Abstract
Intracranial pressure (ICP) measurement from the epidural space is desirable mainly because of its high protection against infections. The main problem, however, is how to exclude the effect of tension of the dura mater which makes the epidural pressure lower than ICP. The authors developed a hydrostatic pressure balance method, which keeps the nonelastic soft detector membrane contacting flat with the dura mater. The detector pouch is filled with saline of the proper volume and its pressure is transmitted to the pressure transducer through a slender tube. This pressure transmission through a tube realizes in principle an insensitive feature during the rotation of the patient's head, which otherwise causes a marked error from the true ICP. Over 60 clinical usages assure practical and infection-free features of this system. This system demonstrated high speed response and satisfactory accuracy. The pouch was easily inserted during craniotomy and extracted without any surgical procedures. It was also confirmed experimentally that this system is hardly affected by small particles or blood clots lying between the pouch and the dura mater. A comparison with conventional methods is discussed.
