title: A Biphasic Change of Regional Blood Volume in the Frontal Cortex during Non-Rapid Eye Movement Sleep: A Near-Infrared Spectroscopy Study.
abstract: OBJECTIVE
  Current knowledge on hemodynamics in sleep is limited because available techniques do not allow continuous recordings and mainly focus on cerebral blood flow while neglecting other important parameters, such as blood volume (BV) and vasomotor activity.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  Continuous measures of hemodynamics over the left forehead and biceps were performed using near-infrared spectroscopy (NIRS) during nocturnal polysomnography in 16 healthy participants in sleep laboratory.
  
  
  RESULTS
  Temporal dynamics and mean values of cerebral and muscular oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (HHb), and BV during different sleep stages were compared. A biphasic change of cerebral BV was observed which contrasted a monotonic increase of muscular BV during non-rapid eye movement sleep. A significant decrement in cerebral HbO2 and BV accompanied by an increase of HHb was recorded at sleep onset (Phase I). Prior to slow wave sleep (SWS) HbO2 and BV turned to increase whereas HHb began to decrease in subsequent Phase II suggested increased brain perfusion during SWS. The cerebral HbO2 slope correlated to BV slope in Phase I and II, but it only correlated to HHb slope in Phase II. The occurrence time of inflection points correlated to SWS latencies.
  
  
  CONCLUSIONS
  Initial decrease of brain perfusion with decreased blood volume (BV) and oxygenated hemoglobin (HbO2) together with increasing muscular BV fit thermoregulation process at sleep onset. The uncorrelated and correlated slopes of HbO2 and deoxygenated hemoglobin indicate different mechanisms underlying the biphasic hemodynamic process in light sleep and slow wave sleep (SWS). In SWS, changes in vasomotor activity (i.e., increased vasodilatation) may mediate increasing cerebral and muscular BV.
authors.affiliation: Center for Sleep Medicine and Sleep Research, Clinic Barmelweid, Barmelweid, Switzerland.|Department of Neurology, University Hospital Bern, Bern, Switzerland.
authors.forename: Zhongxing
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Center for Sleep Medicine and Sleep Research, Clinic Barmelweid, Barmelweid, Switzerland.|Department of Neurology, University Hospital Bern, Bern, Switzerland.|ZIHP, Zurich Center for Integrative Human Physiology, Zürich, Switzerland.
authors.forename: Ramin
authors.initials: R
authors.lastname: Khatami
mesh_terms: D001810:Blood Volume; D001833:Body Temperature Regulation; D005260:Female; D005625:Frontal Lobe / Q000098:blood supply* / Q000502:physiology*; D006439:Hemodynamics; D006454:Hemoglobins / Q000032:analysis / Q000378:metabolism; D006801:Humans; D008297:Male; D009132:Muscles / Q000098:blood supply / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D017286:Polysomnography; D012894:Sleep Stages / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared; D014664:Vasodilation; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D010100:Oxygen
keywords: cerebral blood volume; sleep onset; vasodilatation