John J, Drefeldt B, Taskar V, Månsson C, Jonson B
Department of Clinical Physiology, University Hospital of Lund, Sweden.
J Appl Physiol (1985). 1994 Jul;77(1):152-9. doi: 10.1152/jappl.1994.77.1.152.
A model incorporating compliance, resistance, inertia, and the thermal time constant of plethysmographs is used to describe the effect of its dynamic properties on measured respiratory parameters. Using numerical simulation we studied the effect of distortion of flow signals from 13 infants in whom flow and esophageal pressure had been recorded. The distortion in amplitude, shape, and timing of the recorded flow patterns was dependent on the dynamic properties of the plethysmograph. For constant-volume "pressure" plethysmographs, errors of derived parameters such as compliance and resistance are very important if the thermal time constant is short. These errors are not corrected by calibrating the plethysmograph at the breathing frequency. Time correction of the flow signals in volume-displacement plethysmographs gives accurate results when the plethysmograph resistance and compliance are low. Overall, a volume-displacement plethysmograph with moderately high resistance of the flowmeter, corrected for internal pressure and inertia, gives the best possible results.
一个包含顺应性、阻力、惯性以及体积描记器热时间常数的模型被用于描述其动态特性对所测呼吸参数的影响。通过数值模拟，我们研究了13名记录了气流和食管压力的婴儿的气流信号失真情况。记录的气流模式在幅度、形状和时间上的失真取决于体积描记器的动态特性。对于定容“压力”体积描记器，如果热时间常数较短，诸如顺应性和阻力等导出参数的误差会非常重要。通过在呼吸频率下校准体积描记器并不能校正这些误差。当体积描记器的阻力和顺应性较低时，对容积位移体积描记器中的气流信号进行时间校正可得到准确结果。总体而言，流量计阻力适中偏高、已针对内部压力和惯性进行校正的容积位移体积描记器能给出尽可能好的结果。
