笑氣在人體的攝取：吸入性麻醉劑攝取的新觀點

Nitrous Oxide Uptake in Man: A New Concept of Uptake of Inhalation Anesthetics

背景：當我確認肺功能殘氣量與肺泡膜的生理性屏障存在的事實時，笑氣在人體的攝取過程，不能再如過去文獻所描述的以時間平方根倒數關係來估計笑氣的體內攝取。本研究即以笑氣的體內攝取為模式探討吸入性麻醉劑攝取之新觀念。方法：針對接受以大量鴉片類藥物為主麻醉常規心臟手術病人為實驗對象，探討人體攝掫笑氣的過程，重點在持續記錄吸入與吐出笑氣濃度值，再使用簡單的數學的方式，將吸入與吐出濃度值相減計量，以描述笑氣體內攝取量與時間的關係。結果：施行笑氣全身麻醉，當描述笑氣在人體真正一開始的攝取時，首先認清肺功能殘氣量的存在。而先將肺功能殘氣量填充完成後的才是真正的人體內真正的攝取。本實驗證實，笑氣在人體的真正的攝取是從零開始而逐步增加，笑氣在人體攝取最高點的時間是在完成肺功能殘氣量的空間洗進填充之後，爾後隨時間進行逐步緩慢的減少。結論：從笑氣在人體攝取的過程中發現與過去文獻描述截然不同。過去以笑氣肺泡與吸入濃度比值曲線以下作為描述笑氣的攝取情形並不正確。實驗發現正確的實際體內攝取應以笑氣在肺泡與吸入濃度比真曲線以上表示，而一開始絕大部份笑氣是用在洗進填充肺功能殘氣量的空間，絕不是被人體攝取。

Background: With proper recognition of the functional residual capacity (FRC) and the existence of the alveolar membrane in consideration of gas uptake, the uptake of nitrous oxide does not follow the previously described power function of time, 1,000 ml x t -1/2. Methods: By use of a simple subtraction method, nitrous oxide uptake was measured in patients undergoing anesthesia with nitrous oxide in oxygen and a high-dose narcotic for cardiac surgery. Results: When FRC washin was considered separately, the uptake of nitrous oxide which started from zero, reached its peak value at the end of washin, and then diminished slowly. Conclusions: In contrast to previous publications, in which the time course of FA/FI was used to express the uptake of nitrous oxide, in spite of the area under the curve of FA/FI should not be used to express uptake, instead, the area above the curve, (1 - FA/FI), fits the results and should be considered as representing uptake.