# Feedback Devices for Cardiopulmonary Resuscitation: A Narrative Review
## 2 Classification of Feedback Devices for Cardiopulmonary Resuscitation
### Audio-Visual Feedback Devices  
In 2015, the American Heart Association endorsed the use of feedback devices during CPR to enhance resuscitation quality [4]. Even for medical professionals, accurately assessing the depth and frequency of CPR may be challenging [9; 10], and the quality of resuscitation may decline due to fatigue. Additionally, perceived compression depth and rate may differ from actual ones [11], which underscores the need for audio-visual feedback devices to improve CPR quality and enhance resuscitation quality. The existing and past audio-visual feedback devices available on the market for cardiopulmonary resuscitation were screened. The analysis includes miniaturized devices specifically designed for manual chest compression, which must accurately measure and display the compression depth during the resuscitation process. Using PubMed, we conducted a comprehensive search for articles published between 1995 and 2023 with the specific keyword \"cardiopulmonary resuscitation feedback\". This search yielded a total of 90 publications. Subsequently, we applied relevant filters such as \"clinical trial\", \"randomized controlled trial\", and \"review\", while also limiting the language to English. Thirty-three publications met the above criteria. Furthermore, we conducted meticulous web searches and PubMed searches for the names of audio-visual feedback devices to assess the clinical effectiveness of various audio-visual feedback devices utilized in cardiopulmonary resuscitation. Table 1 outlines the evolution of CPR audio-visual feedback devices. Currently, the development of audio-visual feedback devices for CPR has reached a relatively mature stage. These devices are predominantly based on two main components: pressure sensors and accelerometers. Pressure sensors measure the force applied to the patient's chest, which is set based on the patient's weight and the desired depth of compression. However, since it cannot detect individual compression, a pressure sensor-based feedback device can only provide feedback on compression depth and not on compression rate. On the other hand, accelerometers measure the acceleration of the patient's chest and use these data to calculate the distance moved during compression. The latest CPR feedback devices on the market are predominantly based on accelerometers, with some models also integrating pressure sensors. While an accelerometer-based feedback device isequipped with an electronic processor capable of calculating the compression rate, it is not well-suited for monitoring the quality of ventilation [12]. As the earliest device with cardiopulmonary resuscitation feedback function, CPR-plus boasts several advantages, including non-invasiveness, portability, and easy use. The CPR-plus is shown in Figure 1a. It achieves compression depth measurement via a pressure-sensitive compression plate and features a metronome for prompt pacing. In a comparative study examining CPR-plus usage versus non-usage, results showed that nurses using CPR-plus exhibited greater accuracy in compression and more standardized hand positions compared to those not using the device [13].