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CHK BOONE wrote: > > In a message dated 98-01-14 20:05:55 EST, you write: > > << If this is right then it is impossible > > to achieve 100% O2 in the alveoli since you are always off gassing > > at least CO2 (unless, of course, you're dead and someone has you > > on a DAN O2 kit). > > If your dead 'clinicly', and the guy with the DAN 02 is properly doing > CPR, he is evacuating CO2. The PPCO2 may even be higher than otherwise, > as anaerobic oxidation has taken plasce which leads to an acidosis. If > you're 'biologically' dead, yes, then maybe there will not be any CO2, > but then what is the point :-)?!?! > > Tom >> > > ------------------------------------------------------------------- > Now I'm not a physiologist but anaerobic respiration yields lactic acid. This is true. > Is blood acidity due to lactic acid considered acidosis as is that caused by > CO2 > (carbonic acid) ? Yes, acidosis is just having an acidodic blood pH. There are a multitude of causes, including hyperventilation (anxiety/panic attack) and asprin overdose. > Surely it does not stimulate breathing as does CO2. Only CO2 is monitored, or more essentially the pH of blood is monitored. The nuerons actually monitor H+, the hydrogen ion. (pH is the inverse log of the h+ concentration). H+ is derived from CO2 by the following means. CO2 in the blood can combine with H20 to make carbonic acid, H2CO3, like you said. H2CO3 can then split into an a simpler acid, H+ and a simple base, the bicarbonate ion, HCO3-. Most C02 not combined with hemaglobin is converted to the acid and base. You body then can maintain its pH easily, by having you breathe off CO2, as the formula can reverse iteself. Overdose on asprin, acetylesalasilic 'acid', and your pH is acidic. Your body will increase ventilation to blow off CO2, which it builds by reversing the formula. The pH returns to normal. This is the bodies first and most short term line of defense against pH changes. There are two more that are longer lasting. > > I don't know if the receptors that sense the CO2 level monitor the lungs or > the blood stream; I would think the lungs since the level of CO2 in the blood > would probably be relatively constant and it is a variation that must be > monitored. > The recepters are in the respitory center in the brainstem, in the carotid arteries and the arch of the aorta. They are measuring H+ concentrations and they are very 'fine tuned'. > If there is no circulation there is nothing delivering CO2 to the alveoli from > the tissues except for what feable circulation is able to be maintained by > chest compressions so that the level of CO2 should drop quickly to near zero > in the alveoli. Surely some will continue to diffuse through the static > blood stream towards the alveoli from a distance that is increasing as CO2 is > removed from the blood still in the proximity of the alveoli but I would think > that ventilations with 100%O2 should be able to get you very close to 100% in > the lungs with little or no accompanying circulation. > On healthy diver types like us you would be surprised at the amount of blood movement you can get during well administered CPR, so there will be CO2 being ventilated out. (When someone is 'down' you are at that point concerned about the major organs, the heart, lungs and brain only, the deco effects of resusitation are almost moot. They do go hand in hand though, ventilation with 100% 02, chest compressions. Hyperventilation is best, get as many breaths in the cycle as you can.) > I have no idea if the stimulus to breath induced by CO2 level comes into play > in resusitation attempts or if the heart action must come first but I was > thinking that if it did then prehaps mouth to mouth may be more condusive to > restoring breathing itself. It is quite possible that getting O2 to the > heart muscle is far more important and that breathing reflexes will follow > naturally. > The hollywood idea that someone goes into cardiac arrest and minutes later is awake and thanking everyone for the CPR is just that - hollywood. If your lucky, circulation will restart on its own, with the help of all that 02 saturating the heart and the mechanical action of the chest compressions. Chest compressions create a tiny electric current, sometimes enough to defibrilate the heart if its in that lethal arrythmia. It is hypothesized this is the only instance when pulses spontaneously are restored. Mostly CPR is a time buying measure, until other therapies can be brought to bear. Over time, if the body recovers from being in such a state of stress, spontaneous breathing will begin again. > There is no point really, just wanted to cover the bases in anticipation of > someone comming back with the one way you could get 100% O2 into the lungs. > There are a lot of bored people out there. Could I be one of them?!?! This does raise some insights into oxtox I think. I may post them seperately after more thought. I thought some of this would be of intrest to the list as opposed to my initial response, which wasn't on the list. Tom -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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