Avoid the Valsalva Maneuver for Equalizing!

[doctormike]

It appears that some divers do not perceive pain until too late.
A missed BTV is easily detected, because a succesfull BTV is clearly perceived. A missed Valsalva instead can be confused with a succesful one, as the strong pressure caused by lungs overwhelms the neural receptors of the tube.
It is also an acoustical effect. Whie doing the BTV, the driver is breathing normally. The regulator is very noisy, so when the BTV is opening the tube, you hear the loud noise of the reg through it.
It is impossible to confuse a working BTV with a failed one.
During a Valsalva the airways are closed, so there is no loud noise perceived when the tubes open...

Sorry, I really don't understand the physiology you are describing here, or the terminology. Missed equalization means a pressure gradient across the tympanic membrane, which stretches it, which hurts. Has nothing to do with noise, this is a pain signal, primarily via the trigeminal nerve. There either is or isn't a gradient. Don't know what the neural receptors of the ET have to do with it.

 

[Angelo Farina]

Sorry, I really don't understand the physiology you are describing here, or the terminology. Missed equalization means a pressure gradient across the tympanic membrane, which stretches it, which hurts. Has nothing to do with noise, this is a pain signal, primarily via the trigeminal nerve. There either is or isn't a gradient. Don't know what the neural receptors of the ET have to do with it.

As said, a (small) number of divers perceive no pain despite an harmful pressure difference. I witnessed a couple of complete eardrum ruptures with no pain at all, just vertigo thereafter, due to cold water flowing inside the medium ear.
The thing about acoustic feedback when BTV opens the tubes can be understood only by people who can open their tubes at will. Actually making them patulent...
After experiencing this weird acoustic effect, you cannot confuse a succesfull BTV with a failed one.
Instead those divers with no pain, are also less able to distinguish a succesfull equalization from an incomplete one.
The student usually reports to have equalized, as he closed the nose and exerted a large pressure with his lungs. Actually he does not perceive the tube opening (or not).
I always explained this with the fact the the stress on tissues caused by the large pressure makes it difficult to perceive the tube opening (or not).
But another possible explanation is that there is people with poor neurotransmitters in their ears, so they do not experience pain, nor they sense the tube opening.
I really do not know the physiology of what happens, but I have seen this kind of accidents happing at least a couple dozens of times. With no pain!
Only once the diver did (later) report strong pain, and despite this, she decided to still descend.
She was an hostess, and she was used to experience strong pain during each flight. She did never ever attempt to equalize: for her, ear pain was just normal, so she continued to descend, until she ruptured an ear drum.
I was very sorry, and still I feel guilty, as I had no perception of what was heppening.

 

[Alaskan Scuba Dude]

Have gone that deep that requires equalizing.