Equipment IPE and Regulator Adjustments

[kensuf]

When I took a breath, I noticed some water enter my mouth. I immediately purged the second stage and had maybe 2 more breaths (w/o water) that felt strained. On my next breath, took in a mouthful of water. That is when I suddenly couldn’t breath in or breath out/cough. Sorry you experienced something like this is well. Definitely a scary feeling.

Given that you had water coming in when you were trying to breathe, it really sounds like a laryingospasm. Basically the vocal chords lock up when a little bit of water splashes on them.

 

[Nemrod]

When I took a breath, I noticed some water enter my mouth. I immediately purged the second stage and had maybe 2 more breaths (w/o water) that felt strained. On my next breath, took in a mouthful of water. That is when I suddenly couldn’t breath in or breath out/cough. Sorry you experienced something like this is well. Definitely a scary feeling.

This did happen to me. I have spoken of it enough times I do not want to go through it again. Not only did I begin an equipment upgrade and simplification and some changes in my approach to group dives and some other things as well. In fact, it was a watershed moment for me and I do many things differently now. Yeah, it was not fun, it was scary and not being able to breath at 110 feet, on the verge of deco and cannot ascend, wow, it was bad. And yes, I got pneumonia due to seawater aspiration into my lungs and yeah, I had a for real laryngeal spasm. Yes, I lived to tell about it but it was touch and go. Turns out, I am sorta hard to kill. Not going to count on that again.

 

[dmaziuk]

I’ve only owned and used adjustable 2nd stages for a few years now and have experimented with dialling the knob back and forth just to check how it feels and understand regulator behaviour. On some dives, I have had to dial it down to stop the force feeding of air

+1. I almost always have mine turned all the way in for that reason. It has nothing to do with gas mileage except maybe when it's "force feeding" I lose marginally more gas to... overflow, for lack of a better term.

 

[BoltSnap]

+1. I almost always have mine turned all the way in for that reason. It has nothing to do with gas mileage except maybe when it's "force feeding" I lose marginally more gas to... overflow, for lack of a better term.

Turned in all the way in for no reason while you are using it underwater is wrong, wrong usage and/or in tunning from technician. The regulator should be at least effort at all the way out per mfg specifications.

 

[rsingler]

+1. I almost always have mine turned all the way in for that reason. It has nothing to do with gas mileage except maybe when it's "force feeding" I lose marginally more gas to... overflow, for lack of a better term.

I hear you, partly. On an occasional hot-tuned second, I can sense "wasted gas" when I turn face down and the valve opens and bubbles gently out the exhaust valve even when I'm not breathing. I don't know that the loss is in any way significant, but I'll concede the phenomenon's relationship to cracking effort.
However, I'll beg to differ with you on force feeding of gas. When a reg shifts into freeflow mode during a breath, that is the portion of the ANSTI loop above zero, that is solely a Venturi related function. While increasing cracking effort will fix it, it also makes the net loop inhalation WOB greater across the board. Instead, a tiny dial-back on the Venturi lever (sometimes only 10%) will completely fix the problem, while leaving the negative portion of the loop unchanged.
Good example is the SP C350 and balanced C370. They've got a roaring Venturi augmentation that Scubapro only partially fixed with those louvers on the outflow. At depth, you simply have to twitch the Venturi lever a hair. I honestly don't think you need to make cracking effort harder to solve that issue.

 

[grf88]

Instead, a tiny dial-back on the Venturi lever (sometimes only 10%) will completely fix the problem, while leaving the negative portion of the loop unchanged.

I only discovered how effective this was a year or so back and have to wonder how many others have never thought of this.

 

[rsingler]

I only discovered how effective this was a year or so back and have to wonder how many others have never thought of this.

You can thank the mfrs for dumbing down our sport, and changing this precise Venturi control into a simple (and incorrect) "Dive/Predive" switch.

 

[clownfishsydney]

I think it is almost certain that the reason you thought the regulator was hard to breath was the fact that you were suffering the onset of IPE. All people I have spoken to or being with a person who suffered (some fatal) have reported that the person thought they had gear problems as it was hard to breath. Probably the regulator was not a contributory problem.

 

[dmaziuk]

I hear you, partly. On an occasional hot-tuned second, I can sense "wasted gas" when I turn face down and the valve opens and bubbles gently out the exhaust valve even when I'm not breathing. I don't know that the loss is in any way significant, but I'll concede the phenomenon's relationship to cracking effort.
However, I'll beg to differ with you on force feeding of gas. When a reg shifts into freeflow mode during a breath, that is the portion of the ANSTI loop above zero, that is solely a Venturi related function. While increasing cracking effort will fix it, it also makes the net loop inhalation WOB greater across the board. Instead, a tiny dial-back on the Venturi lever (sometimes only 10%) will completely fix the problem, while leaving the negative portion of the loop unchanged.

Well, maybe I should have mentioned I have a mikron w/o a separate venturi lever so... beggars, choosers. On rental regs I have turned the venturi lever all the way to "-" and sometimes it worked. Other times I had to "blow" on it at the end of inhalation to stop it freeflowing out the nose and mask.

I assume swimmer's lungs have something to do with it. But we digress: OP has asked in #43 if/why some people detune their regs.

 

[CG43]

How inportant is tunning the reg ?

A very easily breathing reg. is said to have 0.508J/L WoB.
This can be divided into 0.254tJ/L each for inhale and exhale.
How big is the negative inhale sucction then?

The work of moving gas under constant pressure is simple :
W = pressure * volume : then pressure = W / volumen
In m , kg , sec. units
1 bar = 100 000N/m^2 : 1mbar = 100N/m^2 comparable to 1 cmsw . 1 L = 0,001m^3

pressure = 0,254 Nm/0,001m^3 = 254 N/m^2 = 2,54 cmsw = 1" sw

Power for 25/L per 60sek. : Power = W/L * L/60sec. = 0,254 J * 25 /60 = 0,11 watt

Every inch more cracking sucction need 0,254 J/L more WoB and 0,11 watt more power .
The same applies if the second stage diaphragm comes 1" higher than the respiratory center,
and this difference can be up to10".
If you think that you breathe easier and dive more relaxed with a 0.5" tuned reg., do it .
You will be able to save air and have a better dive .
Other divers like me put every halfway usable reg. in their mouths and forget under water
that they breathe through a reg. This is also true at great depths,
because there the resistances in the diver's airways limit ventilation more than the reg.