How long using 100% oygen before I am nitrogen clean?

[iainwilliams]

Greetings!

Just curious here, but does anyone know on average how long it takes to flush nitogen (accumulated from earlier dives - not micro bubbles) from your system using 100% oxygen.

I realise that to calculate this is quite difficult, but if you did a dive, flushed your system at the safety stop with 100% oxygen at 5m for say 15 minutes - would it bring you almost back to an almost zero nitrogen level? Obviously depth and time comes into play here - but my question is theoretical.

Surely doing the above will make a third dive for the day a LOT safer DCI wise, than if you did not flush at all with oxygen.

Cheers................Iain

 

[LUBOLD8431]

Dude, get in the water, dive some more, take some more classes, and spend less time on scubaboard. You will find your answers...

 

[BRW]

For dissolved gases, it would take 5 - 6 times any
tissue compartment halftime to drop to 98%+ clear
of any inert gas loading above any ambient pressure
(whether zero ambient inert gas pressure for pure
O2 breathing, or anything else).

For bubbles to clear, it would depend on the properties
of whatever is coating the inside of the bubble, plus whatever
the halftime of the tissue offloading bubble and tissue gas.
Estimates suggest 8 - 12 times the tissue halftimes for lipid
surfactants, and about 5 - 6 times tissue halftimes for
aqueous surfactants.

If breathing pure O2 to reduce inert gas pressures to
ambient (.79 atm for N2, etc), times are less than listed
above. See TDID (under Time Remaining), and use
ambient inert gas pressure as the desired end pressure,
and present gas loading as the initial pressure. For
recreational diving, back of the envelope suggests
40% - 60% of the above quoted times for dissolved gases
and bubbles.

Worrying about this and breathing pure O2 in the
water, as LUBOLD points out, for recreational diving
is hardly warranted. Gas and bubble loadings below
NDLs are well regulated by existing protocols.

 

[iainwilliams]

Dude, get in the water, dive some more, take some more classes, and spend less time on scubaboard. You will find your answers...

Love to! Unfortunately where I live at the moment, advanced nitrox and other tech courses do not exist!

I've been diving for many years (check my profile) and have over 2000 dives logged, however these are on air. I am new to NITROX and I find that this board, in addition to books and other net sites, is an ideal way to increase my knowledge. Therefore, I don't really understand why you suggest to stop using the board and take addtional classes!. Best to you.......Iain

 

[BRW]

For dissolved gases, it would take 5 - 6 times any
tissue compartment halftime to drop to 98%+ clear
of any inert gas loading above any ambient pressure
(whether zero ambient inert gas pressure for pure
O2 breathing, or anything else).

For bubbles to clear, it would depend on the properties
of whatever is coating the inside of the bubble, plus whatever
the halftime of the tissue offloading bubble and tissue gas.
Estimates suggest 8 - 12 times the tissue halftimes for lipid
surfactants, and about 5 - 6 times tissue halftimes for
aqueous surfactants.

If breathing pure O2 to reduce inert gas pressures to
ambient (.79 atm for N2, etc), times are less than listed
above. See TDID (under Time Remaining), and use
ambient inert gas pressure as the desired end pressure,
and present gas loading as the initial pressure. For
recreational diving, back of the envelope suggests
40% - 60% of the above quoted times for dissolved gases
and bubbles.

Worrying about this and breathing pure O2 in the
water, as LUBOLD points out, for recreational diving
is hardly warranted. Gas and bubble loadings below
NDLs are well regulated by existing protocols.

 

[iainwilliams]

Thank you BRW - appreciate your time...............Iain

 

[Dr Deco]

Dear Iain:

Flummoxed

I am somewhat perplexed by one responders comment to spend less time on SCUBA BOARD, since that is one way to obtain answers to the question you seek. I doubt that you will find it by diving. You could find it by reading the scientific literature, but that is often difficult to understand. In addition, without the benefit of being a researcher in that particular field, it is often difficult to “separate the wheat from the chaff” - that is, the "fine print."

Nitrogen Washout in Humans

From my research, nitrogen washout depends on the blood flow to the tissues and this can be regulated by exercise in the tissue of interest. We use this technique to reduce the time required to eliminate dissolved nitrogen from the astronaut’s body prior to extravehicular activity (EVA). Since the expenditure of breathing duration and high-pressure oxygen supplies is important, a reduction of this prebreathe time is of importance. The study has several aspects and was begun by me in 1989.

This work indicates that anatomically distinct tissues do not in reality exist with respect to gas loading as defined in diving. [This is different from various flows to kidneys and skin – organs that do not get “the bends.”] By modifications of heart rate, the muscle pump, and regional hormonal factors, halftimes can be shifted from 360 minutes to 40 minutes – surprising as this may seem. Thus the “longest half time” is not necessarily a fixed quantity despite the fact that they are employed as fixed quantities in decompression tables.

Recreational Diving

The use of oxygen is really not warranted in recreational diving in the no-stop situations described here. The tables and meters assure the safety of recreational diving when used in the manner in which they were tested (important consideration). Further protection is best gained through the modification of post-dive activity levels to prevent nucleation. That is my opinion, but it is supported by 60 years of research.

Bubble Washout

Since the gaseous nitrogen present in a bubble is at approximately ambient pressure (plus the Laplace pressure from surface tension effects), it will not exit the tissues as rapidly as dissolved nitrogen. It is essentially sequestered in a reservoir. The exit of this gas is modified in part by the surface coating of the bubble (as described by Fox and Hertzfeld and by Epstein and Plesset) and by the degree of stirring outside the bubble interface. Nitrogen washout from a bubble is slow where it has been measured. This has been, however, in anesthetized animals and not moving (stirring effects), awake ones.

There are known cases where a frank gas phase persisted and produced DCS in divers going to altitude three days after treatment for a hit. This shows that gaseous nitrogen can persist and is not some tautology or verbal prestidigitation. It is a difficult topic to cover in this space.

Dr Deco :doctor:

Please note the next class in Decompression Physiology :
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[iainwilliams]

Thank you Dr. Deco for your answer, and answers to some of my other listings.

You are quite correct. It is difficult to sometimes seperate fact from fiction and I've found this board to be on most occassions exceptionally helpful and informative. Take care.........Iain

 

[TheDarknessLord]

Hi There!

You don't have to worry about Nitrogen, the problem with O2 is th CNS Tox %. Take care about it! It could be worst than Nitrogen in your body.
The best way is take a Nitrox course, and must be a tec course, because recreationalo courses doen't talk about O2 at 100%.
Usually O2 is used to spend less time in a deco dive!
I'm using Air, Nitrox and 80/20 for deco diving, max depth 60 mts. with 1.6 ppo2 for air and 1.4 ppo2 for nitrox.
I was reading some info about 80/20 and those articles says that 80/20 is no a very effective mix! 100% is much better... 6 mts max! But I'm still using 80/20