# Feedback Devices for Cardiopulmonary Resuscitation: A Narrative Review
## 2 Classification of Feedback Devices for Cardiopulmonary Resuscitation
### Integration of Feedback Devices with Defibrillator and Related Equipment
Simple feedback systems for artificial chest compression can enhance compression effectiveness, ensure AHA cardiopulmonary resuscitation guideline adherence, reduce the risk of chest compression, and achieve the recommended compression depth and frequency. However, these systems have a limitation in adjusting compression parameters according to the patient's physiological state. The closed-loop feedback in automatic chest compressors offers a viable solution to this issue. These compressors incorporate a real-time monitoring and closed-loop feedback module for physiological parameters, utilizing the feedback from physiological parameters of cardiac arrest cases to assess the effectiveness of chest compression and achieve individualized closed-loop control of automatic chest compression. In the future, feedback research for CPR will advance towards individualized, intelligent, and multi-functional directions. Vital sign parameters such as ECG, blood pressure, oxygen saturation, ETCO2, etc. will be monitored to enable intelligent closed-loop feedback for patient resuscitation and provide accurate chest compression. Automatic CPR machines are expected to meet these requirements. Currently, closed-loop feedback in automatic CPR machines remains in the research stage and has not been introduced in market products. Most CPR machines on the market can only perform a compression function or CPR quality monitoring function, lacking the integration of multi-function basic life support equipment with feedback systems. In automatic external chest compression, statistical data from adult patients with out-of-hospital cardiac arrest who were admitted have shown that compared to manual compression, mechanical automatic external chest compression devices increase cerebral blood flow, significantly improve organ perfusion pressure, and demonstrate higher endothelial CO2 levels [40] as well as slightly better recovery of spontaneous circulation [4]. However, there was no significant difference in 4 h survival rate between patients who received treatment with a mechanical CPR algorithm and those who received manual CPR treatment based on the AHA guidelines [41]. Moreover, mechanical CPR, when contrasted with manual compression, also fails to yield a noteworthy enhancement in the incidence of ROSC [42]. Automatic external chest compression also lack effective feedback on compression effectiveness, emphasizing the need for equipment that can provide feedback on the quality of chest compression to prevent low-quality compression during CPR. In the future, automatic CPR is expected to utilize various intelligent algorithms to monitor multiple vital sign parameters, combining respiratory support control technology, extracorporeal 3D CPR technology, and synchronous automatic extracorporeal electric resuscitation technology to create a real-time feedback system of multi-parameter analysis and individualization. With the application of 5G and telemedicine, real-time transmission of feedback status and physiological parameters will be realized. Thus, the application of closed-loop feedback to mechanical CPR presents a broad prospect for the future of CPR technology [43].