Too Deep, Too Often, Too Soon?

[naiad]

Originally Posted by wet

The problem with hearing UW is presence of air in bone cavities, once air is replaced with water, sounds carry well, no need for loud clicks, even soft clicks carry a ways. Simply ticking the teeth together works too for a short distance. Some shrimp, crabs and fish make clicking sounds in various ways. There's no loss of air in clicking, unlike vocal speech or humming.

Totally OT now, but I am not sure about the role of air in underwater hearing. The most advanced orders of fish, Cypriniformes (carp, minnows, most coarse fish, danios, loaches etc.), Characiformes (tetras), Siluriformes (catfish), and Gymnotiformes (electric eels, knifefish), have a series of bones connecting the air bladder to the inner ear, allowing them to hear a much wider range of sounds than other fish. This must be important, because species which no longer need an air bladder for buoyancy (catfish, loaches), still have a small one for hearing, and in some cases for producing sounds.

[DeepThought]

Originally Posted by wet

Do you know whether, upon switching from inhaling air to O2, does blood N2 drop down to zero?

In other words, you're asking if we can off-gas N2 to zero or is there some minimum N2 level in the blood due to metabolic production?
AFAIK most of our nitrogenic waste products are oganic (Amonia+CO2=Urea) and urinating is the primary way of getting rid of it. If I remember correct there are some biochemical reactions in our body that create N2 as a byproduct, but they are not a primary mean of getting rid of excess Nitrogenic compounds, if that was the case then we could've just exhaled N2 all the time and not need to pee.

Originally Posted by wet

If so, would digestion of hi-protein food rich in nitrogen compounds (molluscs) cause an increase in N2 in the body, especially in the blood?

From the reasons I mentioned above I tend to guess that the change would be very minimal if at all.
But it's just an estimation based on my incomplete knowledge.
By the way, NO is also a vasodilator.

[diveoceanos]

Originally Posted by wet

Hi Deep Thought, thanks much for checking.

I erred, mixing (apples) inert N2 from air, and (oranges) Nitrogen compounds from high protein molluscs. I'd thought that N2 was not easily absorbed into blood, that scuba at depth increased absorption, but that a significant part came from high-protein foods, and that adding N2 at depth was just a part of it, the straw that broke the camel's back.

Do you know whether, upon switching from inhaling air to O2, does blood N2 drop down to zero? If so, would digestion of hi-protein food rich in nitrogen compounds (molluscs) cause an increase in N2 in the body, especially in the blood? That is what I thought happened, which is why I thought of excretion. I was thinking of other chemicals which end in the bloodstream (drugs etc.).
Anyway, I'll review and edit my post, for now i'll just box it off.
Yes, I know, i need to take a course or 3. If only...

Note on NO production sources: From Wikipedia:

"In the body, nitric oxide (the 'endothelium-derived relaxing factor',
or 'EDRF') is synthesized from arginine

Arginine - Wikipedia, the free encyclopedia and oxygen
Oxygen - Wikipedia, the free encyclopedia by various nitric oxide synthase
Nitric oxide synthase - Wikipedia, the free encyclopedia (NOS) enzymes
Enzyme - Wikipedia, the free encyclopedia and by sequential reduction of inorganic nitrate."
(dang complex biochemical pathways!!)

DDeden

Hi pal,

Nitrogen is considered an inert gas. It can not be metabolised / utilised from the human body. It is only absorbed, distributed and disolved in the body tissues according to the pressure difference in the alveoli and in the blood in the lung vessels. When this pressure is reversed the excess Nitrogen starts to off-gasing i.e. return to the alveoli from the blood and gradually from all other tissues back in the blood and alveoli. The main driving factor is again the pressure gradient.

Definitely if one breath pure oxygen for several days the blood Nitrogen would drop to zero but before that one would suffer a condition called pulmonary oxygen toxicity.

Nitrogen is also a part of almost all biomolecules but that is something different than gaseous nitrogen. The nitrogen containing byproducts of metabolism do not include gaseous nitrogen.

[wet]

Originally Posted by naiad

Totally OT now, but I am not sure about the role of air in underwater hearing. The most advanced orders of fish, Cypriniformes (carp, minnows, most coarse fish, danios, loaches etc.), Characiformes (tetras), Siluriformes (catfish), and Gymnotiformes (electric eels, knifefish), have a series of bones connecting the air bladder to the inner ear, allowing them to hear a much wider range of sounds than other fish. This must be important, because species which no longer need an air bladder for buoyancy (catfish, loaches), still have a small one for hearing, and in some cases for producing sounds.

Do most of those fish live somewhat amphibiously, compared to pelagic ocean fish? If so, air conduction would be significant, as it is in frogs and seals. AFAIK most ocean pelagic fish have one inner bone connected to the inner ear, while mammals have three. (I'd guess sharks have none). Do you know for certain that these (catfish, loaches) fish while at depth have air-filled bladders connected to their ears? Can the bladders empty at depth, (or fill with water or oil) and then refill with air at the surface? It is also possible that their ears are functionally deaf at depth but they pick up (hydrosonic) vibrations via their lateral line and/or bones.

I think there's a freshwater fish that squirts water up at flying insects, I would guess that fish has good air-conduction aural capabilities (ear-air-sac), but also good water-conduction aural capabilities.

o0O0o0O0o0O0o `<8{(((>< o0O0o0O0o0O0o

Regarding hearing underwater Too Deep, Too Often and Too Soon; although I think that ancestral humans dove at equatorial seashores in warm surface water, I've no doubt they encountered cool to cold water at depth and especially during coastal migrations farther from the equator. Evidence of ear exostosis (bony ear canal rings) has been found in a number of human fossils (Upper Nile River, Peruvian coast, Rome coldwater baths), this occurs due to sustained periodic exposure to cold water in the external ear canal over time.

I think exostosis indicates mostly youthful single males habitually competing at greater depths without sufficient surface intervals to warm the ear canal and cerumen, over time this would produce bony accretion around the canal. This may indicate spearfishing more than mollusc hunting, since spearing requires a longer time at depth. However the fact that humans are no where nearly as hydrodynamic mammals like dolphins, sea lions, etc. indicates that spearfishing or "fast" chasing pelagic fish was not as common as "slow" diving for sessile/benthic foods (molluscs, oysters, marine snails, etc.). I'd guess spears were more jabbing-thrusting-prying tools, rather than shooting weapons; useful for crabs, flounder, immobile camoflaged octopi and such.

AFAICT, paired archaic divers backfloated/dove in rotation at warm sunlit surface, the middle ear was warm-water filled and the external canal also warm-water filled, the earwax kept this warm water in place during the dive into the colder depths when the MDR was engaged, acting like thermal ear-plugs but not air-holding ear plugs.

Although yet unconfirmed, I feel quite certain that simultaneously a similar thermo-retention system was employed in the sinunasal cavity and affiliated middle ears (via the eustacian tubes) by allowing warm surface water (larynx was valved shut) in and then closing the nasal passage via the swollen tissues of the inferior concha (VR) and/or philtrum closure (both of these are found only in humans, not our arboreal kin) early during the dive into the cooler depths, preventing the "sinus-ice cream headache" otherwise sure to affect the diver (and which is now often covered by mask or hood) and alleviating the need for continuous equalizing with each elevation/pressure gradient.

Ear extoses: Diving into the cold w/o retaining the warm

DiBartolomeo JR 1979
Exostoses of the external auditory canal
Ann Otol Rhinol Laryngol Suppl 88 (6 Pt 2 Suppl 61) :2-20.

Exostosis of the external ear canal is a disease unique to man. It has been
identified in prehistoric man, affecting the aborigines of the N.American
continent. Aural exostoses are typically firm, sessile, multi-nodular bony
masses which arise from the tympanic ring of the bony portion of the
external auditory canal. These growths develop subsequent to prolonged
irritation of the canal. The large, primitive jaw of prehistoric man placed
great mechanical stress on the tympanic ring. Chronic aural suppuration seen
in the pre-antibiotic era was soon followed by exostoses. Today, prolonged
contact of the external ear canal with cold sea water is the most prevalent
cause (aquatic theory). As a result the disease is now essentially limited
to coastal regions. In this way we have seen exostoses appear in different
stages of the evolution of man as a result of mechanical, chemical and now
thermal irritation.

The author, DiBartolomeo JR, is an otolaryngologist in a coastal region.
In examining 11,000 patients during a 10-year period, 70 cases of
symptomatic exostoses of the external auditory canal were identified. The
incidence of exostoses was found to be 6.36 per 1000 patients examined for
otolaryngologic disease. It is a predominantly male disease. The development
of these "irritation nodules" is painless until the tenth year of aquatic
exposure to irritation, when symptoms of obstruction occur. The hearing loss
associated with exostoses is usually a conductive type, secondary to
occlusion of the canal by impacted cerumen or acute external otitis. The
results of studying the thermal characteristics of the body of water used
for such aquatic activities is presented.

DDeden (Thanks MV at AAT for noting article and VR info)

[naiad]

Originally Posted by wet

Do most of those fish live somewhat amphibiously, compared to pelagic ocean fish? If so, air conduction would be significant, as it is in frogs and seals. AFAIK most ocean pelagic fish have one inner bone connected to the inner ear, while mammals have three. (I'd guess sharks have none). Do you know for certain that these (catfish, loaches) fish while at depth have air-filled bladders connected to their ears? Can the bladders empty at depth, (or fill with water or oil) and then refill with air at the surface? It is also possible that their ears are functionally deaf at depth but they pick up (hydrosonic) vibrations via their lateral line and/or bones.

Most of those fish live in relatively shallow water (less than 10m) because most freshwater habitats are not very deep. The Carp and Tetras do not ever leave the water, but many of the Catfish and Loaches will leave the water in wet weather, in search of new ponds and rivers. Most species in these orders can breathe air, using their intestinal tract (Loaches, Corys, Plecos) or modified gill chamber (large Catfish).

More about the air bladder...
http://forums.deeperblue.net/627049-post70.html

Originally Posted by wet

I think there's a freshwater fish that squirts water up at flying insects, I would guess that fish has good air-conduction aural capabilities (ear-air-sac), but also good water-conduction aural capabilities.

It is the Archerfish, Toxotes sp. It hunts by sight, so it probably does not need to hear its prey.

Archerfish - Wikipedia, the free encyclopedia

Archerfish - Wikipedia, the free encyclopedia
Archerfish - Wikipedia, the free encyclopedia

Originally Posted by wet

o0O0o0O0o0O0o `<8{(((>< o0O0o0O0o0O0o

Good one, I have been trying to make fish pictures too.

[wet]

Originally Posted by naiad

Most of those fish live in relatively shallow water (less than 10m) because most freshwater habitats are not very deep. The Carp and Tetras do not ever leave the water, but many of the Catfish and Loaches will leave the water in wet weather, in search of new ponds and rivers. Most species in these orders can breathe air, using their intestinal tract (Loaches, Corys, Plecos) or modified gill chamber (large Catfish).

More about the air bladder...
http://forums.deeperblue.net/627049-post70.html

It is the Archerfish, Toxotes sp. It hunts by sight, so it probably does not need to hear its prey.
Archerfish - Wikipedia, the free encyclopedia

Good one, I have been trying to make fish pictures too.

=d(@^@)b= <-- funky fish!

Ok, so if fish which use air-conduction hearing typically dwell within 10 m of the surface, then that fits with my expectation, that it is a surface adaptation advantageous to them, regarding predators and/or prey. Perhaps some deep dwelling fish also use air-hearing for special functions.

AFAICT, this does not conflict with what I was saying about archaic human seashore divers/backfloaters using water-conduction hearing during their dive-foraging cycles, when hearing the dive partner was more significant than hearing prey or predator.

Allowing sun-warmed, UV-sterilized blood-temperature surface saline into the external ear, middle ear & sinonasal cavities just before diving deep meant that cold water at depth would trigger the facial and trigeminal nerves on the face maximizing the MDR, (unlike a full face mask & hood), yet (presumably) avoid the accompanying ice cream headache typical of prolonged cold water immersion of the bare face and forehead. This kept the brain warm at depth (conserving oxygen and energy), while the blood from the extremities moved towards the body core and the rest of the body acclimatised to the chilly temperature. Upon resurfacing, backfloating allowed maximum solar absorption, and blood returned to the small blood vessels of the sunwarmed extremities.

DDeden

[ricki]

I put together a summary of sorts of some of the suggestions in this thread regarding deeper scooter free diving on another website, portions reproduced below. Any other ideas? That is aside from seeking out a genetic throwback from possible artesinal free diving foraging ancestors? Wouldn't be all that much fun anyway, they'd get to do all the diving.

- You don't want to be further down than you are able to ascend from without aid of the scooter. If something happens to it, you ditch the scooter and ascend. I've decided to rig a small pony bottle across the small of my back just in case. Might even use it for a safety stop at times.

- Some have said to be sure to ascend particularly slowly in the last 33 ft. and even to stop for a while there to off gas. One diver mentioned doing an O2 safety stop at the end of the day, could make an important difference.

- As always, hydrating thoroughly is advisable.

- Others have indicated some issues with very rapid ascent, faster than I could go with the VS scooter on the order of almost 10 ft. per second. I think the VS was moving at less than 1/3 that speed. Anyway, all that speed can lead to barotrauma and disorientation or vertigo due to middle ear issues. So, motoring at reduced speed on ascent seems to be prudent.

- Still others talked about lung and trachea squeeze at depth, perhaps a bit deeper than I was hitting on this series of dives. It was advised to increase diving depth slowly over weeks to try to allow the body to acclimate to the new stresses.

- Another warned of hitting the wreck while under power. You could easily knock yourself out going fast on a scooter. A helmet is a good idea to try to reduce impact damage along with slow operating speeds and careful vigilance to avoid slamming into stuff. It is pretty easy to hit things motoring around a wreck, so have a care.

- It doesn't appear to be a good idea to mix SCUBA diving with this sort of activity. We still don't know a lot about residual nitrogen from SCUBA diving and impacts of free diving on promoting DCS other that it sometimes does just that! Some advise treating free diving like flying, only do it once you have cleared out all residual nitrogen or 24 hours or more after your last SCUBA dive. Seems strict but DCS hits are no picnic and worse tend to reoccur even easier at the same locations.

- Have your buddy carefully examine you for signs of cyanosis upon surfacing and other unusual indications. If you start to feel odd, break, increase surface interval for recovery or call it a day as indicated.

There is more along with some photos related to the wreck dive that got me thinking about this at:
http://fksa.org/showthread.php?t=4490
Thanks for all the ideas and suggestions!

Rick

[ricki]

Just went out today for some shallow scooter free diving under 70 ft. closer to home off Boca Raton. I was hoping to do some of that gradual transitioning that Paul Kotik recommended. Unfortunately, the weather and current conditions deteriorated shifting the destination away from the planned wrecks. With fairly poor viz., about 30 ft. and raging supercells just inland it made for a fairly distracting session. Despite that it was still good for some evaluation.

It was the first time out with a functioning Sea Doo Explorer scooter. They are selling them pretty inexpensively currently, around $600. USD. I rigged a tee seat expecting it to be a bit faster than the VS scooter. It is still a low end consumer scooter but I was hoping it would perform reasonably well anyway. Still checking the quality out and am hoping for the best at this point. This model as three speed settings readily switchable by repeated trigger pulls and a reported 2 hour battery duration.

On descent I motored at full speed using one hand for the trigger and the other for equalizing making things easy. On ascent a few dives into it I experienced some slight vertigo similar to that described by Eric. I was a little congested initially and suspect differential equalization was at the root of things as he indicated from ear pops and squeaks on ascent and not descent per normal form. So, I backed off to the middle speed setting for ascents or even the low setting at times. Later I trimmed for a bit more positive bouyancy and would turn the scooter off and gently ascend close to the speed of slow bubbles in the upper 20 or so feet. This allowed a time to relax a bit. I need to experiment with the tee seat bridling some more to improve performance.

The speed of the unit was good on the high setting but still just over 3 mph per the spec sheet. Hope to get it out again soon in good viz. and minimal current for more evaluation and practice.

Rick

[ricki]

Just an update, I wanted to pass along some hardware experiences for divers thinking about moving into scooter free diving. I have had a Seadoo VS scooter for several years. It wasn't a powerhouse but it was inexpensive, light and functioned reasonably well.

Wanting to move up a bit I recently bought a Seadoo Explorer just before a quick trip out of town. I wasn't able to take it into the water before flight time so I discovered the problem after I arrived. The drive shaft from the motor apparently has an internal linkage that decoupled within the motor housing. I shipped that one back to the retailer, who was very helpful by the way. He offered me a full refund and I figured, well lets try again. I asked that another unit be shipped out.

The second unit collected about 1/2 inch of water in the battery compartment after a few free dives under 70 ft. the first time out. All the seals were in place, lubed and free of grit, hairs, etc. that might impair sealing. Hoping it might have been a fluke, I took it out the next day for a beach free dive no deeper than 15 ft.. This time I collected water droplets within the battery compartment. Also, I noticed gas escaping from the "sealed" motor housing at the base of the battery compartment. Looking online, I understand some other Explorer units have had leakage problems. I've spoken to Body Glove the importer who was sympathetic and have attempted to speak with their repair center about time frames and likely outcomes several times without getting a call back. So, I will throw the towel in and ship the second scooter back to the retailer for a refund and start over. I understand another fairly large retailer took them off the floor and shipped them back recently.

Bad luck, to be sure but at the same time apparently fairly poor QA/QC at the factory. I am now looking around for another scooter to buy and may bite the bullet and get something more expensive again. Anyway, for what it is worth, buyer beware. You may fair better, then again, maybe not.

Rick

[harbour seal]

ricki,

thanks for the updates from the wide-world of scooter freediving.

sorry to hear of your latest mechanical malfuntion. keep us posted on your continued progress.

cheers,
sean

[cdavis]

Ricki,

Ebay is a good source for this kind of thing, at deep discounts off retail. Just make sure the model has a common and cheap battery and is little used.

The Dacor is not supposed to be nearly as good a scooter as a Mako or particularly a Gavin, but the one I tried (Jon's) seemed pretty fabulous to me. Given how long he's had it and used it, it must be a pretty tough machine.
There has been a fair amount of negative comment about Seedoos on these boards.

Good luck looking.

Connor

[Jon]

My father-in-law has a Gavin, great scooter but way too expensive, and he owned a Frallon before that. I've used both of those as well as the Makos and Tekna's. The Mako is a nicely balanced unit, but it costs too much more, compared to the Dacor/Apollo, to ever make me think of buying one. The Tekna needs to be balanced out with PVC tubes to make it trim out correctly. i also am not sure if you can even get parts for the Teknas anymore. I thought that George was giving partital trade in credit for a Tekna scooter toward the purchase of a new Gavin- he rewinds the motors and puts them in the Gavin's.

The one nice thing about my scooter, over the more expensive ones, is that the battery changes out in less than a minute. I have two main batteries and two more, older ones, in reserve. I can run the thing all day long. Some of my buddies owned other scooters of similar size, i think it was an Aeris and a Mako, and you needed a screw driver to change out the battery- too much trouble.

I've seen used Dacor/Apollos go for around $700- $1,000 on Ebay and that seems to be about the best "bang for the buck" from everything I've seen and used.

Now, if money wasn't an issue I'd rush out and buy one of those X-scooters that Longfins has. That thing is powerful and tiny! The cost is a bit high, but they have some very cool accessories- like a built in video camera!

Has far as safety goes, I have never had any kind of vertigo problems in the 10+ years I've used mine for freediving. I have hit my head on shipwrecks with it- going full blast in less than perfect vis, and I even impaled myself on a tree up in wazee once- search through the old threads and you'll find pictures of it. The big issue is not going too fast for the vis you dive in. I ended up dialing my speed back a bit this past week when I was diving up north. It seemed a bit safer and I actually saw more going a little bit slower in that level of vis.

Jon

[ricki]

Thank you for the input on potential scooters Conner and Jon. Sean, it's the way it goes sometimes. I am reminded of the time I was running a Remora wetsub with a 220 V 40 A power umbilical running to a generator on the surface. You lay on this thing and I looked down and saw this interesting bubbling glowing arc about 2 inches in diameter a few inches from my stomach. The power coupling had pulled out exposing wires but was still tethered by a line. Cutting it free was interesting. Gadgets will act up at times. It make take a bit of time but I hope to find something in the not too distant future. The weight, burn time, speed and certainly the price of the Explorer are ideal, even when compared with some more costly DPV's. The poor QA/QC is a killer though, too bad.

I had a Tekna that I liked very much but you can't rebuild old stuff forever unfortunately. I think the Apollo might be the way to go, hope to rent one this weekend with the funky seat. Will be interesting to have both hands free for a change. The X-scooter does look intriguing too, and pricey as you say.

I just received a lightweight, low drag helmet to evaluate for kitesurfing. I may have to see how it does for scooter free diving around confined spaces and wrecks too.

Rick

[ricki]

Here is an interesting question regarding the Oceanic Geo deco meter. I had done about eight scooter dives ranging from 60 to 125 ft. at which point I heard an alarm. I was shooting video during the dive so I caught the gage face below. It is the "High Nitrogen" alarm. Bottom times were typically on the order of 1.5 to 2 minutes. Surface intervals were usually five to ten minutes or longer. I surfaced, stayed there for about ten minutes at which time the alert cleared from the gage. I did about five more dives with minimum ten minute surface intervals with no other gage issues or alerts. I had been scooter diving in a similar fashion about 48 hours previously without incident and hadn't been SCUBA diving in several weeks.

I spoke to Oceanic tech support about this wondering about the algorithmic basis for the alert. The fellow was uncertain about that aspect but said he would look into it and get back to me after vacation. He did say the intent is to have the diver surface, wait for a sufficient interval before resuming diving and was not an indication of the immediate need for decompression or immanent DSC. Still, it makes me wonder particularly about avoiding repetitions. Any ideas out there?



BTW, I got to use the Apollo AV-2 Evolution dive scooter with the seat attachment. It is an excellent system allowing not only hands free operation but also very easy maneuvering just from minor fin placement. It actually modifies how you move UW in a real positive way. I could see the seat displacing use of conventional scooter directional controls, handles, bridals, etc. for free diving anyway. This allows not only easy equalization but even filming if you are of a mind to do this in addition to precise, simple directional control. The speed was good as was the battery duration (with the expensive Ni-MH battery pack).



I was thinking some form of a leash-kill switch might be a good idea. Separating from a powered DPV is conceivable during a dive. That would likely result in the scooter spiraling off into the deep, with you slogging towards the surface. Use of a static leash could result in you being hauled off somewhat out of control, not good either. Anyway, I was thinking it would be good to develop a leash that loops into the seat housing and in turn attaches to the seat speed control lever. "Ideally" if you separate from the scooter, the leash is tensioned and the power control is pulled back to "off." You would want a reliable quick release on the leash just in case things failed to work as intended. I noticed a side benefit of using the scooter. When you surface just keep the scooter engaged. This makes doing initial recovery breathing even easier than normal. With all that maneuverability AND the absence of a scooter in front of you, extra care during operation and use of a reasonable helmet make good sense. Simply hitting bottom or a coral head is possible with even more objects to bounce off of in a higher profile reef or wreck. Finally, carrying a reasonable pony bottle seems like an appropriate precaution in scooter diving. You shouldn't notice the drag all that much and in deeper dives, it could make an important difference in a power failure.

[ricki]

It doesn't focus strictly on safety but there is a video about some recent scooter free diving along one of the Cayman Walls at:

http://fksa.org/forumdisplay.php?f=92