Abstract 437: The Relation Between Cerebral Oxygenation and Blood Flow During CPR in Swine

Abstract

Introduction: The physiology underlying cerebral oxygenation and blood flow during resuscitation from cardiac arrest (CA) is poorly understood. This study examined the relation between cerebral oxygenation and blood flow during standard CPR (SCPR) and CPR with active decompression and lift (ACD) plus an impedance threshold device (ITD). Methods: Ventricular fibrillation (VF) was electrically induced in 15 domestic swine. Following 6 minutes of untreated VF, chest compressions were initiated at 100 cpm and 10% anterior-posterior distance. Depth increased to 20% anterior-posterior distance over a 2-min period, and was then maintained for 6 minutes (SCPR). ACD+ITD was performed for an additional 6 minutes at the same rate and depth as SCPR, but with 20% anterior-posterior distance of active lift. Microspheres were injected 2 minutes after the start of SCPR and ACD+ITD to measure blood flow. Cerebral oxygenation was measured using NIRS, and 8-sec averages collected 2 minutes following microsphere injection were used for comparison. Changes in oxygenation and blood flow that occurred in response to ACD+ITD relative to SCPR were analyzed using linear regression to predict oxygenation based on blood flow. Results: ACD+ITD increased blood flow in 13 animals and oxygenation in 12 animals relative to SCPR. Changes in cerebral oxygenation were directly proportional to changes in blood flow for 12 of 15 animals in response to ACD+ITD following SCPR. Cerebral blood flow explained 34% of the variance in cerebral oxygenation ( R 2 = 0.34, F (1, 13) = 6.7, P = 0.02). Conclusions: Changes in cerebral oxygenation during CA are associated with measured changes in cerebral blood flow, however 66% of the variance in cerebral oxygenation remains unexplained. Other physiological parameters should be considered to further understand how NIRS may provide clinically useful information during resuscitation.