It's crucial to determine whether a pulse is present or not in patient with cardiac arrest. But more and more studies have shown that manual palpation is unreliable for detecting pulse 1-4. Failure to detect pulselessness may cause delay of chest compression and directly affect the patient's outcome. Likewise, failure to rapidly detect return of spontaneous circulation may cause prolonged chest compression and increase associated injury during resuscitation.

More and more studies have demonstrated that echo guided pulse detection is feasible 5-7. The aim of our study is to check carotid pulse via ultrasound. This is a prospective study and the patient selection is in-hospital or out of hospital cardiac arrest. A curvilinear ultrasonography transducer is used and placed transversely on either right/left carotid artery under pulsed-wave doppler mode to check whether the pulse is present or not. The result of ultrasonography will be compared with manual palpation and to determine the accuracy and effectiveness of clinical usage.

Inclusion Criteria:

• any patient presenting at ER with cardiac arrest older than 20 years-old

Exclusion Criteria:

• younger than 20 years-old
• patient who is pregnant

any patient presenting at ER with cardiac arrest older than 20 years-old, including trauma or non-trauma cardiac arrest, in-hospital or out-of-hospital cardiac arrest