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How many cats for each gas? How many controls? Age, sex and where did cats come from? Standard deviation of changes? Is 12 different from 7? Rod On Mon, 18 Mar 1996 BrianE@an*.an*.ui*.ed* wrote: > In 1965, Peter Bennett studied the effect of breathing different gas mixtures at > 10.8 ATA total pressure on cortical (brain) oxygen and carbon dioxide levels in > spontaneously breathing anesthetized cats 1. Baseline cortical CO2 was 53 mmHg > and O2 was 77mmHg at 1 ATA air. Below is a table of the results with different > gas mixtures. All changes represent changes from the baselines above. > > Gas CO2 % change O2 % change > 1 ATA O2 +5.6% +86% > 2.34 ATA O2 +7% +214% > 8.67 ATA He/2.34 ATA O2 +5.1% +297% > 8.67 ATA N2/2.34 ATA O2 +12.1% +121% > 8.67 ATA Ar/2.34 ATA O2 +20.5% +91% > > So, as the density of gas increased, the cortical CO2 increased. Unfortunately, > arterial levels of CO2 and O2 were not measured, so it is difficult to say that > the increase is from increased systemic CO2 production. Interestingly, as the > density of gas mixture increased, the increase in cortical O2 was limited. > Again, this is not specifically addressed in this study, but it could be due to > decreased respiratory efficiency with the denser gases. CO2 also increased > slightly at 1 ATA O2. The mechanism of this was not addressed, but could be > related to decreased dexoyhemoglobin transport of CO2 from the tissue (normally > an important mechanism by which CO2 is removed from the tissue is by binding to > the hemoglobin that has given up it's oxygen to the tissue. When PO2's are > high, there is less desaturated hemoglobin.). > > Increased CO2 can clearly exacerbate hyperoxic seizures. The mechanism is not > clear, however. One potential explanation could be due to increased > catecholamines in the brain. Production of hydrogen peroxide from > catecholamines by monoamine oxidase seems to be a very important mechanism in > hyperoxic seizures. When CO2 increases, catecholamines increase (and this could > also be an explanation of why stress can cause seizures). > > FYI, > Eddie Brian > > 1. Bennett PB: Cortical CO2 and O2 at high pressures of argon, nitrogen, helium, > and oxygen. J Appl Physiol 1965;20:1249-1252 > -- > Send mail for the `techdiver' mailing list to `techdiver@terra.net'. > Send subscription/archive requests to `techdiver-request@terra.net'. >
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