Noninvasive Diagnosis of Intracranial Hypertension with a Backpack Optical Spectroscopy System
Abstract
Intracranial pressure (ICP) is the pressure on cerebral tissue inside the skull. Elevated ICP is commonly caused by swelling inside the brain, is a common consequence of severe TBI, and is a critical cause of additional brain injury after the primary insult. In far-forward military environments, approximately 15-20% of combat-related injuries involve the head. Evacuation of injured warriors to higher-level care is often not immediately possible and, accordingly, effective field care is vital. The longer a necessary intervention is delayed, the more brain damage could occur. To manage ICP in the field, intravenous administration of osmotic therapy (i.e., hypertonic saline) is recommended. A major barrier to effective osmotic therapy though, is the current inability for ICP assessment in the field. If osmotic therapy is unnecessarily administered to Warriors with normal ICP, there is increased risk of hemorrhagic stroke. Conversely, if the dose or interval of osmotic therapy is not adequate to relieve elevated ICP, there is high risk of brain herniation and additional brain injury. Existing invasive ICP monitors require a skin incision and placement of an instrument through the skull, which precludes their use in the field. To overcome this barrier, we have pioneered a novel optical method to non-invasively assess ICP. The method, which requires manual placement of an adhesive fiberoptic sensor on the skin of the forehead, is well suited for field use. Our objective is to develop an early prototype of a portable device that non-invasively measures ICP in far-forward military environments. The optical device, which will be used by first-responders/medics, will provide a real-time assessment of ICP in the field. The device uses a near-infrared diffuse correlation spectroscopy (DCS) technique, which was invented at the University of Pennsylvania. DCS has the unique capability for non-invasive measurement of microvascular cerebral blood flow cardiac waveforms. We’ve recently developed a model that derives an optical ICP index based on these waveforms, and we have strong preliminary data to support it. To date, we have constructed a research-grade optical device for ICP measurement (not designed for field use) and used it to acquire pilot ICP data in 30 infants and 47 older children with hydrocephalus caused by cerebral spinal fluid (CSF) blockage. Hydrocephalus results in elevated ICP and progressive expansion of the CSF filled spaces within the brain (i.e., the ventricles). It is treated through surgical placement of a shunt in the ventricles to divert CSF and relieve ICP. We compared intraoperatively measured optical ICP to invasively measured ICP (the gold standard) in both human and pig studies and found that optically measured ICP measurements mirrored invasive ICP measurements. In this proposal, we aim to demonstrate that optical ICP measurements acquired in clinically relevant young adult swine models of severe TBI can accurately diagnose elevated ICP and accurately determine when elevated ICP is appropriately treated. We will measure optical and invasive ICP in clinically relevant and well-described swine models of two different injury types: severe, focal, blunt-force TBI and severe, diffuse (percussive) TBI. These injury models bracket the range seen in real-life injury and the use of both models increases the likelihood of our results being generalizable to use in the field. Sixty pigs will be measured in the first 2 years of the project. Half will receive a severe focal contusion injury induced with a controlled cortical impact device, while the other half will receive a severe percussive injury induced by a rapid non-impact rotation. Optical and invasive ICP will be continuously monitored for 4 hours post-injury. At 2 hours post-injury all pigs will receive a bolus of hypertonic saline to mimic the therapy used to reduce ICP in the field. We will compare optical and invasive ICP measurements to validate the accur
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 28, 2022
- Source ID
- W81XWH2210888
Entities
People
- Todd Kilbaugh
Organizations
- United States Army