Continuous Optical Monitoring of Cerebral Hemodynamics During Head-of-Bed Manipulation in Brain-Injured Adults

Abstract

Introduction Head-of-bed manipulation is commonly performed in the neurocritical care unit to optimize cerebral blood flow (CBF), but its effects on CBF are rarely measured. This pilot study employs a novel, non-invasive instrument combining two techniques, diffuse correlation spectroscopy (DCS) for measurement of CBF and near-infrared spectroscopy (NIRS) for measurement of cerebral oxy- and deoxy-hemoglobin concentrations, to monitor patients during head-of-bed lowering. Methods Ten brain-injured patients and ten control subjects were monitored continuously with DCS and NIRS while the head-of-bed was positioned first at 30° and then at 0°. Relative CBF (rCBF) and concurrent changes in oxy- (ΔHbO2), deoxy- (ΔHb), and total-hemoglobin concentrations (ΔTHC) from left/right frontal cortices were monitored for 5 minutes at each position. Patient and control response differences were assessed. Results rCBF, ΔHbO2, and ΔTHC responses to head lowering differed significantly between brain-injured patients and healthy controls (P<0.02). For patients, rCBF changes were heterogeneous, with no net change observed in the group average (0.3% ± 28.2%, P=0.938). rCBF increased in controls (18.6% ± 9.4%, P<0.001). ΔHbO2, ΔHb, and ΔTHC increased with head lowering in both groups, but to a larger degree in brain-injured patients. rCBF correlated moderately with changes in cerebral perfusion pressure (R=0.40, P<0.001), but not intracranial pressure. Conclusion DCS/NIRS detected differences in CBF and oxygenation responses of brain-injured patients versus controls during head-of-bed manipulation. This pilot study supports the feasibility of continuous bedside measurement of cerebrovascular hemodynamics with DCS/NIRS and provides the rationale for further investigation in larger cohorts.

Fast localization method of an anomaly in tissue based on differential optical density

“…Britton Chance [9] proposed the differential Optical Density (OD) method, which is based on the difference between the optical density of normal tissue and abnormal tissue. It has been fully used in brain tumors [10], tissue hemoglobin detection [11,12] and rapid cerebral hematoma detection [13,14] with good results. For example, the Infrascanner has been great clinical application in the hematoma detection.…”

NIR light propagation in a digital head model for traumatic brain injury (TBI)

“…This increase is due in part to increased awareness of TBI and improved diagnostic equipment, but it also indicates the importance of TBI and the importance of diagnosing TBI correctly. TBI can cause hemorrhage and acute changes in blood flow, oxygenation, and edema that may potentially be detected by one or more clinical imaging modalities: near infrared spectroscopy (NIRS), magnetic resonance imaging (MRI) [3][4][5], magnetic resonance spectroscopy (MRS) [5], diffusion tensor imaging (DTI) [6], computed tomography (CT) [7], single-photon emission CT (SPECT) [8], diffuse correlation spectroscopy (DCS) [9,10], and others [11].…”

“…In a review of TD fNIRS technology, Torricelli, et al, present the benefits of TD for imaging depth and resolution [22]. Advanced optical techniques related to TD fNIRS focus on the distribution of time of flight (DTOF) [23] and the correlation between diffuse time signals [9,10]. These advanced techniques have proven useful in non-invasive neurocritical monitoring.…”

“…This is a more challenging proposition than intracranial hematoma detection because it requires quantifying changes in blood oxygenation and water content over time. TD NIRS as a continuous bedside monitor for cerebral blood flow has been explored previously [9,10,23,43], and recent advances in TD fNIRS instrumentation allows for estimation of oxygenation in the brain cortex [21].…”

The effect of obstructive sleep apnea on the cerebral blood flow response to orthostatic stress

“…To that end we have utilized a modified version of a protocol involving orthostatic stress induced by head-of-bed positioning that was used to study acute ischemic stroke patients [14], traumatic brain injury patients [15] and a cohort of healthy subjects [16]. The key result from these studies was that DCS was able to observe altered CVR in brain hemispheres affected by conditions such as ischemic strokes [14,15].…”