Brain Tissue Oxygen Saturation Increases During the Night in Adolescents

Abstract

How does the oxygen metabolism change during sleep? We aimed to measure the change in brain tissue oxygen saturation (StO2) before and after sleep with near-infrared spectroscopy (NIRS) using an in-house developed sensor. According to the synaptic homeostasis hypothesis [1], synaptic downscaling during sleep would result in reduced energy consumption. Thus, this reduced energy demands should be reflected in the oxygen metabolism and StO2. Thirteen nights of 7 male subjects (age 11-16 years, one subject contributed only one night, all others two) were included in the analysis. We performed NIRS measurements throughout the entire night. The NIRS sensor was placed close to electrode position Fp1 (international 10/20 system), over the left frontal cortex. Absolute StO2 and total haemoglobin (tHb) were calculated from the NIRS measurements using a self-calibrating method [2]. StO2 and tHb during the awake period prior to sleep and after awakening were compared. The subjects were instructed to lie in bed in the same position before and after sleep. Values of the two nights were averaged for each subject. Furthermore, a linear regression line was fit through the all-night StO2 recordings. We found an increase in StO2 by 4.32 ± 1.76 % (mean ± SD, paired t-test p < 0.001, n = 7) in the morning compared to evening, while tHb did not change (1.02 ± 6.81 M p = 0.704, n = 7). Since the tHb remained at a similar level after sleep, this increase in StO2 indicates that in the morning more oxygenated blood and less deoxygenated blood was present in the brain compared to the evening. The slope of the regression line was 0.37 ± 0.13 % h(-1) leading to a similar increase of StO2 in the course of sleep. This may be interpreted as a reduced oxygen consumption or energy metabolism after sleep. Abstract How does the oxygen metabolism change during sleep? We aimed to measure the change in brain tissue oxygen saturation (StO 2 ) before and after sleep with near-infrared spectroscopy (NIRS) using an in-house developed sensor. According to the synaptic homeostasis hypothesis [1] synaptic downscaling during sleep would result in reduced energy consumption. Thus, this reduced energy demands should be reflected in the oxygen metabolism and StO 2 . Thirteen nights of 7 male subjects (age 11-16 years, 1 subject contributed only one night, all others two) were included in the analysis. We performed NIRS measurements throughout the entire night. The NIRS sensor was placed close to electrode position Fp1, (international 10/20 system) over the left frontal cortex. Absolute StO 2 and total haemoglobin (tHb) were calculated from the NIRS measurements using a self-calibrating method [2]. StO 2 and tHb during the awake period prior to sleep and after awakening were compared. The subjects were instructed to lie in bed in the same position before and after sleep. Values of the two nights were averaged for each subject. Furthermore, a linear regression line was fit through the all-night StO 2 recordings. We found an increase in StO 2 by 4.32 ± 1...

Frontal cerebral oxygenation asymmetry: intersubject variability and dependence on systemic physiology, season, and time of day

“…112 This increase could also be linked to circadian effects, e.g., cortisol rhythm exerting its wake-promoting effect in the morning hours. 113,114 Moreover, the present findings indicated that the time of day has no significant influence on FCOA, which is in line with the literature. 115 It was also shown in this study that FCOA in StO 2 decreased with increasing room temperature.…”

Sleep Is a Refreshing Process: An fNIRS Study

“…Even, brain and muscle hemodynamics were compared in regard to different stages by fNIRS (Zhang and Khatami, 2015). In one study the oxygen saturation of the brain tissue after sleep was compared with the one prior to sleep (Metz et al, 2013). But there has been no comparison of brain oxygenation values of sleep stages between the beginning and end of sleep.…”

A New Approach for Automatic Removal of Movement Artifacts in Near-Infrared Spectroscopy Time Series by Means of Acceleration Data

“…However, the values depend on the specific characteristics of the input NIRS signals, e.g., number of MAs, frequency of occurrence of the MAs, amplitude of the MAs within the data, or the noise level. These parameters were chosen empirically to give the best result for the data sets comprising long-term NIRS measurements as reported by Metz et al [21,22]. ( ): unfiltered acceleration signal.…”

“…Twelve healthy adolescent males (age 10-16 years) slept on two separate nights in the sleep laboratory of the University Children's Hospital Zurich, Switzerland. The mean sleep time was 8.5 h. The detailed protocol is described in Metz et al [21,22]. The study was approved by the ethical committee of the Canton of Zurich and informed consent was signed by the legal representatives of the adolescents.…”

“…For example, brain activity has been assessed using NIRS in adults [3,[5][6][7][8][9][10][11], infants and neonates [12][13][14][15], or animals [16][17][18]. During long-lasting NIRS recordings in particular, for example during sleep [19][20][21][22][23][24][25], artifacts in the NIRS data due to movements of the subjects are a common problem.…”