title: Acute hypoxia diminishes the relationship between blood pressure and subarachnoid space width oscillations at the human cardiac frequency.
abstract: BACKGROUND
  Acute hypoxia exerts strong effects on the cardiovascular system. Heart-generated pulsatile cerebrospinal fluid motion is recognised as a key factor ensuring brain homeostasis. We aimed to assess changes in heart-generated coupling between blood pressure (BP) and subarachnoid space width (SAS) oscillations during hypoxic exposure.
  
  
  METHODS
  Twenty participants were subjected to a controlled decrease in oxygen saturation (SaO2 = 80%) for five minutes. BP and heart rate (HR) were measured using continuous finger-pulse photoplethysmography, oxyhaemoglobin saturation with an ear-clip sensor, end-tidal CO2 with a gas analyser, and cerebral blood flow velocity (CBFV), pulsatility and resistive indices with Doppler ultrasound. Changes in SAS were recorded with a recently-developed method called near-infrared transillumination/backscattering sounding. Wavelet transform analysis was used to assess the relationship between BP and SAS oscillations.
  
  
  RESULTS
  Gradual increases in systolic, diastolic BP and HR were observed immediately after the initiation of hypoxic challenge (at fifth minute +20.1%, +10.2%, +16.5% vs. baseline, respectively; all P<0.01), whereas SAS remained intact (P = NS). Concurrently, the CBFV was stable throughout the procedure, with the only increase observed in the last two minutes of deoxygenation (at the fifth minute +6.8% vs. baseline, P<0.05). The cardiac contribution to the relationship between BP and SAS oscillations diminished immediately after exposure to hypoxia (at the fifth minute, right hemisphere -27.7% and left hemisphere -26.3% vs. baseline; both P<0.05). Wavelet phase coherence did not change throughout the experiment (P = NS).
  
  
  CONCLUSIONS
  Cerebral haemodynamics seem to be relatively stable during short exposure to normobaric hypoxia. Hypoxia attenuates heart-generated BP SAS coupling.
authors.affiliation: Institute of Human Physiology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Wszedybyl-Winklewska
authors.affiliation: Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Wolf
authors.affiliation: Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Swierblewska
authors.affiliation: Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kunicka
authors.affiliation: Department of Radiology Informatics and Statistics, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Gruszecka
authors.affiliation: Department of Radiology Informatics and Statistics, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Marcin
authors.initials: M
authors.lastname: Gruszecki
authors.affiliation: Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Wieslawa
authors.initials: W
authors.lastname: Kucharska
authors.affiliation: Institute of Human Physiology, Medical University of Gdansk, Gdansk, Poland.|Institute of Health Sciences, Pomeranian University of Slupsk, Slupsk, Poland.
authors.forename: Pawel J
authors.initials: PJ
authors.lastname: Winklewski
authors.affiliation: Institute of Human Physiology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Zabulewicz
authors.affiliation: Department of Computer Communications, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Guminski
authors.affiliation: Department of Biomedical Engineering, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Pietrewicz
authors.affiliation: Institute of Human Physiology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Andrzej F
authors.initials: AF
authors.lastname: Frydrychowski
authors.affiliation: Centre for Medical Simulation, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Leszek
authors.initials: L
authors.lastname: Bieniaszewski
authors.affiliation: Department of Hypertension and Diabetology, Medical University of Gdansk, Gdansk, Poland.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Narkiewicz
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001784:Blood Gas Analysis; D001794:Blood Pressure; D001921:Brain / Q000502:physiology; D002245:Carbon Dioxide / Q000737:chemistry; D002555:Cerebrospinal Fluid; D002560:Cerebrovascular Circulation; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000502:physiology*; D006339:Heart Rate; D006439:Hemodynamics; D006706:Homeostasis; D006801:Humans; D000860:Hypoxia; D008297:Male; D009991:Oscillometry; D010100:Oxygen / Q000378:metabolism; D010108:Oxyhemoglobins / Q000737:chemistry; D017156:Photoplethysmography; D012542:Scattering, Radiation; D013346:Subarachnoid Space / Q000378:metabolism* / Q000473:pathology; D014172:Transillumination / Q000379:methods; D058067:Wavelet Analysis; D055815:Young Adult
chemical_list: D010108:Oxyhemoglobins; D002245:Carbon Dioxide; D010100:Oxygen