Assessment of chest compression depth obtained ...

American Journal of Emergency Medicine xxx (2016) xxx–xxx

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Correspondence

Assessment of chest compression depth obtained using the PocketCPR as an educational tool according to smartphone attachment site☆ To the Editor, The American Heart and the European Resuscitation Council 2015 guidelines recommended a chest compression depth between 5 and 6 cm [1]. Some smartphone applications provide real-time audiovisual feedback for chest compression by collaboration between an accelerometer and gyrosensor [2-9]. To improve the quality of cardiopulmonary resuscitation (CPR) education, we assessed the validity and reliability of the feedback depth measured by smartphone applications according to the smartphone attachment sites as an educational tool. This was a diagnostic test assessment study, the primary objective of which was to compare the chest compression depth measured by a smartphone PocketCPR (Zoll Medical Corporation, Chelmsford, MA) application with that of the Resusci AnneSkillReporter (Laerdal Medical, Stavanger, Norway). The following methods were used to attach the smartphone: (a) grasping the smartphone in the hand (the grasp-inhand method), (b) grasping the armband in the hand (the armband-inhand method), and (c) wearing an armband around the upper arm (the armband-on-arm method; Fig. 1). The subjects performed 150 compressions in each session and rested for at least 30 minutes; additional rest was provided as needed. To compare the subjective efficacy according to the smartphone attachment site, we rated their comfort during chest compression performance using a visual analog scale, with the greatest comfort rated as 0 and the greatest discomfort rated as 10. We used an iPhone 4S to manage the CPR feedback application (Fig. 2). Bland-Altman plots were used to compare the averages of 2 measurements. To estimate the reliability of compression depth measurements among chest compressors according to smartphone attachment site, we calculated intraclass correlation coefficients (ICCs) for compression depth. The subjective efficacy according to the smartphone attachment site was analyzed by McNemar test. Thirty-four subjects included 22 men (64.7%) and 12 women (35.3%) and had an average age of 31.4 ± 4.8 years and an average body mass index of 22.7 ± 2.5 kg/m 2. A total of 15 300 compressions were available for analysis. The mean CPR rate was 104 beats/min. The mean differences in the chest compression depths measured using the 2 assessed devices were 0.43 ± 1.58 cm for the grasp-inhand method (P = .0058), −0.57 ± 1.56 cm for the armband-in-hand method (P = .0004), and −0.82 ± 1.65 cm for the armband-on-arm

method (P b .0001; Fig. 3). The ICC for the grasp-in-hand method was −0.307 (95% confidence interval [CI], −0.632 to −0.020) and was not statistically significant (P = .983). The ICC for the armband-in-hand method was 0.596 (95% CI, 0.496-0.684; P b .001) and that for the armband-on-arm method was 0.888 (95% CI, 0.859-0.913, P b .001; Table 1). Using the visual analog scale, the grasp-in-hand method was rated 6.41 ± 2.16, the armband-in-hand method was rated 4.59 ± 1.96, and the armband-on-arm method was rated 3.06 ± 1.95. Thus, the compression providers reported that the armband-on-arm method was the most comfortable, whereas the grasp-in-hand method was the most uncomfortable. This study demonstrated that for all attachment methods, there was a statistically significant difference between the depths of chest compression measured using the PocketCPR application and the SkillReporter system. These trends indicate that the 2 examined measurement tools cannot be used interchangeably. We analyzed the reason for this difference from the point of view of physics. Because chest compressions are repetitive vertical movements, the sensors were influenced by gravity in addition to the real movement of the smartphone [10]. In the grasp-in-hand method, the smartphone was held between the hands, and there was no additional movement by inertial forces. In the armband method, whether in-hand or in-arm, the compression performer reported more convenience; however, the weight of the smartphone amplified the inertial force to produce additional linear movement. Because the accelerometer measures the vertical acceleration, which is the sum of the vertical movement of the smartphone and gravity, there is an inevitable bias in the measurements [11]. The ICC for the grasp-in-hand method was greater than the ICCs for other methods, indicating that the armband method showed a smaller deviation than the grasp-in-hand method in compression depth among the chest compression performers. This study had some limitations. First, this study tested only one CPR application and smartphone. Second, we limited the compression depth range between 5 and 6 cm by real-time visual feedback, and this limitation could not assess the validity and reliability of the various ranges of compression depth. In conclusion, measurements of chest compression depth obtained using a smartphone did not exhibit validity for any of the 3 attachment sites, although the use of an armband resulted in the smaller variation among compression providers.

☆ This work was supported by the Soonchunhyang University Research Fund. 0735-6757/© 2016 Elsevier Inc. All rights reserved.

Please cite this article as: Park J, et al, Assessment of chest compression depth obtained using the PocketCPR as an educational tool according to smartphone attachment site, Am J Emerg Med (2016), http://dx.doi.org/10.1016/j.ajem.2016.08.066

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Correspondence / American Journal of Emergency Medicine xxx (2016) xxx–xxx

Fig. 2. Screenshot of the PocketCPR application in a smartphone during chest compression.

Fig. 1. Three methods for smartphone attachment to the arm or hand: the grasp-in-hand method (a), the armband-in-hand method (b), and the armband-on–arm method (c).


Correspondence / American Journal of Emergency Medicine xxx (2016) xxx–xxx

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Joonbum Park, Emergency Department, College of Medicine, Soonchunhyang University Seoul, Republic of Korea

Taeho Lim, Emergency Department, College of Medicine, Hanyang University Seoul Republic of Korea

Youngjoo Lee, Emergency Department, College of Medicine, Soonchunhyang University Seoul, Republic of Korea

Wonhee Kim, Emergency Department, College of Medicine, Hallym University, Seoul Republic of Korea

Yongil Cho, Emergency Department, Soegwipo Medical Center, Jeju, Republic of Korea

Hyunggoo Kang⁎, Emergency Department, College of Medicine, Hanyang University, Seoul Republic of Korea ⁎Corresponding author. Emergency Department College of Medicine, Hanyang University, 222 Wangsimni-ro(st), Seongdong-gu, Seoul 04763 Republic of Korea. Tel.: +82 2 2290 8999 E-mail addresses: emer0905@hanyang.ac.kr, emer0905@gmail.com

http://dx.doi.org/10.1016/j.ajem.2016.08.066 References

Fig. 3. Bland-Altman plots for the grasp-in-hand method (a), the armband-in-hand method (b), and the armband-on-arm method (c).

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Table 1 ICCs of chest compression depths among chest compressors according to smartphone attachment site

Grasp-in-hand method Armband-in-hand method Armband-on-arm method

n

ICC

95% CI

P

34 34 34

−0.307 0.596 0.888

−0.632 to −0.020 0.496 to 0.684 0.859 to 0.913

P = .983 P b .001 P b .001
