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Diving Safety, Accidents and Incidents Post here to discuss accidents, incidents, ideas, gear, or anything else to improve spearfishing safety. Memorials and condolences threads should be placed in that separate forum.

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Old 05-18-2015, 04:52 PM   #1
Mkumar98
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Some food for thought

Ive been reading about all of the SWB the diving community has been hit with lately. I was brainstorming ideas about how to prevent this, sure an FRV is good but they're pretty expensive and bulky. And isn't it better for the blackout never to happen in the first place then have something that will save you from it? Anyway I've never blacked out, but from what I understand most of them are self inflicted, meaning either caused by a dropped gun in which the diver descends again to recover, staying down too long for that fish, or wanting to outdive your buddies. Sure the oddities occur, entanglements, etc. but for the most part they can be prevented. Any way my idea is a free diving oximeter. Something that wraps around either your ear, not like earphone because that would complicate equalization, but just wraps around your ear, maybe around fingertip that can measure oxygen levels in blood and create an audible alarm when they get low. Most divers know not to push their limits, but when your presented with that big fish or your new PB depth is right in front of you, it's hard to know when to turn around and head for the surface. This would let you know when your O2 levels are getting low and you should head for the surface and a second alarm when your levels are critical and NEED to head for the surface. Just brainstorming so any input would be appreciated.
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Old 05-18-2015, 05:13 PM   #2
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Re: Some food for thought

Oximeters have become cheap and readily available but they do not work underwater, and are sensitive to vibration. I have worn one for pool training by bagging my hand but it is barely practical for pool to testing in 4' of water, much less spearing.
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Old 05-18-2015, 05:35 PM   #3
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Re: Some food for thought

x2 very sensitive to vibration and not accurate.... I've done a static with one on and up to 4 min it was saying i was at 98% so i scrapped the idea
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Old 05-18-2015, 05:40 PM   #4
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Re: Some food for thought

Pressure change would also make them very inaccurate. High partial pressure means you'd typically have close to 100% O2 saturation on the bottom, even when you had over-reached and already committed yourself to a BO. The drop would be rapid and only occur quite close to the surface, long after you could do anything about it. I know oximeters measure ratio of saturated / desaturated haemoglobin rather than actual partial pressure, but the effect would be the same.
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Old 05-18-2015, 05:47 PM   #5
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Re: Some food for thought

temp also plays a big roll in how well they work
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Old 05-18-2015, 06:17 PM   #6
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Re: Some food for thought

I'm not actually saying throw an oximeter in a waterproof case and go diving, I'm just using the term because I didn't know how else to convey it. I'm thinking of a silicone ear mold that uses some of the technology of an oximeter. I'm really not an expert on the subject I'm just trying to figure out how to slow down all of these deaths seven been having.
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Old 05-18-2015, 06:29 PM   #7
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Re: Some food for thought

Quote:
Originally Posted by Mkumar98 View Post
I'm not actually saying throw an oximeter in a waterproof case and go diving, I'm just using the term because I didn't know how else to convey it. I'm thinking of a silicone ear mold that uses some of the technology of an oximeter. I'm really not an expert on the subject I'm just trying to figure out how to slow down all of these deaths seven been having.
Personally i think just a HR monitor or better yet HR counter is very promising but Freedive watches that do that are nearly as expensive as an FRV. I read a study on seals once, most of them dive a set number of heart beats--athletic dive is shorter in time for instance but total beats when compared to long static dive stays remarkably consistent. I would like to see studies on human freedivers; i have a feeling it would similar for experienced freedivers. This would not address the issue of changing partial pressure causing an SWB but it is food for thought as you say.
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Old 05-18-2015, 08:31 PM   #8
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Re: Some food for thought

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Originally Posted by growingupninja View Post
Personally i think just a HR monitor or better yet HR counter is very promising but Freedive watches that do that are nearly as expensive as an FRV. I read a study on seals once, most of them dive a set number of heart beats--athletic dive is shorter in time for instance but total beats when compared to long static dive stays remarkably consistent. I would like to see studies on human freedivers; i have a feeling it would similar for experienced freedivers. This would not address the issue of changing partial pressure causing an SWB but it is food for thought as you say.
Interesting, I didn't even know that there were five watches with a hr monitor, hey if you ever find that link about the study I'd love to read it some time.
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Old 05-21-2015, 07:18 AM   #9
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Re: Some food for thought

[quote=Mkumar98;2046030] sure an FRV is good but they're pretty expensive and bulky. QUOTE]

Check out the latest streamlined version, One FII instructor says he cannot feel the drag -- there is none. Five of us are here in Panama banging away at the tuna with our FRVs protecting us. One diver exceeded his pre-set depth limit at 66 feet and rocketed to the surface. After 7 minutes the FRV was repacked and he was diving again. Take a look at the Diving for a Cause page on Facebook, and you can see the latest FRV design at: www.oceanicss.com
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Old 05-21-2015, 07:46 AM   #10
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Re: Some food for thought

There's some really interesting comments in this thread!
Nice thinking!
I am interested in the heartrate fact about seals. neat! I do know that the difference between my heartrate in the water and some buddies is totally different, although our dive times may not be. Is there any correlation to other dives that you know, Ninja?
Also, the o2 counter would be cool, for a reference, not a life-saving mechanism.
I would like to comment on the FRV, though. I don't think you will find a more effective deterrent to SWB than an vest. The new streamlined FRV is phenomenal. The cleaning is easier, the re-pack is faster, and you dont' really know it's there. Even if you dont have 'surface reminder' on, if you try to dive within a short window (similar to blackout), the vest will inflate.
Honestly, it's expensive and I am cheap. I asked my family to chip in for birthday and xmas. Also, comparing the cost to the rest of my dive gear, it makes sense to get it. I am personally more prone to trying to get a new super-cool roller speargun or carbon fins, or yet another wetsuit- but the FRV can and will literally save your life.
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Old 05-21-2015, 10:34 AM   #11
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Re: Some food for thought

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There's some really interesting comments in this thread!
Nice thinking!
I am interested in the heartrate fact about seals. neat! I do know that the difference between my heartrate in the water and some buddies is totally different, although our dive times may not be. Is there any correlation to other dives that you know, Ninja?
O2 saving/dive response triggers vary a great deal among individuals. Fitness and technique would be a big influence on HR at the start of the dive, before DR kicks in when you are basically just swimming, and then past that there would be a variety of factors--genetics, exertion, training, water temp/movement, exposed skin, hypoxia, diet over the last week, calories burned since last meal, depth/pressure, starting lung volume, muscle fatigue, number/type of prior drops.

One factoid is that even seals themselves show variance--sample size is small but I read a study where they were fitted with various monitors and left alone, the HR drop was fairly consistent across individual animals, although there were a few outliers who were noticeably different in their dive response. That a marine mammal like a seal can be so divergent certainly speaks to the human condition.

Sorry I don't have links to articles, try google. I read all the pub meds about apnea, seals, and hypoxia.

I do want to try one of the new low drag FRV's at some point.
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Old 05-22-2015, 03:22 AM   #12
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Re: Some food for thought

Thanks everyone for the insight, it really is appreciated.

Terry, I want to thank you for making a great product that I'm sure has already saved lives, I will definitely be looking into a vest in the future.

Keep the comments coming, everyone's ideas offer something new.
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Old 05-22-2015, 08:01 AM   #13
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Re: Some food for thought

This is interesting. I don't know about the practicality of it, but it'd be neat to be able to do some experimenting. (given a budget of someone else's money...)

For instance, If you kept with the idea of a pulse/oximeter, would it give you reliable results from an extremity, like a fingertip, at depth, or would you need something closer to the core to get a reliable result?

If the finger tip would work, could you make a rubber glove that had the oximeter built into a fingertip?
What if you stuck with Ninja's heartbeat idea as opposed to oxygen level. would the glove be good enough for that? what about a choker that looks like an oversized fitbit? (Although it could assuredly be thinner.) Is this a bad idea out of the gate because it would put any strain at ALL on the neck while diving? (probably).

If you had a reliable oximeter, could you write a program using a small computer, like a raspberry pi, that would take into account the pressure of the water surrounding you and calculate the partial pressure based on that?

This would be fun to play with over a couple beers! Even if it turned out to be completely impractical.
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Old 05-22-2015, 09:37 AM   #14
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Re: Some food for thought

Quote:
Originally Posted by Mullins View Post
Pressure change would also make them very inaccurate. High partial pressure means you'd typically have close to 100% O2 saturation on the bottom, even when you had over-reached and already committed yourself to a BO. The drop would be rapid and only occur quite close to the surface, long after you could do anything about it. I know oximeters measure ratio of saturated / desaturated haemoglobin rather than actual partial pressure, but the effect would be the same.
This is the answer here. There is no tool that will measure anything in your body to tell you it's time to head back to the surface to avoid a blackout.

The Freedivers Recovery Vest on the other hand, is amazingly streamlined and is definitely not bulky by any measure and will put you back on the surface face up if you exceed parameters.

I have dove with all three versions of the vest and none of them inhibited my diving effort in any way.
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Old 05-22-2015, 03:21 PM   #15
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Re: Some food for thought

Fingertip pulse oxymeter is great training tool and the fact that in the last ten years the price on them has dropped so dramatically has helped the sport of apnea move forward, but they have limitations especially for divers experiencing strong vasoconstriction. Better results are had I think from ear lobe models but those are still medical only. I honestly doubt if anyone will develop a submersible one--no market to speak of.

The pulse watches work via chest strap, no need for fingertip pulse meter. As far as partial pressure being computed it would be interesting but the diver's surface inhalation lung volume and rate of burn would need to be computed, with depth and time being measured by the watch and figured in. Rate of burn could be approximated by HR to some degree... Regardless the device would need time to 'learn' and individual diver, and again there is enormous individual variance in hypoxia tolerance--one guy may still be conscious (albeit foggy!) and swimming at 50% O2while another blacked out at 70%. Pretty soon you would have a safety device that takes a lot of the 'free' out of 'freediving'.

The pulse counter on the other hand would just be software upgrade on existing tech (Galeleo for instance), although it would take a very experienced diver to make any use the metric and it would also need calibrating to the diver over the course of hundreds of drops, and it isn't going to actually save you, unlike an FRV which is failsafe as mechanically possible in that department...
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