Apparatus and method for monitoring intracranial pressure

• US 6,231,509 B1
• Filed: 12/05/1998
• Issued: 05/15/2001
• Est. Priority Date: 12/05/1997
• Status: Expired due to Term

• Current Assignee: Huntleigh Technology, Inc.
• Original Assignee: KCI Licensing Incorporated (3M Company)
• Inventors: Johnson, Royce, Quirk, William H. IV
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Imam, Ali M.
• Application Number:
  US09/206,203
• Time in Patent Office: 892 Days
• Field of Search: 600/437, 600/438, 600/451, 600/561
• US Class Current: 600/438
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 8/0875 for diagnosis of bone A61B5/4504 takes precedence
• CPC Class Codes: A61B 8/4227 characterised by straps, belts, cuffs or braces

Abstract

An apparatus and a method that permit the accurate measurement and continuous monitoring of the intracranial pressure of humans and vertebrates that eliminates the requirement of direct contact with the patient'"'"'s head, obviates problems previously encountered with the “soft” interface between transducers and the patient, and minimizes patient discomfort during the measurement process. The apparatus includes a pair of diametrically opposed acoustic transducers controlled and monitored through a switching device by a constant frequency pulsed phase-locked loop signal generator/analyzer. The transducers provided signal data that permits a discrimination of cranial vault width using appropriate signal processing devices. Digital logic devices or microprocessor based devices permit the identification of changes in cranial vault width from which intracranial pressure changes are determined. The method includes transmitting incrementally offset (in time) interrogating acoustic signals from the transducers and receiving reflected signals that include indications of the interior distance between the cranial vault walls. Repeated transmissions and receptions permit a comparison of cranial vault signal transit times and the identification of changes in the cranial vault width. Such changes are correlated with intracranial pressure changes after reference to an initial measured pressure.

Claims

1. A method for monitoring changes in the intracranial pressure of humans and other vertebrates, comprising the steps of:

providing a first acoustic transducer and positioning said first transducer externally adjacent to the cranium of said human or other vertebrate;

providing a second acoustic transducer and positioning said second transducer externally adjacent to the cranium of said human or other vertebrate and diametrically opposed to said first transducer;

transmitting a first acoustic signal into the cranial vault of said human or other vertebrate from said first transducer towards said second transducer;

receiving a first reflected acoustic signal at said first transducer, said first reflected signal comprising at least a signal component indicative of a first wall of said cranial vault near said first transducer and a signal component indicative of a second wall of said cranial vault opposite said first transducer;

transmitting a second acoustic signal into the cranial vault of said human or other vertebrate from said second transducer towards said first transducer;

receiving a second reflected acoustic signal at said second transducer, said second reflected signal comprising at least a signal component indicative of said second wall of said cranial vault near said second transducer and a signal component indicative of said first wall of said cranial vault opposite said second transducer;

calculating a signal transit time across said cranial vault from said signal components indicative of said walls of said cranial vault;

determining from said calculated transit time a relative width of said cranial vault;

repeating said steps of transmitting and receiving said acoustic signals, calculating said transit time, and determining said relative width to identify changes in said relative width of said cranial vault; and

associating changes in said relative width of said cranial vault with corresponding changes in said intracranial pressure.

2. An apparatus for monitoring changes in the intracranial pressure of humans and other vertebrates, comprising:

a first acoustic transducer positioned externally adjacent to the cranium of said human or other vertebrate, said first transducer transmitting an interrogating signal into the cranial vault of said human or vertebrate and receiving a reflected signal therefrom;

a second acoustic transducer positioned externally adjacent to the cranium of said human or other vertebrate and diametrically opposed to said first transducer, said second transducer transmitting an interrogating signal into the cranial vault of said human or vertebrate and receiving a reflected signal therefrom;

means for generating and transmitting a control signal to said acoustic transducers;

means for receiving and analyzing said reflected signals from said acoustic transducers;

means for alternately switching said control signal between said first transducer and said second transducer;

means for alternately switching said reflected signals between said first transducer and said second transducer;

means for discriminating a cranial vault transit time from said analyzed reflected signals; and

means for identifying changes in said cranial vault transit time and correlating said transit time changes with changes in said intracranial pressure.