Original article 253
Optimal chest compression rate in cardiopulmonary resuscitation: a prospective, randomized crossover study using a manikin model Seong Hwa Leea, Ji Ho Ryub, Mun Ki Minb, Yong In Kimb, Maeng Real Parkb, Seok Ran Yeoma, Sang Kyoon Hana and Seong Wook Parka Objectives When performing cardiopulmonary resuscitation (CPR), the 2010 American Heart Association guidelines recommend a chest compression rate of at least 100 min − 1, whereas the 2010 European Resuscitation Council guidelines recommend a rate of between 100 and 120 min − 1. The aim of this study was to examine the rate of chest compression that fulfilled various quality indicators, thereby determining the optimal rate of compression. Methods Thirty-two trainee emergency medical technicians and six paramedics were enrolled in this study. All participants had been trained in basic life support. Each participant performed 2 min of continuous compressions on a skill reporter manikin, while listening to a metronome sound at rates of 100, 120, 140, and 160 beats/min, in a random order. Mean compression depth, incomplete chest recoil, and the proportion of correctly performed chest compressions during the 2 min were measured and recorded. Results The rate of incomplete chest recoil was lower at compression rates of 100 and 120 min − 1 compared with that at 160 min − 1 (P = 0.001). The numbers of
Introduction The 2010 American Heart Association (AHA) guidelines emphasize the importance of high-quality cardiopulmonary resuscitation (CPR) for optimal patient outcomes [1]. High-quality CPR consists of sufficient pressure (compression depth greater than 5 cm), sufficient frequency (a rate of greater than 100 min − 1), and complete chest recoil between compressions. Similarly, the 2010 European Resuscitation Council (ERC) guidelines recommend a chest compression depth between 5 and 6 cm and a compression rate between 100 and 120 min − 1 [2]. Compared with the previous AHA and ERC guidelines (2005), the new consensus recommends deeper and more frequent compressions [1,2]. Although the 2010 ERC guidelines provide a recommended rate range, the 2010 AHA guidelines do not specify an upper limit.
compressions that fulfilled the criteria for high-quality CPR at a rate of 120 min − 1 were significantly higher than those at 100 min − 1 (P = 0.016). Conclusion The number of high-quality CPR compressions was the highest at a compression rate of 120 min − 1, and increased incomplete recoil occurred with increasing compression rate. However, further studies are needed to confirm the results. European Journal of Emergency Medicine 23:253–257 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. European Journal of Emergency Medicine 2016, 23:253–257 Keywords: basic life support, quality, rate of chest compression, resuscitation a
Department of Emergency Medicine, Pusan National University Hospital and Department of Emergency Medicine, Pusan National University Yangsan Hospital, Busan, Republic of Korea b
Correspondence to Ji Ho Ryu, MD, PhD, Department of Emergency Medicine, Pusan National University Yangsan Hospital, Geum-o-ro 20, Mulgeum-eup, Yangsan-si, Gyeongnam, 626-770, Republic of Korea Tel: + 82 55 360 2143; fax: + 82 55 360 2173; e-mail: [email protected] Received 13 July 2014 Accepted 12 January 2015
studied the association between quality and rate of chest compression, and suggested that rates above 120 min − 1 reduced compression quality, and therefore recommended a rate of 100–120 min − 1 for high-quality CPR. However, their study was carried out according to the outdated 2005 AHA guidelines, and the authors acknowledged that further research was needed on the basis of the more recent 2010 guidelines [3]. We hypothesized that the chest compression rate influences depth of compression and rate of complete chest recoil. We therefore aimed to determine an optimal chest compression rate that results in a compression depth of more than 5 cm and complete chest recoil on the basis of the 2010 guideline recommendations.
Methods Study design
In the past, whenever guidelines have been updated, the recommended rate of chest compression has also been increased, although the upper limit of compression rates remains a controversial topic. Field and colleagues 0969-9546 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
This was a randomized-controlled crossover study, carried out in one regional emergency medical center, using a skill reporter manikin. Our study examined four experimental groups of compression rates, corresponding DOI: 10.1097/MEJ.0000000000000249
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
254 European Journal of Emergency Medicine 2016, Vol 23 No 4
Fig. 1
Assessed for eligibility (n = 38)
30 min training program consisting of continuous chest compression
Randomized by lot with 22 numbers of occasion Performed by determined order
Allocated to 4 groups
Group 1 (n = 38)
Group 2 (n = 36)
Group 3 (n = 37)
Group 4 (n = 37)
Chest compression rate
Chest compression rate
Chest compression rate
Chest compression rate
140 min−1
160 min−1
100 min−1
120 min−1
Analyzed 4 groups, respectively Excluded from analysis of missing data (n = 3) Personal reasons (n = 2) Manikin error (n = 1)
Flow diagram of the study.
to 100, 120, 140, and 160 min − 1. In each group, chest compressions were performed by volunteers continuously for 2 min. The order of chest compression rates was determined by lot using 22 numbers in a random order. Each participant performed chest compressions for each of the four different rates (Fig. 1).
Participants
Volunteers were recruited between June and December 2013 from a regional emergency medical center. Thirtytwo trainee emergency medical technicians and six emergency medical technicians agreed to participate, all of whom had received training in basic life support (BLS). Informed consent was obtained from all participants. Data from three participants were not included
in the final analysis because of withdrawal for personal reasons or manikin error.
Study protocols
Approximately 30 min before the participants performed CPR, the 2010 AHA and ERC guidelines related to BLS were explained to the participants. The order of chest compression rates was determined randomly, and compressions were performed in the assigned order. After performing a single group of compressions, each participant rested for at least 12 h to eliminate bias because of fatigue. The following instructions were given to participants: ‘after listening carefully to the metronome sound for 20 s, compress the chest in time with the metronome’. Each participant performed continuous compressions on
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Optimal chest compression rate in CPR Lee et al. 255
the manikin for 2 min at each compression rate, while listening to a metronome set at rates of 100, 120, 140, and 160 min − 1 in a random order. The manikin used in the study was the Laerdal Resusci-Anne model (Laerdal Medical AS, Stavanger, Norway) using software that had been updated according to the 2010 guidelines. An electronic metronome (Flash metronome, www.gieson.com) was used to guide chest compression rates. Ethics and regulatory approval
The study received ethical approval from our institutional review board. Statistical analysis
All data were analyzed using PASW, 18.0 for Windows (SPSS Inc., Chicago, Illinois, USA). The number of incomplete chest recoils, mean depth of compression, the proportion of correctly performed chest compressions, and the number of participants who performed chest compression perfectly were analyzed using the Kruskal–Wallis test. Our post-hoc test was evaluated using Bonferroni correction, and P values of less than 0.05 were considered significant.
Results We analyzed 38 participants (21 men and 17 women). The mean age of the participants was 22.0 years (range, 20.0–23.8 years). We found that 21 participants had BLS certification and 16 participants did not; one participant did not provide a response on the BLS certification status (Table 1). The main quality indicators associated with the compression rates are shown in Table 2. At 120 min − 1, the numbers of compressions that fulfilled the criteria for high-quality CPR (depth > 5 cm, full recoil) were significantly higher than those at 100 min − 1 (P = 0.016). However, the quality comparisons between the other groups did not show any significant differences (Fig. 2). The numbers of incomplete chest recoils were significantly higher at 160 min − 1 compared with those at 100 and 120 min − 1 (P = 0.001) (Table 2). The ratio of correctly performed to total compressions was highest at 120 min − 1 and lowest at 160 min − 1, although this result was not statistically significant (P = 0.646). The mean Table 1
General characteristics of the participants
Characteristics Sex [n (%)] Male Female Average age Average weight (kg) Average height (cm) BMI (kg/m2) BLS certification Possession No possession Unknown BLS, basic life support.
Data 21 17 22.0 64.0 170.5 21.3
(55.3) (44.7) (20.0–23.3) (53.0–70.0) (160.8–177.0) (20.4–23.4) 21 16 1
compression depth was not statistically significant between all groups (P = 0.760) (Fig. 3). The number of participants who performed the correct compression depth for 2 min was higher at the rate of 120 min − 1, although this finding was also not statistically significant (P = 0.052).
Discussion Chest compression rate, compression depth, and complete chest recoil are all important factors for performing high-quality CPR [1], and many researchers have studied the relationship between CPR quality and compression rate, on the basis of the 2005 AHA guidelines [2–4]. According to these dated guidelines, optimal compression depth is ∼ 5 cm and the optimal compression rate is ∼ 100 min − 1 [5]. However, the more recent 2010 AHA guidelines cite the optimal compression depth as greater than 5 cm and the optimal chest compression rate as greater than 100 min − 1. We therefore studied the relationship between CPR quality and compression rate, on the basis of the 2010 AHA and ERC guidelines, to determine whether the newer guidelines improved CPR quality. Monsieurs et al. [4] found that higher compression rates (>120 min − 1) were associated with a clinically significant reduction in compression depth, and suggested that avoiding higher compression rates might lead to greater optimal compression depth. Field et al. [3] suggested that compression depth was greatest at a compression rate of 80 min − 1, although these results were based on outdated guidelines. In our study, the mean compression depth over a period of 2 min was deepest at the rate of 120 min − 1, but this result was not statistically significant. However, at 120 min − 1, the number of compressions that fulfilled the criteria for high-quality CPR (depth > 5 cm, full recoil) was significantly higher than those at 100 min − 1, and the proportion of participants fulfilling compression depth criteria was the highest, although statistically not significant. The P value was 0.052, which is very close to 0.05, and indicates that a true difference might be present. Several studies have reported that the use of metronome affects chest compression depth. Oh et al. [6] have reported that audio tone guidance CPR ensures better chest compression and ventilation rates, but decreases the mean compression depth significantly. Chung and colleagues also studied the relationship between compression depth and metronome rate, and found that the average compression depth was lowest at a rate of 80 min − 1 and highest at 140 min − 1, although incomplete chest recoil was not affected by higher rates of compression. The authors therefore suggest that a rate of chest compression over 120 min − 1 is necessary for highquality, metronome-guided CPR [7]. Although not statistically significant, Jäntii et al. [8] also found that the average compression depth during metronome-guided
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
256
European Journal of Emergency Medicine 2016, Vol 23 No 4
Factors associated with quality of chest compression at rates from 100 to 160 min − 1
Table 2
Total numbers of compression delivered for 2 min Numbers of compression fulfilled the criteria of highquality CPR Numbers of incomplete chest recoil Proper depth compressions/total compressions (%) Mean depth for 2 min (mm) The proportion of participants who fulfilled compression depth criteria [n/N (%)]
100 min − 1
120 min − 1
140 min − 1
160 min − 1
P value
199.0 (199.0–201.0) 132.0a (50.5–199.0)
240.0 (239.0–240.0) 233.5b (98.5–239.0)
279.0 (278.0–280.0) 226.0a,b (48.5–277.5)
318.0 (310.3–320.0) 182.5a,b (52.0–312.0)
0.000 0.016
0.0a 65.0 51.5 9/38
(0.0–0.0) (26.4–99.5) (46.8–58.0) (23.7)
0.0a 97.7 55.0 9/36
0.0a,b 81.0 53.0 7/37
(0.0–0.0) (40.4–99.6) (48.3–58.0) (25.0)
(0.0–4.5) (17.3–99.7) (45.0–58.5) (18.9)
1.0b 58.2 51.0 1/36
(0.0–15.5) (16.3–99.4) (44.8–57.8) (2.8)
0.001 0.646 0.760 0.052
CPR, cardiopulmonary resuscitation. The same letters indicate nonsignificant differences between groups on the basis of Bonferroni correction.
a,b
Fig. 3
Fig. 2
70
350
60 Mean compression depth (mm)
The number of compression (N)
300
250
200
150
50
40
30
20
100
10
50
0 100
120
140
160
Chest compression rate (min−1) 0 100
120
140
Chest compression rate
160
(min−1)
The number of compressions that fulfilled high-quality cardiopulmonary resuscitation criteria. †There was a statistically significant difference between 100 and 120 min − 1 in post-hoc analysis (P = 0.001).
CPR was lower than that in CPR without metronome guidance, although this did not affect the quality of CPR. Our results are in agreement with these studies, in that the mean compression depth is not affected significantly by compression rates during metronome-guided chest compressions. Complete chest recoil is also important during CPR as it draws venous blood back to the heart and provides cardiac preload before the next chest compression [9–11], and incomplete chest recoil may have hemodynamic consequences [12]. Lee et al. [13] have studied the relationship between chest compression rate and quality of compression, on the basis of the 2010 AHA guidelines, and found that although compression depth increased
Mean depth for 2 min. There was no significant difference between groups (P = 0.760).
with compression rate, incomplete chest recoil was lowest at a rate of 120 min − 1. Similarly, our results indicate that the number of incomplete chest recoils was lowest at rates of 100 and 120 min − 1 and significantly higher at a rate of 160 min − 1. Our study has several limitations. First, this was a manikin study, and therefore, these results may not be directly applicable to clinical practice. Although many similar manikin studies have been carried out, more clinical studies are now required. Second, the number of participants was small, and many of our results were not statistically significant. Third, we performed chest compression-only CPR, and therefore, the results may differ from those obtained with conventional CPR. Finally, a metronome was used in this study, and audio feedback devices are not generally used when performing CPR in a clinical setting.
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Optimal chest compression rate in CPR Lee et al. 257
Conclusion
We found that the number of high-quality CPR compressions was highest at a compression rate of 120 min − 1 and increased incomplete recoil occurred with the increasing compression rate. However, additional clinical studies are needed to confirm these results.
Acknowledgements This work was supported by a grant from the Medical Research Institute, Pusan National University Yangsan Hospital, 2014.
5
6
7
8
9
Conflicts of interest
There are no conflicts of interest. 10
References 1 Berg RA, Hemphill R, Abella BS, Aufderheide TP, Cave DM, Hazinski MF, et al. Part 5: adult basic life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010; 122 (Suppl 3):S685–S705. 2 Nolan JP, Soar J, Zideman DA, Biarent D, Bossaert LL, Deakin C, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 1. Executive summary. Resuscitation 2010; 81:1219–1276. 3 Field RA, Soar J, Davies RP, Akhtar N, Perkins GD. The impact of chest compression rates on quality of chest compressions – a manikin study. Resuscitation 2012; 83:360–364. 4 Monsieurs KG, de Regge M, Vansteelandt K, de Smet J, Annaert E, Lemoyne S, et al. Excessive chest compression rate is associated with
11
12
13
insufficient compression depth in prehospital cardiac arrest. Resuscitation 2012; 83:1319–1323. Handley AJ, Koster R, Monsieurs K, Perkins GD, Davies S, Bossaert L. European Resuscitation Council guidelines for resuscitation 2005. Section 2. Adult basic life support and use of automated external defibrillators. Resuscitation 2005; 67 (Suppl 1):S7–S23. Oh JH, Lee SJ, Kim SE, Lee KJ, Choe JW, Kim CW. Effects of audio tone guidance on performance of CPR in simulated cardiac arrest with an advanced airway. Resuscitation 2008; 79:273–277. Chung TN, Kim SW, You JS, Cho YS, Chung SP, Park I. A higher chest compression rate may be necessary for metronome-guided cardiopulmonary resuscitation. Am J Emerg Med 2012; 30:226–230. Jäntti H, Silfvast T, Turpeinen A, Kiviniemi V, Uusaro A. Influence of chest compression rate guidance on the quality of cardiopulmonary resuscitation performed on manikins. Resuscitation 2009; 80:453–457. Lurie KG, Zielinski T, McKnite S, Aufderheide T, Voelckel W. Use of an inspiratory impedance valve improves neurologically intact survival in a porcine model of ventricular fibrillation. Circulation 2002; 105:124–129. Lurie KG, Mulligan KA, McKnite S, Detloff B, Lindstrom P, Lindner KH. Optimizing standard cardiopulmonary resuscitation with an inspiratory impedance threshold valve. Chest 1998; 113:1084–1090. Lurie K, Voelckel W, Plaisance P, Zielinski T, McKnite S, Kor D, et al. Use of an inspiratory impedance threshold valve during cardiopulmonary resuscitation: a progress report. Resuscitation 2000; 44:219–230. Yannopoulos D, McKnite S, Aufderheide TP, Sigurdsson G, Pirrallo RG, Benditt D, Lurie KG. Effects of incomplete chest wall decompression during cardiopulmonary resuscitation on coronary and cerebral perfusion pressures in a porcine model of cardiac arrest. Resuscitation 2005; 64:363–372. Lee SH, Kim K, Lee JH, Kim TY, Kang CW, Park CJ, et al. Does the quality of chest compression deteriorate when the chest compression rate is above 120/min? Emerg Med J 2014; 31:645–648.
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Optimal chest compression rate in cardiopulmonary resuscitation: a prospective, randomized crossover study using a manikin model Seong Hwa Leea, Ji Ho Ryub, Mun Ki Minb, Yong In Kimb, Maeng Real Parkb, Seok Ran Yeoma, Sang Kyoon Hana and Seong Wook Parka Objectives When performing cardiopulmonary resuscitation (CPR), the 2010 American Heart Association guidelines recommend a chest compression rate of at least 100 min − 1, whereas the 2010 European Resuscitation Council guidelines recommend a rate of between 100 and 120 min − 1. The aim of this study was to examine the rate of chest compression that fulfilled various quality indicators, thereby determining the optimal rate of compression. Methods Thirty-two trainee emergency medical technicians and six paramedics were enrolled in this study. All participants had been trained in basic life support. Each participant performed 2 min of continuous compressions on a skill reporter manikin, while listening to a metronome sound at rates of 100, 120, 140, and 160 beats/min, in a random order. Mean compression depth, incomplete chest recoil, and the proportion of correctly performed chest compressions during the 2 min were measured and recorded. Results The rate of incomplete chest recoil was lower at compression rates of 100 and 120 min − 1 compared with that at 160 min − 1 (P = 0.001). The numbers of
Introduction The 2010 American Heart Association (AHA) guidelines emphasize the importance of high-quality cardiopulmonary resuscitation (CPR) for optimal patient outcomes [1]. High-quality CPR consists of sufficient pressure (compression depth greater than 5 cm), sufficient frequency (a rate of greater than 100 min − 1), and complete chest recoil between compressions. Similarly, the 2010 European Resuscitation Council (ERC) guidelines recommend a chest compression depth between 5 and 6 cm and a compression rate between 100 and 120 min − 1 [2]. Compared with the previous AHA and ERC guidelines (2005), the new consensus recommends deeper and more frequent compressions [1,2]. Although the 2010 ERC guidelines provide a recommended rate range, the 2010 AHA guidelines do not specify an upper limit.
compressions that fulfilled the criteria for high-quality CPR at a rate of 120 min − 1 were significantly higher than those at 100 min − 1 (P = 0.016). Conclusion The number of high-quality CPR compressions was the highest at a compression rate of 120 min − 1, and increased incomplete recoil occurred with increasing compression rate. However, further studies are needed to confirm the results. European Journal of Emergency Medicine 23:253–257 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. European Journal of Emergency Medicine 2016, 23:253–257 Keywords: basic life support, quality, rate of chest compression, resuscitation a
Department of Emergency Medicine, Pusan National University Hospital and Department of Emergency Medicine, Pusan National University Yangsan Hospital, Busan, Republic of Korea b
Correspondence to Ji Ho Ryu, MD, PhD, Department of Emergency Medicine, Pusan National University Yangsan Hospital, Geum-o-ro 20, Mulgeum-eup, Yangsan-si, Gyeongnam, 626-770, Republic of Korea Tel: + 82 55 360 2143; fax: + 82 55 360 2173; e-mail: [email protected] Received 13 July 2014 Accepted 12 January 2015
studied the association between quality and rate of chest compression, and suggested that rates above 120 min − 1 reduced compression quality, and therefore recommended a rate of 100–120 min − 1 for high-quality CPR. However, their study was carried out according to the outdated 2005 AHA guidelines, and the authors acknowledged that further research was needed on the basis of the more recent 2010 guidelines [3]. We hypothesized that the chest compression rate influences depth of compression and rate of complete chest recoil. We therefore aimed to determine an optimal chest compression rate that results in a compression depth of more than 5 cm and complete chest recoil on the basis of the 2010 guideline recommendations.
Methods Study design
In the past, whenever guidelines have been updated, the recommended rate of chest compression has also been increased, although the upper limit of compression rates remains a controversial topic. Field and colleagues 0969-9546 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
This was a randomized-controlled crossover study, carried out in one regional emergency medical center, using a skill reporter manikin. Our study examined four experimental groups of compression rates, corresponding DOI: 10.1097/MEJ.0000000000000249
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
254 European Journal of Emergency Medicine 2016, Vol 23 No 4
Fig. 1
Assessed for eligibility (n = 38)
30 min training program consisting of continuous chest compression
Randomized by lot with 22 numbers of occasion Performed by determined order
Allocated to 4 groups
Group 1 (n = 38)
Group 2 (n = 36)
Group 3 (n = 37)
Group 4 (n = 37)
Chest compression rate
Chest compression rate
Chest compression rate
Chest compression rate
140 min−1
160 min−1
100 min−1
120 min−1
Analyzed 4 groups, respectively Excluded from analysis of missing data (n = 3) Personal reasons (n = 2) Manikin error (n = 1)
Flow diagram of the study.
to 100, 120, 140, and 160 min − 1. In each group, chest compressions were performed by volunteers continuously for 2 min. The order of chest compression rates was determined by lot using 22 numbers in a random order. Each participant performed chest compressions for each of the four different rates (Fig. 1).
Participants
Volunteers were recruited between June and December 2013 from a regional emergency medical center. Thirtytwo trainee emergency medical technicians and six emergency medical technicians agreed to participate, all of whom had received training in basic life support (BLS). Informed consent was obtained from all participants. Data from three participants were not included
in the final analysis because of withdrawal for personal reasons or manikin error.
Study protocols
Approximately 30 min before the participants performed CPR, the 2010 AHA and ERC guidelines related to BLS were explained to the participants. The order of chest compression rates was determined randomly, and compressions were performed in the assigned order. After performing a single group of compressions, each participant rested for at least 12 h to eliminate bias because of fatigue. The following instructions were given to participants: ‘after listening carefully to the metronome sound for 20 s, compress the chest in time with the metronome’. Each participant performed continuous compressions on
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
Optimal chest compression rate in CPR Lee et al. 255
the manikin for 2 min at each compression rate, while listening to a metronome set at rates of 100, 120, 140, and 160 min − 1 in a random order. The manikin used in the study was the Laerdal Resusci-Anne model (Laerdal Medical AS, Stavanger, Norway) using software that had been updated according to the 2010 guidelines. An electronic metronome (Flash metronome, www.gieson.com) was used to guide chest compression rates. Ethics and regulatory approval
The study received ethical approval from our institutional review board. Statistical analysis
All data were analyzed using PASW, 18.0 for Windows (SPSS Inc., Chicago, Illinois, USA). The number of incomplete chest recoils, mean depth of compression, the proportion of correctly performed chest compressions, and the number of participants who performed chest compression perfectly were analyzed using the Kruskal–Wallis test. Our post-hoc test was evaluated using Bonferroni correction, and P values of less than 0.05 were considered significant.
Results We analyzed 38 participants (21 men and 17 women). The mean age of the participants was 22.0 years (range, 20.0–23.8 years). We found that 21 participants had BLS certification and 16 participants did not; one participant did not provide a response on the BLS certification status (Table 1). The main quality indicators associated with the compression rates are shown in Table 2. At 120 min − 1, the numbers of compressions that fulfilled the criteria for high-quality CPR (depth > 5 cm, full recoil) were significantly higher than those at 100 min − 1 (P = 0.016). However, the quality comparisons between the other groups did not show any significant differences (Fig. 2). The numbers of incomplete chest recoils were significantly higher at 160 min − 1 compared with those at 100 and 120 min − 1 (P = 0.001) (Table 2). The ratio of correctly performed to total compressions was highest at 120 min − 1 and lowest at 160 min − 1, although this result was not statistically significant (P = 0.646). The mean Table 1
General characteristics of the participants
Characteristics Sex [n (%)] Male Female Average age Average weight (kg) Average height (cm) BMI (kg/m2) BLS certification Possession No possession Unknown BLS, basic life support.
Data 21 17 22.0 64.0 170.5 21.3
(55.3) (44.7) (20.0–23.3) (53.0–70.0) (160.8–177.0) (20.4–23.4) 21 16 1
compression depth was not statistically significant between all groups (P = 0.760) (Fig. 3). The number of participants who performed the correct compression depth for 2 min was higher at the rate of 120 min − 1, although this finding was also not statistically significant (P = 0.052).
Discussion Chest compression rate, compression depth, and complete chest recoil are all important factors for performing high-quality CPR [1], and many researchers have studied the relationship between CPR quality and compression rate, on the basis of the 2005 AHA guidelines [2–4]. According to these dated guidelines, optimal compression depth is ∼ 5 cm and the optimal compression rate is ∼ 100 min − 1 [5]. However, the more recent 2010 AHA guidelines cite the optimal compression depth as greater than 5 cm and the optimal chest compression rate as greater than 100 min − 1. We therefore studied the relationship between CPR quality and compression rate, on the basis of the 2010 AHA and ERC guidelines, to determine whether the newer guidelines improved CPR quality. Monsieurs et al. [4] found that higher compression rates (>120 min − 1) were associated with a clinically significant reduction in compression depth, and suggested that avoiding higher compression rates might lead to greater optimal compression depth. Field et al. [3] suggested that compression depth was greatest at a compression rate of 80 min − 1, although these results were based on outdated guidelines. In our study, the mean compression depth over a period of 2 min was deepest at the rate of 120 min − 1, but this result was not statistically significant. However, at 120 min − 1, the number of compressions that fulfilled the criteria for high-quality CPR (depth > 5 cm, full recoil) was significantly higher than those at 100 min − 1, and the proportion of participants fulfilling compression depth criteria was the highest, although statistically not significant. The P value was 0.052, which is very close to 0.05, and indicates that a true difference might be present. Several studies have reported that the use of metronome affects chest compression depth. Oh et al. [6] have reported that audio tone guidance CPR ensures better chest compression and ventilation rates, but decreases the mean compression depth significantly. Chung and colleagues also studied the relationship between compression depth and metronome rate, and found that the average compression depth was lowest at a rate of 80 min − 1 and highest at 140 min − 1, although incomplete chest recoil was not affected by higher rates of compression. The authors therefore suggest that a rate of chest compression over 120 min − 1 is necessary for highquality, metronome-guided CPR [7]. Although not statistically significant, Jäntii et al. [8] also found that the average compression depth during metronome-guided
Copyright r 2016 Wolters Kluwer Health, Inc. All rights reserved.
256
European Journal of Emergency Medicine 2016, Vol 23 No 4
Factors associated with quality of chest compression at rates from 100 to 160 min − 1
Table 2
Total numbers of compression delivered for 2 min Numbers of compression fulfilled the criteria of highquality CPR Numbers of incomplete chest recoil Proper depth compressions/total compressions (%) Mean depth for 2 min (mm) The proportion of participants who fulfilled compression depth criteria [n/N (%)]
100 min − 1
120 min − 1
140 min − 1
160 min − 1
P value
199.0 (199.0–201.0) 132.0a (50.5–199.0)
240.0 (239.0–240.0) 233.5b (98.5–239.0)
279.0 (278.0–280.0) 226.0a,b (48.5–277.5)
318.0 (310.3–320.0) 182.5a,b (52.0–312.0)
0.000 0.016
0.0a 65.0 51.5 9/38
(0.0–0.0) (26.4–99.5) (46.8–58.0) (23.7)
0.0a 97.7 55.0 9/36
0.0a,b 81.0 53.0 7/37
(0.0–0.0) (40.4–99.6) (48.3–58.0) (25.0)
(0.0–4.5) (17.3–99.7) (45.0–58.5) (18.9)
1.0b 58.2 51.0 1/36
(0.0–15.5) (16.3–99.4) (44.8–57.8) (2.8)
0.001 0.646 0.760 0.052
CPR, cardiopulmonary resuscitation. The same letters indicate nonsignificant differences between groups on the basis of Bonferroni correction.
a,b
Fig. 3
Fig. 2
70
350
60 Mean compression depth (mm)
The number of compression (N)
300
250
200
150
50
40
30
20
100
10
50
0 100
120
140
160
Chest compression rate (min−1) 0 100
120
140
Chest compression rate
160
(min−1)
The number of compressions that fulfilled high-quality cardiopulmonary resuscitation criteria. †There was a statistically significant difference between 100 and 120 min − 1 in post-hoc analysis (P = 0.001).
CPR was lower than that in CPR without metronome guidance, although this did not affect the quality of CPR. Our results are in agreement with these studies, in that the mean compression depth is not affected significantly by compression rates during metronome-guided chest compressions. Complete chest recoil is also important during CPR as it draws venous blood back to the heart and provides cardiac preload before the next chest compression [9–11], and incomplete chest recoil may have hemodynamic consequences [12]. Lee et al. [13] have studied the relationship between chest compression rate and quality of compression, on the basis of the 2010 AHA guidelines, and found that although compression depth increased
Mean depth for 2 min. There was no significant difference between groups (P = 0.760).
with compression rate, incomplete chest recoil was lowest at a rate of 120 min − 1. Similarly, our results indicate that the number of incomplete chest recoils was lowest at rates of 100 and 120 min − 1 and significantly higher at a rate of 160 min − 1. Our study has several limitations. First, this was a manikin study, and therefore, these results may not be directly applicable to clinical practice. Although many similar manikin studies have been carried out, more clinical studies are now required. Second, the number of participants was small, and many of our results were not statistically significant. Third, we performed chest compression-only CPR, and therefore, the results may differ from those obtained with conventional CPR. Finally, a metronome was used in this study, and audio feedback devices are not generally used when performing CPR in a clinical setting.
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Optimal chest compression rate in CPR Lee et al. 257
Conclusion
We found that the number of high-quality CPR compressions was highest at a compression rate of 120 min − 1 and increased incomplete recoil occurred with the increasing compression rate. However, additional clinical studies are needed to confirm these results.
Acknowledgements This work was supported by a grant from the Medical Research Institute, Pusan National University Yangsan Hospital, 2014.
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Conflicts of interest
There are no conflicts of interest. 10
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