Maintenance of arterial pressure and consciousness by vigorous coughing during ventricular fibrillation has been previously documented. Observations in 4 additional patients with unstable rhythms and in fibrillating dogs confirm that coughing: (1) produces an arterial pulse; (2) produces opening of the aortic valve; (3) generates forward blood flow; and (4) can maintain consciousness during circulatory arrest. The authors speculate that cough-induced systemic perfusion results from compression of the pulmonary vascular beds by a rise in intrathoracic pressure, the left heart acting only as a one-way conduit to the lower pressure extrathoracic vascular outlets. Recent data suggest that conventional CPR likewise produces blood flow by compression of the pulmonary vascular blood pool, and not by cardiac compression as previously thought.