頭蓋腔の圧脈波伝播特性の実験的研究 : 頭蓋内圧亢進および高CO_2血症時の伝達関数
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概要
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A cranial cavity with its contents was modeled as an unknown system and the technique of systems analysis was applied to it. The carotid arterial pulse wave was employed as the input and the epidural pulse wave as the output. The relationship between input and output was shown as the transfer function that contains all physical features of the system. Fifteen adult mongrel dogs were divided into three groups, and subjected to the following experimental conditions: intracranial hypertension by epidural balloon inflation (Group 1), intracranial hypertension by saline infusion into the cisterna magna (Group 2), and hypercapnia by decreasing the tidal volume (Group 3). The carotid arterial and epidural pulse waves were simultaneously recorded under resting intracranial pressure and each experimental condition. The data were analyzed using a computer program developed in the laboratory. The transfer functions were plotted on Bode diagrams. The transfer function under resting intracranial pressure showed resonance, that is, the gain curve formed a sharp peak within the range of 10 to 15 Hz and the phase shift curve changed from positive to negative within the same frequency range. In Groups 1 and 2, however, the sharp peak of the gain curve under resting pressure became increasingly obscure as intracranial pressure rose. This phenomenon occurs with intracranial hypertension because the gain is already high in the lower frequencies (less than 10 Hz) while unchanged in the resonant frequency. Changes in the transfer functions could not be distinguished between Group 1 and Group 2. In Group 3, the gain also became high in the lower frequencies and the resonance was obscure. However, at less than l0 Hz the gain curve was flatter than those of Groups 1 and 2, and the phase shift at less than 10 Hz was near zero. This study indicates that resonance gradually disappears with intracranial hypertension and hypercapnia. But it is supposed that this is apparent disappearance, because a peak within the range of 10 to 15 Hz still exists under severe intracranial hypertension and hypercapnia.
- 日本脳神経外科学会の論文
- 1987-05-15