Keywords

pulse-oximetry; plethysmography; ICP; hyperventilation; waveform analysis

Abstract

Intracranial pressure is a critical metric used when managing tumors, strokes, TBIs, hydrocephalus, and other operative conditions. Traditional methods for continuous ICP monitoring, intraparenchymal catheters, epidural transducers etc., are invasive and carry a high risk of infection. Previous attempts to create accurate, easy to use, and non-invasive ICP monitoring techniques have been unsuccessful. In this study, we investigated the utility of supraorbital and posterior auricular photoplethysmography to monitor changes in ICP during orthostatic tilt and hyperventilation, which increase and decrease ICP respectively.

Through a continuous 5-minute recording on a tilt-table we characterized SOA and PAA waveforms in 12 participants (ages 19-21). Participants underwent four conditions: +45° head-up tilt (HUT), -45° head-down tilt (HDT), -45° post hyperventilation, and +45° HUT post HDT. Capnography ensured proper hyperventilation occurred and n ECG provided context for the plethysmographic waveforms.

Results demonstrated that SOA measurements showed greater sensitivity to HDT changes in systolic amplitude, diastolic amplitude, and slope ratio. SA and PTT did not respond to hyperventilation, and dicrotic notch and systolic time exhibited minimal changes across conditions and locations. Increased DA and F wave presence during HDT suggest venous congestion may play a significant role in HDT ICP elevation. Disappearance of these features during hyperventilation indicates improved venous outflow. These findings support the SOA as an effective site for non-invasive monitoring of ICP-related physiological changes.

Thesis Completion Year

2026

Thesis Completion Semester

Spring

Thesis Chair

Mansy, Hansen

College

College of Engineering and Computer Science

Department

Department of Mechanical and Aerospace Engineering

Thesis Discipline

Biomedical Devices and Instrumentation

Language

English

Access Status

Open Access

Length of Campus Access

None

Campus Location

Orlando (Main) Campus

Non-Invasive Detection of Intracranial Pressure Changes.docx (4964 kB)
Non-Invasive Detection of Intracranial Pressure Changes

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