Saucez P, Remy M, Renotte C, Mauroy M
Faculté Polytechnique de Mons, Laboratoire d'Automatique, Mons, Belgique.
IEEE Trans Biomed Eng. 1995 Mar;42(3):269-77. doi: 10.1109/10.364513.
The thermal behavior of the constant volume body plethysmograph under the thermal effect of the patient and the thermostatic bag is modeled by two relations: the first is between the temperature in the box and the heat flux generated by the patient and the bag, and the second is between the pressure in the box and the same flux. When the heat flux evolves as a step function, the temperature and the pressure are characterized by four time constants, the theoretical values of which are functions of the heat transfer coefficients by natural convection between the faces of the walls, and the air inside and outside the box. Only two of these four theoretical constants can be experimentally measured with reasonable precision. One of these is responsible for an important delay between the installation of the patient in the box and the disappearance of the disturbance thereby created in the pressure signal. Investigations with patients and with three different plethysmographs each built of a different material (wood, PVC, and Perspex) show the influence of the construction material on the waiting period before the disappearance of the disturbance in the pressure signal.
第一个是箱内温度与患者和袋子产生的热通量之间的关系，第二个是箱内压力与同一热通量之间的关系。当热通量以阶跃函数形式变化时，温度和压力由四个时间常数表征，其理论值是箱壁各面之间、箱内空气与箱外空气之间自然对流换热系数的函数。这四个理论常数中只有两个能够以合理的精度通过实验测量。其中一个导致患者进入箱内后到压力信号中由此产生的干扰消失之间存在重要延迟。对患者以及分别由不同材料（木材、聚氯乙烯和有机玻璃）制成的三种不同体积描记器进行的研究表明了构建材料对压力信号中干扰消失前等待时间的影响。
