemoglobin's half-life period is 5 hours. The dive session was 19-20 hours after the last jeep ride which MIGHT leave me with 6.25% CO of the amount I abosrbed. I have no idea how much influence that could have had.
Food: I don't recall what I ate but it couldn't be noticeably different from what I ate any other day in Dahab.
Sleep: I did wake up a couple of times in the middle of the night (including the moque at 2:30am due to Ramadan), but it wasn't the first night it happened and it's not that uncommon for me. I didn't feel any fatique in the morning.
Blood pressure: I usually have normal BP, inclining to high if anything. I don't see a reason to think it was different that day.
Pre-dive preparation: I did my normal (very few) diaphragmatic and ribcage stretches (with a few packs).
[To be continured on the next post]
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