Henning B, Löfgren R, Sjöström L
Department of Medicine, Sahlgrenska Hospital, Göteborg, Sweden.
Med Biol Eng Comput. 1996 May;34(3):207-12. doi: 10.1007/BF02520075.
A chamber for indirect calorimetry has been constructed that utilises previously published general equations for the calculation of respiration. Owing to the large size of the chamber, the changes in gas concentration caused by a subject are very small. Therefore, algorithms are developed for noise suppression and trend identification. Using the exact solution of the equations for steady state, each gas concentration is fitted by a least square method to two connected exponential segments, of variable length, for the preceding 30 min period. Independently of the location of the join between the two segments, the gas concentration and its time derivative are evaluated at -15 min. This process is repeated, and its results are presented once every minute. As proven by gas injection tests, this procedure gives an instantaneous response to a single change in respiration, a correct averaging of repeated changes in respiration with periods of less than 15 min and noise suppression. It is concluded that this chamber is useful not only for traditional 24 h energy expenditure measurements, but also for experiments requiring rapid responses.
已构建了一个用于间接测热法的腔室，该腔室利用先前发表的用于计算呼吸的通用方程。由于腔室体积较大，受试者引起的气体浓度变化非常小。因此，开发了用于噪声抑制和趋势识别的算法。利用稳态方程的精确解，在之前30分钟的时间段内，通过最小二乘法将每种气体浓度拟合为两个长度可变的相连指数段。与两个段之间的连接位置无关，在 -15分钟时评估气体浓度及其时间导数。重复此过程，结果每分钟呈现一次。如气体注入测试所证明的，该程序对呼吸的单次变化给出即时响应，对周期小于15分钟的呼吸重复变化进行正确平均并抑制噪声。得出的结论是，该腔室不仅可用于传统的24小时能量消耗测量，还可用于需要快速响应的实验。
