A chest compression feedback device monitors five core metrics during CPR: compression rate, compression depth, chest recoil, hand position, and chest compression fraction (the percentage of time compressions are actively being delivered). These measurements are tracked in real time and compared against guideline targets, giving the rescuer immediate audio or visual cues to correct their technique.
The Five Core Metrics
Compression depth is one of the most critical measurements. Current guidelines from the American Heart Association recommend pushing the chest at least 5 centimeters (about 2 inches) deep in adults. Studies of thousands of patients have found improved survival to hospital discharge at that depth compared to compressions shallower than 4 centimeters. Pushing too deep, beyond 6 centimeters, has been linked to reduced survival as well. The device alerts you if you’re pressing too lightly or too hard.
Compression rate refers to how many compressions you deliver per minute. Research involving over 13,700 patients found the best survival outcomes at rates between 100 and 119 compressions per minute. Go slower and blood flow drops. Go faster and each individual compression tends to become too shallow. The device typically uses a metronome, voice prompt, or visual indicator to keep you in that window.
Chest recoil measures whether you’re fully lifting your weight off the chest between compressions. Leaning on the chest, even slightly, prevents it from fully expanding and refilling with blood. Feedback devices detect this residual pressure and prompt you to release completely. Studies using these devices have shown that real-time feedback significantly reduces leaning force during CPR.
Hand position tracking tells you whether your hands are placed correctly on the lower half of the breastbone. Compressions delivered off-center or too high are less effective and more likely to cause injury.
Chest compression fraction is the percentage of total resuscitation time during which compressions are actually happening. Every pause, whether for a breath, a rhythm check, or switching rescuers, means blood stops flowing. Some devices, like ZOLL’s CPR Dashboard, display an idle timer that starts counting after just 3 seconds without compressions. A visual indicator empties rapidly during pauses, reinforcing how quickly the benefit of compressions drops off when you stop.
How the Sensors Work
Most feedback devices rely on accelerometers, which are small chips that detect motion and calculate how far and how fast the chest moves with each compression. This is the same type of sensor found in smartphones. Some devices pair an accelerometer with a pressure sensor to get a more accurate reading, since accelerometers alone can drift slightly over time.
One device, True-CPR, takes a different approach entirely. It uses a three-dimensional magnetic field between a chest pad and a back pad to measure the exact distance the chest travels. This avoids the cumulative measurement errors that accelerometer-only devices can experience on soft surfaces like mattresses. Purely mechanical devices also exist. The Cardio First Angel, for example, uses a spring mechanism that clicks audibly when you reach the correct compression depth, with no electronics at all.
Device Formats
Chest compression feedback devices come in several forms. The most common in clinical settings are small puck-like devices placed on the patient’s chest between your hands and the breastbone. Products like the Laerdal CPRmeter and ZOLL PocketCPR fall into this category. They display feedback on a small screen or through LED lights and audio prompts.
Some defibrillators have feedback technology built directly into their electrode pads. ZOLL’s AED Plus, for instance, uses an accelerometer embedded in the defibrillator electrodes to provide real-time depth and rate feedback without any additional equipment. This integration means the same pads used for defibrillation are simultaneously coaching your compressions.
Smartphone-based options are also emerging. Because modern phones contain built-in accelerometers, a dedicated app paired with the phone placed on the chest can estimate compression depth and rate. These are more accessible than dedicated medical devices, though they are less precise and less widely validated.
Real-Time Feedback vs. Post-Event Review
During CPR, the device provides real-time correction. This typically comes as voice prompts (“push harder,” “push faster”), colored LED indicators that shift from red to green when you hit the target range, or visual gauges on a screen. ZOLL’s Perfusion Performance Indicator, for example, uses a diamond shape that fills up when both depth and rate are within guidelines. The goal is to keep the diamond full. As soon as compressions stop, it visually drains, giving an intuitive sense of how quickly perfusion is lost.
After the event, many devices store the full compression data for debriefing. Teams can review a timeline showing compression depth, rate, and pauses throughout the entire resuscitation. This post-event data is valuable for quality improvement. It lets teams identify patterns they wouldn’t notice in the moment, like compressions gradually becoming shallower as a rescuer fatigues, or pauses that lasted longer than anyone realized.
Do They Improve Outcomes?
Feedback devices consistently improve CPR technique. Studies show measurable improvements in compression rate, depth, and the fraction of time compressions are being delivered. Whether that translates to more patients surviving is harder to pin down. A large German registry analysis of over 107,000 cardiac arrest cases found that patients resuscitated with feedback devices had a 2.6 percentage point higher rate of hospital admission with a pulse (35.9% vs. 33.3%). After adjusting for other variables, the effect was modest but statistically present for achieving any return of spontaneous circulation.
Three separate human studies found significant improvements in compression quality metrics without a clear jump in survival. This gap likely reflects the reality that survival after cardiac arrest depends on many factors beyond compression quality, including how quickly CPR started, the underlying heart rhythm, and how fast advanced care arrives. Better compressions are one piece of a much larger puzzle.
Limitations With Children
Most feedback devices are designed and validated for adult patients. The AHA has noted that there is currently insufficient evidence to recommend for or against their use in infants and children. Pediatric patients need shallower compressions, and the target depths vary by age and size. Devices calibrated for adult thresholds would give misleading feedback on a child. If you encounter a pediatric feedback device in a training setting, it will have adjusted targets, but widespread clinical use in pediatric populations remains limited.