Simbruner G, Timischl W, Karigl G, Zeitlhuber U
Anaesthesist. 1981 Jul;30(7):358-63.
The continuous evaluation of the oxygen consumption and peripheral blood flow is technically difficult and practically not feasible in the newborn infant. We attempted to assess these two variables by means of a thermodynamic model, where only a set of geometrical variables and a set of temperatures have to be measured. The body is represented by a central cylinder (head, trunk) and a peripheral cylinder (extremities) and the heat flux therein is described by mathematical formulas. Only steady state conditions are considered. From the heat flux "surface leads to environment" the oxygen consumption and from the heat flux "central cylinder leads to peripheral cylinder" the peripheral blood flow is derived. On the patient only one core temperature (rectum) and two skin temperatures--one on the chest and the other one on the calf--have to be measured. The validity of the model was tested in 17 healthy newborns (body weight 1,100-3,850 g) and 6 diseased newborns (body weight 1,500-3,400 g). Comparing the computed oxygen consumption to values from the literature for a similar group showed good agreement. In 7 newborns the calculated oxygen consumption correlated well (r = 0.88, p less than 0.01) with the directly and synchroneously measured oxygen consumption. Indirect proof that the model also gives a reasonable index for the peripheral blood flow was obtained by relating the computed peripheral blood flow a) to values from the literature for a similar group and b) by demonstrating the dependence of the (calculated) peripheral blood flow on the haematocrit (r = -0.58, p less than 0.01).
在新生儿中持续评估氧耗量和外周血流在技术上难度较大且实际操作中不可行。我们试图通过一个热力学模型来评估这两个变量，该模型只需测量一组几何变量和一组温度。人体由一个中央圆柱体（头部、躯干）和一个外周圆柱体（四肢）表示，其中的热通量由数学公式描述。仅考虑稳态条件。从“体表至环境”的热通量可得出氧耗量，从“中央圆柱体至外周圆柱体”的热通量可得出外周血流。对于患者，只需测量一个核心温度（直肠温度）和两个皮肤温度——一个在胸部，另一个在小腿。该模型在17名健康新生儿（体重1100 - 3850克）和6名患病新生儿（体重1500 - 3400克）中进行了有效性测试。将计算得出的氧耗量与文献中类似群体的值进行比较，结果显示吻合度良好。在7名新生儿中，计算得出的氧耗量与直接同步测量的氧耗量相关性良好（r = 0.88，p < 0.01）。通过将计算得出的外周血流a）与文献中类似群体的值相关联，以及b）证明（计算得出的）外周血流对血细胞比容的依赖性（r = -0.58，p < 0.01），间接证明该模型也能为外周血流提供合理指标。
