Surgery – Diagnostic testing – Measuring fluid pressure in body
Reexamination Certificate
2000-04-03
2003-03-25
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Measuring fluid pressure in body
C600S411000
Reexamination Certificate
active
06537232
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the design, construction, and use of a device for acute and chronic measurement of intracranial pressures in the human central nervous system, particularly during magnetic resonance (MR) imaging procedures, in particular during the injection or infusion of therapeutic drugs into the brain parenchyma. The present invention is an improvement over conventional methods and apparatus for measuring intracranial pressure, such as ventriculostomy with an external transducer, epidural strain gauge transducer, pressure sensitive epidural capsule, pressure sensitive subdural capsule, or subarachnoid pressure transducer.
2. Background of the Prior Art
Elevated intracranial pressure (ICP) can result from a variety of pathophysiological disturbances and frequently presents a major problem in the management of patients with head injury or other neurological disorders and diseases, including brain tumors and intracerebral hemorrhage. Although numerous autoregulatory and compensatory mechanisms protect the brain against elevations in ICP, if the ICP is increased to levels approximately equal to or greater than those of the arterial blood pressure, cerebral blood flow can be severely compromised leading to brain herniation and death.
The primary aim of ICP monitoring is to provide an early warning of a deteriorating condition so as to enable corrective therapy to be implemented. The accuracy required when measuring ICP is typically of the order of 1-2 mm Hg, but equally important is the reliability of the data. To ensure reliability, the calibration of any measuring device must be easily checked and adjusted as necessary. In addition to the steady-state accuracy of any sensing device and recording system, it is essential to have adequate dynamic response characteristics in the measuring device.
It is also essential that measurements can be made with minimum interference to the patient. To satisfy this objective, non-invasive methods of determining changes in ICP indirectly have been attempted using, for example, impedance plethysmography. Such non-invasive methods have been used successfully in neonates. However, in adults, methods which give the most accurate measurements require access into the cranial cavity and are therefore more invasive.
Invasive ICP devices have generally evolved in two basic directions. The first is based on implanting a sensor within the cranium. The second is based on mounting the sensor externally and connecting the measurement site through a fluid-filled transmission line. The three main sites for ICP Ring are the lateral ventricle, the extradural space, and the subdural or subarachmoid spaces.
U.S. Pat. No. 4,014,319 to Favre discloses an intracranial pressure transducer comprising a small sealed capsule positioned in a trephined hole in the patient's skull, wherein a sensor diaphragm in contact with the dura mater is displaced by changes in intracranial pressure and produces an output signal proportional to the change in intracranial pressure. U.S. Pat. No. 4,026,276 to Chubbuck discloses a pressure monitoring apparatus implantable in the cranium, wherein the apparatus comprises a passive resonant circuit with inductance and capacitance capability for measuring intracranial pressure by comparison to a reference ambient pressure.
U.S. Pat. No. 4,062,354 to Taylor et al. discloses an intracranial pressure transducer system comprising a holding bracket containing sensor elements which is positioned against the dura of the brain, wherein the elements within the holding bracket transmit electromagnetic signals related to the intracranial pressure to a receiver outside the patients body.
U.S. Pat. No. 4,080,653 to Barnes et al. discloses a method and apparatus for recording intracranial pressure utilizing a transducer amplifier.
U.S. Pat. No. 4,114,603 discloses an intracranial pressure monitoring device comprising a pressure-sensitive catheter insertable between the dura mater and arachnoid membrane. U.S. Pat. No. 4,114,606 discloses a monitoring apparatus for intracranial pressure measurement, wherein electromagnetic radiation is imposed on a passive circuit implanted in the cranium, the frequency at which the radiation is absorbed reflecting intracranial pressure.
U.S. Pat. No. 4,147,161 to Ikebe et al. discloses a system for measuring or monitoring intracranial pressure which comprises a non-elastic detecting pouch inserted between the skull and the brain, wherein a pressure measuring device in the liquid in the pouch indirectly measures the intracranial pressure.
U.S. Pat. No. 4,156,422 to Hildebrandt discloses an apparatus for treating hydrocephalus comprising housing which contains subcutaneously implantable components for measuring and controlling fluid pressure, wherein a second housing outside the patient contains measuring and control components whereby an intracerebral space may be automatically drained in response to a predetermined adjustable ICP.
U.S. Pat. No. 4,210,029 to Porter discloses a differential sensor unit utilizing fiber optic light guides, wherein three light guides pass within a pneumatic line into one end of a rigid cylindrical envelope implanted in the skull. Detectors are arranged to actuate pressure display and pneumatic controls to adjust the internal pressure of the envelope to match the ICP and thereby measure the ICP. U.S. Pat. No. 4,265,252 to Chubbuck discloses an implantable transsensor device containing a passive RF resonant circuit which is responsive to changes in ICP.
U.S. Pat. No. 4,385,636 to Cosman discloses an implantable telemetric differential pressure sensing device comprising a planar closed conductive loop which moves with a flexible diaphragm, wherein the resonant frequency of the conductive loop is detected telemetrically to determine pressure in a body compartment.
U.S. Pat. No. 4,343,038 to McKean discloses a magnetic field generator and magnetic pick-up coil contained in an implanted ICP monitoring device. U.S. Pat. No. 4,354,506 to Sakaguchi et al discloses an intracranial pressure gauge which comprises a powerless resonance circuit composed of a coil and a condenser, a sensor equipped with an implantable pressure-sensitive section capable of changing the inductance or the capacitance of the condenser in response to a change in ICP. U.S. Pat. No. 4,438,773 to Letterio discloses an implantable subarachnoid bolt for use in measuring ICP. U.S. Pat. No. 4,465,075 to Swartz discloses an integrated circuit including a pressure transducer and temperature compensation circuit.
U.S. Pat. No. 4,471,786 to Inagaki discloses a telemetering intracranial pressure transducer for detecting ICP, wherein a pressure-receiving layer disposed in contact with the dura mater transmits an output signal to an telemetering transmission circuit housed entirely beneath the patients scalp.
U.S. Pat. No. 4,600,013 to Landy et al. discloses a probe for ICP measurements in the subarachnoid space, said probe comprising a threaded shaft having a lumen in contact with a pressure transducer.
U.S. Pat. No. 4,621,647 to Loveland discloses an apparatus for monitoring and regulating ICP, wherein a manometer, transducer and regulator are interconnected by tubing and stopcocks. U.S. Pat. No. 4,627,443 to Chubbuck discloses an X-ray readable implantable pressure sensor,,wherein shifting of the radiopaque means is observed to indicate the change in pressure of a body cavity.
U.S. Pat. No. 4,677,985 to Bro et al. discloses an intracranial probe to monitor both ICP and blood flow by thermal diffusion and hydrogen clearance techniques.
U.S. Pat. No. 4,703,757 to Cohen discloses an optical fiber pressure transducer, wherein variations in transversely applied pressure to an elongated flexible fiber results in proportional light refraction and corresponding output signal.
U.S. Pat. No. 4,711,246 to Alderson discloses a miniaturized pressure transducer, wherein light transmitted through a single optical fiber is reflected by a diaphragm in accordance with the pressure being meas
Kucharczyk John
Truwit Charles L.
Jaworski Francis J.
Mark A. Litman & Assoc. P.A.
Qaderi Runa Shah
Regents of the University of Minnesota
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