Accurate feedback of chest compression depth on a manikin on a soft surface with correction for total body displacement☆
Introduction
According to the Guidelines 2010 for cardiopulmonary resuscitation (CPR) chest compression is given in periods of 2 min, interrupted briefly (5 s) for ventilation. The optimal chest compression depth according to the ERC Guidelines 2010 includes: compressing the chest to a depth of at least 5 cm (for an adult), but not exceeding 6 cm and allowing the chest to relax completely after each compression.1
Chest compression depth is linearly related to cardiac output, which is also linked to the likelihood of achieving a return of spontaneous circulation after defibrillation.2, 3 Fatigue, limited muscle strength and fear of doing harm frequently result in delivery of chest compressions less deep than recommended.
Rescuers can be assisted to achieve the recommended compression rate and depth by prompt/feedback devices that measure the displacement of the sternum during compressions. These devices may be built into an automated external defibrillator (AED) or manual defibrillator, or are stand-alone devices. The use of such prompt/feedback devices to improve the quality of CPR have shown to be beneficial with less deviation from recommended rate and depth.4, 5, 6 When chest compressions are performed on a victim lying on a soft surface such as a mattress, the chest is displaced downwards as well as being compressed. Because accelerometer based devices measure the motion of the surface of the chest, they are unable to distinguish between chest displacement and chest compression and, consequently, may overestimate compression depth.7
The TrueCPR (Physio-Control Inc, Redmond, WA, USA) is a new, commercially available device that claims to measure true chest compression depth and consists of a chest pad which is placed on the sternum and a back pad, which is placed beneath the patient. The device measures distance by sending and receiving electromagnetic signals between the chest pad and the back pad. The compression depth, chest recoil and compression rate are displayed on the device for visual corrective feedback, as well as a metronome for auditive rate support.
The objective of the study is to investigate if the TrueCPR is accurate by measuring compression depth on a manikin, independent from the stiffness properties of the surface. We compared the TrueCPR with a pressure-accelerometer based device, the Q-CPR (Laerdal Medical, Stavanger, Norway) that measures sternal displacement and the pressure given by the rescuers hand, and tested both devices on a manikin on a hard surface and various types of softer surfaces.
Section snippets
Study design
The Laerdal manikin model Resusci Anne SkillReporter (Laerdal Medical, Stavanger, Norway) is a common manikin used for teaching CPR performance. The manikin weighs 9.5 kg and allows the recording of depth parameters during CPR using the Laerdal PC SkillReporting System. The Resusci Anne SkillReporter was used during all evaluations. Data measuring chest compression (sternal–spinal displacement) were recorded directly to a laptop with dedicated software (Laerdal PC SkillReporting system). Because
Accuracy of the TrueCPR device in the drill press
The TrueCPR showed a systematic underestimation of 2–3 mm in the drill press on a hard surface compared to the depth as measured by the manikin (p < 0.05), over the whole range (30–55 mm) of compression depth (Fig. 3).
Manual manikin chest compressions
When CPR was guided by feedback from the TrueCPR on the manikin on the floor, the TrueCPR measured a mean(±SD) chest compression depth of 50.4(±1.6) mm, while the simultaneous measurement of the manikin was significantly higher with mean(±SD) chest compression depth 54.9(±1.8) mm (p <
Discussion
This is the first study of the TrueCPR device, a novel device that is commercially available for training and clinical use. The main finding of this study is that the TrueCPR measures depth on a manikin with a systematic underestimation of 3–4.5 mm independent of the stiffness of the surface upon which CPR is being performed. The TrueCPR therefore is an instrument with a known but constant small inaccuracy. In contrast, the accelerometer, while slightly more accurate on a hard surface, has a
Limitations
Quality of CPR involves more than chest compression depth, but also includes full relaxation and compression rate. In this study we focused only on compression depth, as this is influenced by the surface on which CPR is performed.
There are several factors that limit the applicability of findings from manikin studies to device use in humans. The chest compression feedback devices we tested use force information in addition to displacement information. Although standard manikins have a linear
Conclusion
The TrueCPR measures depth precisely, independent of the stiffness of the surface upon which CPR is being performed but with a constant inaccuracy of 3–4.5 mm. It eliminates the inaccuracy and overestimation of the true compression depth caused by a soft surface. Correction for body displacement on a soft surface is essential for accurate delivery of chest compressions within the recommended depth range under all clinical circumstances. Data from outcome of cardiac arrests that are calculated
Conflict of interest statement
RWK receives support for the ARREST study with an unconditional grant of Physio-Control Inc, Redmond, WA, USA, which had no control over data analysis or the writing process of the paper. The TrueCPR device used for this study was made available by Physio-Control.
Acknowledgment
We thank Cees Kes from the mechanical department of the Academic Medical Center for manufacturing the manikin support and dedicated drill head.
References (10)
- et al.
European Resuscitation Council Guidelines for Resuscitation 2010 Section 2 Adult basic life support and the use of automated external defibrillators
Resuscitation
(2010) - et al.
Relationship of blood pressure and flow during CPR to chest compression amplitude: evidence for an effective compression threshold
Ann Emerg Med
(1983) - et al.
Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest
Resuscitation
(2006) - et al.
Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study
Resuscitation
(2006) - et al.
CPR quality improvement during in-hospital cardiac arrest using a real-time audiovisual feedback system
Resuscitation
(2007)
Cited by (0)
- ☆
A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.08.005.