Doc Bruce - DIY Oxygen system

[Doggtyred]

I purchased a 15 cf aluminum tank and have a 40cf steel tank sitting. Any advice on where to purchase some set up to fill from the 40cf? I don't see us on oxygen often but it will be nice to have, just in case.

The FBO at Wilmington wanted $50 to fill the tank (15cf) and I told them they were crazy! I said all the 100LL fuel I buy out of this place and that's the best you all can do? After a brief discussion they said $25 and even though I thought that was still a bit high I had them fill the tank. I didn't want to wait until the following Monday when the welding shop would fill it.

The 40 CF wont give you that much in the way of "fill" power... Maybe twice before you have to refill it... BUT..

Go to a welding gas shop, and have them either sell you the parts, or assemble the parts to allow you to transfill. Essentially 2 CGA-540 fittings on either end of a high pressure hose.

Things that make it BETTER are a small bleed valve in the hose. Closed when filling, then when both tanks are closed, you bleed off the pressure in the line before loosening. Not necessary but goes easier on the threads than loosening a hose under pressure.

CGA 540 valve stems need to be on both tanks. This is the Compressed Gas Association's industry standard.. and this way these tanks and your hoses will be compatible with other oxygen filling systems elsewhere. The CGA 540 specs out thread pitch, fitting diameter and fitting length, to prevent incompatible gas systems from being connected. Different gasses have different CGA numbers. The guys at the gas shop should know this.

It would be a VERY GOOD IDEA to have the steel tank inspected first, and ensure that its within hydro (hydrostatic test date), especially if its been empty. Again, gas shop can help.

 

[Doggtyred]

About the only major risk for burns comes from patients or well-intentioned nurses who rub petroleum jelly into the nostrils of someone receiving O2 by cannula

Or for patients who insist on smoking while getting oxygen by nasal cannula (not in the hospital, but at home..)

I haven't seen a dive shop doing a wet fill for several years now, but your mileage apparently varies.

It HAS been quite a long time since I've been scuba diving.. well over 5 years. My mileage may not vary that much.

 

[SteveinIndy]

Or for patients who insist on smoking while getting oxygen by nasal cannula (not in the hospital, but at home..)

This is true but I didn't think I needed to mention that since we were discussing spontaneous ignition of materials exposed to high concentration, high pressure O2.

That said, I will never forget the fire we had in the ICU at a hospital I used to work after the patient decided she had to have a cigarette while on a Venturi mask (60% oxygen being delivered to the mask). The patient survived and said she was never going to smoke again. I think having to have the burn surgeon cut the melted remnants of the mask from her cheek might have had something to do with her ability to successfully quit.

It HAS been quite a long time since I've been scuba diving.. well over 5 years. My mileage may not vary that much.

Ah, I only go in for the tank inspections, new gear, refresher courses (I believe in proficiency "check dives" ), etc. I "donate" $75/year to a local volunteer fire department in exchange for unlimited air refills off their cascade system.

 

[Doggtyred]

That said, I will never forget the fire we had in the ICU at a hospital I used to work after the patient decided she had to have a cigarette while on a Venturi mask (60% oxygen being delivered to the mask). The patient survived and said she was never going to smoke again. I think having to have the burn surgeon cut the melted remnants of the mask from her cheek might have had something to do with her ability to successfully quit

At least your patient survived.. I made an EMS call where we found pawpaw dead on the couch, a sheet at his feet.

While waiting for the coroner, we started looking around for clues to his medical history.. and saw an oxygen machine in the other room.. and a charred nasal cannula draped across the dark rug to his feet. The cannula was unplugged and the machine was turned off.

We looked under the sheet and about half of a 25 ft cannula was charred, starting at the patient end. A few cigarette ashes were there too. Apparently he was smoking, on oxygen, lit off his cannula and the flame was traveling up the tubing to his concentrator. He had enough energy to get up and turn his machine off before he apparently went back to the couch and suffocated to death.

 

[SteveinIndy]

Actually that sounds like he died from an inhalation injury. I don't know many non-hospitalized COPDers who are going to die simply from going without there oxygen for a few minutes, although I have a feeling that is not what you were trying to imply but I do hear the mistaken belief from the general public on a fairly frequent basis ("Hurry up and get his oxygen back on him! He'll die without it!") so I figured I would use this as a teaching opportunity.

 

[Doggtyred]

Actually that sounds like he died from an inhalation injury. I don't know many non-hospitalized COPDers who are going to die simply from going without there oxygen for a few minutes, although I have a feeling that is not what you were trying to imply but I do hear the mistaken belief from the general public on a fairly frequent basis ("Hurry up and get his oxygen back on him! He'll die without it!") so I figured I would use this as a teaching opportunity.

Perhaps.. or plastic smoke triggered a worse flare of his disease.. or he flared his disease from the mad dash to turn off his machine.. Who knows.

The call was a welfare check, lived alone, nobody (family) had been able to reach him that day. Really DONT know how long went between fire, death and us being summoned, only that he was beyond resuscitation when we arrived. The fire damage was not readily apparent on initial entry - it was limited to a charred cannula that blended in against a dark carpet.

I agree wholeheartedly with your teaching point.. that its rare for an otherwise stable home oxygen patient to decompensate over a matter of minutes without their supply.

 

[SteveinIndy]

Perhaps.. or plastic smoke triggered a worse flare of his disease.. or he flared his disease from the mad dash to turn off his machine.. Who knows.

The call was a welfare check, lived alone, nobody (family) had been able to reach him that day. Really DONT know how long went between fire, death and us being summoned, only that he was beyond resuscitation when we arrived. The fire damage was not readily apparent on initial entry - it was limited to a charred cannula that blended in against a dark carpet.

I agree wholeheartedly with your teaching point.. that its rare for an otherwise stable home oxygen patient to decompensate over a matter of minutes without their supply.

It would be interesting to see the autopsy findings on that case. Certainly peaks my curiosity at least.

 

[Doggtyred]

It would be interesting to see the autopsy findings on that case. Certainly peaks my curiosity at least.

Now that we are talking about it, me too. But.. considering I am working indoors now.. and have been for 10 years... I'd be hard pressed to research it.

Is it safe to say that smoking on oxygen = very bad thing?

 

[SteveinIndy]

Is it safe to say that smoking on oxygen = very bad thing?

Yes. I think it is safe to say that.

 

[ScottM]

Is it safe to say that smoking on oxygen = very bad thing?

My cousin would smoke when she was on oxygen with end stage emphysema. Her biggest complaint was that it made the cigarette burn too fast so she would have to smoke more. It was sad to watch.

 

[bbchien]

Way back in '80 there was a patron of the Iowa City VAH who arrived with third degree burns and nylon melted into his cheeks consistent with cannulas.

He was immortalized in song at Morning Report.

 

[GMascelli]

The 40 CF wont give you that much in the way of "fill" power... Maybe twice before you have to refill it... BUT..

Go to a welding gas shop, and have them either sell you the parts, or assemble the parts to allow you to transfill. Essentially 2 CGA-540 fittings on either end of a high pressure hose.

Things that make it BETTER are a small bleed valve in the hose. Closed when filling, then when both tanks are closed, you bleed off the pressure in the line before loosening. Not necessary but goes easier on the threads than loosening a hose under pressure.

CGA 540 valve stems need to be on both tanks. This is the Compressed Gas Association's industry standard.. and this way these tanks and your hoses will be compatible with other oxygen filling systems elsewhere. The CGA 540 specs out thread pitch, fitting diameter and fitting length, to prevent incompatible gas systems from being connected. Different gasses have different CGA numbers. The guys at the gas shop should know this.

It would be a VERY GOOD IDEA to have the steel tank inspected first, and ensure that its within hydro (hydrostatic test date), especially if its been empty. Again, gas shop can help.

Dave,

Thanks for the info! I just purchased the skyox set up (off the AOPA classifieds) but didn't feel like lugging the 40cf steel tank for just two of us. It was emptied in order to ship to me via UPS. I'll get moving on the hook up this weekend.

 

[Doggtyred]

Dave,

Thanks for the info! I just purchased the skyox set up (off the AOPA classifieds) but didn't feel like lugging the 40cf steel tank for just two of us. It was emptied in order to ship to me via UPS. I'll get moving on the hook up this weekend.

One clarification... and it may be nothing..

when I read 40 cf steel and 20 cf AL tank.. I ASSUMED that you were talking about using the 40 cf tank as a filler tank.. it would work poorly in that role

It will last twice as long (but 3 times or more as heavy) as the 20 cf AL tank for use in the plane.

If you use the big tanks from the gas shop to fill from, dont forget to chain them standing up (or chock them laying down) and leave the valve covers on them when not secured and protected. Nothing like a missile with 1 ton of thrust per sq inch when a valve gets knocked off..

 

[SkyHog]

But, if you're flying high, and you need O2, how are you supposed to smoke?

 

[GMascelli]

One clarification... and it may be nothing..

when I read 40 cf steel and 20 cf AL tank.. I ASSUMED that you were talking about using the 40 cf tank as a filler tank.. it would work poorly in that role

It will last twice as long (but 3 times or more as heavy) as the 20 cf AL tank for use in the plane.

If you use the big tanks from the gas shop to fill from, dont forget to chain them standing up (or chock them laying down) and leave the valve covers on them when not secured and protected. Nothing like a missile with 1 ton of thrust per sq inch when a valve gets knocked off..

That was the plan for the 40 cf. I'll try it and see how often I use it to fill from and then decide if I should keep it or just sell it. Thanks again Dave, appreciate the info.

 

[Ted]

But, if you're flying high, and you need O2, how are you supposed to smoke?

Pressurized aircraft. Malibu, 414, 421, P210 will all fit the bill.

 

[bigred177]

Ok, these questions may already be answered somewhere in the forum but I'm being lazy at the moment. I have an AL40 that is set up for a SCUBA regulator, could I build a regulator system to go on that valve? Also, do you just try to maintain your PO2 at or above 90% or what is the magic number?

 

[Doggtyred]

Ok, these questions may already be answered somewhere in the forum but I'm being lazy at the moment. I have an AL40 that is set up for a SCUBA regulator, could I build a regulator system to go on that valve?

You could. I would recommend against it. Are you positive that the regulator and its innards are hydrocarbon free? Something that might be safe with compressed air might not be safe with pure ox. I DO know that pure oxygen under pressure with hydrocarbon will react violently. I dont know the answer here, and cant guarantee its safety.

You also would be unable to have it filled away from your home base, and you would have to have an adapter made. Valves are cheap, regulators, not so much.. I would really recommend using the right valves on the tank so that you dont get stuck someday without... or have a mis-fill when someone tries to rig up something for you.

There are purpose built aviation (and medical) regulators that will do much of the math for you, and can even do "pulsed" flow that give equivalent bursts of oxygen on inspiration that prevent wastage and make the tanks last even longer.

Also, do you just try to maintain your PO2 at or above 90% or what is the magic number?

A minimum Sp02 of 90-92% is a good number to shoot for. This is 92% of your hemoglobin is saturated out of 100% possible. An otherwise healthy person should have 99-100% at sea level.

This is not ironclad, and does not directly indicate oxygen delivery. If your hemoglobin level is low, or unavailable, it will not be reflected on a typical pulse oximeter (as in, anemia or more importantly, carbon monoxide poisoning). In other words, you can have a "normal" saturation and be hypoxic. The oximeter is a tool. Works great but you have to understand the limitations.

PO2 (the term you used) is a gas pressure typically measured in mmHg when referring to its measurement in whole blood. This is distinct and separate from what an sP02 measures, but 90 is a good number, only its not a percentage.

 

[bigred177]

The tanks are O2 cleaned and have 100% O2 in them at the moment, I use them for decompression diving. That makes sense about the valves vs the regs though.

On the PO2, I am used to the diving terms of ppO2 and I was being lazy and not thinking. Which I know ppO2 is still different than SpO2 but that is more what I was trying to say than PO2.

It is interesting looking at things from the other angle, in diving we worry about the O2 becoming toxic at hyperbaric pressures and now looking at how it affects you at hypoxic levels.

 

[Doggtyred]

The tanks are O2 cleaned and have 100% O2 in them at the moment, I use them for decompression diving. That makes sense about the valves vs the regs though.

On the PO2, I am used to the diving terms of ppO2 and I was being lazy and not thinking. Which I know ppO2 is still different than SpO2 but that is more what I was trying to say than PO2.

It is interesting looking at things from the other angle, in diving we worry about the O2 becoming toxic at hyperbaric pressures and now looking at how it affects you at hypoxic levels.

In that case since I'm not dealing with an entry level recreational diver.. make sure the 1st stage puts out 50 psi over ambient, and then put a flowmeter on one of those low pressure ports or at the end of the hose replacing the 2nd stage/mouthpiece. For aviation use you should be fine with a 0-6 lpm flowmeter.

Same caveats about not being able to fill while away without an adapter.

A flowmeter physically like the F00-2C0xx at http://www.floteco2.com/htm/Products/Flowmeter_Page_&_Images/B-Flowmeter_Catalog.htm (adapted to go on the end of the low pressure hose) is the sort of flowmeter I would recommend, as opposed to the ones that have a floating ball in a tube and which have to be held vertical to give accurate flow..

 

[bigred177]

Thanks for your help. I may play with this approach sometime soon. I had not thought about the issue of not being able to get fills though so I might just build a full system. 40cuft would be more than enough for a round trip decently long XC for two people around 10,000 ft wouldn't it?

 

[bigred177]

BTW, this is really just to stay sharp and do some higher night flying and not so much doing much flying over 12,500. It would be hard to justify the time it took to climb that high in a Cherokee 180.

 

[Doggtyred]

Thanks for your help. I may play with this approach sometime soon. I had not thought about the issue of not being able to get fills though so I might just build a full system. 40cuft would be more than enough for a round trip decently long XC for two people around 10,000 ft wouldn't it?

Should be. Its been a while since I did the math.
28.3 liters per cu ft., so a 40 cf tank has 1132 liters.

aviation flowmeters are set in thousands of feet but this comes out to about about 0.25 liters/min at low altitudes to 0.50 liters/min at higher altitudes (up to the service alt of 18,000 for cannulae). One brand is non adjustable and gives 0.60 liters/min flow per user regardless of altitude.

Medical regulators do liters/min and typically can do 0.5, 1, 1.5, 2, 3,4, 5,6 etc.. 4 is the upper comfortable limit for medical patients, and 6 is pretty much an absolute limit, anything above that simply is wasted flow.

As you can see, healthy people needing just a little extra for altitude dont need all that much.


For flow at 0.5 lpm for a 2200 psi tank holding 40 cu ft/1132 liters
1 person - 37.7 hrs
2 person - 18.6 hrs
3 person - 12.5 hrs
4 person - 9.4 hrs

This is at the upper flow rate for higher altitude. You could double this at lower flows and lower altitudes, but medical regulators are difficult to get this low. Aviation style can allow you to pick lower flows accurately.

If you get a pulsed regulator that gives short blasts of o2 at very high flow rates but ONLY during inspiration you can increase those durations by over 50%.

Each person needs their own regulator/flowmeter if you are cobbling a system together. If you use purpose built aviation regulators, each person has their own spigot on the regulator assembly.

 

[Ted]

I'm looking at doing my DIY system here (finally), and am trying to go over what I need exactly. I'm getting a cylinder that will come with appropriate CGA 540 valve on it. From what I can tell, I'll then need a stepdown regulator, and then another regulator, plus appropriate cannulas. And, of course, a pulse oximeter.

I'd like to have a 4-place oxygen setup as even though my plane has 6 seats, I'm not sure I'd want to try to stuff more than 4 people and luggage in it and take it to oxygen altitudes. It wouldn't be very happy, I can tell you that. So, whatever setup I choose it should have the ability to have up to 4 people plugged in, although I doubt I'd ever have more than 2 realistically, unless there were some big winds up high coming home from Gaston's or some other event with a bunch of people.

I don't figure this would get used all that often, but when I use it it'll probably be for long trips (i.e. when I'm traveling 600+ nm and there are good tailwinds up high). Would something like this:

http://cgi.ebay.com/H-M-Medical-Oxy...in_0?hash=item2554501d27&_trksid=p3286.c0.m14

For each person and then the appropriate cannula coming off of it work?

 

[Doggtyred]

Would something like this:

http://cgi.ebay.com/H-M-Medical-Oxy...in_0?hash=item2554501d27&_trksid=p3286.c0.m14

For each person and then the appropriate cannula coming off of it work?

It would work poorly from a practical standpoint. You'd need 4 of them tied into a HIGH pressure hose or hardline (2200 psi) which is undesirable compared to the other options. This particular flow regulator is good for 15 liters per minute flow when for aviation use you will be using 2 lpm or less.

I went looking and couldn't find one on ebay used this time, but if you are going to cobble something together, get a regulator that has a 50 psi DISS fitting on it (that is NOT regulated by a flowmeter). You can then run 50 psi hose (much safer/easier) to each station and then put a flowmeter on it.

Or you could spend 300 bucks and just get an aviation regulator with 4 ports on it.

 

[chambers]

I have a transfer hose (8 ft.) complete with pressure guage, fittings for welding tank and fitting required to fill on board o2 tank. I used this to fill the tank in my Cessna TU206 from a large welder's tank. It is complete with instructions and in as new condition as mfg by Aerox. I no longer need it and would be willing to part with it if anyone is interested. Bob

 

[Ted]

I just got my pretty darn large O2 tank (my cousin works for Luxfer - got me a good deal). It has a CGA 540 valve on it. I really can't think of any times when I'd need to have more than just me on the O2 in the current configuration. So often I'm carrying dogs so I'd stay at or below 15,000 ft anyway, and without turbos I have a feeling the Aztec would be pretty doggy (no pun intended) up there unless it were just me.

So, I'm looking at which regulator to buy. I also plan on getting the oxisaver cannulas for me. I'm seeing some CGA 540 regulators with appropriately small flow numbers on the low end, but on the high end only go up to 8 l/m (most of the aviation ones I see go up to 15 l/m).

So the question: For just me with oxisavers, is there any reason why 8 would be insufficient, especially given the relatively low altitudes I intend on running? I'm going for the "on the cheap" system at the moment and may upgrade the system later.

I also ordered my pulse oximeter yesterday - looking forward to having that! Should have it in time for my next dog flight in two weekends, and would like to have the rest of the O2 system ready by then so I can start playing with it.

 

[Doggtyred]

So the question: For just me with oxisavers, is there any reason why 8 would be insufficient, especially given the relatively low altitudes I intend on running? I'm going for the "on the cheap" system at the moment and may upgrade the system later.

I also ordered my pulse oximeter yesterday - looking forward to having that! Should have it in time for my next dog flight in two weekends, and would like to have the rest of the O2 system ready by then so I can start playing with it.

I will be genuinely surprised if you get over 3-4. Anything over that will start to really dry out your nose. Anything over 6 lpm into a cannula is wasted.. period.. at that rate of flow you will spill out past your storage capacity of the cannula, as well as the storage capacity of your mouth and nose between breaths.

15 LPM will suck a tank down in less than an hour. Thats typically the flow rate for 100% inspired o2.. for medical use.. for sick people.

For aviation use you are simply trying to maintain the same "partial pressure" of oxygen at altitude that you get with room air/21% oxygen at sea level.. we are talking very low flows to achieve that.

Again.. be very surprised if you need more than 3-4 liters/min.

 

[GMascelli]

I am thinking of selling the system SkyoxSK 11-40 system I purchased. I added a 15cf aluminum tank thinking it would be fine for Mary and I. I havent had the chance to try it and would rather spend the money on an AP upgrade or get my 496 panel mounted. The Skyox purchase was intended primarily for our night flights.

AOPA classified July 09 http://forums.aopa.org/showthread.php?t=56547

 

[Ted]

Thank you, Dave. That's what I figured was the case but I wanted to get info from one of the more knowledgeable folks before buying anything.

 

[bbchien]

Ted- I use a regular welding regulator (make sure it has a vented diaphragm) on the tank, and the Skyox regulator/divider on the end of a six foot hose so that the business end lies between the two PIC seats. (80 psi hose, pressurized to 40 psi)

The Skyox regulator is an impressive piece of machine work, built by the same guys who do the hospital oxygen systems- Puritan Bennett. It's $200 and I've never seen it cheaper.

Above 2 Liters per minute cannulas (even oxysavers) get very inefficient. You shoulld be able to sustain SaO2 above 90% at 16,000 on 2 liters.

How many cu Ft is your tank? Is it a "A"? A Super "D"? It sounds bigger than an E!

 

[Ted]

Thanks for the info, Bruce. Going on the "get the biggest tank you can fit" mentality and seeing as I have a lot of room that I can fit stuff in, it's a 60 cu ft tank. Still pretty compact as far as I'm concerned - 7.3" diameter x 23.5" length, and weighs 22.5 lbs empty. Since my cousin got me a discount on it, it was still very cheap (I'll have my complete system working for under $200 using all new parts, including pulse-ox). It will conveniently fit between the front seats and the cages in a location where I can get at it easily.

For now, I just went ahead and bought a standard mini regulator and normal cannulas for myself. I will probably upgrade to the SkyOx at some point in time, but since my plane doesn't have turbos, I can't see being above 15k with anything more than just me.

I should have all my parts before the end of next week, which will allow me the opportunity to start playing with them. I'm looking forward to it! Next thing you know I'll want turbos...

 

[gismo]

It will conveniently fit between the front seats and the cages in a location where I can get at it easily.

I assume you already know it needs to be well secured. You don't want a tank like that flying around in severe turbulence or an off runway excursion. The hold downs should be strong enough (and anchored to something strong enough) to withstand about 5 times the weight of the full tank.

 

[GMascelli]

For now, I just went ahead and bought a standard mini regulator and normal cannulas for myself. I will probably upgrade to the SkyOx at some point in time, but since my plane doesn't have turbos, I can't see being above 15k with anything more than just me.

Ted,

Where did you purchase the regulator? I might sell my set up but keep the 15CF and two cannulas for Mary and I but I need a two place regulator.

 

[Ted]

I assume you already know it needs to be well secured. You don't want a tank like that flying around in severe turbulence or an off runway excursion. The hold downs should be strong enough (and anchored to something strong enough) to withstand about 5 times the weight of the full tank.

That's one of the things I've been thinking about long term. The current setup is going to be a portable one, and the only really good place for tie downs is in the back of the plane. Where I'll be keeping it for the moment, it will be so wedged in place that it won't have much opportunity to move.

 

[bbchien]

That's one of the things I've been thinking about long term. The current setup is going to be a portable one, and the only really good place for tie downs is in the back of the plane. Where I'll be keeping it for the moment, it will be so wedged in place that it won't have much opportunity to move.

Some Aztrucks came with tiedown rings on the floor of the baggage space. You need that 80 psi intermediate hose to be plenty long.....pressurize it on preflight, shut it down after landing.

 

[gprellwitz]

I'm now seeing pulse oximeters below $30. Any reason I should be suspicious of these? (Of course, I still have one that I bought years ago when they were $150, but for others...)

 

[Doggtyred]

I'm now seeing pulse oximeters below $30. Any reason I should be suspicious of these? (Of course, I still have one that I bought years ago when they were $150, but for others...)

When they approach disposable pricing, they have corresponding durability. The indications will be accurate. They just won't hold up to as much abuse.

 

[Ted]

Regarding pulse oximeters, can children (in this case specifically a 4-month old infant) use the standard pulse oximeter or would we be best off buying a specific pediatric one? My guess would be the latter, but wanted to get opinions.

We don't intend on going into oxygen levels with the baby in the plane (although I have added to our O2 system so that we can provide all three of us with oxygen), it's more so that we can keep an eye on things and see how altitude impacts him.

 

[bbchien]

Ted, in the first six months there is a predominance of fetal hemoglobin which has a different spectrum. You would not want to rely on an adult POX in this situation. However, the unloading curve in the neonate favors unloading the available oxygen in the brain.

As a practical limit, when the kid vomits, his Saturation is wayyy to low. Don't ask me how I know this....