A New Equal Area Method to Calculate and Represent Physiologic, Anatomical, and Alveolar Dead Spaces
A New Equal Area Method to Calculate and Represent Physiologic, Anatomical, and Alveolar Dead Spaces
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计算和表示生理、解剖和肺泡死腔的新等面积方法
DOI：
10.1097/00000542-200604000-00013
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发表时间：
2006
期刊：
影响因子：
8.8
通讯作者：
A. Baker
中科院分区：
文献类型：
--
作者：
Yongquan Tang;M. J. Turner;A. Baker
背景：生理死腔通常由Bohr-Enghoff方程或弗莱彻法估计。肺泡死腔计算为通过Fowler等面积法估计的解剖死腔与生理死腔之间的差异。这项研究介绍了一种图形方法，使用类似的原则，测量和显示解剖，生理和肺泡死腔。方法：提出了一种新的生理死腔估计的等面积图解法。采用Bohr-Enghoff方程、弗莱彻面积法和新的图形等面积法计算10例机械通气患者的1,200张二氧化碳血管造影图的生理死腔，并采用Bland-Altman分析进行比较。死腔通过改变每例患者的潮气量、呼气末压、吸气呼气比和吸气保持而变化。结果如下：新的图形等面积法计算生理死腔分析表明，是相同的玻尔-恩格霍夫计算。通过新的等面积法和Bohr-Enghoff方程计算的生理死腔之间的平均差异（一致性限）为−0.07 ml（−1.27至1.13 ml）。新等面积法和弗莱彻面积法之间的平均差异为−0.09 ml（−1.52至1.34 ml）。结论：作者提出的计算、显示和可视化生理死腔的等面积法易于理解，并产生与经典Bohr-Enghoff方程和弗莱彻面积法相同的结果。所有三个死腔-生理的、解剖的和肺泡的-连同它们与呼气量的关系，可以方便地显示在二氧化碳呼吸图的x轴上。
Background: Physiologic dead space is usually estimated by the Bohr-Enghoff equation or the Fletcher method. Alveolar dead space is calculated as the difference between anatomical dead space estimated by the Fowler equal area method and physiologic dead space. This study introduces a graphical method that uses similar principles for measuring and displaying anatomical, physiologic, and alveolar dead spaces. Methods: A new graphical equal area method for estimating physiologic dead space is derived. Physiologic dead spaces of 1,200 carbon dioxide expirograms obtained from 10 ventilated patients were calculated by the Bohr-Enghoff equation, the Fletcher area method, and the new graphical equal area method and were compared by Bland-Altman analysis. Dead space was varied by varying tidal volume, end-expiratory pressure, inspiratory-to-expiratory ratio, and inspiratory hold in each patient. Results: The new graphical equal area method for calculating physiologic dead space is shown analytically to be identical to the Bohr-Enghoff calculation. The mean difference (limits of agreement) between the physiologic dead spaces calculated by the new equal area method and Bohr-Enghoff equation was −0.07 ml (−1.27 to 1.13 ml). The mean difference between new equal area method and the Fletcher area method was −0.09 ml (−1.52 to 1.34 ml). Conclusions: The authors' equal area method for calculating, displaying, and visualizing physiologic dead space is easy to understand and yields the same results as the classic Bohr-Enghoff equation and Fletcher area method. All three dead spaces—physiologic, anatomical, and alveolar—together with their relations to expired volume, can be displayed conveniently on the x-axis of a carbon dioxide expirogram.