From Event: SPIE BiOS, 2019
Oscillations in the tissue concentrations of deoxyHemoglobin ([Hb]) and OxyHemoglobin ([HbO]) can be measured in the human brain using Near InfraRed Spectroscopy (NIRS). These oscillations may be driven by temporal dynamics of Arterial Blood Pressure (ABP). Coherent Hemodynamics Spectroscopy (CHS) is a technique that measures oscillations of [Hb] and [HbO] that are coherent with ABP. These oscillations, at a frequency of 0.1 Hz in this work, can then be interpreted with CHS to get physiologically relevant parameters to monitor cerebral AutoRegulation (AR) and microvascular integrity. Systemic oscillations in ABP can be induced with cyclic inflation and deflation of pneumatic thigh cuffs or by paced breathing. ABP oscillations may also occur spontaneously during resting conditions. Here, these three types of ABP oscillations (induced with thigh cuffs, induced with paced breathing, and spontaneously occurring) are considered, and the phase between coherent [Hb] and [HbO] oscillations is interpreted in terms of AR. In two healthy human subjects, it was found that paced breathing may be subjective, either improving or impairing AR depending on the individual paced breathing amplitude. Cuff cyclic inflations and spontaneous hemodynamics resulted in no significant difference in the relative phase of cerebral [Hb] and [HbO] oscillations at 0.1 Hz. These initial results suggest that spontaneous hemodynamics may be used for CHS in place of induced ABP oscillations, with the advantage of not relying on subject’s actions (like paced breathing) or special equipment (like pneumatic thigh cuffs).
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Giles Blaney, Nishanth Krishnamurthy, Angelo Sassaroli, Thao Pham, and Sergio Fantini, "Comparison of spontaneous and induced coherent hemodynamics in the human brain," Proc. SPIE 10874, Optical Tomography and Spectroscopy of Tissue XIII, 108741I (Presented at SPIE BiOS: February 06, 2019; Published: 1 March 2019); https://doi.org/10.1117/12.2509894.