Coronary perfusion pressure during cardiopulmonary resuscitation

Coronary perfusion pressure (CPP) generated during cardiopulmonary resuscitation (CPR) is a key component for successful resuscitation. Defined as the pressure gradient between the aorta and the right atrium during the 'diastolic' or decompression portion of chest compression-decompression, this gradient has been correlated with both myocardial blood flow generated with CPR and ultimately with resuscitation outcome. Several unique features of cardiac arrest physiology, specifically the loss of vascular auto-regulation, make this pressure gradient even more important and the principal determinant of myocardial blood flow during CPR. Additionally, the loss of the ability to selectively vasoconstrict and vasodilate before and after an intra-coronary lesion results in increased significance of any coronary obstruction (even lesions less than 50%) with profound compromising effects on distal flow. Although CPP has been measured in patients undergoing CPR it remains difficult to acquire, secondary to the time needed to insert the pressure-measuring catheters. Alternative non-invasive measures of coronary perfusion are needed. Expired end-tidal carbon dioxide has been one suggested possibility.