Apparatus and method for determining intracranial pressure and local cerebral blood flow

• US 4,677,985 A
• Filed: 08/12/1985
• Issued: 07/07/1987
• Est. Priority Date: 08/12/1985
• Status: Expired due to Term

• Current Assignee: Barrow Neurological Institute, Philip L. Carter, William J. Bro
• Original Assignee: Barrow Neurological Institute, Philip L. Carter, William J. Bro
• Inventors: Bro, William J., Carter, L. Philip
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Sykes, Angela D.
• Application Number:
  US06/764,496
• Time in Patent Office: 694 Days
• Field of Search: 128/691-692, 128/736, 128/670-671, 128/748
• US Class Current: 600/504
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution
• CPC Class Codes: A61B 5/031 Intracranial pressure

Abstract

An intracranial probe to monitor both intracranial pressure and blood flow by thermal diffusion and hydrogen clearance techniques. The probe includes a casing or housing having internal bore which houses a reciprocal piston. The casing is provided with pressure port for commuting pressure to a remote pressure monitor. A pair of platinum or platinum alloy plates are associated with the two terminal integrated circuit which produces an output current proportional to the absolute temperature of the probe contact plate with which temperature transducer is associated. One temperature transducer monitors the temperature of the cold plate of the probe and the other monitors that of the hot plate. The signals are processed at a differentially amplified and fed to a monitor. In addition, the current generated by the platinum contact plates provides an input to a hydrogen clearance monitor to simultaneously determine blood flow by this technique.

Claims

1. An intracranial probe for measuring local cerebral blood flow and intracranial pressure comprising:

(a) a casing defining a generally cylindrical bore, said casing having an exterior portion for securement to the skull of a body and further including a pressure port communicating with said bore and adapted to communicate pressure to a remote pressure monitor;

(b) a piston reciprocal in said bore;

(c) a first platinum-containing contact plate forming at least a portion of said piston;

(d) a second platinum-containing contact plate forming at last a portion of said piston;

(e) first signal means coupled to said first contact plate for outputting a signal proportional to the temperature of the first plate;

(f) second signal means coupled to said second contact plate for outputting a signal proportional to the temperature of said second plate, said first and second means adapted to be connected to comparative means;

(g) first conductor means connected to said first plate;

(h) second conductor means connected to said second plate, said first and second conductor means adapted to be connected to polygraph means to monitor current generated by said plates; and

(i) means for polarizing said contact plates whereby said probe is securable in said skull with the said portions of the piston adapted to be in contact with the dura for measuring local cerebral blood flow by both thermal and hydrogen clearance techniques and means associated with said piston communicating a pressure signal indicative of intracranial pressure whereby the internal pressure is communicated across said piston to said bore to said pressure port.

2. The probe of claim 1 having a thermoelectric heat pump coupled to said contact plates.

3. The probe of claim 2 having power supply means coupled to said heat pump for providing the necessary drive to power the heat pump.

4. The probe of claim 1 wherein said casing is provided with a removable cap and said piston is removable from the bore of said casing.

5. The probe of claim 1 wherein said casing is provided with an exterior surface adapted to receive a tightening tool.

6. The probe of claim 1 wherein said signal means and said conductor means are incorporated in a single cable connected at said piston.

7. The probe of claim 6 wherein said single cable exerts a biasing force on said piston.

8. The probe of claim 1 wherein said piston defines flow passages.

9. The probe of claim 1 further including signal conditioning means and a microprocessor based control unit operationally connected to one another and to said contact plates.

10. The probe of claim 1 including temperature transducer means encased within said piston.

11. A method of measuring intracranial pressure and blood flow in a patient comprising:

(a) placing a probe in the skull of the patient having temperature transducer and contact plates therein adapted to contact a portion of the brain and float to maintain contact therewith;

(b) establishing a voltage proportional to the temperature difference between the contact plates and determining blood flow therein by thermal difference;

(c) administering hydrogen to the patient;

(d) polarizing said contact plates;

(e) measuring the hydrogen clearance ratio by determining the decline in current in said control plate; and

(f) simultaneously monitoring intracranial pressure along with the thermal difference and hydrogen clearance measurement.