Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Medical Biophysics

Supervisor

Diop, Mamadou

Abstract

Premature birth is associated with increased susceptibility to cerebral injuries because of the compounded effects of underdeveloped cerebral vascular and unstable hemodynamics. Notably, premature infants are highly vulnerable to intraventricular hemorrhage, which often leads to hydrocephalus and subsequently to high intracranial pressure (ICP). Current monitoring methods such as ultrasonography can only detect injuries that have already occurred, highlighting the need for prognostic tools. We hypothesize that concomitant measures of cerebral blood flow (CBF), blood oxygenation, and oxygen metabolism will be sensitive to high ICP. To test this hypothesis, experiments were conducted in a piglet model of high ICP using a noninvasive optical device that combines hyperspectral near-infrared spectroscopy and diffuse correlation spectroscopy. Measurements were acquired in nine piglets. Increases in ICP were associated with increases in deoxyhemoglobin and decreases in oxyhemoglobin, cerebral oxygenation, CBF, and cerebral perfusion pressure. These results demonstrated that optical measurements of CBF and cerebral oxygenation are sensitive to high ICP. The findings underscore the potential of optical techniques for non-invasive neuromonitoring in neonatal care, especially in the detection of compromised cerebral hemodynamics resulting from elevated ICP in cases of hydrocephalus.

Summary for Lay Audience

Premature neonates are highly susceptible to brain injuries because their brains are still in a critical developmental stage. Injuries such as bleeding in the cerebral ventricles can lead to hydrocephalus, which can adversely affect cerebral blood flow and metabolism. Hydrocephalus is an abnormal accumulation of cerebrospinal fluid in the brain that can cause high intracranial pressure (ICP; pressure inside the brain) and additional brain injuries. Current neuromonitoring techniques, such as ultrasonography, can only detect injuries that have already occurred. However, recent advances in biomedical optics have provided new tools that can non-invasively monitor the brain in real time.

In this study, we used a hybrid optical device that combines two optical techniques, near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS), to measure the effects of increased ICP on cerebral metabolism and blood flow in newborn piglets, to mimic what happens in neonates. This optical device can measure cerebral blood flow, deoxygenated hemoglobin (hemoglobin without oxygen), oxygenated hemoglobin (hemoglobin with oxygen), and cytochrome c oxidase (an enzyme involved in cellular energy production).

The measurements reveal that increases in ICP results in an increase in the concentration of deoxygenated hemoglobin and a decrease in the concentration of oxygenated hemoglobin, suggesting a reduction in the brain's oxygen supply. The patterns in these alterations correlated with changes in cerebral perfusion pressure, which controls the direction of blood flow to the brain. Additionally, the study showed that during ICP changes, there were strong relationships between changes in hemoglobin, oxygenation, cerebral blood flow, and cerebral perfusion pressure.

In conclusion, this study demonstrates that noninvasive optical measures of cerebral oxygenation and cerebral blood flow are sensitive to high intracranial pressure. This study additionally shows the noninvasive optical device can provide real-time detection of hemodynamic parameters that are involved in neonatal brain injury.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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