Abdominal counterpulsation in cardiopulmonary resuscitation: animal models and theoretical considerations.

Abdominal counterpulsation improves blood flow during otherwise standard CPR in animal models and in electronic models of the circulation. The method generates both central aortic and central venous pressure pulses. Success depends upon maximizing the former and minimizing the latter. Solution of a simple, first-order, differential equation may provide insight into proper technique. The equation suggests that the central arteriovenous pressure difference is maximized when pressure is applied directly over the abdominal aorta and when fluid loading is avoided. Proper technique may be critical in generating the largest possible arteriovenous pressure difference.