Equipment IPE and Regulator Adjustments

[SubSoul]

This is sounding more like the laryngospasm that @rsingler mentioned up-thread. It can happen post-extubation following surgery as he suggested, and it can also happen with water aspiration. In either case it can lead to negative pressure pulmonary edema (NPPE), so that alone could explain this event. I am not familiar with MTX regulators so can't speak to whether it's possible to dial one in far enough for inspiratory effort to have been a factor.

If immersion pulmonary edema was the precipitating event, you would have been able to move air but you would have felt short of breath. This too can lead to unconsciousness, but that isn't what you've described. I don't think it can be completely ruled out, but it seems less likely given all the information you've provided here.

I am a bit concerned about your mention of elevated troponin and demand ischemia, but if the physicians who examined you in person are confident of your cardiac health then I'd defer to them.

Just so it's not lost, your buddies deserve a lot of credit for making a safe and controlled rescue especially in the setting of laryngospasm, which can result in air trapping. The fact that you're able to tell your story here is a testament to their skill and level-headeness under extreme pressure.

Best regards,
DDM

I am beyond grateful to my dive buddies. They literally saved my life!!! And thank you for your insight and for sharing your knowledge.

 

[Pearlman]

the cracking pressure knob was turned all the way in

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, and on many dives, simply turned it in a bit - finding a comfort zone with a higher cracking pressure, and believing that it helped me conserve air better. Until I got wiser and realised through trial and error that the best setting was the lowest cracking pressure without force feeding of air, and re-learning how to drive one’s own breathing in a more controlled fashion without that “overflowing” lung expansion feeling.

Most importantly, I remember feeling alarmed with borderline survival instincts kicking in when I experimented with dialling the knob in a bit too much due to the suction effort and resultant W.O.B. More than the Venturi being “-“ my gut feeling and suspicion is that your predicament was the combined result of the water being sucked in and the negative suction pressure on your lungs due to the adjust knob being dialled all the way in … as I have experienced at times with poorly tuned rental gear for entire dives, fortunately without serious consequences.

Yes others posting here are more knowledgeable and have shared their insights, but reading this thread starkly reminded me of that uncomfortable physical sensation and the resulting momentary fear of self-harm … just wanted to share that!

 

[SubSoul]

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, and on many dives, simply turned it in a bit - finding a comfort zone with a higher cracking pressure, and believing that it helped me conserve air better. Until I got wiser and realised through trial and error that the best setting was the lowest cracking pressure without force feeding of air, and re-learning how to drive one’s own breathing in a more controlled fashion without that “overflowing” lung expansion feeling.

Most importantly, I remember feeling alarmed with borderline survival instincts kicking in when I experimented with dialling the knob in a bit too much due to the suction effort and resultant W.O.B. More than the Venturi being “-“ my gut feeling and suspicion is that your predicament was the combined result of the water being sucked in and the negative suction pressure on your lungs due to the adjust knob being dialled all the way in … as I have experienced at times with poorly tuned rental gear for entire dives, fortunately without serious consequences.

Yes others posting here are more knowledgeable and have shared their insights, but reading this thread starkly reminded me of that uncomfortable physical sensation and the resulting momentary fear of self-harm … just wanted to share that!

Thank you for sharing! I was wondering what others have experienced with a similar reg setting.

 

[Dr Simon Mitchell]

Hello,

Interesting case SubSoul, so thanks for sharing it.

Four - five minutes is very short latency for an episode of immersion pulmonary edema (IPE), though in the presence of exaggerated negative pressure breathing it is certainly possible as illustrated by the stories about flash negative pressure pulmonary edema in clinical settings where there is laryngospasm. It is difficult to know whether a regulator on non-optimal settings (combined with dense gas) could cause you to generate sufficient negative inspiratory pressure to provoke rapid onset IPE, but we certainly cannot rule it out.

However, the other aspect of your history that has not received much attention in this thread is that you became unconscious and were rescued to the surface over a period of several minutes. During this period your airway would have been unprotected to at least some extent, even if the regulator was still in place. Under these circumstances the risk of aspirating water is particularly high. It follows that the changes seen in your chest radiography could have been caused by aspiration too. It is even possible that there were elements of both IPE and aspiration in your case.

I think the future diving advice you have received from your physicians is probably fine, provided you understand that if this was IPE then a repeat event is possible, and some repeat events have been fatal. Consequently, we often advise divers who have clearly suffered IPE not to dive again. In your case I think there is sufficient uncertainty over cause to avoid strong advice in any direction. Decisions about diving are for you to make (and take responsibility for) as an informed risk acceptor. If you dive and if it happens again in a less equivocal set of circumstances, then I really would advise avoiding diving.

Simon M

 

[kensuf]

Yes. What I remember is taking in a little water and the choking. But I felt like I couldn’t get any air in or cough anything out. Thankfully we were diving in a close group so I signaled for help and then went unconscious. The ascent was faster than ideal but still took 3 minutes so we didn’t “shoot” to the surface.

I'm not a doctor and I didn't sleep in a holiday inn express. Explain the taking in a little water bit?

There's a thing called an esophageal laryngospasm. It is a protective mechanism that can happen when you aspirate a little bit of water and the result of it is you can't breathe for a brief moment, like a minute or two. I had one once, it was most unpleasant because I thought I was going to choke to death.

 

[SubSoul]

Hello,

Interesting case SubSoul, so thanks for sharing it.

Four - five minutes is very short latency for an episode of immersion pulmonary edema (IPE), though in the presence of exaggerated negative pressure breathing it is certainly possible as illustrated by the stories about flash negative pressure pulmonary edema in clinical settings where there is laryngospasm. It is difficult to know whether a regulator on non-optimal settings (combined with dense gas) could cause you to generate sufficient negative inspiratory pressure to provoke rapid onset IPE, but we certainly cannot rule it out.

However, the other aspect of your history that has not received much attention in this thread is that you became unconscious and were rescued to the surface over a period of several minutes. During this period your airway would have been unprotected to at least some extent, even if the regulator was still in place. Under these circumstances the risk of aspirating water is particularly high. It follows that the changes seen in your chest radiography could have been caused by aspiration too. It is even possible that there were elements of both IPE and aspiration in your case.

I think the future diving advice you have received from your physicians is probably fine, provided you understand that if this was IPE then a repeat event is possible, and some repeat events have been fatal. Consequently, we often advise divers who have clearly suffered IPE not to dive again. In your case I think there is sufficient uncertainty over cause to avoid strong advice in any direction. Decisions about diving are for you to make (and take responsibility for) as an informed risk acceptor. If you dive and if it happens again in a less equivocal set of circumstances, then I really would advise avoiding diving.

Simon M

Thank you for your insight.

 

[SubSoul]

I'm not a doctor and I didn't sleep in a holiday inn express. Explain the taking in a little water bit?

There's a thing called an esophageal laryngospasm. It is a protective mechanism that can happen when you aspirate a little bit of water and the result of it is you can't breathe for a brief moment, like a minute or two. I had one once, it was most unpleasant because I thought I was going to choke to death.

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.

 

[scubadada]

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.

@Nemrod reported a particularly vivid episode of aspiration and laryngospasm that I will not forget

Info - IPE may be more prevalent than previously thought, click through to find out why!

https://www.snorkelsafetystudy.com/wp-content/uploads/2021/07/SSS-Final-Report.pdf It’s not directly diving related, but a three year study of snorkeling deaths in Hawaii, the ocean drowning capital of America indicates that the majority of deaths can be attributed to IPE rather than direct...

scubaboard.com

 

[SubSoul]

@Nemrod reported a particularly vivid episode of aspiration and laryngospasm that I will not forget

Info - IPE may be more prevalent than previously thought, click through to find out why!

https://www.snorkelsafetystudy.com/wp-content/uploads/2021/07/SSS-Final-Report.pdf It’s not directly diving related, but a three year study of snorkeling deaths in Hawaii, the ocean drowning capital of America indicates that the majority of deaths can be attributed to IPE rather than direct...

scubaboard.com

Oh wow. Thank you for this link. This is the very same sensation that I felt prior to passing out.

 

[scubadada]

Oh wow. Thank you for this link. This is the very same sensation that I felt prior to passing out.

Many of us have had less dramatic, minor episodes of saltwater aspiration. I have had a couple that were likely associated with mild, short-lived laryngospasm, an alarming reaction.

Best of luck in your future diving.