Age-correlated changes in cerebral hemodynamics assessed by near-infrared spectroscopy

William W Mantulin,Rajarsi Gupta,Jee H Choi,Larisa P Safonova,Chiara Polzonetti,Martin Wolf,Ursula Wolf,Dennis M Hueber,Enrico Gratton,Antonios Michalos

doi:10.1016/j.archger.2004.03.007

Abstract

Cerebral hemodynamic responses due to normal aging may interfere with hormonal changes, drug therapy, diseases, life style, and other factors. Age-correlated alterations in cerebral vasculature and autoregulatory mechanisms are the subject of interest in many studies. Near-infrared spectroscopy (NIRS) is widely used for monitoring cerebral hemodynamics and oxygenation changes at the level of small vessels. We believe that the compensatory ability of cerebral arterioles under hypoxic conditions and the dilatatory ability of cerebral vessels due to vasomotion may decline with normal aging. To test this hypothesis we used frequency-domain NIRS to measure changes in cerebral tissue oxygenation and oxy- and deoxy-hemoglobin concentrations caused by hypoxia during breath holding. We also assessed cerebral vasomotion during profound relaxation. Thirty seven healthy volunteers, 12 females and 25 males, ranging from 22 to 56 years of age (mean age 35±11 years) participated in the study. We observed age-correlated changes in the cerebral hemodynamics of normal subjects: diminished cerebral hemodynamic response to hypoxia due to breath holding in middle-aged subjects (38–56 years) and reduced amplitude of cerebral hemodynamic changes due to vasomotion during rest. Snoring related changes in cerebral hemodynamics did not allow us to observe the effect of age in a group of snorers. The prolonged supine position influenced measured changes due to hypoxia. In this investigation NIRS methodology allowed detection of age-correlated changes in cerebral oxygenation and hemodynamics. Other variables, such as snoring or posture impacted the observations in our group of healthy volunteers.

Highlights

Using frequency domain (FD), multi-distant near-infrared spectroscopy (NIRS) instrumentation we developed and implemented experimental protocols to assess brain oxygenation and hemodynamic changes in normal subjects (1) during hypoxia induced by voluntary breath holding and (2) attributed to vasomotion during rest
SaO2 and heart rate (HR) were used as reference parameters to monitor that changes due to hypoxia were in a normal range
Hypoxia during breath holding generated a decrease in SaO2, which is an indication of arterial blood hemoglobin de-oxygenation, and changes in [O2Hb], [HHb], SO2, and [tHb] denoting the existence of an autoregulatory mechanism of cerebral tissue oxygenation

Summary

Introduction

Normal aging is associated with marked structural and functional alterations in the cardiovascular and cerebrovascular systems, which are linked to neurophysiological and neuropsychological changes (Kastrup et al, 1998; Matteis et al, 1998; Koshimoto et al, 1999; Buckner et al, 2000; Slosman et al, 2001). Age-correlated changes in regional cerebral blood flow (CBF), cerebral tissue oxygenation, cerebral autoregulation, and cerebrovascular CO2 reactivity (CCO2R) were detected in normal subjects by SPECT, transcranial Doppler sonography (TCD), MRI, and near-infrared spectroscopy (NIRS) (Hock et al, 1995; Smielewski et al, 1995; Ross et al, 1997; Kastrup et al, 1998; Matteis et al, 1998; Koshimoto et al, 1999; Buckner et al, 2000; Scheel et al, 2000; Terborg et al, 2000; Niehaus et al, 2001; Slosman et al, 2001; Mehagnoul-Schipper et al, 2002). Several studies have demonstrated age-related alterations in cerebral hemodynamics during the task-activation of the brain (Orlandi and Murri, 1996; Ross et al, 1997; Buckner et al, 2000; Niehaus et al, 2001; Mehagnoul-Schipper et al, 2002) as well as age-related reduction in CBF during rest (Koshimoto et al, 1999; Scheel et al, 2000; Slosman et al, 2001)

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