The use of the PocketCPR application in basic life support training
Correspondence / American Journal of Emergency Medicine 35 (2017) 171-190 189
Waeckerle JF, Seamans S, Whiteside M, Pons PT, White S, Burstein JL, et al. Executive summary: developing objectives, content, and competencies for the training of emergency medical technicians, emergency physicians, and emergency nurses to care for casualties resulting from nuclear, biological, or chemical incidents. Ann Emerg Med 2001;37(6):587-601.
training do our interns receive during medical school? Am J Med Qual 2013;28(5):407-13.
Custers EJFM. Long-term retention of basic science knowledge: a review study. Adv Health Sci Educ 2010;15(1):109-28.
knowledge retention: an application to resident education. Am J Obstet Gynecol 2005;193(5):1827-30.
Shaw TJ, Pernar LI, Peyre SE, Helfrick JF, Kaitlin R, Vogelgesang KR, et al. Impact of on- line education on intern behavior around joint commission national patient safety goals: a randomised trial. BMJ Qual Saf 2012;21(10):819-25.
The use of the PocketCPR application in basic life support training
Dear Editor,
We read the report by Park et al. with interest [1], but have some concerns. Although Park et al. concluded that there was a significant dif- ference between the chest compression depth measured using the PocketCPR application (Zoll Medical Corp., Chelmsford, MA, USA) and the Resusci Anne SkillReporter (Laerdal Medical, Stavanger, Norway), we partly disagree with that conclusion. The absolute differ- ence with the grasp-in-hand method was 4.3 +- 15.8 mm. The CCD mea- sured with an accelerometer Feedback device is known to be slightly lower than CCD measured with a manikin by as much as 1.9 mm when cardiopulmonary resuscitation (CPR) was conducted on the floor [2]. In our experience, another type of accelerometer feedback de- vice, the CPRmeter (Laerdal Medical) also underestimates CCD by as much as 3.5 +- 2.1 mm compared with a use of a manikin (N = 50). Since the PocketCPR application measures CCD by using an accelerome- ter sensor installed in a smartphone, similar results can be expected. In addition, the absolute cost difference of the PocketCPR application must be compared with that of the CPRmeter, a high-priced feedback device (over 1600 USD in the Republic of Korea). Anyone can download the PocketCPR application in their smartphone for free from an application store. If there are no available Feedback devices at the basic life support training site, the PocketCPR application can be an alternative tool to val- idate the performance of CPR, measured by average chest compression rate and depth. However, some precautions should be kept in mind. Al- though the mean absolute difference in reported values between the PocketCPR application and the manikin is similar to that with use of the CPRmeter, the standard deviation was significantly larger. This means that the accuracy of the PocketCPR application for CCD measure- ment is not good. In addition, the feedback system of the PocketCPR ap- plication was ineffective in improving the performance of CPR [3,4]. The rescuer would have to hold the smartphone with one hand during CPR (grasp-in-hand method) to use the feedback functions of the PocketCPR application. This creates an uncomfortable hand position. In addition, the smartphone cannot be placed beneath the heel of the hand because
it cannot withstand compression force (about 500 N). Moreover, the smartphone screen is moved rapidly during CPR. The rescuer might not recognize the feedback information during CPR because the aver- age rate and depth are expressed in small text. The only useful feed- back signal is auditory guidance with a metronome, which is included in the PocketCPR application.
The main purpose of the study by Park et al. was to confirm whether the PocketCPR application can measure CCD in other positions, such as the armband-in-hand method and armband-on-arm method, as well as in the standard position (grasp-in-hand method). If the PocketCPR application is able to provide similar CCD values in three different posi- tions, the preferred position will enable comfortable Hand placement and will fix the smartphone screen. However, the absolute differences in CCD increased with the armband-in-hand method (5.7 +- 15.6 mm) and armband-on-arm method (8.2 +- 16.5 mm), compared with the grasp-in-hand method (which is recommended by the manufacturer). In addition, CCD was overestimated by the PocketCPR compared with the manikin using the latter two methods. Park et al. explained this result as being due to additional motion from inertial forces. We agree that addi- tional motion accounts for these results. However, the source is joint movement during CPR, not inertial force. If the rescuer lifts one hand from the patient’s chest wall to sustain complete chest wall recoil, the ac- celerometer sensor attached to the dorsal side of the rescuer’s hand (arm- band-in-hand method) will move a greater distance compared with the grasp-in-hand method. If the rescuer bends the elbow joint during chest compression, the accelerometer sensor attached to the rescuer’s upper arm (armband-on-arm method) will move a greater distance compared with attachment to an arm in a straightened position.
In conclusion, the PocketCPR application could be an alternative tool for checking average chest compression rate and depth during CPR training if feedback devices are not available. However, we should keep in mind that the accuracy of the PocketCPR application is not con- firmed and CPR according to the feedback signals provided by the PocketCPR application is not even recommended for training. If the PocketCPR application is used during CPR training, the recommended position (grasp-in-hand) should be used.
Financial disclosure statement
The authors have no financial relationships relevant to this article to disclose.
Conflict of interest statement
The authors have no conflicts of interest relevant to this article to disclose.
Je Hyeok Oh, MD, PhD* Department of Emergency Medicine, College of Medicine Chung-Ang University, Seoul, Republic of Korea
E-mail address: [email protected]
Chan Woong Kim, MD, PhD Department of Emergency Medicine, College of Medicine Chung-Ang University, Seoul, Republic of Korea
http://dx.doi.org/10.1016/j.ajem.2016.10.082
References
- Park J, Lim T, Lee Y, Kim W, Cho Y, Kang H. Assessment of chest compression depth obtained using the PocketCPR as an educational tool according to smartphone attach- ment site. Am J Emerg Med 2016;34:2243-6.
- Beesems SG, Koster RW. Accurate feedback of chest compression depth on a manikin on a soft surface with correction for total body displacement. Resuscitation 2014;85:1439-43.
190 Correspondence / American Journal of Emergency Medicine 35 (2017) 171-190
Kurowski ASL, Bogdanski L, Zasko P, Czyzewski L. Comparison of the effective- ness of cardiopulmonary resuscitation with standard manual chest compres- sions and the use of TrueCPR and PocketCPR feedback devices. Kardiol Pol 2015;73:924-30.
- Zapletal B, Greif R, Stumpf D, et al. Comparing three CPR feedback devices and stan-
dard BLS in a single rescuer scenario: a randomised simulation study. Resuscitation 2014;85:560-6.
The authors respond to the letter: The use of the PocketCPR(R) application in basic life support training
Dear Editor,
We are very happy to discuss further about our study [1] and thank Oh et al. for their careful and insightful reading of our article.
The first issue is whether to accept the bias from measuring chest compression depth (CCD) by accelerometer-based device (ABD) or not. It is true that there exist a difference between the depth measured by ABD and manikin. Since, in our study, the depth measured by ABD with grasp-in-hand method showed statistically significant difference (0.43 +- 1.58 cm, p = 0.0058) from that measured by manikin, we can- not conclude that ABD could replace the manikin. Even if the absolute depth can be corrected by the improvement of software [2], CCD mea- suring device with low reliability cannot be applied for CPR education. In our study, standard deviation of CCD with grasp-in-hand method was 1.58 cm and intraclass correlation coefficient of grasp-in-hand method was - 0.307 (95% CI - 0.632, - 0.020) that was lower than those of other two armband methods. Therefore, ABD could feedback wrong results when it is applied for random performer.
In their letter, they wrote that “If there are no available feedback de- vices at the basic life support training site, the PocketCPR(R) application can be an alternative tool to validate the performance of CPR, measured by average chest compression rate and depth.” We do not agree with their opinion. On using a free feedback device is better than not using a feedback device when there is no other choice. Even if the PocketCPR(R) application is free, it should be used only when there are supporting sta- tistical evidence of validity and reliability as the measuring tool. In addi- tion, we considered grasp-in-hand method may mislead the beginner into learning the incorrect posture in chest compression.
The second issue is the overestimation of CCD in the use of armband methods. ABD estimates the depth by calculating the instantaneous ac- celeration of movement. Measured distance (depth) by using instanta- neous acceleration is directly proportional to the distance of the movement of the mass in the accelerometer sensor. Since the acceler- ometer sensor is fixed in the smartphone, the distance of movement of the mass in the accelerometer sensor is transformed to the distance of movement of the smartphone. Therefore, overestimation of the ABD
in armband methods can be explained by the additional movement of the smartphone. Because chest compressors in our study were basic life support (BLS) providers or instructors, we thought that the bias from the inexperienced subject like the movement of wrist or elbow could be excluded. In armband-on-arm method, armband was fixed on the upper arm tied horizontally to the ground. Because the force pro- duced in chest compression is vertical to the ground, it is possible for the smartphone in armband to additionally move. Therefore, we thought that the inertial force to the smartphone in armband and imperfect fixation of the armband have caused the overestimation in the depth- measurement of ABD. Subjects appealed that the armband moved dur- ing the chest compression in spite of fixing it as tightly as possible. This problem is not because of the ABD but the armband, so we plan another study to minimize the movement of the smartphone in armband.
In terms of mechanics, the abrupt directional change in push and re- coil make noise to the ABD. Gyrosensor is not the perfect complementa- ry tool for accelerometer in the measuring such movement. We think that it is necessary for the additional measuring sensor like pressure sensor or dual accelerometer to compensate the error of ABD [3].
Acknowledgement
This work was supported by the Soonchunhyang University Research Fund.
Joonbum Park Emergency department, College of medicine Soonchunhyang university, Seoul, Korea
Hyunggoo Kang Emergency department, College of medicine Hanyang university, Seoul, Korea Corresponding author at: 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 address: [email protected] http://dx.doi.org/10.1016/j.ajem.2016.10.084
References
Park J, Lim T, Lee Y, Kim W, Cho Y, Kang H. Assessment of chest compression depth ob- tained using the PocketCPR(R) as an educational tool according to smartphone attachment site. Am J Emerg Med 2016;34(11):2243-6.
- Song Y, Oh J, Chee Y. A new chest compression depth feedback algorithm for high- quality CPR based on smartphone. Telemed J E Health Jan 2015;21:36-41.
- Song YT, Chee Y. The development of feedback monitoring device for CPR. Conf Proc IEEE Eng Med Biol Soc 2011;2011:3294-7.