Cardiopulmonary Resuscitation Without Aortic Valve Compression Increases the Chances of Return of Spontaneous Circulation in Out- of-Hospital Cardiac Arrest: A Prospective Observational Cohort Study Cardiopulmonary Resuscitation Without Aortic Valve Compression Increases the Chances of Return of Spontaneous Circulation in Out- of-Hospital Cardiac Arrest: A Prospective Observational Cohort Study