[Systems analysis of pressure transmission in intracranial cavity]

Systems analysis of intracranial pressure pulse waveform was carried out in 6 dogs during normal condition (normocapnia and intracranial normotension) in order to explore how to transmit the pressure pulse through the intracranial cavity. Pulses originated in the heart travel in the intracranial cavity through the vessels, transmit into the cerebral tissue and finally reach to the dural surface. It can be speculated that the epidural pressure pulse waveform might be influenced by the property of intracranial components. The intracranial cavity which consists of brain parenchyma, vessels, cerebrospinal fluid, blood, pia, arachnoid, dura and skull is considered as a kind of system. The systems analysis method was applied to it. The common carotid arterial pressure pulse wave was used as the input signal of system, and the epidural pressure pulse wave was used as the output. The intracranial pressure was measured by an epidural pressure transducer attached to the dural surface through a parietal burr hole. The common carotid arterial pressure pulse wave and the epidural pressure pulse wave were recorded on FM analog tape. The characteristics of transmission are evaluated by the exact transfer function of system. We consider that the exact transfer function of system is obtained by the randomized input signal caused by the cardiac pacemaker or the aorta balloon. The power spectrum of input signal in this method didn't have a flat profile like completely random wave (or white noise) but a gentle slope between 1 Hz and 20 Hz. Therefore, the result in our method may be reliable only on the waves between 1 Hz and 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)