title: Pial artery and subarachnoid width response to apnoea in normal humans.
abstract: BACKGROUND
  Little is known about intracranial pressure (ICP)-cerebral haemodynamic interplay during repetitive apnoea. A recently developed method based on near-infrared transillumination/backscattering sounding (NIR-T/BSS) noninvasively measures changes in pial artery pulsation (cc-TQ) as well as subarachnoid width (sas-TQ) in humans.
  
  
  METHODS
  We tested the complex response of the pial artery and subarachnoid width to apnoea using this method. The pial artery and subarachnoid width response to consecutive apnoeas lasting 30, 60 s and maximal breath-hold (91.1 ± 23.1 s) were studied in 20 healthy volunteers. The cc-TQ and sas-TQ were measured using NIR-T/BSS; cerebral blood flow velocity (CBFV), pulsatility index and resistive index were measured using Doppler ultrasound of the left internal carotid artery; heart rate (HR) and beat-to-beat SBP and DBP blood pressure were recorded using a Finometer; end-tidal CO2 (EtCO2) was measured using a medical gas analyser.
  
  
  RESULTS
  Apnoea evoked a multiphasic response in blood pressure, pial artery compliance and ICP. First, SBP declined, which was accompanied by an increase in cc-TQ and sas-TQ. Directly after these changes, SBP exceeded baseline values, which was followed by a decline in cc-TQ and the return of sas-TQ to baseline. During these initial changes, CBFV remained stable. Towards the end of the apnoea, BP, cc-TQ and CBFV increased, whereas pulsatility index, resistive index and sas-TQ declined. Changes in sas-TQ were linked to changes in EtCO2, HR and SBP.
  
  
  CONCLUSIONS
  Apnoea is associated with ICP swings, closely reflecting changes in EtCO2, HR and peripheral BP. The baroreflex influences the pial artery response.
authors.affiliation: aInstitute of Human Physiology bDepartment of Hypertension and Diabetology cDepartment of Radiology Informatics and Statistics, Medical University of Gdansk dDepartment of Computer Communications, Faculty of Electronics, Telecommunications and Informatics, Gdansk University of Technology, Gdansk, Poland eDepartment of Cardiovascular Diseases, International Clinical Research Center, St. Anne's University Hospital in Brno (FNUSA), Brno, Czech Republic.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Wszedybyl-Winklewska
authors.forename: Jacek
authors.initials: J
authors.lastname: Wolf
authors.forename: Ewa
authors.initials: E
authors.lastname: Swierblewska
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kunicka
authors.forename: Marcin
authors.initials: M
authors.lastname: Gruszecki
authors.forename: Wojciech
authors.initials: W
authors.lastname: Guminski
authors.forename: Pawel J
authors.initials: PJ
authors.lastname: Winklewski
authors.forename: Andrzej F
authors.initials: AF
authors.lastname: Frydrychowski
authors.forename: Leszek
authors.initials: L
authors.lastname: Bieniaszewski
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Narkiewicz
mesh_terms: D000293:Adolescent; D000328:Adult; D001049:Apnea / Q000503:physiopathology*; D017704:Baroreflex; D001794:Blood Pressure / Q000502:physiology; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging; D002536:Cerebral Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D064368:Healthy Volunteers; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D009929:Organ Size; D013346:Subarachnoid Space / Q000033:anatomy & histology* / Q000502:physiology*; D018608:Ultrasonography, Doppler; D055815:Young Adult