I’ve seen it many times, a person is worked up and hyperventilating. They are given a paper bag to breathe into.
What good does this do?
I’d think if you wanted the person to get more oxygen you’d have them take slow deep breaths of fresh air?
Why would re-breathing your own co2 be better than fresh air?
You want them to get LESS oxygen. A person who is hyperventilating is breathing too fast, taking in too much oxygen, and breathing out CO2 faster than normal. Recycling the CO2 forces the blood levels which have been made abnormally low back up.
Some quick googling indicates that the problem with hyperventilating is that it can make the O[sub]2[/sub] concentration of the blood too high. Forcing the person to breathe into a bag will cause them to breathe in more CO[sub]2[/sub] then normal, which can help bring down the O[sub]2[/sub] concentration.
My thought was, a person hyperventilating is is need of oxygen. It appears that that is not the case.
I was unaware that co2 is a good thing to have in your body.
I should have googled.
Thanks
The goal is only to return CO2 levels to normal. Oxygen levels aren’t really a factor. Increased CO2 causes the blood vessels in the brain to constrict. If the person continues to drive up the CO2, they will shut down brain function, and go unconscious. Of course, as soon as s/he goes down, breathing returns to normal, so no real harm done.
Breathing into a paper bag just makes one re-breathe some of their exhaled CO2. The bag still contains air, with the normal 21% oxygen.
The practice is just to keep people from falling down and hurting themselves.
Since the patient is rebreathing the air in the bag, wouldn’t the oxygen percentage decrease with each breath, as some is retained by the lungs each time?
I always thought it was because it showed you how bad your breath smelled and so you’d instinctively breath out less once the gusts of nachoes and toothpaste hit your own nose.
The bag is far from airtight as it doesn’t seal well around the mouth/nose.
Well, if it is tight enough to increase the CO2, it is tight enough to decrease the O2. I don’t see how a paper bag could selectively do one without doing the other.
Perhaps it’s fitting that one of my last posts as a doper clears up a little ignorance. I am always amused at people taking shots at an answer without actually knowing it.
Hyperventilators get side effects from breathing so rapidly that they lower the partial pressure of carbon dioxide in their blood to a point where they develop a profound respiratory alkalosis. The therapeutic effect of breathing into a paper bag has nothing to do with oxygen levels.
Normally the PC02 (Partial pressure of carbon dioxide) in the blood is about 40 mm Hg. When you increase the minute ventilation by breathing too deeply or too rapidly with otherwise normal physiology, the PCO2 will drop–in a healthy person I’ve seen it drop as low as 10 or so. Carbon dioxide affects, among other things, the pH (acidity and alkalinity) of the blood. Lowering the PCO2 raises the pH. Raising the pH (in this case, a respiratory alkalosis, b/c the root cause is getting rid of too much carbon dioxide via the pulmonary exchange) affects the concentration of calcium ions. This in turn causes muscle cramps which can be a severe symptom in a hyperventilator.
Breathing into a paper bag increases the CO2 concentration back to normal.
Where ya going, Chiefy? I’ll miss you.
Good for you. It drives me bats, at least in GQ.
That’s very true, but you’ve described what happens on a celluar level. My explanation is just as true, but on a more practical level.
One would have to hyperventilate long and hard to cause muscle cramps for more than a minute or so, unless, of course, the person is hyperventilating on top of Mount Rainier.
Altitude sickness is about the only thing that will cause, an otherwise healthy individual, to become so alkylotic as to cause direct injury. The body self corrects very quickly.
Acidosis, on the other hand, is much harder to correct, and is, in many cases, life threatening.
The only reason to offer a paper bag to someone having a simple anxiety attack, is to keep them from fainting and falling down, risking real injury.
IANAD, but my understanding is that the dangers of cerebral hypoxia from vasoconstriction in the brain are more serious than the other secondary effects of hypocapnia.
[QUOTE=Chief Pedant]
Perhaps it’s fitting that one of my last posts as a doper clears up a little ignorance. I am always amused at people taking shots at an answer without actually knowing it.
What? you’re leaving, why?
He’s fed up to the back teeth with people who can’t get quote tags right. 
:smack:
Or attempting to run a marathon when you haven’t trained properly. I got to 21 miles, collapsed, and started hyperventilating. My muscles cramped up and by the time I was brought back to the main first aid tent, my arms and legs were contorted in weird positions from the random muscles contracting from the whole calcium debacle.
That was more likely from dehydration. The serum alkylamia from hyperventilation lasts in the range of a minute or so.
The reason I know this is because I worked ERs and ICUs in several level I trauma centers.
One of the things we do for profound head injury, is to intubate and hyperventiate, to decrease brain swelling. If the hyperventilation is stopped for more than a minute, they become symptomatic; as soon as the respiratory rate is pushed up again, symptoms decrease.
If extreme exertion causes muscle cramps, it’s because the muscles are starved of oxygen, due to dehydration, and electrolyte loss. You sweat away a ton of sodium and potassium (calcium, not so much) The muscles need those electrolytes to function. They cry when they don’t get them.
Can I ask a related question relating to mouth to mouth resuscitation? I always wondered, if someone is not breathing, how breathing carbon dioxide into them via mouth to mouth was helping. Wouldn’t they need oxygen? Or are you just trying to keep their lungs inflated? 
We don’t breathe at anything close to 100% efficiency. What you breathe out still contains enough oxygen to be useful to someone else. Also, I suspect if you breathe in hard then out hard for the purpose of breathing into someone else, you will be taking even less oxygen out than you would in normal breathing because you’re taking in more air than you require, and you are then quickly breathing it out.