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.
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.
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.
Apnoea is associated with ICP swings, closely reflecting changes in EtCO2, HR and peripheral BP. The baroreflex influences the pial artery response.
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
Correspondence to Magdalena Wszedybyl-Winklewska, MD, PhD, Institute of Human Physiology, Medical University of Gdansk, Tuwima Str. 15, 80-210 Gdansk, Poland. Tel/Fax: +48 58 3491515; e-mail: email@example.com
Abbreviations: BP, blood pressure; CBF, cerebral blood flow; CBFV, cerebral blood flow velocity; cc-TQ, pial artery pulsation; CSF, cerebrospinal fluid; EtCO2, end-tidal CO2; HR, heart rate; NIR-T/BSS, near-infrared transillumination/backscattering sounding; OSA, obstructive sleep apnoea; pCO2, carbon dioxide partial pressure; SAS, subarachnoid space; sas-TQ, width of subarachnoid space; SiO2, oxyhaemoglobin saturation
Received 22 January, 2015
Revised 26 March, 2015
Accepted 26 March, 2015