Akagi M, Tasaka K
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Methods Find Exp Clin Pharmacol. 1988 Mar;10(3):143-50.
The transthoracic impedance method for measurement of bronchomotor tone was studied in anesthetized guinea pigs. Impedance change (delta Z) recorded from the 2nd to the 6th rib level increased linearly in accordance with the increment of inspirated volume (delta V); the maximum ratio of delta Z to delta V with the least cardiac artifact was measured at the level of the 6th rib. Histamine (5 micrograms/kg, i.v.) caused an increase in intratracheal pressure and a decrease in delta Z in guinea pigs. The fact that the delta Z peak lagged behind that of intratracheal pressure indicated that air flow movement was disturbed at the restricted bronchioles. In anesthetized dogs, the waveform of DC-impedance was similar to that of both flow volume and intraesophageal pressure. The waveform of AC-impedance, the signals of which are differentiated from DC-impedance, was similar to that of the flow rate. Following histamine administration (10 micrograms/kg, i.v.), the flow rate amplitude increased during inspiration and decreased during expiration. In passively immunized guinea pigs, antigen challenge induced a rapid increase in intratracheal pressure and a concomitant decrease in the amplitude of AC -impedance. Pretreatment with fenoterol (5-20 micrograms/kg, i.v.) inhibited these changes dose-dependently. It was concluded that delta Z measurement is a beneficial method for investigating respiratory dynamics in guinea pigs and is especially useful for evaluating the efficacy of bronchodilating action of test compounds.
在麻醉的豚鼠中研究了用于测量支气管运动张力的经胸阻抗法。从第2至第6肋水平记录的阻抗变化（ΔZ）随吸气量（ΔV）的增加呈线性增加；在第6肋水平测量了具有最小心脏伪影的ΔZ与ΔV的最大比值。组胺（5微克/千克，静脉注射）可导致豚鼠气管内压升高和ΔZ降低。ΔZ峰值滞后于气管内压峰值这一事实表明，在狭窄的细支气管处气流运动受到干扰。在麻醉犬中，直流阻抗的波形与流量和食管内压的波形相似。交流阻抗的波形（其信号与直流阻抗不同）与流速的波形相似。静脉注射组胺（10微克/千克）后，吸气期间流速幅度增加，呼气期间流速幅度降低。在被动免疫的豚鼠中，抗原激发导致气管内压迅速升高，同时交流阻抗幅度降低。用非诺特罗（5 - 20微克/千克，静脉注射）预处理可剂量依赖性地抑制这些变化。得出的结论是，ΔZ测量是研究豚鼠呼吸动力学的一种有益方法，尤其有助于评估受试化合物的支气管舒张作用效果。
