推 hipoobell:GJ 謝啦 12/15 01:09
共筆 P.6 上面的 2. Augmented inflow effect 文字解釋那裡
請把「1% second gas、19% O2再加上40% N2O」
直接改成 80% N2O！ 打這一段時深深感覺老師講的不清不楚…頭腦好昏～
這裡我的共筆好像解釋得很糟…不好意思！！
附上一段原文書讓大家更了解一下這三個效應的意思囉～
Concentration
The effects of uptake can also be reduced by increasing the inspired
concentration. Interestingly, increasing the inspired concentration not only
increases the alveolar concentration but also increases its rate of rise (ie,
increases FA/FI). This has been termed the concentration effect,
which is really the result of two phenomena. The first is confusingly
called the concentrating effect. If 50% of an anesthetic is taken
up by the pulmonary circulation, an inspired concentration of 20% (20 parts of
anesthetic per 100 parts of gas) will result in an alveolar concentration of
11% (10 parts of anesthetic remaining in a total volume of 90 parts of gas).
On the other hand, if the inspired concentration is raised to 80%
(80 parts of anesthetic per 100 parts of gas), the alveolar concentration will
be 67% (40 parts of anesthetic remaining in a total volume of 60 parts of gas).
Thus, even though 50% of the anesthetic is taken up in both examples, a
higher inspired concentration results in a disproportionately higher alveolar
concentration. In this example, increasing the inspired concentration 4-fold
results in a 6-fold increase in alveolar concentration. The extreme case is
an inspired concentration of 100% (100 parts of 100), which, despite a 50%
uptake, will result in an alveolar concentration of 100% (50 parts of
anesthetic remaining in a total volume of 50 parts of gas).
The second phenomenon responsible for the concentration effect is the
augmented inflow effect. Using the example above, the 10 parts of
absorbed gas must be replaced by an equal volume of the 20% mixture to
prevent alveolar collapse. Thus, the alveolar concentration becomes 12% (10
plus 2 parts of anesthetic in a total of 100 parts of gas). In contrast,
after absorption of 50% of the anesthetic in the 80% gas mixture, 40 parts of
80% gas must be inspired. This further increases the alveolar concentration
from 67% to 72% (40 plus 32 parts of anesthetic in a volume of 100 parts of
gas).
The concentration effect is more significant with nitrous oxide than with the
volatile anesthetics, as the former can be used in much higher
concentrations. Nonetheless, a high concentration of nitrous oxide will
augment (by the same mechanism) not only its own uptake but theoretically
that of a concurrently administered volatile anesthetic. The concentration
effect of one gas upon another is called the second gas effect, which is
probably insignificant in the clinical practice of anesthesiology.
以上來自Clinical Anesthesiology, 4th Edition
希望有幫到忙～SORRY！
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