Rosenbaum Abraham, Kirby Christopher, Breen Peter H
Department of Anesthesiology UCI Medical Center, University of California, Irvine, Building 53, Room 227, 101 The City Drive South, Orange, CA 92868, USA.
J Clin Monit Comput. 2007 Apr;21(2):71-82. doi: 10.1007/s10877-006-9058-4. Epub 2007 Mar 1.
Indirect calorimetry, the determination of airway carbon dioxide elimination (V(CO2),and oxygen uptake (V(O2)), can be used to non-invasively detect non-steady state perturbations of gas kinetics and mirror tissue metabolism. Validation of monitoring instruments in patients is difficult because there is no standard reference measurement, a wide range of physiologic values is required, and steady state is difficult to achieve and confirm. We present the development, critical details, and validation of a practical bench setup of a metabolic lung simulator, to generate a wide range of accurate, adjustable, and stable reference values of V(CO2) and V(O2), for development, calibration, and validation of indirect calorimetry methodology and clinical monitors.
We utilized a metered alcohol combustion system, which allowed safe, precise, and adjustable delivery of ethanol to a specially designed wick system to stoichiometrically generate reference V(CO2) and V(O2). Gas was pumped through a circular circuit between the separate metabolic chamber and mechanical lung, to preserve basic features of mammalian gas kinetics, including a physiologic ventilation waveform and the ability to induce non-steady state changes. Accurate and precise generation of V(CO2) and V(O2) were validated against separate measurements of gas flow and gas fractions in a collection bag.
For volume control ventilation, average error for V(CO2) and V(O2) was -0.16% +/- 1.77 and 1.68% +/- 3.95, respectively. For pressure control ventilation, average error for V(CO2) and V(O2) was 0.90% +/- 2.48% and 4.86% +/- 2.21% respectively. Low values of measured ethanol vapor and carbon monoxide supported complete and pure combustion.
The comprehensive description details the solutions to many problems, to help future investigations of metabolic gas exchange and contribute to improved patient monitoring during anesthesia and critical care medicine.
间接测热法，即测定气道二氧化碳排出量（V(CO2)）和氧摄取量（V(O2)），可用于无创检测气体动力学的非稳态扰动并反映组织代谢情况。在患者中对监测仪器进行验证很困难，因为没有标准参考测量值，需要广泛的生理值范围，并且难以实现和确认稳态。我们介绍了一种代谢肺模拟器实用实验台设置的开发、关键细节和验证，以生成广泛的准确、可调节且稳定的V(CO2)和V(O2)参考值，用于间接测热法方法和临床监测仪的开发、校准和验证。
我们使用了一个计量酒精燃烧系统，该系统允许将乙醇安全、精确且可调节地输送到专门设计的灯芯系统，以化学计量方式生成参考V(CO2)和V(O2)。气体通过独立的代谢室和机械肺之间的循环回路泵送，以保留哺乳动物气体动力学的基本特征，包括生理通气波形和诱导非稳态变化的能力。通过在收集袋中对气体流量和气体分数的单独测量，验证了V(CO2)和V(O2)的准确精确生成。
对于容量控制通气，V(CO2)和V(O2)的平均误差分别为-0.16%±1.77和1.68%±3.95。对于压力控制通气，V(CO2)和V(O2)的平均误差分别为0.90%±2.48%和4.86%±2.21%。测得的乙醇蒸气和一氧化碳值较低，支持完全和纯燃烧。
全面描述详细说明了许多问题的解决方案，有助于未来对代谢性气体交换的研究，并有助于改善麻醉和重症医学期间的患者监测。
