Chest compression (CC) feedback devices are used to perform CC measurements effectively and accurately on patients in hospital beds. However, these devices do not take account of the compression of the mattress, which results in overestimation of CC depth. This study is the validation study to demonstrate that a new method using one accelerometer(U-cpr) is useful to overcome this limitation and thus measure compression depth more accurately when performing cardiopulmonary resuscitation (CPR) on patients.

Data collection The participants will be divided into three groups by random drawings. Each performer in the three-groups will compress the chest of the manikin on the bed with real-time 5cm,6cm and 7cm feed-back by one accelerometer (U-cpr).We will use two beds [Stryker ST104-747(Transport stretcher®, 760 x 2110 mm, 228 kg, Stryker Co., Kalamazoo, Michigan, US) ,Shinchang SB-34p (Transport stretcher® , 850 x 2080 mm,Shinchang Co.,Busan,ROK)]. Each participants will do 6 cycles of chest compression and 1cyle will be 2minutes. Between each cycles, participants will take a rest 5minutes.

Inclusion Criteria:

• Postgraduates year 1,2,3,4 and Emergency physicians in emergency department

Exclusion Criteria:

• Wrist or Low back disease