kwinter
PITA
Thought you yanks where still using fathoms!
No, it's just that Don wants to maintain readiness for his upcoming dives in Myanmar, the only country remaining on the stupid Imperial system besides us.
Impaired ventilation at depth due to gas density?
- Thread starter Raptor^
- Start date
No, it's just that Don wants to maintain readiness for his upcoming dives in Myanmar, the only country remaining on the stupid Imperial system besides us.
Naumachos
Member
My mistake,diving in fresh water with sea water setting is more conservative (+ 3% in depth)
It's not important to the topic anyway.
nickb
The JJ Kid
The salinity setting makes no difference to the deco - it just helps to make the indicated depth more accurate.
The deco is calculated from the pressure.
paulraymaekers
Active Member
Mark, did you ever try a rEvo III, the current CE unit? as I think that is the ony one you can compare with the JJ, and then I think no human beiing can notice a difference (as on the test machine the difference is marginal)
Igor P
New Member
Exactely. Salinity settings have no influence on decompression calculations. It relates just to display of depth. Bigger number of salinity less meters of depth at pressure of 1 bar and so on...
Sent from my PAP4500DUO using Tapatalk 2
Naumachos
Member
I agree with deco,but i dive a spot in salt water at 100 (depth sounded) and my Predator (set for salt w.) show 103.
Sorry to hijack the 3d.
Igor P
New Member
Check your salinity settings to match salinity of water at the site of the dive. ..
Sent from my PAP4500DUO using Tapatalk 2
paulraymaekers
Active Member
correct, in formal WOB tests, the WOB in back-mounted counterlungs is usualy better: just look at the market: the best WOB are always found on these unit. It is related to design limitations, how to get the gas around with the minimum number of connections, gas direction changements etc
where we all confuse is mixing up WOB with hydrostatic imbalance: hydrostatic imbalance will directly influence lung loading, more then pure WOB.
hydrostatic imbalance can easier be minimised on front/over the shoulder counterlungs, there will be less change in mouth-piece pressure when a diver rotates around one of his axes
the choice for back mounted, or OTS counterlungs is a compromise, where many parameters must be taken into consideration
Naumachos
Member
also 2 digital Uwatech and other computers have the same data ...
I go back to read the 3d, thank you.
Igor P
New Member
Michael Thornton
Rebreather Enthusiast
Thanks for the spreadsheets. Now I just have to convert all that voodoo into feet instead of meters.
Nothing like taking simple equations and making them more complicated by using imperial.
Sent from my iPhone using Tapatalk
Very interesting thread and I try to understand it the best I can not being a doctor. I have a few questions though I hope you can help me with?
From what I gathered low flow rates decreases the risk of collapse. Could not this be part of the answer to Harry***8217;s question?
I also have been wondering about something I read a long time ago about how we breathe and it relates to the theory of negative or positive pressure.
From what I remember the paper I read theorized that the human body is not primarily designed to breathe in but to breathe out. An ANSTI machine would not notice this as it is the same strong in both directions but the body, according to this theory is not. Breathing in was a process helped by the difference in the external higher pressure outside the lungs and the lower pressure inside them after exhaling. The mussels and construction of the lungs had because of this adapted to be stronger at exhaling than inhaling.
If this is correct, would not this serve as an extra negative effect when having to forcefully breathe in sucking gas down from a lower pressure?
From what I gathered low flow rates decreases the risk of collapse. Could not this be part of the answer to Harry***8217;s question?
Can it be possible that when diving air diluent at 42m the narcosis would lower the breathing rate and thus also the risk of collapse?
I also have been wondering about something I read a long time ago about how we breathe and it relates to the theory of negative or positive pressure.
From what I remember the paper I read theorized that the human body is not primarily designed to breathe in but to breathe out. An ANSTI machine would not notice this as it is the same strong in both directions but the body, according to this theory is not. Breathing in was a process helped by the difference in the external higher pressure outside the lungs and the lower pressure inside them after exhaling. The mussels and construction of the lungs had because of this adapted to be stronger at exhaling than inhaling.
If this is correct, would not this serve as an extra negative effect when having to forcefully breathe in sucking gas down from a lower pressure?
Last edited:
Mark Chase
ATB=AlwaysTalkingBollocks
Good point I had a non ce unit
Whats the wob of the latest units at 40m on air?
Atb
paulraymaekers
Active Member
2.0 J/l horizontal, 2.17 J/l vertical
Mark Chase
ATB=AlwaysTalkingBollocks
OK so what does this mean to us the diver when compairing it to 1.7 for the JJ and 1.6 for the Boris?
Is it important?
Is it not important till we get to X depth?
I personaly found the WOB on the non CE rEvo to be perfictly fine. I never felt it weas an issue. But if i were planning a 200m+ dive is there a meeningfull advantage having a WOB of 1.6/7 over a unit with 2.0?
As a lay person, I am thinking if gas density with 5% nitrogen in the mix is a serious issue, then isnt a WOB advantage of 0.3 significant?
Seen as a number 0.3 dosent sound much but seen as a percentage? 15% sounds significant.
Let me stress again that i dont consider it relevent for "normal" diving but for super deep significantly past 100m stuff, perhaps it is?
ATB
Mark
paulraymaekers
Active Member
the deeper the less important
as these are values in air, 40m, with extreme ventilation rates
at 100m using 10/90 the WOB drops to below 1.5..
remember CE limit is 2.75
Mr Walker
Relax /Frankie
I believe it has been established that one can't feel by oneself if WOB is fine or not. ANSTI is required for that purpose.
Some arguments were made a while ago about high WOB was a factor contributing to heart attacks amongst RB-divers. But I don't think it has ever been susbstansiated by research.
/nils
Mark Chase
ATB=AlwaysTalkingBollocks
You obviously never dived a CCR with a early Golum Mk1 BOV
I can tell you the WOB on that was defo not fine and I could tell as could many other users.
ATB
Mark
Mark Chase
ATB=AlwaysTalkingBollocks
the deeper the less important
as these are values in air, 40m, with extreme ventilation rates
at 100m using 10/90 the WOB drops to below 1.5..
remember CE limit is 2.75
OK so we have a diver on a twin meg unit with a WOB somewhwere arround the 2.5 mark on air at 40m and hes on 5/90 at 240m and coughing which is a clear sign of C02 retention.
Would he be better off on a unit that had a WOB of 1.6 at 40m on air at that moment, or dosent it matter?
ATB
Mark