American Journal of Emergency Medicine 32 (2014) 50–54
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Original Contribution
Quality of chest compressions during compression-only CPR: a comparative analysis following the 2005 and 2010 American Heart Association guidelines Zhengfei Yang, MD a, b, Heng Li, MD b, c, Tao Yu, MD, PHD a, b, Changwei Chen, MD b, c, Jiefeng Xu, MD d, Yueyong Chu, MD a, b, Tianen Zhou, MD a, b, Longyuan Jiang, MD a, b, Zitong Huang, MD a, b,⁎ a b c d
Department of Emergency Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China Institute of Cardiopulmonary Cerebral Resuscitation, Sun Yat-sen University, Guangzhou, China Department of Emergency Medicine, Taiping People’s Hospital, Medical School of Jinan University, Dongguan, China Department of Emergency Medicine, Yuyao People’s Hospital, Medical School of Ningbo University, Ningbo, China
a r t i c l e
i n f o
Article history: Received 8 August 2013 Accepted 28 September 2013
a b s t r a c t Objective: The latest guidelines both increased the requirements of chest compression rate and depth during cardiopulmonary resuscitation (CPR), which may make it more difficult for the rescuer to provide highquality chest compression. In this study, we investigated the quality of chest compressions during compression-only CPR under the latest 2010 American Heart Association (AHA) guidelines (AHA 2010) and its effect on rescuer fatigue. Methods: Eighty-six undergraduate volunteers were randomly assigned to perform CPR according to the 2005 AHA guidelines (AHA 2005) or AHA 2010. After the training course and theoretical examination of basic life support, eight min of compression-only CPR performance was assessed. The quality of chest compressions including rate and depth of compression was analyzed. The rescuer fatigue was evaluated by the changes of heart rate and blood lactate, and rating of perceived exertion. Results: Thirty-nine participants in the AHA 2005 group and 42 participants in the AHA 2010 group completed the study. Significantly greater mean chest compression depth and compression rate were both achieved in the AHA 2010 group than in the AHA 2005 group. And significantly greater rescuer fatigue was observed in the AHA 2010 group. In addition, the female in the AHA 2010 group could perform the compression rate required by the guidelines, however, significantly shallower compression depth and greater rescuer fatigue were observed when compared to the male. Conclusions: The quality of chest compressions was significantly improved following the 2010 AHA guidelines, however, it’s more difficult for the rescuer to meet the guidelines due to the increased fatigue of rescuer. © 2013 Elsevier Inc. All rights reserved.
1. Introduction Early initiation of cardiopulmonary resuscitation (CPR) and defibrillation are critical for reducing the mortality and morbidity in patients suffering from cardiac arrest (CA) [1]. For every minute that CPR is delayed, the likelihood of survival would decrease approximately 10%. However, approximately 67% of CA victims are first witnessed by bystanders and the time interval for Emergency Medical Services arrival is eight min or more [2,3]. Thus, it is most important for the laypersons to initially build the functional chain of survival.
⁎ Corresponding author. Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, P. R. China. Tel.: +86 20 81332410; fax: +86 20 81332650. E-mail addresses: [email protected] (Z. Yang), [email protected] (H. Li), [email protected] (T. Yu), [email protected] (C. Chen), [email protected] (J. Xu), [email protected] (T. Zhou), [email protected] (L. Jiang), [email protected] (Z. Huang). 0735-6757/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajem.2013.09.043
Nevertheless, bystanders may be reluctant to perform CPR due to the lack of confidence, unfamiliarity with resuscitation guidelines, fear of possible harm to the victims and so on [4]. Recently, chest compression-only CPR become more attractive because it is simpler to perform and also deliver a greater number of chest compressions than conventional CPR [5]. A latest meta-analysis showed that dispatcher-assisted chest compression-only CPR improved survival to hospital discharge by 22% [6]. Chest compressiononly CPR has been encouraged by American Heart Association (AHA) to serve as an alternative to conventional CPR for untrained lay rescuers and trained lay rescuers who are not able to perform rescue breathing [7]. High-quality CPR is essential for successful resuscitation following CA, defined as compressions of adequate rate and depth, complete chest recoil, minimized pauses and avoiding excessive ventilation. The quality of chest compressions is the main prerequisite for good outcomes, and especially a deeper chest compression depth has been
Z. Yang et al. / American Journal of Emergency Medicine 32 (2014) 50–54
associated with a higher rate of defibrillation success and better shortterm survival [8,9]. Updated AHA guidelines in 2010 both increased the requirements of compression depth (from 38 to 50 mm to at least 50 mm) and compression rate (from approximately 100/min to at least 100/min) [10]. However, since rescuer fatigue may be a primary reason for decreasing the quality of chest compressions during CPR over time, this new guidelines may further increase physical exertion for the rescuer and the perceived fatigue greater and earlier. In the present study, we sought to investigate the quality of chest compressions during compression-only CPR when CPR was performed according to the 2010 AHA guidelines (AHA 2010), and its effect on rescuer fatigue. Eight min of compression-only CPR was evaluated in a manikin model. Rescuers were randomly assigned to perform CPR according to the 2005 AHA guidelines (AHA 2005) or AHA 2010. We hypothesized that the application of 2010 AHA guidelines would improve the quality of chest compressions when compared with the 2005 AHA guidelines, even if rescuer fatigue would be increased. 2. Methods 2.1. Study design and participants This study was a prospective, randomized and controlled study, which was conducted in Guangzhou, China. Two different methods of compression-only CPR based on AHA 2005 or AHA 2010 were performed. The aim was to evaluate the effectiveness of chest compressions under the latest 2010 AHA CPR guidelines. The study protocol was approved by the Institutional Review Board of Sun Yatsen Memorial Hospital. Eighty-six undergraduate volunteers, inexperienced in basic life support training and real CPR, were recruited to participate in this study between May 2012 and July 2012. After written informed consent was obtained, participants were randomly assigned to receive the training course, theoretical examination and the assessment of compression-only CPR performance following one of the CPR guidelines. Two instructors certified by AHA were invited to teach the classes of AHA 2005 or AHA 2010, while they didn’t know the goal of the training course. In addition, the instructors were told not to refer to the publication date of AHA guidelines during training course so that the participants couldn’t know which guideline was taught. 2.2. Study protocol After a 4-hour training course for all participants was conducted, and then a 30-min theoretical examination was taken. Full score was considered to pass the theoretical examination. Subsequently, the qualified participants were programmed into next step. After a short rest when the participants felt comfortable, they were brought into a case-based scenario of sudden CA in the simulation room. During the evaluation of resuscitation skills, all participants were individually tested and not allowed to communicate with each other. Every participant was required to perform eight min of compression-only CPR. CPR was performed using the Resusci Anne Skill Reporter manikin. The data on CPR performance were automatically collected by Laerdal PC Skill Reporting System Program (Laerdal Medical Corporation, Stavanger, Norway). No feedback was provided to the participants during the entire CPR procedure. If the participants felt too tired to continue, they could end ahead of schedule. Demographic information of every participant was also recorded, including age, gender, height, weight, and calculated body mass index. 2.3. Measurements Quality of chest compressions were evaluated by the following parameters: (1) mean chest compression depth for every minute
51
during eight min of resuscitation attempt; (2) the number of appropriate compression depth and chest compressions at a depth of N 38 mm for every minute; (3) chest compression rate for every minute; (4) abnormal chest recoil; (5) abnormal hand placement. In the AHA 2005 group, the appropriate chest compression depth was defined as 38 to 50 mm; In the AHA 2010 group, the appropriate chest compression depth was defined as N 50 mm. Rescuer fatigue was assessed in the following ways: (1) heart rate and blood lactate level, measured prior to and after the performance of compression-only CPR; (2) rating of perceived exertion (PRE). Blood sample was obtained via finger prick and analyzed using a YSI 1500 Sport Lactate analyzer (YSI Inc, Yellow Springs, OH). PRE was recorded at the end of each minute of CPR performance based on Borg’s method [11]. The score “6” of PRE was considered “no exertion at all”, “7-8” was “extremely light”, “9-10” was “very light”, “10-12” was “light”, “13-14” was “somewhat hard”, “15-16” was “hard”, “17-18” was “very hard”, “19” was “extremely hard”, and “20” was “maximal exertion”. 2.4. Statistical analysis Continuous variables were compared with parametric Student’s t test or the Mann-Whitney U test for nonparametric data. Normal distribution was confirmed with the Kolmogorov-Smirnov test. Comparisons between time-based measurements within each group were performed with a paired sample Student’s t test. For the comparison of categorical variables such as the proportion of gender, the chi-square test was used. P b .05 was considered significant. 3. Results 3.1. Baseline characteristics of participants Originally, 86 participants were recruited into this study. Of these, three participants in the AHA 2005 group temporarily dropped out, and one participant in each group was excluded because they failed to pass the theoretical examination. Consequently, 39 participants in the AHA 2005 group and 42 participants in the AHA 2010 group completed this study. There were no significant differences in baseline characteristics of participants, including demographic data such as gender, age, height and body mass index, physical signs such as blood pressure and heart rate, and blood lactate level. Detailed data were shown in Table 1 and Table 3. 3.2. Quality analysis of chest compressions During eight min of compression-only CPR, mean chest compression depth in both groups declined over time. However, significantly deeper mean chest compression depth was achieved in the AHA 2010 group throughout the entire CPR performance when compared to the AHA 2005 group (Fig. 1A). Although chest compression rate for every minute was maintained stably in both groups; however, significantly
Table 1 Baseline characteristics of participants
Male, n (%) Age, y Height, cm Weight, kg BMI, kg/m2 SBP, mmHg DBP, mmHg
AHA 2005 (n = 39)
AHA 2010 (n = 42)
P
24 (61.5) 20 ± 1 167 ± 7 56.3 ± 10.0 20.1 ± 2.8 117 ± 10 71 ± 7
24 (57.1) 20 ± 1 167 ± 8 54.7 ± 6.8 19.6 ± 1.5 113 ± 11 68 ± 8
.69 .25 .96 .41 .30 .14 .11
BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure.
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Table 2 The number of chest compressions in two different depths 1 min
2 min
No. of compressions in appropriate depth AHA 2005 60 ± 33 AHA 2010 47 ± 52 No. of compressions at a depth of N38 mm AHA 2005 65 ± 34 AHA 2010 103 ± 33⁎⁎ No. of compressions in appropriate depth AHA 2010 (Male) 73 ± 52## AHA 2010 (Female) 13 ± 27 No. of compressions at a depth of N38 mm AHA 2010 (Male) 116 ± 19## AHA 2010 (Female) 85 ± 39
3 min
4 min
5 min
6 min
7 min
8 min
39 ± 43 31 ± 45
35 ± 46 25 ± 41
38 ± 44 21 ± 38
34 ± 43 19 ± 34
31 ± 43 15 ± 33
30 ± 46 12 ± 25⁎
28 ± 44 8 ± 24⁎
43 ± 45 82 ± 50⁎⁎
38 ± 47 75 ± 52⁎⁎
41 ± 45 65 ± 55⁎
36 ± 45 66 ± 55⁎
35 ± 46 64 ± 57⁎
35 ± 49 65 ± 57⁎
34 ± 48 60 ± 57⁎
52 ± 48## 0±2
43 ± 46## 0±0
36 ± 45## 0±0
32 ± 40## 0±0
25 ± 40# 0±1
18 ± 30# 1±6
15 ± 29# 1±4
105 ± 37## 52 ± 50
105 ± 34## 34 ± 44
98 ± 41## 21 ± 35
100 ± 40## 20 ± 35
99 ± 44## 18 ± 36
100 ± 43## 18 ± 37
92 ± 48## 16 ± 34
No., number. Values are presented as mean ± SD. **P b .01, *P b .05 vs. AHA 2005 group; ##P b .01, #P b .05 vs. female in the AHA 2010 group.
greater rate of chest compressions were observed in the group following the 2010 AHA guidelines (Fig. 1B). According to the AHA guidelines, appropriate depth was required to achieve effective chest compression. In the AHA 2010 group, the number of chest compressions in appropriate depth for every minute was less over the eight-min observation and significantly less for the last two min of CPR performance than that in the AHA 2005 group. However, the number of chest compressions at a depth of N 38 mm for every minute was significantly more in participants receiving the training course of 2010 AHA guidelines (Table 2). When considering the demographic information of participants in this study, the gender might become a major factor influencing the quality of chest compressions. In the AHA 2010 group, mean chest compression depth for every minute was markedly deeper in the male than in the female (Fig. 2A). Although an even rate of chest compressions were achieved in both genders in the AHA 2010 group, however, the number of chest compressions in appropriate depth and at a depth of N 38 mm for every minute were both significantly more in the male than in the female (Fig. 2B, Table 2). Incomplete chest recoil and wrong hand placement were not observed in every participant in both groups during the entire CPR performance.
3.3. Rescuer fatigue Across all participants, the PRE recorded at the end of each minute was significantly higher for participants’ CPR performance guided by the 2010 AHA guidelines. After the completion of CPR performance, heart rate and blood lactate levels were immediately measured and showed the significantly greater values in the AHA 2010 group than in the AHA 2005 group (Fig. 3A, Table 3). Although no significant differences in heart rate and blood lactate levels after CPR performance were observed between the male and the female in the AHA 2010 group, however, all female participants
Table 3 Heart rate and blood lactate level AHA 2005
Heart rate (beats/min) Baseline Post-CPR Lactate (mmol/L) Baseline Post-CPR
AHA 2010
AHA 2010 Male
Female
72 ± 10 103 ± 12
75 ± 10 116 ± 15⁎
74 ± 10 116 ± 17
71 ± 18 110 ± 28
1.5 ± 0.5 2.7 ± 0.8
1.4 ± 0.7 3.6 ± 1.0⁎
1.4 ± 0.5 3.7 ± 1.0
1.2 ± 0.7 3.4 ± 1.2
Values are presented as mean ± SD. * P b .01 vs. AHA 2005 group.
felt significantly greater fatigue which was presented by the PRE score (Fig. 3B, Table 3). 4. Discussion The present study demonstrated that during eight min of compression-only CPR, significantly greater compression depth and rate were achieved in the AHA 2010 group when compared to the AHA 2005 group. Although the number of appropriate compressions were less in the AHA 2010 group; however, the number of chest compressions at a depth of N 38 mm was significantly more than that in the AHA 2005 group. Consequently, greater physical exertion and significantly greater rescuer fatigue was observed in the AHA 2010 group. In addition, the compression rate performed by the female in the AHA 2010 group reached the requirement of the guidelines, however, significantly shallower compression depth and greater PRE were observed when compared to the male. In 2010, the increases in rate and depth of chest compressions became a major update in the new CPR guidelines, whose importance was well embodied by the song “push hard and fast to stayin’ alive”. Initially, Bellamy et al demonstrated that the increased depth of chest compression was closely related with the improvement in coronary blood flow during three different Thumper piston strokes of 1.5, 2, and 2.5 in. [12]. Recently, several animal studies demonstrated that chest compression performed at a deeper depth improved myocardial perfusion and electrocardiographic amplitude spectrum area during CPR, and finally achieved significantly greater rate of resuscitation success and 24-hour survival when compared with that at a shallower depth [13–15]. In the clinical setting, another three human studies also demonstrated that increased chest compression depth was closely related to the improvement in defibrillation and resuscitation success and short-term survival [8,9,16]. However, a decay in compression depth was often observed over time in the actual CPR performance and especially obvious when the compression rate was faster [17]. A recent manikin study investigated the impact of compression rate on the quality of chest compressions and concluded that a compression rate of 100 to 120 per minute was feasible for the rescuer to deliver sufficient compression depth [18]. The 2010 European Resuscitation Council (ERC) guidelines have recommended 120 per minute as an upper limit of chest compression rate [19]. However, an upper chest compression depth wasn’t mentioned by both the latest AHA and ERC guidelines because the optimal depth of chest compression was still unknown. Early CPR is vitally important for improving the likely survival of CA victims, however, out-of-hospital CPR is often not initiated until the professional emergency responders arrive [20]. Recently, the guidelines have encouraged the laypersons to perform compressiononly CPR, which requires the rescuer to only provide continuous chest
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Fig. 1. A, Mean chest compression depth per minute for the AHA 2005 and AHA 2010 groups. B, Chest compression rate per minute for the AHA 2005 and AHA 2010 groups. #P b .05, ⁎P b .01 vs. AHA 2005 group.
compressions without rescue breathing. In the present study, 8 minutes of compression-only CPR performance was chosen to evaluate the quality of chest compressions performed by laypersons following the latest 2010 AHA guidelines. In the AHA 2010 group, the participants delivered a stable compression rate consistent with the requirement of 2010 AHA guidelines, which was significantly more than that in the AHA 2005 group. Although it was more difficult for the participants to compress at an appropriate depth in the AHA 2010 group, however, mean chest compression depth and the number of chest compressions at a depth of N 38 mm were significantly better than that in the AHA 2005 group. Consequently, the quality of chest compressions was significantly improved under the 2010 AHA guidelines. In addition, based on the fact that bystander CPR was more often performed by the female [21], we analyzed the effects of gender factor on the quality of chest compressions. Consequently, the compression rate required by 2010 AHA guidelines was well achieved and further stably maintained for eight min by the female; however, significantly shallower compression depth was observed when compared to the male, which was mainly due to the physiologic differences between both genders. In the future, a frequent training of CPR guidelines for the public may be necessary to achieve high quality of chest compressions in the actual CPR performance. Currently, rescuer fatigue has been considered as the main reason for the deterioration in the quality of chest compressions over time during CPR performance [22–24]. Especially when compression-only CPR was performed without a rest, the quality of chest compressions may decrease much more than that in conventional CPR [25,26]. Both
the AHA and ERC guidelines have recommended changing the rescuer every two min to prevent a serious decline in the quality of chest compressions resulted from rescuer fatigue [7,27]. However, the majority of CA occurs out of hospital so that it is not easy to achieve this rotation strategy. In line with previous studies, gradually decreased quality of chest compressions was observed in every participant during eight min of compression-only CPR in the present study. Due to the increased requirements in rate and depth of chest compressions in the latest 2010 guidelines, significantly greater rescuer fatigue as a result of increased heart rate, blood lactate and RPE was observed in the AHA 2010 group; however, significantly higher quality of chest compressions was performed by the participants when compared with that following the previous 2005 guidelines. It may be helpful for improving the quality of chest compressions following the latest guidelines even if increased physical exertion and rescuer fatigue were avoided. 5. Limitations There were certain limitations in our study. First, these undergraduate volunteers participated in this study had only an average age of 20 years. They were younger and physically fitter for CPR performance than most of the actual rescuers who were at a middle and old age. This difference in age might cause a difference in the quality of chest compressions. Second, we evaluated the effectiveness of compression-only CPR in a simulated scenario. CPR on a manikin model couldn’t appropriately take into account those issues such as
Fig. 2. A, Mean chest compression depth per minute for the AHA 2010 group in gender factor. B, Chest compression rate per minute for the AHA 2010 group in gender factor. ⁎P b .01 vs. female in the AHA 2010 group.
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Z. Yang et al. / American Journal of Emergency Medicine 32 (2014) 50–54
Fig. 3. A, Rating of perceived exertion per minute for the AHA 2005 and AHA 2010 groups. B, Rating of perceived exertion per minute for the AHA 2010 group in gender factor. **P b .01, *P b .05 vs. AHA 2005 group. ##P b .01, #P b .05 vs. female in the AHA 2010 group.
chest-wall molding and physiologic differences among CA victims so that the resuscitation efficacy in a real situation of CPR was unknown. 6. Conclusions The quality of chest compressions was significantly improved following the 2010 AHA guidelines, however, it’s more difficult for the rescuer to meet the requirements of the guidelines due to the potential factors of increased physical exertion and rescuer fatigue. Acknowledgments This study was supported by National Nature Science Foundation of China (NSFC 81000823) and Dongguan City Science and Technology Foundation of China (201310515000183). Zhengfei Yang and Heng Li contributed equally to this work; Tao Yu and Zitong Huang contributed equally to this work. References [1] Ali B, Zafari AM. Narrative review: cardiopulmonary resuscitation and emergency cardiovascular care: review of the current guidelines. Ann Intern Med 2007;147: 171–9. [2] Müller D, Agrawal R, Arntz HR. How sudden is sudden cardiac death? Circulation 2006;114:1146–50. [3] van Alem AP, Vrenken RH, de Vos R, et al. Use of automated external defibrillator by first responders in out of hospital cardiac arrest: prospective controlled trial. BMJ 2003;327:1312. [4] Abella BS, Aufderheide TP, Eigel B, et al. Reducing barriers for implementation of bystander-initiated cardiopulmonary resuscitation: a scientific statement from the American Heart Association for healthcare providers, policymakers, and community leaders regarding the effectiveness of cardiopulmonary resuscitation. Circulation 2008;117:704–9. [5] Heidenreich JW, Sanders AB, Higdon TA, et al. Uninterrupted chest compression CPR is easier to perform and remember than standard CPR. Resuscitation 2004;63: 123–30. [6] Hüpfl M, Selig HF, Nagele P. Chest-compression-only versus standard cardiopulmonary resuscitation: a meta-analysis. Lancet 2010;376:1552–7. [7] Berg RA, Hemphill R, Abella BS, et al. Part 5: adult basic life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl 3):S685–705. [8] Edelson DP, Abella BS, Kramer-Johansen J, et al. Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest. Resuscitation 2006;71:137–45.
[9] Kramer-Johansen J, Myklebust H, Wik L, et al. Quality of out-of-hospital cardiopulmonary resuscitation with real time automated feedback: a prospective interventional study. Resuscitation 2006;71:283–92. [10] Travers AH, Rea TD, Bobrow BJ, et al. Part 4: CPR overview: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl 3):S676–84. [11] Borg G. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med 1970;2:92–8. [12] Bellamy RF, DeGuzman LR, Pedersen DC. Coronary blood flow during cardiopulmonary resuscitation in swine. Circulation 1984;69:174–80. [13] Li Y, Ristagno G, Bisera J, et al. Electrocardiogram waveforms for monitoring effectiveness of chest compression during cardiopulmonary resuscitation. Crit Care Med 2008;36:211–5. [14] Ristagno G, Tang W, Chang YT, et al. The quality of chest compressions during cardiopulmonary resuscitation overrides importance of timing of defibrillation. Chest 2007;132:70–5. [15] Wu JY, Li CS, Liu ZX, et al. A comparison of 2 types of chest compressions in a porcine model of cardiac arrest. Am J Emerg Med 2009;27:823–9. [16] Babbs CF, Kemeny AE, Quan W, et al. A new paradigm for human resuscitation research using intelligent devices. Resuscitation 2008;77:306–15. [17] Stiell IG, Brown SP, Christenson J, et al. What is the role of chest compression depth during out-of-hospital cardiac arrest resuscitation? Crit Care Med 2012;40: 1192–8. [18] Field RA, Soar J, Davies RP, et al. The impact of chest compression rates on quality of chest compressions - a manikin study. Resuscitation 2012;83:360–4. [19] Nolan JP, Soar J, Zideman DA, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 1 Executive summary. Resuscitation 2010;81: 1219–76. [20] Sasson C, Rogers MA, Dahl J, et al. Predictors of survival from out-of-hospital cardiac arrest: a systematic review and meta-analysis. Circ Cardiovasc Qual Outcomes 2010;3:63–81. [21] Swor R, Khan I, Domeier R, et al. CPR training and CPR performance: do CPRtrained bystanders perform CPR? Acad Emerg Med 2006;13:596–601. [22] Ochoa FJ, Ramalle-Gómara E, Lisa V, et al. The effect of rescuer fatigue on the quality of chest compressions. Resuscitation 1998;37:149–52. [23] Hightower D, Thomas SH, Stone CK, et al. Decay in quality of closed-chest compressions over time. Ann Emerg Med 1995;26:300–3. [24] Ashton A, McCluskey A, Gwinnutt CL, et al. Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min. Resuscitation 2002;55:151–5. [25] Nishiyama C, Iwami T, Kawamura T, et al. Quality of chest compressions during continuous CPR; comparison between chest compression-only CPR and conventional CPR. Resuscitation 2010;81:1152–5. [26] Hong DY, Park SO, Lee KR, et al. A different rescuer changing strategy between 30: 2 cardiopulmonary resuscitation and hands-only cardiopulmonary resuscitation that considers rescuer factors: a randomised cross-over simulation study with a time-dependent analysis. Resuscitation 2012;83:353–9. [27] Koster RW, Baubin MA, Bossaert LL, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 2 Adult basic life support and use of automated external defibrillators. Resuscitation 2010;81:1277–92.
Contents lists available at ScienceDirect
American Journal of Emergency Medicine journal homepage: www.elsevier.com/locate/ajem
Original Contribution
Quality of chest compressions during compression-only CPR: a comparative analysis following the 2005 and 2010 American Heart Association guidelines Zhengfei Yang, MD a, b, Heng Li, MD b, c, Tao Yu, MD, PHD a, b, Changwei Chen, MD b, c, Jiefeng Xu, MD d, Yueyong Chu, MD a, b, Tianen Zhou, MD a, b, Longyuan Jiang, MD a, b, Zitong Huang, MD a, b,⁎ a b c d
Department of Emergency Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China Institute of Cardiopulmonary Cerebral Resuscitation, Sun Yat-sen University, Guangzhou, China Department of Emergency Medicine, Taiping People’s Hospital, Medical School of Jinan University, Dongguan, China Department of Emergency Medicine, Yuyao People’s Hospital, Medical School of Ningbo University, Ningbo, China
a r t i c l e
i n f o
Article history: Received 8 August 2013 Accepted 28 September 2013
a b s t r a c t Objective: The latest guidelines both increased the requirements of chest compression rate and depth during cardiopulmonary resuscitation (CPR), which may make it more difficult for the rescuer to provide highquality chest compression. In this study, we investigated the quality of chest compressions during compression-only CPR under the latest 2010 American Heart Association (AHA) guidelines (AHA 2010) and its effect on rescuer fatigue. Methods: Eighty-six undergraduate volunteers were randomly assigned to perform CPR according to the 2005 AHA guidelines (AHA 2005) or AHA 2010. After the training course and theoretical examination of basic life support, eight min of compression-only CPR performance was assessed. The quality of chest compressions including rate and depth of compression was analyzed. The rescuer fatigue was evaluated by the changes of heart rate and blood lactate, and rating of perceived exertion. Results: Thirty-nine participants in the AHA 2005 group and 42 participants in the AHA 2010 group completed the study. Significantly greater mean chest compression depth and compression rate were both achieved in the AHA 2010 group than in the AHA 2005 group. And significantly greater rescuer fatigue was observed in the AHA 2010 group. In addition, the female in the AHA 2010 group could perform the compression rate required by the guidelines, however, significantly shallower compression depth and greater rescuer fatigue were observed when compared to the male. Conclusions: The quality of chest compressions was significantly improved following the 2010 AHA guidelines, however, it’s more difficult for the rescuer to meet the guidelines due to the increased fatigue of rescuer. © 2013 Elsevier Inc. All rights reserved.
1. Introduction Early initiation of cardiopulmonary resuscitation (CPR) and defibrillation are critical for reducing the mortality and morbidity in patients suffering from cardiac arrest (CA) [1]. For every minute that CPR is delayed, the likelihood of survival would decrease approximately 10%. However, approximately 67% of CA victims are first witnessed by bystanders and the time interval for Emergency Medical Services arrival is eight min or more [2,3]. Thus, it is most important for the laypersons to initially build the functional chain of survival.
⁎ Corresponding author. Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, P. R. China. Tel.: +86 20 81332410; fax: +86 20 81332650. E-mail addresses: [email protected] (Z. Yang), [email protected] (H. Li), [email protected] (T. Yu), [email protected] (C. Chen), [email protected] (J. Xu), [email protected] (T. Zhou), [email protected] (L. Jiang), [email protected] (Z. Huang). 0735-6757/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajem.2013.09.043
Nevertheless, bystanders may be reluctant to perform CPR due to the lack of confidence, unfamiliarity with resuscitation guidelines, fear of possible harm to the victims and so on [4]. Recently, chest compression-only CPR become more attractive because it is simpler to perform and also deliver a greater number of chest compressions than conventional CPR [5]. A latest meta-analysis showed that dispatcher-assisted chest compression-only CPR improved survival to hospital discharge by 22% [6]. Chest compressiononly CPR has been encouraged by American Heart Association (AHA) to serve as an alternative to conventional CPR for untrained lay rescuers and trained lay rescuers who are not able to perform rescue breathing [7]. High-quality CPR is essential for successful resuscitation following CA, defined as compressions of adequate rate and depth, complete chest recoil, minimized pauses and avoiding excessive ventilation. The quality of chest compressions is the main prerequisite for good outcomes, and especially a deeper chest compression depth has been
Z. Yang et al. / American Journal of Emergency Medicine 32 (2014) 50–54
associated with a higher rate of defibrillation success and better shortterm survival [8,9]. Updated AHA guidelines in 2010 both increased the requirements of compression depth (from 38 to 50 mm to at least 50 mm) and compression rate (from approximately 100/min to at least 100/min) [10]. However, since rescuer fatigue may be a primary reason for decreasing the quality of chest compressions during CPR over time, this new guidelines may further increase physical exertion for the rescuer and the perceived fatigue greater and earlier. In the present study, we sought to investigate the quality of chest compressions during compression-only CPR when CPR was performed according to the 2010 AHA guidelines (AHA 2010), and its effect on rescuer fatigue. Eight min of compression-only CPR was evaluated in a manikin model. Rescuers were randomly assigned to perform CPR according to the 2005 AHA guidelines (AHA 2005) or AHA 2010. We hypothesized that the application of 2010 AHA guidelines would improve the quality of chest compressions when compared with the 2005 AHA guidelines, even if rescuer fatigue would be increased. 2. Methods 2.1. Study design and participants This study was a prospective, randomized and controlled study, which was conducted in Guangzhou, China. Two different methods of compression-only CPR based on AHA 2005 or AHA 2010 were performed. The aim was to evaluate the effectiveness of chest compressions under the latest 2010 AHA CPR guidelines. The study protocol was approved by the Institutional Review Board of Sun Yatsen Memorial Hospital. Eighty-six undergraduate volunteers, inexperienced in basic life support training and real CPR, were recruited to participate in this study between May 2012 and July 2012. After written informed consent was obtained, participants were randomly assigned to receive the training course, theoretical examination and the assessment of compression-only CPR performance following one of the CPR guidelines. Two instructors certified by AHA were invited to teach the classes of AHA 2005 or AHA 2010, while they didn’t know the goal of the training course. In addition, the instructors were told not to refer to the publication date of AHA guidelines during training course so that the participants couldn’t know which guideline was taught. 2.2. Study protocol After a 4-hour training course for all participants was conducted, and then a 30-min theoretical examination was taken. Full score was considered to pass the theoretical examination. Subsequently, the qualified participants were programmed into next step. After a short rest when the participants felt comfortable, they were brought into a case-based scenario of sudden CA in the simulation room. During the evaluation of resuscitation skills, all participants were individually tested and not allowed to communicate with each other. Every participant was required to perform eight min of compression-only CPR. CPR was performed using the Resusci Anne Skill Reporter manikin. The data on CPR performance were automatically collected by Laerdal PC Skill Reporting System Program (Laerdal Medical Corporation, Stavanger, Norway). No feedback was provided to the participants during the entire CPR procedure. If the participants felt too tired to continue, they could end ahead of schedule. Demographic information of every participant was also recorded, including age, gender, height, weight, and calculated body mass index. 2.3. Measurements Quality of chest compressions were evaluated by the following parameters: (1) mean chest compression depth for every minute
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during eight min of resuscitation attempt; (2) the number of appropriate compression depth and chest compressions at a depth of N 38 mm for every minute; (3) chest compression rate for every minute; (4) abnormal chest recoil; (5) abnormal hand placement. In the AHA 2005 group, the appropriate chest compression depth was defined as 38 to 50 mm; In the AHA 2010 group, the appropriate chest compression depth was defined as N 50 mm. Rescuer fatigue was assessed in the following ways: (1) heart rate and blood lactate level, measured prior to and after the performance of compression-only CPR; (2) rating of perceived exertion (PRE). Blood sample was obtained via finger prick and analyzed using a YSI 1500 Sport Lactate analyzer (YSI Inc, Yellow Springs, OH). PRE was recorded at the end of each minute of CPR performance based on Borg’s method [11]. The score “6” of PRE was considered “no exertion at all”, “7-8” was “extremely light”, “9-10” was “very light”, “10-12” was “light”, “13-14” was “somewhat hard”, “15-16” was “hard”, “17-18” was “very hard”, “19” was “extremely hard”, and “20” was “maximal exertion”. 2.4. Statistical analysis Continuous variables were compared with parametric Student’s t test or the Mann-Whitney U test for nonparametric data. Normal distribution was confirmed with the Kolmogorov-Smirnov test. Comparisons between time-based measurements within each group were performed with a paired sample Student’s t test. For the comparison of categorical variables such as the proportion of gender, the chi-square test was used. P b .05 was considered significant. 3. Results 3.1. Baseline characteristics of participants Originally, 86 participants were recruited into this study. Of these, three participants in the AHA 2005 group temporarily dropped out, and one participant in each group was excluded because they failed to pass the theoretical examination. Consequently, 39 participants in the AHA 2005 group and 42 participants in the AHA 2010 group completed this study. There were no significant differences in baseline characteristics of participants, including demographic data such as gender, age, height and body mass index, physical signs such as blood pressure and heart rate, and blood lactate level. Detailed data were shown in Table 1 and Table 3. 3.2. Quality analysis of chest compressions During eight min of compression-only CPR, mean chest compression depth in both groups declined over time. However, significantly deeper mean chest compression depth was achieved in the AHA 2010 group throughout the entire CPR performance when compared to the AHA 2005 group (Fig. 1A). Although chest compression rate for every minute was maintained stably in both groups; however, significantly
Table 1 Baseline characteristics of participants
Male, n (%) Age, y Height, cm Weight, kg BMI, kg/m2 SBP, mmHg DBP, mmHg
AHA 2005 (n = 39)
AHA 2010 (n = 42)
P
24 (61.5) 20 ± 1 167 ± 7 56.3 ± 10.0 20.1 ± 2.8 117 ± 10 71 ± 7
24 (57.1) 20 ± 1 167 ± 8 54.7 ± 6.8 19.6 ± 1.5 113 ± 11 68 ± 8
.69 .25 .96 .41 .30 .14 .11
BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure.
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Table 2 The number of chest compressions in two different depths 1 min
2 min
No. of compressions in appropriate depth AHA 2005 60 ± 33 AHA 2010 47 ± 52 No. of compressions at a depth of N38 mm AHA 2005 65 ± 34 AHA 2010 103 ± 33⁎⁎ No. of compressions in appropriate depth AHA 2010 (Male) 73 ± 52## AHA 2010 (Female) 13 ± 27 No. of compressions at a depth of N38 mm AHA 2010 (Male) 116 ± 19## AHA 2010 (Female) 85 ± 39
3 min
4 min
5 min
6 min
7 min
8 min
39 ± 43 31 ± 45
35 ± 46 25 ± 41
38 ± 44 21 ± 38
34 ± 43 19 ± 34
31 ± 43 15 ± 33
30 ± 46 12 ± 25⁎
28 ± 44 8 ± 24⁎
43 ± 45 82 ± 50⁎⁎
38 ± 47 75 ± 52⁎⁎
41 ± 45 65 ± 55⁎
36 ± 45 66 ± 55⁎
35 ± 46 64 ± 57⁎
35 ± 49 65 ± 57⁎
34 ± 48 60 ± 57⁎
52 ± 48## 0±2
43 ± 46## 0±0
36 ± 45## 0±0
32 ± 40## 0±0
25 ± 40# 0±1
18 ± 30# 1±6
15 ± 29# 1±4
105 ± 37## 52 ± 50
105 ± 34## 34 ± 44
98 ± 41## 21 ± 35
100 ± 40## 20 ± 35
99 ± 44## 18 ± 36
100 ± 43## 18 ± 37
92 ± 48## 16 ± 34
No., number. Values are presented as mean ± SD. **P b .01, *P b .05 vs. AHA 2005 group; ##P b .01, #P b .05 vs. female in the AHA 2010 group.
greater rate of chest compressions were observed in the group following the 2010 AHA guidelines (Fig. 1B). According to the AHA guidelines, appropriate depth was required to achieve effective chest compression. In the AHA 2010 group, the number of chest compressions in appropriate depth for every minute was less over the eight-min observation and significantly less for the last two min of CPR performance than that in the AHA 2005 group. However, the number of chest compressions at a depth of N 38 mm for every minute was significantly more in participants receiving the training course of 2010 AHA guidelines (Table 2). When considering the demographic information of participants in this study, the gender might become a major factor influencing the quality of chest compressions. In the AHA 2010 group, mean chest compression depth for every minute was markedly deeper in the male than in the female (Fig. 2A). Although an even rate of chest compressions were achieved in both genders in the AHA 2010 group, however, the number of chest compressions in appropriate depth and at a depth of N 38 mm for every minute were both significantly more in the male than in the female (Fig. 2B, Table 2). Incomplete chest recoil and wrong hand placement were not observed in every participant in both groups during the entire CPR performance.
3.3. Rescuer fatigue Across all participants, the PRE recorded at the end of each minute was significantly higher for participants’ CPR performance guided by the 2010 AHA guidelines. After the completion of CPR performance, heart rate and blood lactate levels were immediately measured and showed the significantly greater values in the AHA 2010 group than in the AHA 2005 group (Fig. 3A, Table 3). Although no significant differences in heart rate and blood lactate levels after CPR performance were observed between the male and the female in the AHA 2010 group, however, all female participants
Table 3 Heart rate and blood lactate level AHA 2005
Heart rate (beats/min) Baseline Post-CPR Lactate (mmol/L) Baseline Post-CPR
AHA 2010
AHA 2010 Male
Female
72 ± 10 103 ± 12
75 ± 10 116 ± 15⁎
74 ± 10 116 ± 17
71 ± 18 110 ± 28
1.5 ± 0.5 2.7 ± 0.8
1.4 ± 0.7 3.6 ± 1.0⁎
1.4 ± 0.5 3.7 ± 1.0
1.2 ± 0.7 3.4 ± 1.2
Values are presented as mean ± SD. * P b .01 vs. AHA 2005 group.
felt significantly greater fatigue which was presented by the PRE score (Fig. 3B, Table 3). 4. Discussion The present study demonstrated that during eight min of compression-only CPR, significantly greater compression depth and rate were achieved in the AHA 2010 group when compared to the AHA 2005 group. Although the number of appropriate compressions were less in the AHA 2010 group; however, the number of chest compressions at a depth of N 38 mm was significantly more than that in the AHA 2005 group. Consequently, greater physical exertion and significantly greater rescuer fatigue was observed in the AHA 2010 group. In addition, the compression rate performed by the female in the AHA 2010 group reached the requirement of the guidelines, however, significantly shallower compression depth and greater PRE were observed when compared to the male. In 2010, the increases in rate and depth of chest compressions became a major update in the new CPR guidelines, whose importance was well embodied by the song “push hard and fast to stayin’ alive”. Initially, Bellamy et al demonstrated that the increased depth of chest compression was closely related with the improvement in coronary blood flow during three different Thumper piston strokes of 1.5, 2, and 2.5 in. [12]. Recently, several animal studies demonstrated that chest compression performed at a deeper depth improved myocardial perfusion and electrocardiographic amplitude spectrum area during CPR, and finally achieved significantly greater rate of resuscitation success and 24-hour survival when compared with that at a shallower depth [13–15]. In the clinical setting, another three human studies also demonstrated that increased chest compression depth was closely related to the improvement in defibrillation and resuscitation success and short-term survival [8,9,16]. However, a decay in compression depth was often observed over time in the actual CPR performance and especially obvious when the compression rate was faster [17]. A recent manikin study investigated the impact of compression rate on the quality of chest compressions and concluded that a compression rate of 100 to 120 per minute was feasible for the rescuer to deliver sufficient compression depth [18]. The 2010 European Resuscitation Council (ERC) guidelines have recommended 120 per minute as an upper limit of chest compression rate [19]. However, an upper chest compression depth wasn’t mentioned by both the latest AHA and ERC guidelines because the optimal depth of chest compression was still unknown. Early CPR is vitally important for improving the likely survival of CA victims, however, out-of-hospital CPR is often not initiated until the professional emergency responders arrive [20]. Recently, the guidelines have encouraged the laypersons to perform compressiononly CPR, which requires the rescuer to only provide continuous chest
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Fig. 1. A, Mean chest compression depth per minute for the AHA 2005 and AHA 2010 groups. B, Chest compression rate per minute for the AHA 2005 and AHA 2010 groups. #P b .05, ⁎P b .01 vs. AHA 2005 group.
compressions without rescue breathing. In the present study, 8 minutes of compression-only CPR performance was chosen to evaluate the quality of chest compressions performed by laypersons following the latest 2010 AHA guidelines. In the AHA 2010 group, the participants delivered a stable compression rate consistent with the requirement of 2010 AHA guidelines, which was significantly more than that in the AHA 2005 group. Although it was more difficult for the participants to compress at an appropriate depth in the AHA 2010 group, however, mean chest compression depth and the number of chest compressions at a depth of N 38 mm were significantly better than that in the AHA 2005 group. Consequently, the quality of chest compressions was significantly improved under the 2010 AHA guidelines. In addition, based on the fact that bystander CPR was more often performed by the female [21], we analyzed the effects of gender factor on the quality of chest compressions. Consequently, the compression rate required by 2010 AHA guidelines was well achieved and further stably maintained for eight min by the female; however, significantly shallower compression depth was observed when compared to the male, which was mainly due to the physiologic differences between both genders. In the future, a frequent training of CPR guidelines for the public may be necessary to achieve high quality of chest compressions in the actual CPR performance. Currently, rescuer fatigue has been considered as the main reason for the deterioration in the quality of chest compressions over time during CPR performance [22–24]. Especially when compression-only CPR was performed without a rest, the quality of chest compressions may decrease much more than that in conventional CPR [25,26]. Both
the AHA and ERC guidelines have recommended changing the rescuer every two min to prevent a serious decline in the quality of chest compressions resulted from rescuer fatigue [7,27]. However, the majority of CA occurs out of hospital so that it is not easy to achieve this rotation strategy. In line with previous studies, gradually decreased quality of chest compressions was observed in every participant during eight min of compression-only CPR in the present study. Due to the increased requirements in rate and depth of chest compressions in the latest 2010 guidelines, significantly greater rescuer fatigue as a result of increased heart rate, blood lactate and RPE was observed in the AHA 2010 group; however, significantly higher quality of chest compressions was performed by the participants when compared with that following the previous 2005 guidelines. It may be helpful for improving the quality of chest compressions following the latest guidelines even if increased physical exertion and rescuer fatigue were avoided. 5. Limitations There were certain limitations in our study. First, these undergraduate volunteers participated in this study had only an average age of 20 years. They were younger and physically fitter for CPR performance than most of the actual rescuers who were at a middle and old age. This difference in age might cause a difference in the quality of chest compressions. Second, we evaluated the effectiveness of compression-only CPR in a simulated scenario. CPR on a manikin model couldn’t appropriately take into account those issues such as
Fig. 2. A, Mean chest compression depth per minute for the AHA 2010 group in gender factor. B, Chest compression rate per minute for the AHA 2010 group in gender factor. ⁎P b .01 vs. female in the AHA 2010 group.
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Fig. 3. A, Rating of perceived exertion per minute for the AHA 2005 and AHA 2010 groups. B, Rating of perceived exertion per minute for the AHA 2010 group in gender factor. **P b .01, *P b .05 vs. AHA 2005 group. ##P b .01, #P b .05 vs. female in the AHA 2010 group.
chest-wall molding and physiologic differences among CA victims so that the resuscitation efficacy in a real situation of CPR was unknown. 6. Conclusions The quality of chest compressions was significantly improved following the 2010 AHA guidelines, however, it’s more difficult for the rescuer to meet the requirements of the guidelines due to the potential factors of increased physical exertion and rescuer fatigue. Acknowledgments This study was supported by National Nature Science Foundation of China (NSFC 81000823) and Dongguan City Science and Technology Foundation of China (201310515000183). Zhengfei Yang and Heng Li contributed equally to this work; Tao Yu and Zitong Huang contributed equally to this work. References [1] Ali B, Zafari AM. Narrative review: cardiopulmonary resuscitation and emergency cardiovascular care: review of the current guidelines. Ann Intern Med 2007;147: 171–9. [2] Müller D, Agrawal R, Arntz HR. How sudden is sudden cardiac death? Circulation 2006;114:1146–50. [3] van Alem AP, Vrenken RH, de Vos R, et al. Use of automated external defibrillator by first responders in out of hospital cardiac arrest: prospective controlled trial. BMJ 2003;327:1312. [4] Abella BS, Aufderheide TP, Eigel B, et al. Reducing barriers for implementation of bystander-initiated cardiopulmonary resuscitation: a scientific statement from the American Heart Association for healthcare providers, policymakers, and community leaders regarding the effectiveness of cardiopulmonary resuscitation. Circulation 2008;117:704–9. [5] Heidenreich JW, Sanders AB, Higdon TA, et al. Uninterrupted chest compression CPR is easier to perform and remember than standard CPR. Resuscitation 2004;63: 123–30. [6] Hüpfl M, Selig HF, Nagele P. Chest-compression-only versus standard cardiopulmonary resuscitation: a meta-analysis. Lancet 2010;376:1552–7. [7] Berg RA, Hemphill R, Abella BS, et al. Part 5: adult basic life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122(18 Suppl 3):S685–705. [8] Edelson DP, Abella BS, Kramer-Johansen J, et al. Effects of compression depth and pre-shock pauses predict defibrillation failure during cardiac arrest. Resuscitation 2006;71:137–45.
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