Oxygen again - this time "Oxygen Bars"

[Acrimonious]

Breathing is basically controlled by 3 reflexes.

1) The reflex that makes you exhale when your lungs are full.
2) The reflex that makes you inhale when they are empty.
3) The reflex that makes you exhale when your lungs contain too much CO2.

The first 2 are to prevent you from blowing up or collapsing your lungs.

The third is a little weird... your body does not actually ever check to see if the air you're breathing contains oxygen. Oxygen is so plentiful, your body just assumes it's always going to have enough as long as it keeps breathing.

This causes problems in situations with carbon monoxide, inert gasses, and heavy gasses. Your body really doesn't care if it's getting oxygen... only that your CO2 level isn't too high. You will go on breathing gases with 0% oxygen (with minor symptoms like headache and fatigue) until you pass out and eventually die.

This site details Carbon Monoxide poisoning quite well. Note that none of the symptoms include gasping for air or choking.



This site explains the hazards of cryogenic liquids. This is a problem for people who work with chemical tank trucks and train cars, because even a small amount of these liquids will evaporate into large volumes of gas that displace breathable air:

Asphyxiation Hazard

When cryogenic liquids form a gas, the gas is very cold and usually heavier than air. This cold, heavy gas does not disperse very well and can accumulate near the floor. Even if the gas is non-toxic, it displaces air. When there is not enough air or oxygen, asphyxiation and death can occur. Oxygen deficiency is a serious hazard in enclosed or confined spaces.

Small amounts of liquid can evaporate into very large volumes of gas. For example, one litre of liquid nitrogen vapourizes to 695 litres of nitrogen gas when warmed to room temperature (21°C).

 

[Dymanic]

Breathing is basically controlled by 3 reflexes.

1) The reflex that makes you exhale when your lungs are full.
2) The reflex that makes you inhale when they are empty.
3) The reflex that makes you exhale when your lungs contain too much CO2.

The first 2 are to prevent you from blowing up or collapsing your lungs.

The third is a little weird... your body does not actually ever check to see if the air you're breathing contains oxygen. Oxygen is so plentiful, your body just assumes it's always going to have enough as long as it keeps breathing.

I don't think it's actually the amount of O2 or CO2 in the lungs that counts--how exactly would that information be available to the reflex?--it's what's in the bloodstream that counts. In a person with healthy lungs, the amount of CO2 is the primary indicator of when it's time to breathe--this is called 'CO2 drive'. Low oxygen can also trigger breathing, but it's just sort of a backup. In persons with damaged lungs, the amount of CO2 is not reliable as an indicator, as there is pretty much always a lot of CO2 present--in this case, the low O2 becomes the primary indicator (this is called 'hypoxic drive').

Whether the lungs are faced with excess CO2 or insufficient O2, taking a breath is their only option--they (reasonably) assume that the air will contain oxygen.

 

[BillyJoe]

In a person with healthy lungs, the amount of CO2 is the primary indicator of when it's time to breathe--this is called 'CO2 drive'. Low oxygen can also trigger breathing, but it's just sort of a backup. In persons with damaged lungs, the amount of CO2 is not reliable as an indicator, as there is pretty much always a lot of CO2 present--in this case, the low O2 becomes the primary indicator (this is called 'hypoxic drive').

Yes, it's all coming back - the "high CO2 drive" of the normal lung and the "low O2 drive" of the emphysematous lung.....
If a doctor gives a hospitalized emphysematous patient with an "low O2 drive" too much oxygen, he can actually stop breathing. Too much oxygen can actually kill him.

Thanks for your input A and D.

 

[Dymanic]

Yes, it's all coming back - the "high CO2 drive" of the normal lung and the "low O2 drive" of the emphysematous lung.....
If a doctor gives a hospitalized emphysematous patient with an "low O2 drive" too much oxygen, he can actually stop breathing. Too much oxygen can actually kill him.

So goes the conventional wisdom, taught to countless health care professionals.

What I have come up with after some digging, is that this risk has been greatly overstated, especially if the patient is conscious. I'm always looking for more input on this.

The best evidence I can offer is circumstantial:
Manufacturers of home oxygen generators have not found it necessary to equip the units with governors to insure that 'dangerously' high levels of oxygen are not administered, either through accident (remember that most of these patients are elderly) or deliberate intent (if excess O2 is potentially lethal, it seems like it would offer an attractive method of either suicide or euthanasia). Yet, apparently none of the manufacturers has been the target of a wrongful death lawsuit.

 

[LucyR]

Breathing shallow and fast (as in hyperventilating during a panic attack) mainly blows off cardon dioxide. The CO2 in the blood stream decreases leading to symptoms of lightheadedness, pins and needles in the finger tips and around the mouth and a senstion that you are not getting enough oxygen which causes you to hyperventilate even faster.

I know very little about this but I believe that CO2 is necessary for maintaining the optimum blood pH for production of oxy-hemoglobin. So as you say, blowing off too much CO2 will lead to oxygen starvation.

Is this pigswill?

 

[BillyJoe]

I know very little about this but I believe that CO2 is necessary for maintaining the optimum blood pH for production of oxy-hemoglobin. So as you say, blowing off too much CO2 will lead to oxygen starvation.

An acidic environment, as is found in metabolising tissues, causes a right shift in the oxyhaemoglobin dissociation curve. This means that the haemoglobin gives up its oxygen more easily - which is what we want because metabolising tissues require oxygen.

As we've said, hyperventilation blows off CO₂.
Looking at the following equation....

CO₂ + H₂O = H⁺ + HCO₃^-

When the CO₂ concentration is reduced the H⁺ and HCO₃^- combine to produce CO₂ and H₂O thereby producing a more alkaline environment. This causes a left shift in the oxyhaemoglobin dissociation curve. This means that the haemoglobin gives up its oxygen less easily resulting , as you say, in "oxygen starvation" of the tissues.

regards,
BillyJoe
(Still welcoming any corrections by those more knowledgeable)

 

[Rose]

Just a quick note on what Corelinx and BillyJoe posted.

I wasn't aware of diver's tricks, but in Fire/EMS, at least locally, the cure for a hangover is to come into the station and suck on some oxygen via non rebreather mask for a few minutes. From ancedotal stories, it seems to work well enough, though it may take a half hour or so to ween off from the oxygen.

As far as COPDers/emphesema patients go, the figure out of one of my text books is 1 in 3 COPDers relying on hypoxic drive are suseptibal to respiratory arrest due to oxyygination. In 13 years I've had exactly one patient in whom I observed this phenomena. It was quite an interesting transport. As soon as I gave her enough O2 to oxgyenate her, her respiratory rate dropped down drastically. Cutting back on the O2 increased respiratory rate but made her oxygen sats drop into the 70% range. It made for an interesting and nerve wracking transport.

 

[corplinx]

Just a quick note on what Corplinx and BillyJoe posted.

I didn't claim it was true, just that I had heard it. The only thing I know for sure is not to dive too deep after eating fried fish covered in tabasco sauce. If you reflux at 60 feet, there is no quick way up to wash your mouth out.