Interesting Article | How Do Deep-Diving Cetaceans Avoid DCS?

Whales and dolphins have a special adaptation that allow them to explore the ocean’s depths.

 

Beaked whales can spend two hours beneath the surface. Dolphins descend down to 1,000 feet and ­routinely make as many as 20 dives in a row to 300 feet.

Good luck finding that type of profile on a dive table.

So, how do these mammals avoid getting hit with decompression sickness?

Special lung architecture helps protect them from the bends, according to a study by researchers at Woods Hole Oceanographic Institution and Spain’s Fundacion Oceanografic.

When air-breathing animals dive underwater, increasing pressure causes nitrogen bubbles to collect in the bloodstream and tissue. Ascending slowly allows nitrogen to return to the lungs and be exhaled. Ascend too fast, and nitrogen bubbles don’t have time to diffuse back into the lungs. Instead, they begin to expand in blood and tissues, causing pain and damage — DCS, or the bends.

Under deep-sea pressure, the lungs of cetaceans — whales, dolphins and porpoises — create two different regions, one filled with air and one collapsed. This creates a gradient in the amount of blood flow and gas exchange, taking advantage of differences in solubility of oxygen, carbon dioxide and nitrogen.

“These animals have the ability to change that rate,” says biologist Michael Moore, senior scientist at WHOI and a study co-author. “They can manipulate the gradient to favor conditions that transfer oxygen and carbon dioxide but not nitrogen, so as not to increase the risk of DCS. Blood flowing mainly through the compressed region allows absorption of some oxygen while minimizing or preventing the exchange of nitrogen.”

The scientists observed this phenomenon by inflating the lungs from different animals and putting them in a hyperbaric water chamber to simulate dives to different depths. “We compared dolphin, seal and pig lungs, and found dramatic differences,” says Moore. “Terrestrial mammals just don’t have the anatomical and functional adaptations that marine mammals do.”

Marine mammals are not completely immune to DCS, however. Scientists have detected decompression gas bubbles in seals and dolphins that drowned at depth in gill nets. Fourteen dead whales in a 2002 stranding event linked to U.S. Navy sonar exercises had gas bubbles in their tissues — a sign of DCS.

“We know that loud noises are stressful for marine animals,” says Moore. “It can cause a fight-or-flight response, increasing heart rate and vascular dilation. That messes with this protective mechanism — with the way the animal has programmed its dive — and increases absorption of nitrogen in blood.”

The research doesn’t explain why DCS might cause a cetacean to beach, says co-author Andreas Fahlman.

“But just knowing that stress can cause failure of this adaptation means we might find ways to mitigate it,” he says. “The solution could be as simple as starting sonar at low levels so the animals don’t freak out, then increasing levels gradually to give them a chance to move away.”

 

 

Article by Shane Gross,

REF: https://www.scubadiving.com/how-do-deep-diving-cetaceans-avoid-dcs 

Interesting Article | Don’t let your ears ruin your dives

A great article by DAN South Africa and DiveIN Magazine on the full guide to ear and diving

 

Don’t let your ears ruin your dives

You’ve just started your first dive of the day. Everything is going great! You pinch your nose and blow to equalize your ears, but nothing happens. You try again, but same issue.

Your ears starts to hurt…you try again but it’s the same.

So what now?

Accent and end the dive or push on?

No!
It’s time to learn how to equalise the right way!

According to a survey* we did, we discovered that:

  • 89% of divers doesn’t equalize the correct way
  • 29% of divers had to stay out of the water for weeks or months due to problems caused by equalizing
  • 6.3% of divers have gotten permanent ear damage due to problems with equalizing

That’s right, you might be Equalising the wrong way!

The real issue is that the way most of us was thought to equalise, and the method that usually works, is the wrong way to do it.

It’s the Valsalva Maneuver: Pinch your nostrils and blow through your nose. The resulting overpressure in your throat usually forces air up your Eustachian tubes.

How come it works if it’s the wrong way? It works perfectly fine as long as you keep the tubes open ahead of the pressure changes. However, if you do not equalize early or often enough, the pressure differential can force the soft tissues together, closing the ends of the tubes. Forcing air against these soft tissues just locks them shut.

5 Better ways to Equalize

Toynbee Maneuver – Pinch Your Nose and Swallow
With your nostrils pinched or blocked against your mask skirt, swallow. Swallowing pulls open your Eustachian tubes while the movement of your tongue, with your nose closed, compresses air against them.

Lowry Technique – Pinch Your Nose, Blow and Swallow
A combination of Valsalva and Toynbee: while closing your nostrils, blow and swallow at the same time.

Edmonds Technique – Pinch Your Nose and Blow and Push Your Jaw Forward
While tensing the soft palate (the soft tissue at the back of the roof of your mouth) and throat muscles and pushing the jaw forward and down, do a Valsalva maneuver.

Frenzel Maneuver – Pinch Your Nose and Make the Sound of the Letter “K”
Close your nostrils, and close the back of your throat as if straining to lift a weight. Then make the sound of the letter “K.” This forces the back of your tongue upward, compressing air against the openings of your Eustachian tubes.

Voluntary Tubal Opening – Tense Your Throat and Push Your Jaw Forward
Tense the muscles of the soft palate and the throat while pushing the jaw forward and down as if starting to yawn. These muscles pull the Eustachian tubes open. This requires a lot of practice, but some divers can learn to control those muscles and hold their tubes open for continuous equalization.

When to Equalize
Sooner, and more often, than you might think. Most recommend equalizing every two feet (.6 meters) of descent, but often that’s too late. At a fairly slow descent rate of 60 ft (18.288 m) per minute, that’s an equalization every two seconds. Many divers descend much faster and should be equalizing constantly.

The good news: as you go deeper, you’ll have to equalize less often!

10 Quick tips to make equalizing easier

Listen for the “pop”
Before you even board the boat, make sure that when you swallow you hear a “pop” or “click” in both ears. This tells you both Eustachian tubes are open.

Start early
Several hours before your dive, begin gently equalizing your ears every few minutes. “This has great value and is said to help reduce the chances of a block early on descent,” says Dr. Ernest S. Campbell, webmaster of “Diving Medicine Online.” “Chewing gum between dives seems to help,” adds Dr. Campbell.

Equalize at the surface
“Pre-pressurizing” at the surface helps get you past the critical first few feet of descent, where you’re often busy with dumping your BCD and clearing your mask. It may also inflate your Eustachian tubes so they are slightly bigger. The guide here is to pre-pressurize only if it seems to help you and to pressurize gently.

Descend feet first
Air tends to rise up your Eustachian tubes, and fluid-like mucus tends to drain downward. Studies have shown a Valsalva maneuver requires 50 percent more force when you’re in a head-down position than head-up.

Look up
Extending your neck tends to open your Eustachian tubes.

Use a descent line
Pulling yourself down an anchor or mooring line helps control your descent rate  more accurately. Without a line, your descent rate will probably accelerate much more than you realize. A line also helps you stop your descent quickly if you feel pressure, before barotrauma has a chance to occur.

Stay ahead
Equalize often, trying to maintain a slight positive pressure in your middle ears.

Stop if it hurts
Don’t try to push through pain. Your Eustachian tubes are probably locked shut by pressure differential, and the only result will be barotrauma. If your ears begin to hurt, ascend a few feet and try equalizing again.

Avoid tobacco and alcohol
Both tobacco smoke and alcohol irritate your mucus membranes, promoting more mucus that can block your Eustachian tubes.

Keep your mask clear
Water up your nose can irritate your mucus membranes, which then produce more of the stuff that clogs.

 

REFERENCE: https://www.divein.com/articles/diving-ears/ 

Interesting Article | Tips to Conserve Air while Diving

 

‘the best way to observe a fish is to become a fish’  Jacques Cousteau

  1. Keep warm. Make sure that you have the correct thermal protection for the planned dive. Getting cold increases your metabolic rate, consuming more oxygen.
  2. Go slow. Only move if you need to! Sudden jerky movements and increased speed underwater all consume more oxygen. Don’t chase sea life! Don’t try to gather everyone in the dive group to show them what you saw. Don’t fight the current. Use any surge to your advantage.
  3. The more efficient your fins are, the less energy you expend. Get the right fins for you!
  4. Do not use your arms. Try to use your arms as little as possible.
  5. Trim up. Check your weight distribution so that you do not need to constantly compensate for being off-balance.
  6. Streamline your gear to reduce water resistance.
  7. Orally inflate your BCD. If your weighting is correct you will require less air in your bcd, thus reducing your head-on profile.
  8. Swim horizontally. Get your buoyancy correct.
  9. Control your breathing. Breathe deeply. Inhale for 5-7 secs, exhale for 6-8 secs. With practice you will do it automatically without having to count. Otherwise, hum a slow tune to yourself!
  10. Breathing pause. Pause for a second or two at the end of inspiration to allow more oxygen absorption. Usually we pause at the end of expiration, so this takes a little practice. This does not mean ‘skip breathing’.
  11. Restrict air flow. Some DV’s can be set. Otherwise inhale with your tongue against the roof of your mouth creating a natural restriction.
  12. Dive shallower
  13. Use your snorkel if you need to swim on the surface.
  14. Reduce air leaks. Service your gear regularly.
  15. Practice. Dive, dive, dive! The more comfortable you are in the water, the more relaxed you will become, the better your air consumption will be.

 

If you have any other tips to add, please do so!

 

Author: Dr Mark k. Botha

NUC CMAS Rescue Course

Book today to become a contributing member of the diving community! 

Cost: R1500.00

Course dates and format:

Lectures: 11/12 November: 09h00 – 16h00/09h00 – 12h00 (if necessary)

Pool sessions: 18/19 November: 09h00 – 12h00/09h00 – 12h00

Open Water sessions: 25/26 November: 09h00 – 12h00/09h00 – 12h00
 

Participants must have in-date Basic Life Support ( BLS ) and the Oxygen Administrator qualification.

CMAS considers this the highest level of qualification for a diver. Be equipped to assist with the management of any dive emergency, with confidence.

Become a contributing member of the diver community today by participating in this course!

For more info or to book today get in touch with Mark on training@normalair.co.za

NUC 2 Star CMAS Course

Book today for the 2 Star CMAS Training Course! 

Cost R 1200.00 

COURSE FORMAT AND DATES

Lectures : 04/05 November: 09h00 – 16h00/09h00 -12h00

Pool sessions : 11/12 November: 09h00 – 16h00/09h00 – 12h00 (if necessary)

Open Water dives : 18/19 November: 09h00 – 16h00/09h00 – 12h00 (if necessary)

Sea Dives: 01/03 December: Sodwana Bay

Participants must have 15 logged dives. This course expands on the 1 Star Course, especially with regards to deeper diving ie to 30m, and the extra knowledge required to do so.

If you  intend to dive internationally, this is really the qualification to have!

For more info or to book today get in touch with Mark on training@normalair.co.za