Abstract
We propose a new near-infrared spectroscopy (NIRS) method for quantitative measurements of cerebral blood flow (CBF). Because this method uses concepts of coherent hemodynamics spectroscopy (CHS), we identify this new method with the acronym NIRS-CHS. We tested this method on the prefrontal cortex of six healthy human subjects during mean arterial pressure (MAP) transients induced by the rapid deflation of pneumatic thigh cuffs. A comparison of CBF dynamics measured with NIRS-CHS and with diffuse correlation spectroscopy (DCS) showed a good agreement for characteristic times of the CBF transient. We also report absolute measurements of baseline CBF with NIRS-CHS (69 ± 6 ml/100g/min over the six subjects). NIRS-CHS can provide more accurate measurements of CBF with respect to previously reported NIRS surrogates of CBF.
Highlights
Maintaining adequate cerebral blood flow (CBF) is critically important for brain function and tissue viability, especially for patients in the neurocritical care unit (NCCU) with conditions such as acute ischemic stroke, traumatic brain injury, and subarachnoid hemorrhage [1,2]
We observe that the blood flow index obtained from diffuse correlation spectroscopy (DCS) is a direct measure of blood flow and is affected by the speed of moving red blood cells in all vascular compartments, while near-infrared spectroscopy (NIRS)-coherent hemodynamics spectroscopy (CHS) provides an indirect measurement of CBF and is sensitive to the effects of blood flow only in the capillary and venous vascular compartments
We have reported a first comparison of this technique using concurrent and co-localized diffuse correlation spectroscopy (DCS) measurements of local CBF dynamics during transient changes in mean arterial pressure caused by thigh cuffs release following 2 min of cuff inflation at a supersystolic pressure
Summary
Maintaining adequate cerebral blood flow (CBF) is critically important for brain function and tissue viability, especially for patients in the neurocritical care unit (NCCU) with conditions such as acute ischemic stroke, traumatic brain injury, and subarachnoid hemorrhage [1,2]. Continuous bedside monitoring of CBF could improve outcome by providing the ability to detect any signs of impaired CBF in the patients and allow for suitable interventions to prevent ischemia before permanent tissue damage occurs. Conventional imaging techniques, such as oxygen-15 positron emission tomography (PET), single-photon emission computer tomography (SPECT), perfusion magnetic resonance imaging (MRI), and xenon-computed tomography (Xe-CT), can measure CBF accurately, but these techniques are not suited for clinical bedside monitoring because they are costly, unable to provide continuous monitoring, involve major instrumentation, and may require radiation exposure and patient transport [4]. Performance of TCD is operator dependent and may not be applicable in 10-15% of patients due to lack of ultrasound transmission windows [5,6]
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