Yup as rn will testify. I am a math retard but I understand physiology fairly well.
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Yup as rn will testify. I am a math retard but I understand physiology fairly well.
I wouldn't call you a math retard. You got it. It just took you a little longer.Quote:
Originally Posted by adam0321
What exactly are you referring to??? I haven't seen anything negative about Marines in Adam's comments.Quote:
Originally Posted by Puttzer
I think trying to explain it as percentages >100% can just be confusing.
I'd just describe partial pressure as the fraction of a gas and how hard it pushes on the body at the surface. Then illustrate that each fraction pushes harder with depth, without changing the fraction. That way they don't confuse the concept of partial pressure with the pressure-volume relationship.
Maybe put 3 blocks of different widths under a board on a scale, to represent oxygen, nitrogen and helium perhaps. Show the weight reading and draw an analogy between that and partial pressure. 6 lbs total, broken into 1lb, 2lbs, and 3lbs for instance for each block. Then stack weight on top of the board in successive amounts. They could see that the blocks stay proportionally the same, but each one exerts an increasing pressure that is still the same proportion of the total amount.
Then to provide an analogy to O2 toxicity point out that if the bottom of the oxygen block was spiky (maybe rig up a separate block like that), there would be a point at which it would start to hurt if that was pressing against your body whereas the ones that were flat would not.
Simple, but once they have the basic concepts you can move on from there into specifics.
Quote:
Originally Posted by Webmaster
ohhh I like this one... not as funny as spending money and dieing of getting married to oxygen, but quite visual.
Whenever I teach this I use TDI's example of thinking of oxygen as a drug. Too little - you die. Too much - you die. The body must have at least 16% or 0.16ata, but no more than 160% or 1.6ata to survive.
To get too little you must breath a hypoxic mix, do some high altitude climbing or go up in an airplane that is depressurized. You will underdose on this drug and you may not survive.
But how do we get 160% oxygen? (Because talking about percentages over 100% IS confusing...) Standing at sea level breathing 100% pure oxygen you're at a partial pressure of oxygen equal to 1 ata. Now take that 100% oxgen to 20 feet and now you're at 1.6 ata or 160% oxygen. Take it below this depth and it will become toxic. You will overdose on this drug and you may not survive.
I always start by teaching my students how to convert depth in feet to atmospheric pressure (D/33)+1 = ATA.
Then I just go in 10 foot increments down the left side of a sheet of paper having them convert from depth in feet to ATA. I just teach them that these numbers are always remain the same. It's the breathing gas that will change. Off to the right from there I have them figure partial pressures of oxygen of various mixes by multiplying the depth in ATA by the fraction of oxygen in the breathing mix. For instance, air (.21 O2/.79 N2) at 100 feet (4 ata) would be 4 * .21 = 0.84. PO2 = 0.84. Is this within 0.16 and 1.6 ata of oxygen? Yes. Is that an acceptable dose? Yes. Let's try the same formula using 50% nitrox at the same depth of 100 feet (4 ata). It would be 4 * .50 = 2.0. PO2 = 2.0. Is this within 0.16 and 1.6 ata of oxygen? No. Is that an acceptable dose? No. Underwater that partial pressure of oxygen may cause a seizure which will most likely be fatal due to drowning.
I like to use examples of different gasses, starting with a hypoxic mix, then progressing to familiar ones such as air, 32%, 36%, 50%, 80% and 100%. Visually this helped me learn and that's how I now continue to teach it:
12%(.12) air(.21) 32%(.32) 36%(.36) 50%(.50) 80%(.80) 100%(1.0)
10'/1.3ata 0.156 0.27 0.416 0.468 0.65 1.04 1.3
20'/1.6ata 0.192 0.336 0.512 0.576 0.8 1.28 1.6
30'/1.91ata 0.229 0.401 0.611 0.687 0.955 1.528
70'/3.12ata 0.374 0.655 0.998 1.12 1.56
110'/4.33ata 0. 52 0.909 1.385 1.558
130'/4.94ata 0.592 1.037 1.58
210'/7.36ata 0.883 1.54
400'/13.12ata 1.574
Shown here is that "sliding scale" of oxygen vs. depth. The hotter the mix, the shallower its use. The 12% example requires a travel gas to be used until the diver reaches a depth of at least 12 feet where it increases to a PO2 of .16. All of the examples show the MOD of the gasses. This does not have to be complicated. I simply derived these numbers by multiplying the depth expressed in ATA by the fraction of the gas being breathed to create this simple table. Analogies just confuse me. I'm also the guy who took algebra three times in high school and once in college, so if I can do it, anyone can! Now I really enjoy this stuff. I hope this helps.
Thank you for your service.
****My table got jumbled when i posted it, but I hope you get the idea****
Confusing and wrong.Quote:
Originally Posted by Webmaster
To those who ar ein or have been in the Military I appologize if I offendd anyone. Those who know me know that I am a very proud Marine with numerious combat deployments and going on 7 years service in the Corps. I am not and never implied that Marines or any service are not an inteligent group. Some of the most inteligent people I have ever met are in the Military. I am a "grunt" by nature and all my students are "grunts". We are all now in reconnaissiance. Which is the USMC special operations. No one gets to the point they are combat dive school by being stupid. However the military is probaly the most deverse group of people. I have on everage 25 students with 25 different learning styles. I have had students who barely have a Diploma and in my last class I had a student with a masters in micro bio chemistry and physics. Not to mention I have 25 young men with higher then usual testosterone levels usualy recently back from 6-10 month in the desert now sitting in a class room in a building in Panama city florida with hundreds of bars withing 10 miles. So attention span can be a bit tough.
But again I appologize and thank any of those I offended
Semper Fi, Adam! Keep doing what you're doing, and thank you for it!
It's the pressure applied to the O2 and Nitrogen individually. While the percentages don't change 21/79 the concentration or density of the gas increases with depth.
You probably have a chart already showing the relationship between depth atmospheric pressure and volume. Use that in conjunction and show how the ATM and the density of each of the gases increase with depth and it's respective correlation with depth or absolute pressure.
Men tend to learn by looking at pictures.
Hope this helps.
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It's not wrong if it's in relation to what you breathe on the surface. Breathing oxygen at 20 ffw, you're taking in 160% as many molecules of oxygen as you'd be taking in at the surface.Quote:
Originally Posted by Squirrel Girl