J S Minhas1, R B Panerai, T G Robinson. 1. Department of Cardiovascular Sciences, Cerebral Haemodynamics in Ageing and Stroke Medicine (CHIASM) Research Group, University of Leicester, Leicester, United Kingdom.
Abstract
OBJECTIVE: Arterial CO2 (PaCO2) has a strong effect on cerebral blood flow (CBF), but its influence on CBF regulatory mechanisms and circulatory systemic variables has not been fully described over the entire physiological range of PaCO2. APPROACH: CBF velocity (CBFV, transcranial Doppler), blood pressure (BP, Finometer) and end-tidal CO2 (EtCO2, capnography) were measured in 45 healthy volunteers (19 male, mean age 37.5 years, range 21-71) at baseline, and in response to hypo- (-5 mm Hg and -10 mm Hg below baseline) and hypercapnia (5% and 8% CO2), applied in random order. MAIN RESULTS: CBFV, cerebral dynamic autoregulation index (ARI), heart rate (HR), arterial blood pressure (ABP), critical closing pressure (CrCP) and resistance-area product (RAP) changed significantly (all p < 0.0001) for hypo- and hyper-capnia. These parameters were shown to follow a logistic curve relationship representing a 'dose-response' curve for the effects of PaCO2 on the cerebral and systemic circulations. The four logistic model parameters describing each 'dose-response' curve were specific to each of the modelled variables (ANOVA p < 0.0001). SIGNIFICANCE: The ability to model the CBFV, ARI, HR, ABP, CrCP and RAP dependency of PaCO2 over its entire physiological range is a powerful tool for physiological and clinical studies, including the need to perform adjustments in disease populations with differing values of baseline PaCO2.
OBJECTIVE: Arterial CO2 (PaCO2) has a strong effect on cerebral blood flow (CBF), but its influence on CBF regulatory mechanisms and circulatory systemic variables has not been fully described over the entire physiological range of PaCO2. APPROACH: CBF velocity (CBFV, transcranial Doppler), blood pressure (BP, Finometer) and end-tidal CO2 (EtCO2, capnography) were measured in 45 healthy volunteers (19 male, mean age 37.5 years, range 21-71) at baseline, and in response to hypo- (-5 mm Hg and -10 mm Hg below baseline) and hypercapnia (5% and 8% CO2), applied in random order. MAIN RESULTS: CBFV, cerebral dynamic autoregulation index (ARI), heart rate (HR), arterial blood pressure (ABP), critical closing pressure (CrCP) and resistance-area product (RAP) changed significantly (all p < 0.0001) for hypo- and hyper-capnia. These parameters were shown to follow a logistic curve relationship representing a 'dose-response' curve for the effects of PaCO2 on the cerebral and systemic circulations. The four logistic model parameters describing each 'dose-response' curve were specific to each of the modelled variables (ANOVA p < 0.0001). SIGNIFICANCE: The ability to model the CBFV, ARI, HR, ABP, CrCP and RAP dependency of PaCO2 over its entire physiological range is a powerful tool for physiological and clinical studies, including the need to perform adjustments in disease populations with differing values of baseline PaCO2.
Authors: Jatinder S Minhas; William Rook; Ronney B Panerai; Ryan L Hoiland; Phil N Ainslie; Jonathan P Thompson; Amit K Mistri; Thompson G Robinson Journal: Br J Anaesth Date: 2019-12-06 Impact factor: 9.166
Authors: Michael M Tymko; Alexander B Hansen; Joshua C Tremblay; Alexander Patrician; Ryan L Hoiland; Connor A Howe; Matthew G Rieger; Philip N Ainslie Journal: Eur J Appl Physiol Date: 2020-02-07 Impact factor: 3.078
Authors: Meshal Alharbi; Poppy Turner; Jonathan Ince; Mitsuhiro Oura; Kelechi U Ebirim; Alanoud Almudayni; Andrea Lecchini-Visintini; Jatinder S Minhas; Emma M L Chung Journal: Brain Sci Date: 2020-09-06