Is the Perfusion Index an Accurate Predictor of Return of Spontaneus Circulation in Out-of-hospital Cardiac Arrest

The purpose of this pilot feasibility study is to evaluate the ability of the Perfusion Index to predict the return to spontaneous circulation of the out-of-hospital cardiac arrest patient during cardiopulmonary resuscitation. The performance of the perfusion index will also be compared to the current gold standard, end-tidal CO2 (EtCO2).