Non-invasive method of determining absolute intracranial pressure
First Claim
1. A method of determining absolute intracranial pressure (ICP) in a patient, comprising the steps of:
- monitoring skull expansion of the patient as a function of time;
inducing changes in ICP in the patient;
measuring blood pressure of the patient at a time when said skull expansion is approximately zero during said step of inducing wherein said blood pressure at said time is indicative of a reference ICP value;
causing a known change in ICP in the patient after said time;
measuring a change in said skull expansion of the patient associated with said known change in ICP; and
determining a skull expansion calibration factor, wherein the absolute ICP is a function of said reference ICP value, said measured change in skull expansion and said skull expansion calibration factor.
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Abstract
A method is presented for determining absolute intracranial pressure (ICP) in a patient. Skull expansion is monitored while changes in ICP are induced. The patient'"'"'s blood pressure is measured when skull expansion is approximately zero. The measured blood pressure is indicative of a reference ICP value. Subsequently, the method causes a known change in ICP and measures the change in skull expansion associated therewith. The absolute ICP is a function of the reference ICP value, the known change in ICP and its associated change in skull expansion, and a measured change in skull expansion.
10 Citations
37 Claims
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1. A method of determining absolute intracranial pressure (ICP) in a patient, comprising the steps of:
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monitoring skull expansion of the patient as a function of time;
inducing changes in ICP in the patient;
measuring blood pressure of the patient at a time when said skull expansion is approximately zero during said step of inducing wherein said blood pressure at said time is indicative of a reference ICP value;
causing a known change in ICP in the patient after said time;
measuring a change in said skull expansion of the patient associated with said known change in ICP; and
determining a skull expansion calibration factor, wherein the absolute ICP is a function of said reference ICP value, said measured change in skull expansion and said skull expansion calibration factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of determining absolute ICP in a patient, comprising the steps of:
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monitoring skull expansion of the patient as a function of time, wherein said skull expansion is defined in terms of a length l of a path traversing at least a portion of the skull of the patient;
inducing changes in ICP in the patient;
measuring blood pressure of the patient at a time when said skull expansion is approximately zero during said step of inducing wherein said blood pressure at said time is indicative of a venous bed pressure of the patient, and wherein said venous bed pressure at said time is equal to a reference ICP value ICPREF;
causing a known change Δ
ICP in ICP in the patient after said time;
measuring a change Δ
l in said path associated with said known change in ICP; and
determining a skull expansion calibration factor, wherein the absolute ICP is equal to ICPREF+K(Δ
lM) , wherein Δ
lM is the change in l between any measurement of l, and the measurement of l when the skull expansion was approximately zero. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of determining absolute ICP in a patient, comprising the steps of:
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coupling an acoustic signal to a first location on the patient'"'"'s skin adjacent the skull of the patient;
detecting said acoustic signal at a second location on the patient'"'"'s skin adjacent the skull of the patient;
measuring a phase difference between said acoustic signal so-coupled at said first location and said acoustic signal so-detected at said second location, wherein said phase difference is indicative of skull expansion of the patient;
repeating said steps of coupling, detecting, and measuring for a period of time;
inducing changes in ICP in the patient during said period of time;
determining a time during said time period when said phase difference is approximately zero;
measuring blood pressure of the patient at said time, wherein said blood pressure at said time is indicative of a reference ICP value;
causing a known change in ICP in the patient after said time;
measuring a change in said skull expansion of the patient associated with said known change in ICP; and
determining a skull expansion calibration factor, wherein the absolute ICP is a function of said reference ICP value, said measured change in skull expansion, and said skull expansion calibration factor. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
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27. A method of determining absolute ICP in a patient, comprising steps for:
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monitoring skull expansion;
inducing changes in ICP;
determining a reference ICP; and
determining a skull expansion calibration factor, wherein absolute ICP is a function of said reference ICP, said skull expansion factor, and a measured change in skull dimension. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification