Hemodynamic Effect of Deformation of the Descending Thoracic Aorta by Precordial Chest Compression during Standard Cardiopulmonary Resuscitation in Humans

ABSTRACT

PURPOSE: There have been no reports concerning the role of the aorta in explaining why blood flow is low below the diaphragm and a pressure gradient is present between central and peripheral arteries during standard cardiopulmonary resuscitation (CPR). The aim of this study was to assess the morphologic changes of the descending thoracic aorta and its effect on aortic pressure during precordial chest compression in cardiac arrest victims. METHODS: Twelve patients with non-traumatic cardiac arrest (8 males, mean age: 58 years) were enrolled. Transesophageal echocardiography was performed to verify the morphologic changes of the descending thoracic aorta during standard manual CPR. The pressure gradient across the maximally compressed site of the aorta was measured by pullback tracing using a pigtail catheter. RESULTS: Focal compression and deformation of the descending thoracic aorta was uniformly observed in all patients during compression systole. The mean systolic blood pressure of the descending thoracic aorta proximal and distal to the maximally compressed site was 135+/-3 6 mmHg and 115+/-21 mmHg, respectively. The mean systolic pressure gradient across the maximally compressed site was 20.5+/-17.7 mmHg. During compression systole, the pressure gradient between the right atrium and the descending thoracic aorta proximal to the maximally compressed site during compression systole was 49 +/-1 2 mmHg while pressure gradient between the right atrium and the descending thoracic aorta distal to the maximally compressed site was 29+/-8 mmHg. CONCLUSION: We found that the descending thoracic aorta was focally compressed and that a pressure gradient developed across the maximally compressed site during compression systole. This may contribute to limiting blood flow to the subdiaphragmatic region during standard manual CPR in humans.