Coherent Hemodynamics Spectroscopy Based on a Paced Breathing Paradigm — Revisited

Abstract

A novel hemodynamic model has been recently introduced, which provides analytical relationships between the changes in cerebral blood volume (CBV), cerebral blood°ow (CBF), and cerebral metabolic rate of oxygen (CMRO 2 ), and associated changes in the tissue concentrations of oxy-and deoxy-hemoglobin (ÁO and ÁD) measured with near-infrared spectroscopy (NIRS) [S. Fantini, Neuroimage 85, 202-221 (2014)]. This novel model can be applied to measurements of the amplitude and phase of induced hemodynamic oscillations as a function of the frequency of oscillation, realizing the novel technique of coherent hemodynamics spectroscopy (CHS) [S. Fantini, Neuroimage 85, 202-221 (2014); M. L. Pierro et al., Neuroimage 85, 222-233 (2014)]. In a previous work, we have demonstrated an in vivo application of CHS on human subjects during paced breathing [M. L. Pierro et al., Neuroimage 85, 222-233 (2014)]. In this work, we present a new analysis of the collected data during paced breathing based on a slightly revised formulation of the hemodynamic model and an e±cient¯tting procedure. While we have initially treated all 12 model parameters as independent, we have found that, in this new implementation of CHS, the number of independent parameters is eight. In this article, we identify the eight independent model parameters and we show that our previous results are consistent with the new formulation, once the individual parameters of the earlier analysis are combined into the new set of independent parameters.

Reduced speed of microvascular blood flow in hemodialysis patients versus healthy controls: a coherent hemodynamics spectroscopy study

“…NIRS is an ideal technique for the measurement of D, O, and T, and in our first demonstration of CHS we have used paced breathing at 11 different frequencies (0.071, 0.077, 0.083, 0.091, 0.100, 0.111, 0.125, 0.143, 0.167, 0.200, 0.250 Hz) to obtain the CHS spectra that are based on the amplitude and phase of the oscillations of D, O, and T as a function of frequency. 16,17 The high coherence between the driving oscillations in the arterial blood pressure and the induced, measured oscillations in the concentrations of oxy-, deoxy-, and total hemoglobin were exploited to model the cerebral microvasculature response as a linear time invariant system, 15 providing a quantitative framework for CHS and allowing for the determination of a number of physiological parameters by fitting the measured CHS spectra with the model equations. 18 It is the combination of (A) the richer information content of frequency-resolved measurements of hemodynamic oscillations, and (B) the quantitative framework provided by the new hemodynamic model 15 that accounts for the innovation of CHS and for its ability to yield specific physiological parameters related to the cerebral microcirculation.…”

NIRS Brain Studies with a New Hemodynamic Model: Coherent Hemodynamics Spectroscopy and Functional Neuroimaging

“…Furthermore, it can translate coherent hemodynamics spectra such as those of Fig. 2 into a set of physiological parameters related to the cerebral microvascular flow and autoregulation [5,7]. This capability has been demonstrated in the clinical setting of a hemodialysis unit [6].…”

“…(4) and (5) by using typical values for the model parameters [2]. The frequency of cerebral hemodynamic oscillations may be controlled by inducing them with paced breathing [4,5] or with cyclic inflation-deflation of a pneumatic cuff placed around the subject's thigh [6].…”

Detection of primary RGB colors projected on a screen using fNIRS

“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] It can provide both topographic 15,16,[34][35][36] and tomographic 14,37 brain images. Speci¯cally, fNIRS monitors regional cerebral blood°ow (rCBF) variations by measuring, at wavelengths between 700 nm and 1000 nm, the near-infrared-lightabsorption changes caused by concentration variations of HbO and HbR, the two primary absorbing chromophores in brain capillary blood.…”