The Critical Threshold of Pulse Oximetry Plethysmographic Waveform Parameters in High Quality CPR

Inclusion Criteria: * Cardiac arrested * The time from cardiac arrest to receiving basic life support is less than 10 minutes * Get advanced life support (endotracheal intubation and PETCO2 monitoring) Exclusion Criteria: * Defuse CPR * chronic obstructive pulmonary disease (COPD) with type II respiratory failure * Terminal malignant tumors or terminal stage of other diseases * Rib fracture * Cardiac arrest caused by hemorrhagic shock pulmonary embolism and cardiac tamponade * Sever anemia(HGB\<7g/dl) * Untreated tension pneumothorax * Tinea unguium, dyeing Fingernails and other factors affect the monitor of Pulse Oximetry Plethysmographic Waveform such vasculitis and Raynaud's phenomenon