Comparisons of hemodynamic values between groups.

ObjectivesTo investigate right ventricular hemodynamics and determine how vena cava occlusion (VCO) influences right ventricular pressure–volume dynamics during cardiopulmonary resuscitation (CPR).MethodsWe used a swine model of electrically induced ventricular fibrillation. Five animals were allocated to Experiment I to observe right ventricular hemodynamics during standard CPR, and 25 were assigned to Experiment II to assess right ventricular hemodynamic changes following VCO. In Experiment I, all animals received standard CPR. In Experiment II, all animals received CPR but were randomized according to the protocols used, which differed by the order of interventions. The interventions included alternating superior VCO, inferior VCO, and no VCO. Hemodynamic parameters were measured during CPR, and corresponding right ventricular pressure–volume loops were generated.ResultsExperiment I revealed that, during CPR, the right ventricular pressure–volume loop became trapezoidal in shape, with a progressive reduction in right ventricular volumes, including end-systolic volume (p = 0.029) and end-diastolic volume (p = 0.035). Experiment II demonstrated that systolic arterial pressure and end-tidal CO₂ levels were significantly lower during both superior and inferior VCO CPR than during no-VCO CPR (both p ConclusionsDuring CPR, the right ventricular pressure–volume loop transforms into a trapezoidal shape, resembling a left-leaning triangle, because the isovolumetric phases disappear. VCO during CPR reduces ventricular systolic pressures, indicating that a reduction in the venous return affects perfusion pressures during resuscitation.