Abstract TP403: Effect of Hypercapnia on Dynamic Cerebral Autoregulation During Transient Hypotension

Background and Purpose: Hypercapnialeads to increased cerebral blood flowand impaired autoregulationby changing the cerebrovascular resistance (CVR). We studied the effect of hypercapniaon critical closing pressure(CCP) and resistance area product ( RAP) which effectively reflects the role of vascular tone and resistance respectively in altering cerebrovascular resistance and maintaining cerebral autoregulationduring transient hypotension. Methods: –26 healthy subjects had continuous cerebral blood flowvelocity and arterial blood pressure recording. Transient hypotension was induced by sudden release of thigh cuffafter suprasystolic inflation for 3 minutes. 3 trials of thigh cuffmaneuver were performed with normal breathing, 3% CO2breathing and 5% CO2breathing. CO2 inhalation was given for last 45 seconds of thigh cuffmaneuver and continued for 90 seconds after release. Autoregulatory Index (ARI) was calculated for each trial with Tieck’s model. CCP and RAPwere computed for 10 seconds’ window ea...