# Feedback Devices for Cardiopulmonary Resuscitation: A Narrative Review
## 2 Classification of Feedback Devices for Cardiopulmonary Resuscitation
### Audio-Visual Feedback Devices
\begin{table}
\begin{tabular}{c c c c c} \hline
**Device** & **Feedback** & **Feedback** & **Disadvantages** & **References** \\ \hline \multirow{4}{*}{\begin{tabular}{c} Zoll \\ PocketCPTM \\ \end{tabular} } & Compression depth; Compression rate & Accelerometer; Metronome; Voice prompt & Run on batteries; Unable to record historical data; No feedback on pulmonary ventilation; The incorrect angle of compression cannot be detected; May interfere with normal compression & [PERSON] et al. [16] \\ \hline \multirow{4}{*}{\begin{tabular}{c} Laerdal \\ CPRmeterTM \\ \end{tabular} } & Compression depth; Compression rate, duration, and chest compression scores; Full chest relaxation & Accelerometer; Pressure sensor; Metronome & Run on batteries; No feedback on pulmonary ventilation & [PERSON] et al. [16] \\ \hline \multirow{4}{*}{\begin{tabular}{c} TrueCPRTTM \\ \end{tabular} } & Visual overview of compression depth; Compression rate; Compression rate; Compression score; Maximum pause time; Compression with pause time; pause time & Triaxial magnetic field induction & Run on batteries; Unable to connect with external devices; No feedback on pulmonary ventilation & [PERSON] et al. [18] \\ \hline \multirow{4}{*}{\begin{tabular}{c} Feedback \\ Sensor Push \\ \end{tabular} } & Compression depth; Compression rate & / & Run on batteries; No feedback on pulmonary ventilation; The incorrect angle of compression cannot be detected & / \\ \hline \multirow{4}{*}{\begin{tabular}{c} Cardio First \\ AngelTM \\ \end{tabular} } & Compression depth; Full chest relaxation & Tensile springs & Unable to record historical data; Unable to connect with external devices; No feedback on pulmonary ventilation; The incorrect angle of compression cannot be detected & [PERSON] et al. [20] \\ \hline \multirow{4}{*}{\begin{tabular}{c} Beaty \\ \end{tabular} } & Compression depth & Pressure sensor and metronome & Run on batteries; Unable to record historical data; Unable to connect with external devices; No feedback on pulmonary ventilation; The incorrect angle of compression cannot be detected & / \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} CPR-1100 \\ \end{tabular} } & Compression depth; Compression rate; Device tilt; SNaking of patient’s back & Accelerometer & No feedback on pulmonary ventilation; The incorrect angle of compression cannot be detected & / \\ \hline \multirow{4}{*}{
\begin{tabular}{c} SUNLIFE \\ Palm CPR \\ \end{tabular} } & Compression depth; Compression rate & Pressure sensor; Metronome; Voice feedback on pulmonary ventilation; The incorrect angle of compression cannot be detected & \\ \hline \end{tabular}
\end{table} 
Table 1: Cont. is important to note that improper use of CPREzyTM may cause hand injuries to rescue personnel [14]. The Laerdal CPRmeterTM, developed by the Norwegian company Laerdal, is based on an accelerometer design. To enhance measurement accuracy, a pressure sensor was incorporated [16]. The appearance of the CPRmeterTM device is shown in Figure 1c. The top surface of the CPRmeterTM features a gray, hard rubber cap that serves as the contact surface for the rescuer's hand. Feedback is provided through a 26 \(\times\) 26 mm color display. Compression depth is represented by a white bar that moves up and down between two green fields, with the two fields turning gray when the compression depth is too deep or too shallow, as seen in Figure 1d. Compression rate is displayed on a speedometer-like display, with the pointer located in the green range and lit up when the rate is appropriate [17]. The CPRmeterTM can be connected to the HeartStart MRx defibrillator (Philips Medical System), allowing for the integration of defibrillation and CPR feedback devices [12; 23]. An effectiveness study showed that when the device was used by professionals, it was able to improve compression depth and rate, as well as reduce irregular inclinations. Most users found the CPRmeterTM to be highly beneficial and easy to use, even after minimal training [17].