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Lung Compliance on Different Volumes

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
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Canada
I'm curious to see if there is any research or opinions supporting something that I have noticed when comparing the sensations diving on Full inhale (no packing), Passive exhale (FRC), and active/forced exhale.

Assuming I have a RV of 25%;

-Full inhale I blow 6.8L: TLC =(around) 8.5L
-RV : 8.5-6.8= 1.7L
-Passive Exhale (FRC) I blow 2.4: 2.4+1.7=4.1L
-Active Exhale blow <0.1L = <1.8L

To summarize Diving on;
Full inhale = 8.5L
Passive exhake = 4.1L
Active Exhale = <1.8L

Current Limits/PB with equivalent depth on Inhale;
-Full inhale = 60-64m (not limit)
  • limiting factors; Close to hypoxic limit, Squeeze if I make a poor turn, Chest pressure starts around 50-55m.
  • Lung volume at depth = 1.21L
  • Equivalent depth = 60-64m
- Passive Exhale (FRC) = 40m (not Limit)
  • Limiting factors; None.. no chest pressure no squeeze even with big movements during turn.
  • Lung volume at depth = 0.82L
  • Equivalent depth on Inhale = 10.4 Atmospheres = 94m
Active Exhale = 22m (Limit)
  • Limiting factors; Equalization.. Small mouthfill after full exhale. No chest pressure, no squeeze, Can extend fully and make hard pulls FIM)
  • Lung volume at depth = 0.56L
  • Equivalent depth on inhale = 15 Atmospheres = 140m


Hopefully all of the math checks out and was presented in a coherent manner.

My question is what exactly causes the decrease in tolerance to pressure with the increased lung volume.
Is it;
  • Tension from the inhale itself
  • Tension from the effort of fighting buoyancy
  • Delayed Bloodshift (Ie; starts right away on exhale vs. starting at 30+m on inhale)
  • Does exhaling relax the mind, similar to a sigh of relief? Allowing us to "let go" on a more subconscious level.
The interesting thing is that I can reach those depth on Exhale without doing any warm up dives or even if I haven't dove for 2 weeks. Yesterday I did 2 warmups, dove to 60 and had a small squeeze even though I've been diving 5/7 days for the last week.
 
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Chad StClair

Member
Nov 15, 2016
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California Bakersfield
I am kind of a rookie but for me doing RV dives I don't get contractions and pressure is not bad equalization stops me at 8 meters but if I do RV stretchs I obviously get contractions as do I on depth dives generally around 30-40 meters and the pressure is more felt I guess from the effort of the descent but I think contractions strongly effect squeeze and depth... I know this post is older have you found anything new on what's holding you back??? Or what causes the increased pressure on full inhale vs not
 
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Nathan Vinski

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
Contractions/ urge to breath was the issue.

I ended up making 29 RV and 47 FRC both of them also had no chest pressure. Inhale is still different and I had another trachea squeeze at around 60 (1 week after doing 47 FRC). although I did 70,72,74 VWT a few days the next week with no issues or pressure (static descent= no CO2). The squeeze was caused by a big contraction at the bottom, the tightness is oncoming urge to breath during the freefall. I changed my breath up to be a little more aggressive taking into consideration the effort required on the descent on inhale compared to none on exhale. That took care of the tightness from urge to breath. I also started using a technique to avoid having any contractions during the turn. I seem to always get the urge to have a contraction just when I flip over at the bottom and now I "force" myself to not have it.
 
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Nathan Vinski

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
Contractions/ urge to breath was the issue.

I ended up making 29 RV and 47 FRC both of them also had no chest pressure. Inhale is still different and I had another trachea squeeze at around 60 (1 week after doing 47 FRC). although I did 70,72,74 VWT a few days the next week with no issues or pressure (static descent= no CO2). The squeeze was caused by a big contraction at the bottom, the tightness is oncoming urge to breath during the freefall. I changed my breath up to be a little more aggressive taking into consideration the effort required on the descent on inhale compared to none on exhale. That took care of the tightness from urge to breath. I also started using a technique to avoid having any contractions during the turn. I seem to always get the urge to have a contraction just when I flip over at the bottom and now I "force" myself to not have it.
 

Chad StClair

Member
Nov 15, 2016
37
2
18
34
California Bakersfield
Have you been doing any training to push out the contractions?? For me if I try and hold back contractions I get them more suddenly and same goes for purge breaths I will get a huge one on the bottom vs small ones if I breath up more relaxed and natural. If I get big contractions I get trechea squeeze.. I quit doing co2 tables and have been trying to do more pranyama breathing practices for delaying the contractions to come later 20 seconds inhale 20 seconds hold 20 seconds exhale it's brutal but I don't get contractions but think it's helping with controlling urge to breath. But time will tell. Co2 tables just make me get contractions earlier they are not bad to deal with but think it's the wrong direction for me! I haven't been doing it yet but soon I am going to start doing hill runs as it is a great way to generate huge Co2 tolerance.
 
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Nathan Vinski

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
So yeah, first of all I agree that CO2 tables make them come earlier. Also, I don't think, at least for my own body, that co2 is the direct cause of contractions when doing deep dives. Even when I have the urge to breath it's mostly just an uncomfortable sensation. The contraction on the turn is partly due to shifting air, and partly mental. My squeeze in tenerife (when I first posted) was due to my lanyard getting stuck on the bottom for 25 seconds, I only realised 2 days later what happened when I went through my computers logbook. Mentally I was nervous around 60 because of that and it was amplifying contraction urge. I've always been able to resist contractions at around RV (wet or dry) and I did some full exhale dry practice just to get the hang of it again. Just a few days ago I finally went back to 60, after lots and lots of 50s, and everything was fine. No urge to breath or discomfort on descent, turn (urge for contraction but I didn't have it), and ascent with contractions in last 15m at high lung volume just like normal (before tenerife).
 
Mar 20, 2011
704
150
83
Los Angeles
Your contractions may be caused by dive response triggers. I cannot speak to the dive world at large but in my own testing anytime I am experiencing strong dive response I am also experiencing strong contractions. This is completely independent of CO2 load.

Sent from my SM-G930T using Tapatalk
 
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Nathan Vinski

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
Your contractions may be caused by dive response triggers. I cannot speak to the dive world at large but in my own testing anytime I am experiencing strong dive response I am also experiencing strong contractions. This is completely independent of CO2 load.

Sent from my SM-G930T using Tapatalk
How do you know you are having dive response? Are the strong contractions maybe triggering DR and not the other way around?

I agree contractions are independant from CO2 in depth, mostly caused by tension... in my experience however, chest tightness is influenced by CO2 level. I found this by experimenting with max frenzel depth and different breathups.. High CO2 (bi-fins) = 55m. Low CO2 bi fins = 60m (not limit, just the bottom of the line). Low CO2 + no CO2 production (VWT) = 74m (not limit, bottom of line)
 
Mar 20, 2011
704
150
83
Los Angeles
How do you know you are having dive response? Are the strong contractions maybe triggering DR and not the other way around?

I agree contractions are independant from CO2 in depth, mostly caused by tension... in my experience however, chest tightness is influenced by CO2 level. I found this by experimenting with max frenzel depth and different breathups.. High CO2 (bi-fins) = 55m. Low CO2 bi fins = 60m (not limit, just the bottom of the line). Low CO2 + no CO2 production (VWT) = 74m (not limit, bottom of line)
The strong contractions may be triggering DR, but point is they are independent of CO2. I know this mostly from cold water facial immersion tests. On a dry hold with a relaxed/unconscious diaphramatic breath-up (no purge) I usually get no contractions for at least 2 or 3 minutes. Also no DR. As soon as contractions are starting, pulse drops and fingertip EKG starts to flatline (vasoconstriction). If dry, this usually coincides with falling blood O2.

Cold water facial immersion, same breath-up, I get huge contractions within 30 seconds, accompanied by significant bradycardia and vasoconstriction (as seen on pulse oximeter with EKG graph). Of course blood O2 is still pegging the dial at 98% and will be for some minutes. In the ocean (our surface water is cold enough to trigger DR if you are not wearing a mask), I can do 30M - 40M CWT dive and never get a contraction provided I recovered from previous dive. But with just a noseclip, I am getting wracked with contractions before I even fumble down to 10M for a hang.

New divers feel contractions from CO2, but this is certainly trainable. I have a very high CO2 tolerance and even during CO2 sets don't really experience CO2 contractions anymore.

CO2 could certainly influence chest tightness and relaxation. I think it is a given with deep divers, even if you don't need a lot of CO2 tolerance to do the actual breathhold portion of the dive, CO2 training seems to make EQ easier at limit. Tension may also contribute to contractions.
 
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Nathan Vinski

Nathan Vinski

Well-Known Member
Apr 19, 2015
247
146
58
24
Canada
Very cold water on the face, or anywhere on the body can, in addition to induce DR, cause the urge to gasp. Like when jumping into a freezing cold pool of water its hard to control your breathing. 2 separate responses are working at the same time, one is the dive response, the other is the gasp response. Holding your breath with the latter will cause contractions.

For me it was initially difficult to transition to noseclip diving (after my initial post) because of this, the water flow on my eyes was causing the urge to inhale (gasp reflex) and with practice, starting with giant flooded goggles, then fluid goggles, it also went away.

throughout all of the noseclip issues, I've still noticed a more aggressive breathup reduced chest tightness and limited my urge to have contractions, but also slightly reduced my relaxation causing a few early turns on deep dives due to a less relaxed preparation.

Interestingly I was thinking about this post today, before I saw your comment, because I can finally do eyes open with nose clip and no urge to inhale, and tried changing my breath up to be only slightly more aggressive than my FRC breath up (with positive results), instead of what it was for the past 2 months.
 
Mar 20, 2011
704
150
83
Los Angeles
Interesting, yes gasp response and contractions could be mistaken for each other, although it is also very possible that they are somewhat the same physical manifestation. Many students who do not experience contractions in the more traditional sense describe an overpowering urge to swallow.

I think in some cases the 'gasp' response may trigger earlier contractions/DR, after all we know that DR is a sort of shock response.

Sent from my SM-G930T using Tapatalk
 
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