Dolphins DO get bent

[EddieP]

BBC News - Dolphins 'decompress like humans'

 

[monkeyhatfork]

so do whales and other aquatic mammals, one of the concerns with high intensity naval sonar is that its scaring them and they may be surfacing way to fast as a result of a scare

 

[EddieP]

But the significance of the article was that they also do decompression submersions after a deep dive.

 

[Delfino]

Below is a link to a paper on the subject that was published in 2007. In the whale's dive profile you will see that after each deep dive for foraging there is a shallower dive that follows which is believed to be for the purpose of decompressing. I attended a presentation on this study in 2007 in the Bahamas. Interesting paper.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3056662/

SHALLOW DIVES POSE DECOMPRESSION RISK IN DEEP-DIVING BEAKED WHALES

1. Walter M. X. Zimmer
2. Peter L. Tyack

The impact of naval sonar on beaked whales is of increasing concern. In recent years the presence of gas and fat embolism consistent with decompression sickness (DCS) has been reported through postmortem analyses on beaked whales that stranded in connection with naval sonar exercises. In the present study, we use basic principles of diving physiology to model nitrogen tension and bubble growth in several tissue compartments during normal diving behavior and for several hypothetical dive profiles to assess the risk of DCS. Assuming that normal diving does not cause nitrogen tensions in excess of those shown to be safe for odontocetes, the modeling indicates that repetitive shallow dives, perhaps as a consequence of an extended avoidance reaction to sonar sound, can indeed pose a risk for DCS and that this risk should increase with the duration of the response. If the model is correct, then limiting the duration of sonar exposure to minimize the duration of any avoidance reaction therefore has the potential to reduce the risk of DCS.

 

[Bill]

I accept as fact that dolphins and whales can get bent but there decomp tables have to be a lot different than for humans. A scuba diver certainly couldn't spend hours at 25 meters with a short trip to the surface every five minutes the way the spinners do. The big question seems to be....How do the tables differ for scuba and breath hold? Can anyone think of a better experiment than hooking a diver up to an empty rebreather. Run the chamber to 4-5 atm. Scrub the CO2 to 5%. Maintain the O2 at 10%. Leave the N2 alone. Bring him to 1 atm in 1 minute and use the latest scan technique to look for the first sign of DCS. One 'dive' per day starting at 5 minutes.

 

[efattah]

It seems that the 'apnea deco' method I have been using is also used by dolphins (surface, take a few breaths then dive shallow and stay there):

From the article:

"If dolphins, he explained, come up too quickly then there is evidence that they grab another gulp of air and go back down again, [....] dolphins avoid the bends by taking long, shallow decompression dives after feeding at depth."

 

[Bill]

Not disagreeing with your decomp advice. My late buddy was a navy diver and he told of some long deep dives with two short decompression stops, surface, remove helmut quickly, into the chamber, 100% O2 and pressure to over 2 atm. Worked for him. Never bent and pretty spry 'til a ripe old age.
My problem is calling the next dive a dolphin makes a decomp dive. Every dive I've seen a dolphin make was followed by a short surface interval and another dive. I think that whales will stay on the surface for more than one lungful if diving deep or feeding but I never saw it.
Point I was trying to make. With todays instruments we could easily do some testing and find out the difference for free diving. How did Wal spend all that time at 100+ meters? I'm pretty sure he survived.

 

[watts]

So Eric you do these deco dives straight after a deep dive?
Just come up recovery breaths and a couple of mins at what depth?

 

[efattah]

The point is that the Dolphins will re-dive at a *shallow* depth for a long period after a deep dive. This is the significance. They could equally well do a short dive, or another deep dive, but for some reason they choose a long shallow dive which is the best option for DCS. I think they do post-dive deco because they cannot hold their breath long enough to deco during the dive (dolphins cannot hold their breath for anywhere close to the length of time that seals and whales can).

Sperm whales, on the other, do apnea deco on the same dive. They ascent from 2000m+, then stop around 10m and hang around for several minutes before surfacing, which is a better approach than the bend-and-mend method.

watts-> I do apnea deco dives in any situation where they are needed, any situation where I exceed the deco limits. It happens most during recreational diving; during extreme deep dives I usually breathe O2 at depth if it is available. If that is not available the next best option is an apnea deco dive taking a breath of O2 at the surface. If that is not available the next best option is an apnea deco dive taking only a breath of regular air. The depth to dive to is usually 6m, for as long as you can hold your breath which will vary from 1 minute to 7 minutes based on exhaustion and the apnea gas.

For dives over 90m I recommend starting the deco at 9-10m for 30 seconds then ascending to 6m for the remainder.

 

[bryson]

efattah / mullins: when you have been spearfishing deep and you use compressed oxygen to decompress, do you just go down to 5m and breathe for 5mins at the end of the day? Or do you do the 5 and 5 before you move spots each time? (multiple deep spots in one day)

Is there a negative side to breathing compressed oxygen at 5m at one spot, then going down to 40-50m at the next, with all the residual compressed oxygen inside you?

I have just looking at some profiles mentioned in the memo thread and figured I best start looking into decompression using compressed oxygen, to avoid the decompression sickness.

Regards Bryson.

 

[efattah]

I'll do O2 at 6m after diving the first spot, then after the O2 I need to wait at least 30 minutes for the slow tissues to off-gas, then I can dive the next spot, and then do O2 again after that, and again wait 30 minutes before the next spot.

 

[Mullins]

I've never done any decompression for spearfishing dives.

 

[bryson]

ok, so two totally different approaches to diving deep.

Efattah, how many dives within that 40-50m range do you find you can do without getting bent, does the breathing of oxy under pressure cause any problems when returning to depth?

mullins, what is your approach to avoiding the bends, i have been talking to fran rose a little about it but also trying to gain as much knowledge from others in the know.

Bryson.

 

[Mullins]

I avoid doing lots of reps of deep dives. I stick to, say, 4 dives @ 60m which is a lot less than sequences I have done in the past without DCS symptoms.

 

[Broseidon]

I'm just going to leave this here....

[ame=http://www.youtube.com/watch?v=FZsB9hsq3_I]homosexual dolphins playing at the mirage - YouTube[/ame]

 

[spudlington]

Not disagreeing with your decomp advice. My late buddy was a navy diver and he told of some long deep dives with two short decompression stops, surface, remove helmut quickly, into the chamber, 100% O2 and pressure to over 2 atm. Worked for him. Never bent and pretty spry 'til a ripe old age.

What you are referring to is Surface Decompression on O2. The final stop time is completed in the chamber normally at 12msw on O2, with the diver having 5minutes travel time from leaving his previous in-water stop to arriving at depth in the chamber. Your friend was certainly bent on occasion, albeit temporarily, the procedure is often referred to as "Bend and Mend".
Despite how it sounds, it can be preferable to having the diver undertaking lengthy in-water decompression when conditions may compromise a safe decompression, eg very heavy swell making it difficult to maintain depth, cold etc.