Circulation time during standard and modified manual CPR determined by retinal photoangiography

We used retinal fluorescein photoangiography to determine the circulation time (CTv-a) from the inferior vena cava (IVC) to the retinal artery in anesthetized, intubated, paralyzed, and fibrillated dogs. Animals received either standard CPR (SCPR) (n = 11) or modified CPR (MCPR) (n = 11) manually at 60 compressions per minute in both groups. MCPR consisted of simultaneous ventilation-compression with abdominal binding to 40 mm Hg. SCPR or MCPR was begun immediately after inducing ventricular fibrillation and was performed for an average of 4.5 minutes prior to bolus injection of fluorescein dye (0.7 mL, 25% solution). To compare CTv-a in the two groups, dye was injected through a catheter into the IVC (below the diaphragm) and timed, rapid, sequential retinal photoangiography was begun. The time to first appearance of dye in the retinal vasculature initially was determined visually by the camera operator and later was substantiated photographically. The camera simultaneously photographed the retinal vasculature and the built-in timer, thus displaying the elapsed time from injection on each frame. Our results showed a significantly shorter CTv-a in the MCPR group (58.9 seconds +/- 18.6) when compared to the SCPR group (112.6 seconds +/- 47.4; P less than .01). In addition, we have documented retinal blood flow during CPR.