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The effect of two different counting methods on the quality of CPR on a manikin—A randomized controlled trial
Resuscitation 80 (2009) 685–688
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Simulation and education
The effect of two different counting methods on the quality of CPR on a manikin—A randomized controlled trial夽 Zhan lei a , He Qing a,∗ , Yang min b a b
Emergency Department, West China Hospital of Sichuan University, Chengdu 610041, China Emergency Department, The Second Hospital of Anhui Medical University, Hefei, China
a r t i c l e
i n f o
Article history: Received 27 October 2008 Received in revised form 25 January 2009 Accepted 5 March 2009 Keywords: Cardiopulmonary resuscitation (CPR) External chest compression (ECC) Manikin
a b s t r a c t Objectives: To compare the quality of cardiopulmonary resuscitation (CPR) and rescuers’ exhaustion using different methods of counting, and to establish an appropriate method of counting. Materials and methods: Forty-eight subjects who had received formal training in basic life support (BLS) were recruited from doctors and nurses working in the Emergency Department of a university hospital. They performed 3 min of continuous chest compressions using two different methods of counting, one after the other, on an adult resuscitation manikin. The total number of compressions, the number of these considered satisfactory, the peak heart rate of subjects and the time to peak heart rate were all recorded. Perceived fatigue and discomfort was evaluated by self-reported survey results with use of a visual analogue scale (VAS). Results: The effective power of external chest compression and the mean compression depth when counting from 1 to 10, repeated three times, were greater than those achieved when counting from 1 to 30 during 3 min of CPR (67.48% vs. 57.81% and 44.52 mm vs. 40.48 mm, P < 0.05). The exhaustion-score using the VAS (22.15 points) was lower and the time to peak heart rate (124.88 s) was longer when counting from 1 to 10, repeated three times, than when rescuers counted from 1 to 30. Conclusions: Counting from 1 to 10 three times in Chinese as opposed to 1–30 results in better quality chest compressions. Counting from 1 to 10 three times was associated with less user feelings of fatigue, and a longer time to peak heart rate. These findings support the teaching of counting compressions 1–10 three times during CPR. © 2009 Elsevier Ireland Ltd. All rights reserved.
1. Introduction The 2005 guidelines for cardiopulmonary resuscitation (CPR), published by both the European Resuscitation Council (ERC) and American Heart Association (AHA), recommend providing CPR with a compression–ventilation (CV) ratio of 30:2.1,2 Minimizing interruptions in chest compression and ensuring high-quality external chest compression are key factors in CPR. The guidelines also recommend that rescuers should count numbers in CPR, in order to ensure the compression rate and compression–ventilation ratio. Anecdotally, we have noticed that, whether in English or Chinese, rescuers find it harder to count numbers from 1 to 30 than to count numbers from 1 to 10 and repeat three times per cycle of CPR. We therefore presume that different methods of counting may have an effect on the quality of CPR and rescuers’ fatigue. The aims of
夽 A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2009.03.017. ∗ Corresponding author. Tel.: +86 158 8248 6334. E-mail address: [email protected] (H. Qing). 0300-9572/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.resuscitation.2009.03.017
the present study were to evaluate the effect of rescuers’ different methods of counting on the quality of CPR and rescuers’ fatigue. 2. Materials and methods We implemented a prospective, randomized, cross-over trial on a manikin. Because there were no risks involved, we did not consult an ethics committee. Forty-eight subjects (28 males, 20 females) competent in basic life support (BLS) were recruited from doctors and nurses working in the Emergency Department of the West China Hospital of Sichuan University. Excluded were subjects who were current or past CPR instructors and also any individual with health-related problems that limited their physical job performance. The subjects were told that investigators were evaluating their quality of CPR but not that the study was assessing the effect of rescuers’ different methods of counting on the quality of CPR and rescuers’ fatigue. Our experimental model (Advanced Resusci Anne Simulator, Prod No. 150-00026, Laerdal, Norway) was used for the CPR training. Data were recorded by the manikin. The total number of compressions attempted, the number considered satisfactory and
686
Z. lei et al. / Resuscitation 80 (2009) 685–688
Table 1 Subject demographics. Total numbers of subjects Age
48 27.52 ± 3.476
22–39
Sex Male Female
28 20
58.3% 41.7%
61.67 ± 10.157 170.54 ± 7.175
Weight Height Role Doctors Nurses
3. Results
45–79 155–187
30 18
62.5% 37.5%
6.56 ± 2.751
Work experience
Non-normally distributed data were presented as medians (with interquartile ranges) and were changed into normally distributed data. They were then analyzed by cross-over analysis of variance. A value of P < 0.05 was considered significant.
2–11
the depths of compression18 were downloaded from the manikin to a laptop computer using PC SkillReporter Software. For the purposes of the study a satisfactory compression was defined as one with a depth of 4–5 cm. To evaluate fatigue, subjects’ heart rates were continuously recorded (Agilent Prod No. M1204A) before, during and after each cycle of CPR. Peak heart rate and the time to peak heart rate were recorded during CPR performance. Perceived fatigue and discomfort was evaluated by self-reported survey results with use of a visual analogue scale (VAS) from a score of 0 (not exhausting at all) to 100 (most exhaustion imaginable).3 By means of throwing a coin, subjects were randomized (Figure 1) to first perform 3 min of single-rescuer CPR with counting from 1 to 30 in Chinese or counting from 1 to 10, repeated three times, in Chinese, during which time the subjects were permitted to view the display of the Skillmeter in order to perfect their performance. They performed 3 min of continuous chest compressions on the manikin at a rate of 100 min−1 with the help of a metronome. Subjects were immediately directed to rectify incorrect hand placement if necessary. Following completion of 3 min of continuous single-rescuer CPR at the randomized method of counting, subjects were allowed to rest for more than 30 min. For each subject the following demographic parameters were recorded: rescuer gender, age, weight, height and profession (doctor or nurse). Sample size estimates suggested that 47 subjects would be needed to achieve 80% power to detect a 25% difference in the percentage of correctly performed chest compressions (˛ = 5%).17 Analyses were conducted using SPSS version 13.0. The data were tested for normality using the Shapiro–Wilk test. Normally distributed data were presented as means (and standard deviations) and were analyzed by cross-over analysis of variance.19
Subject demographics are shown in Table 1. Forty-eight subjects (28 males and 20 females) took part in the study. Thirty (62.5%) were doctors and 18 (37.5%) were nurses. Results are summarized in Tables 2 and 3. Table 2 shows the difference between the total number of correct compressions for counting from 1 to 10 (202.40 ± 6.52), repeated three times, versus counting from 1 to 30 (173.50 ± 5.68). This result was statistically significant (P < 0.001). The mean compression depth for counting from 1 to 10, repeated three times, was 44.52 ± 3.39 mm which was significantly higher than that for counting from 1 to 30, 40.48 ± 2.09 mm (P < 0.001). The exhaustionscore mean, using the VAS, for counting from 1 to 10, repeated three times, was 22.15 ± 3.09 which was significantly lower than that for counting from 1 to 30, 31.10 ± 4.09 (P < 0.001). Also, the difference between the time to peak heart rate for counting from 1 to 10, repeated three times, (124.88 ± 5.40 s) versus counting from 1 to 30 (106.15 ± 6.80 s) was statistically significant (P < 0.001). As shown in Table 3, data were examined for an order effect and no order effect was seen (data not shown). 4. Discussion CPR quality is likely a critical determinant of survival after cardiac arrest. Minimizing interruptions in chest compression is important for increasing the quality of CPR. In animal studies, coronary perfusion pressure, hemodynamic function and survival were adversely affected by even short pauses in chest compression.4,5 There are still many questions and challenges for CPR quality.20 Many studies have shown that in practice cardiopulmonary resuscitation the quality of CPR was inconsistent, and compression rates and compression depth were below published resuscitation recommendations.6,7 Perkins et al. found that, despite some improvements in CPR delivery after the new guidelines were incorporated, the quality of CPR being performed still remained poor immediately after subjects had completed a CPR training course.21 The study by Ashton et al. showed that rescuer fatigue adversely affected the quality of chest compressions when performed without interruption over a 3-min period,8 and rescuers were unaware of the deterioration in the efficacy of their compressions.9,10
Table 2 The effect of counting methods on quality of chest compressions and exhaustion.
Total number of compressions Compression rate/min Total number of correct compressions %Satisfactory compressions Mean compression depth (mm) Exhaustion-score using the VAS Peak heart rate Time to peak heart rate (s)
1–10
1–30
F
P
299.92 ± 0.35 99.97 202.40 ± 6.52 67 ± 2.2 44.52 ± 3.39 22.15 ± 3.09 138.52 ± 5.48 124.88 ± 5.40
299.77 ± 0.72 99.92 173.50 ± 5.68 58 ± 1.9 40.48 ± 2.09 31.10 ± 4.09 138.98 ± 5.56 106.15 ± 6.80
2.41 0.13 With the help of a metronome 532.47 <0.001 518.827 <0.001 58.88 <0.001 159.08 <0.001 0.159 0.69 226.29 <0.001
Table 3 The effect of order on the quality of CPR and exhaustion.
Order
Total number of correct compressions
%Satisfactory compressions
Mean compression depth (mm) Exhaustion-score using the VAS Time to peak heart rate (s)
F
P
F
P
F
P
F
P
F
P
0.172
0.680
0.138
0.712
2.884
0.096
0.082
0.776
0.194
0.662
Z. lei et al. / Resuscitation 80 (2009) 685–688
687
Fig. 1. Randomization.
There are several potential practical solutions for helping to improve CPR quality. The first involves mechanical devices that can provide chest compressions reliably at a set rate and depth. These devices may generate better hemodynamic characteristics than manual chest compression.11,12,22 Another solution is to improve monitoring and feedback to reduce human error during manual CPR, by using devices such as end-tidal CO2 monitors and “smart defibrillators,” which can measure CPR characteristics and provide audio feedback to alert the rescuers to errors such as incorrect chest compression or ventilation rate.13–16,23 Solutions for helping to improve CPR quality are ensuring the effective power of external chest compression and the mean compression depth in CPR. To maintain the compression–ventilation (CV) ratio and the cycle of CPR, rescuers should count the numbers out loudly. Generally, rescuers count numbers contiguously from 1 to another, but after the CV ratio of 30:2, most rescuers find it difficult to count from 1 to 30 contiguously. Our study shows that the method of counting used affected the effective compression ratio and compression depth significantly without an order effect. The effective compression ratio and the mean compression depth are higher using the method of counting from 1 to 10 in Chinese, repeated three times, than using the method of counting from 1 to 30 in Chinese. The time to peak heart rate is longer and the exhaustion-score using the VAS is less using the 1–10 counting, repeated three times, than when using the 1–30 counting method. Whether counting in English or Chinese, counting from 1 to 10 is always monosyllabic, whereas counting from 1 to 30 is both monosyllabic and polysyllabic. We presume that the monosyllabic method of counting is easier than the polysyllabic method for rescuers to set the pace, so they can ensure a better compression rate. In addition, the monosyllabic method can save rescuers’ physical capacity more than the polysyllabic method, so rescuers achieve a better compression depth. However, because the participants in our study counted in Chinese, we suggest that the trial should be repeated in English. Our study is also subject to a number of limitations. Although the Advanced Resusci Anne Simulator is widely used in resuscitation skill studies, there are intrinsic inadequacies in the model. For example, the assessment of whether or not a compression is satisfactory is an all or nothing phenomenon. Thus, a subject performing
chest compressions just short of the required standard would register as unsatisfactory, whereas it could be argued that in vivo these compressions would be of some value. In addition, the randomization process has led to an imbalance in our study. We therefore suggest the trial should be repeated by even randomization. In order to enhance the quality of CPR, a large number of researchers are learning how to maintain the chest compression rate and the compression depth. By learning a detail in the process of CPR, our study shows that the method of counting from 1 to 10, repeated three times, can ensure the effective power of external chest compression and the mean compression depth to some extent. Thus, we consider that using the method of counting from 1 to 10, repeated three times, could also be a solution for enhancing the quality of CPR. 5. Conclusions Counting from 1 to 10 three times, in Chinese, as opposed to 1–30, results in better quality chest compressions. Counting from 1 to 10 three times was also associated with less user feelings of fatigue and a longer time to peak heart rate. These findings support the teaching of counting compressions 1–10 three times during CPR. Conflict of interest The authors do not have any conflict of interests to disclose. Acknowledgements The authors wish to thank all the participants in the study for their enthusiastic collaboration. References 1. American Heart Association. American Heart Association Guideline for cardiopulmonary resuscitation and emergency cardiovascular care. Part 4. Adult basic life support. Circulation 2005;112:IV25. 2. Handley AJ, Koster R, Monsieurs K, et al. European Resuscitation Council Guidelines for resuscitation 2005. Adult basic life support and use of automated external defibrillators. Resuscitation 2005;67:S7–23.
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Z. lei et al. / Resuscitation 80 (2009) 685–688
3. Grant S, Aitchison T, Henderson E, et al. A comparison of the reproducibility and the sensitivity to change of visual analogue scales, Borg scales, and Likert scales in normal subjects during submaximal exercise. Chest 1999;116:1208–17. 4. Steen S, Liao Q, Pierre L, Paskevicius A, Sjoberg T. The critical importance of minimal delay between chest compressions and subsequent defibrillation: a haemodynamic explanation. Resuscitation 2003;58:249–58. 5. Berg RA, Sanders AB, Kern KB, et al. Adverse hemodynamic effects of interrupting chest compressions for rescue breathing during cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest. Circulation 2001;104:2465–70. 6. Abella BS, Alvarado JP, Myklebust H, et al. Quality of cardiopulmonary resuscitation during in hospital cardiac arrest. JAMA 2005;293:305–10. 7. Abella BS, Sandbo N, Vassilatos P, et al. Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest. Circulation 2005;111:428–34. 8. Ashton A, McCluskey A, Gwinnutt CL, Keenan AM. Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min. Resuscitation 2002;55:151–5. 9. Ochoa FJ, Ramalle-Gomara E, Lisa V, Saralegui I. The effect of rescuer fatigue on the quality of chest compressions. Resuscitation 1998;37:149–52. 10. Hightower D, Thomas SH, Stone CK, Dunn K, March JA. Decay in quality of closedchest compressions over time. Ann Emerg Med 1995;26:300–3. 11. Wik L. Automatic and manual mechanical external chest compression devices for cardiopulmonary resuscitation. Resuscitation 2000;47:7–25. 12. Timerman S, Cardoso LF, Ramires JA, Halperin H. Improved hemodynamic performance with a novel chest compression device during treatment of in-hospital cardiac arrest. Resuscitation 2004;61:273–80. 13. Handley AJ, Handley SA. Improving CPR performance using an audible feedback system suitable for incorporation into an automated external defibrillator. Resuscitation 2003;57:57–62.
14. Wik L, Thowsen J, Steen PA. An automated voice advisory manikin system for training in basic life support without an instructor: a novel approach to CPR training. Resuscitation 2001;50:167–72. 15. Abella BS, Edelson DP, Kim S, et al. CPR quality improvement during in-hospital cardiac arrest using a real-time audiovisual feedback system. Resuscitation 2007;73:54–61. 16. 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. 17. Kim JA, Vogel D, Guimond G, Hostler D, Wang HE, Menegazzi JJ. A randomised controlled comparison of cardiopulmonary resuscitation performed on the floor and on a moving ambulance stretcher. Prehosp Emerg Care 2006;10:68– 70. 18. Kramer-Johansen J, Edelson DP, Losert H, Köhler K, Abella BS. Uniform reporting of measured quality of cardiopulmonary resuscitation (CPR). Resuscitation 2007;74:406–17. 19. Chappell AS, Sander JW, Brodie MJ, et al. A crossover, add-on trial of talampanel in patients with refractory partial seizures. Neurology 2002;58:1680–2. 20. Leary M, Abella BS. The challenge of CPR quality: improvement in the real world. Resuscitation 2008;77:1–3. 21. Perkins GD, Boyle W, Bridgestock H, et al. Quality of CPR during advanced resuscitation training. Resuscitation 2008;77:69–74. 22. Krep H, Mamier M, Breil M, Heister U, Fischer M, Hoeft A. Out-of-hospital cardiopulmonary resuscitation with the AutoPulse system: a prospective observational study with a new load-distributing band chest compression device. Resuscitation 2007;73:86–95. 23. Beckers SK, Skorning MH, Fries M, et al. CPREzy improves performance of external chest compressions in simulated cardiac arrest. Resuscitation 2007;72:100–7.
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Simulation and education
The effect of two different counting methods on the quality of CPR on a manikin—A randomized controlled trial夽 Zhan lei a , He Qing a,∗ , Yang min b a b
Emergency Department, West China Hospital of Sichuan University, Chengdu 610041, China Emergency Department, The Second Hospital of Anhui Medical University, Hefei, China
a r t i c l e
i n f o
Article history: Received 27 October 2008 Received in revised form 25 January 2009 Accepted 5 March 2009 Keywords: Cardiopulmonary resuscitation (CPR) External chest compression (ECC) Manikin
a b s t r a c t Objectives: To compare the quality of cardiopulmonary resuscitation (CPR) and rescuers’ exhaustion using different methods of counting, and to establish an appropriate method of counting. Materials and methods: Forty-eight subjects who had received formal training in basic life support (BLS) were recruited from doctors and nurses working in the Emergency Department of a university hospital. They performed 3 min of continuous chest compressions using two different methods of counting, one after the other, on an adult resuscitation manikin. The total number of compressions, the number of these considered satisfactory, the peak heart rate of subjects and the time to peak heart rate were all recorded. Perceived fatigue and discomfort was evaluated by self-reported survey results with use of a visual analogue scale (VAS). Results: The effective power of external chest compression and the mean compression depth when counting from 1 to 10, repeated three times, were greater than those achieved when counting from 1 to 30 during 3 min of CPR (67.48% vs. 57.81% and 44.52 mm vs. 40.48 mm, P < 0.05). The exhaustion-score using the VAS (22.15 points) was lower and the time to peak heart rate (124.88 s) was longer when counting from 1 to 10, repeated three times, than when rescuers counted from 1 to 30. Conclusions: Counting from 1 to 10 three times in Chinese as opposed to 1–30 results in better quality chest compressions. Counting from 1 to 10 three times was associated with less user feelings of fatigue, and a longer time to peak heart rate. These findings support the teaching of counting compressions 1–10 three times during CPR. © 2009 Elsevier Ireland Ltd. All rights reserved.
1. Introduction The 2005 guidelines for cardiopulmonary resuscitation (CPR), published by both the European Resuscitation Council (ERC) and American Heart Association (AHA), recommend providing CPR with a compression–ventilation (CV) ratio of 30:2.1,2 Minimizing interruptions in chest compression and ensuring high-quality external chest compression are key factors in CPR. The guidelines also recommend that rescuers should count numbers in CPR, in order to ensure the compression rate and compression–ventilation ratio. Anecdotally, we have noticed that, whether in English or Chinese, rescuers find it harder to count numbers from 1 to 30 than to count numbers from 1 to 10 and repeat three times per cycle of CPR. We therefore presume that different methods of counting may have an effect on the quality of CPR and rescuers’ fatigue. The aims of
夽 A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2009.03.017. ∗ Corresponding author. Tel.: +86 158 8248 6334. E-mail address: [email protected] (H. Qing). 0300-9572/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.resuscitation.2009.03.017
the present study were to evaluate the effect of rescuers’ different methods of counting on the quality of CPR and rescuers’ fatigue. 2. Materials and methods We implemented a prospective, randomized, cross-over trial on a manikin. Because there were no risks involved, we did not consult an ethics committee. Forty-eight subjects (28 males, 20 females) competent in basic life support (BLS) were recruited from doctors and nurses working in the Emergency Department of the West China Hospital of Sichuan University. Excluded were subjects who were current or past CPR instructors and also any individual with health-related problems that limited their physical job performance. The subjects were told that investigators were evaluating their quality of CPR but not that the study was assessing the effect of rescuers’ different methods of counting on the quality of CPR and rescuers’ fatigue. Our experimental model (Advanced Resusci Anne Simulator, Prod No. 150-00026, Laerdal, Norway) was used for the CPR training. Data were recorded by the manikin. The total number of compressions attempted, the number considered satisfactory and
686
Z. lei et al. / Resuscitation 80 (2009) 685–688
Table 1 Subject demographics. Total numbers of subjects Age
48 27.52 ± 3.476
22–39
Sex Male Female
28 20
58.3% 41.7%
61.67 ± 10.157 170.54 ± 7.175
Weight Height Role Doctors Nurses
3. Results
45–79 155–187
30 18
62.5% 37.5%
6.56 ± 2.751
Work experience
Non-normally distributed data were presented as medians (with interquartile ranges) and were changed into normally distributed data. They were then analyzed by cross-over analysis of variance. A value of P < 0.05 was considered significant.
2–11
the depths of compression18 were downloaded from the manikin to a laptop computer using PC SkillReporter Software. For the purposes of the study a satisfactory compression was defined as one with a depth of 4–5 cm. To evaluate fatigue, subjects’ heart rates were continuously recorded (Agilent Prod No. M1204A) before, during and after each cycle of CPR. Peak heart rate and the time to peak heart rate were recorded during CPR performance. Perceived fatigue and discomfort was evaluated by self-reported survey results with use of a visual analogue scale (VAS) from a score of 0 (not exhausting at all) to 100 (most exhaustion imaginable).3 By means of throwing a coin, subjects were randomized (Figure 1) to first perform 3 min of single-rescuer CPR with counting from 1 to 30 in Chinese or counting from 1 to 10, repeated three times, in Chinese, during which time the subjects were permitted to view the display of the Skillmeter in order to perfect their performance. They performed 3 min of continuous chest compressions on the manikin at a rate of 100 min−1 with the help of a metronome. Subjects were immediately directed to rectify incorrect hand placement if necessary. Following completion of 3 min of continuous single-rescuer CPR at the randomized method of counting, subjects were allowed to rest for more than 30 min. For each subject the following demographic parameters were recorded: rescuer gender, age, weight, height and profession (doctor or nurse). Sample size estimates suggested that 47 subjects would be needed to achieve 80% power to detect a 25% difference in the percentage of correctly performed chest compressions (˛ = 5%).17 Analyses were conducted using SPSS version 13.0. The data were tested for normality using the Shapiro–Wilk test. Normally distributed data were presented as means (and standard deviations) and were analyzed by cross-over analysis of variance.19
Subject demographics are shown in Table 1. Forty-eight subjects (28 males and 20 females) took part in the study. Thirty (62.5%) were doctors and 18 (37.5%) were nurses. Results are summarized in Tables 2 and 3. Table 2 shows the difference between the total number of correct compressions for counting from 1 to 10 (202.40 ± 6.52), repeated three times, versus counting from 1 to 30 (173.50 ± 5.68). This result was statistically significant (P < 0.001). The mean compression depth for counting from 1 to 10, repeated three times, was 44.52 ± 3.39 mm which was significantly higher than that for counting from 1 to 30, 40.48 ± 2.09 mm (P < 0.001). The exhaustionscore mean, using the VAS, for counting from 1 to 10, repeated three times, was 22.15 ± 3.09 which was significantly lower than that for counting from 1 to 30, 31.10 ± 4.09 (P < 0.001). Also, the difference between the time to peak heart rate for counting from 1 to 10, repeated three times, (124.88 ± 5.40 s) versus counting from 1 to 30 (106.15 ± 6.80 s) was statistically significant (P < 0.001). As shown in Table 3, data were examined for an order effect and no order effect was seen (data not shown). 4. Discussion CPR quality is likely a critical determinant of survival after cardiac arrest. Minimizing interruptions in chest compression is important for increasing the quality of CPR. In animal studies, coronary perfusion pressure, hemodynamic function and survival were adversely affected by even short pauses in chest compression.4,5 There are still many questions and challenges for CPR quality.20 Many studies have shown that in practice cardiopulmonary resuscitation the quality of CPR was inconsistent, and compression rates and compression depth were below published resuscitation recommendations.6,7 Perkins et al. found that, despite some improvements in CPR delivery after the new guidelines were incorporated, the quality of CPR being performed still remained poor immediately after subjects had completed a CPR training course.21 The study by Ashton et al. showed that rescuer fatigue adversely affected the quality of chest compressions when performed without interruption over a 3-min period,8 and rescuers were unaware of the deterioration in the efficacy of their compressions.9,10
Table 2 The effect of counting methods on quality of chest compressions and exhaustion.
Total number of compressions Compression rate/min Total number of correct compressions %Satisfactory compressions Mean compression depth (mm) Exhaustion-score using the VAS Peak heart rate Time to peak heart rate (s)
1–10
1–30
F
P
299.92 ± 0.35 99.97 202.40 ± 6.52 67 ± 2.2 44.52 ± 3.39 22.15 ± 3.09 138.52 ± 5.48 124.88 ± 5.40
299.77 ± 0.72 99.92 173.50 ± 5.68 58 ± 1.9 40.48 ± 2.09 31.10 ± 4.09 138.98 ± 5.56 106.15 ± 6.80
2.41 0.13 With the help of a metronome 532.47 <0.001 518.827 <0.001 58.88 <0.001 159.08 <0.001 0.159 0.69 226.29 <0.001
Table 3 The effect of order on the quality of CPR and exhaustion.
Order
Total number of correct compressions
%Satisfactory compressions
Mean compression depth (mm) Exhaustion-score using the VAS Time to peak heart rate (s)
F
P
F
P
F
P
F
P
F
P
0.172
0.680
0.138
0.712
2.884
0.096
0.082
0.776
0.194
0.662
Z. lei et al. / Resuscitation 80 (2009) 685–688
687
Fig. 1. Randomization.
There are several potential practical solutions for helping to improve CPR quality. The first involves mechanical devices that can provide chest compressions reliably at a set rate and depth. These devices may generate better hemodynamic characteristics than manual chest compression.11,12,22 Another solution is to improve monitoring and feedback to reduce human error during manual CPR, by using devices such as end-tidal CO2 monitors and “smart defibrillators,” which can measure CPR characteristics and provide audio feedback to alert the rescuers to errors such as incorrect chest compression or ventilation rate.13–16,23 Solutions for helping to improve CPR quality are ensuring the effective power of external chest compression and the mean compression depth in CPR. To maintain the compression–ventilation (CV) ratio and the cycle of CPR, rescuers should count the numbers out loudly. Generally, rescuers count numbers contiguously from 1 to another, but after the CV ratio of 30:2, most rescuers find it difficult to count from 1 to 30 contiguously. Our study shows that the method of counting used affected the effective compression ratio and compression depth significantly without an order effect. The effective compression ratio and the mean compression depth are higher using the method of counting from 1 to 10 in Chinese, repeated three times, than using the method of counting from 1 to 30 in Chinese. The time to peak heart rate is longer and the exhaustion-score using the VAS is less using the 1–10 counting, repeated three times, than when using the 1–30 counting method. Whether counting in English or Chinese, counting from 1 to 10 is always monosyllabic, whereas counting from 1 to 30 is both monosyllabic and polysyllabic. We presume that the monosyllabic method of counting is easier than the polysyllabic method for rescuers to set the pace, so they can ensure a better compression rate. In addition, the monosyllabic method can save rescuers’ physical capacity more than the polysyllabic method, so rescuers achieve a better compression depth. However, because the participants in our study counted in Chinese, we suggest that the trial should be repeated in English. Our study is also subject to a number of limitations. Although the Advanced Resusci Anne Simulator is widely used in resuscitation skill studies, there are intrinsic inadequacies in the model. For example, the assessment of whether or not a compression is satisfactory is an all or nothing phenomenon. Thus, a subject performing
chest compressions just short of the required standard would register as unsatisfactory, whereas it could be argued that in vivo these compressions would be of some value. In addition, the randomization process has led to an imbalance in our study. We therefore suggest the trial should be repeated by even randomization. In order to enhance the quality of CPR, a large number of researchers are learning how to maintain the chest compression rate and the compression depth. By learning a detail in the process of CPR, our study shows that the method of counting from 1 to 10, repeated three times, can ensure the effective power of external chest compression and the mean compression depth to some extent. Thus, we consider that using the method of counting from 1 to 10, repeated three times, could also be a solution for enhancing the quality of CPR. 5. Conclusions Counting from 1 to 10 three times, in Chinese, as opposed to 1–30, results in better quality chest compressions. Counting from 1 to 10 three times was also associated with less user feelings of fatigue and a longer time to peak heart rate. These findings support the teaching of counting compressions 1–10 three times during CPR. Conflict of interest The authors do not have any conflict of interests to disclose. Acknowledgements The authors wish to thank all the participants in the study for their enthusiastic collaboration. References 1. American Heart Association. American Heart Association Guideline for cardiopulmonary resuscitation and emergency cardiovascular care. Part 4. Adult basic life support. Circulation 2005;112:IV25. 2. Handley AJ, Koster R, Monsieurs K, et al. European Resuscitation Council Guidelines for resuscitation 2005. Adult basic life support and use of automated external defibrillators. Resuscitation 2005;67:S7–23.
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3. Grant S, Aitchison T, Henderson E, et al. A comparison of the reproducibility and the sensitivity to change of visual analogue scales, Borg scales, and Likert scales in normal subjects during submaximal exercise. Chest 1999;116:1208–17. 4. Steen S, Liao Q, Pierre L, Paskevicius A, Sjoberg T. The critical importance of minimal delay between chest compressions and subsequent defibrillation: a haemodynamic explanation. Resuscitation 2003;58:249–58. 5. Berg RA, Sanders AB, Kern KB, et al. Adverse hemodynamic effects of interrupting chest compressions for rescue breathing during cardiopulmonary resuscitation for ventricular fibrillation cardiac arrest. Circulation 2001;104:2465–70. 6. Abella BS, Alvarado JP, Myklebust H, et al. Quality of cardiopulmonary resuscitation during in hospital cardiac arrest. JAMA 2005;293:305–10. 7. Abella BS, Sandbo N, Vassilatos P, et al. Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest. Circulation 2005;111:428–34. 8. Ashton A, McCluskey A, Gwinnutt CL, Keenan AM. Effect of rescuer fatigue on performance of continuous external chest compressions over 3 min. Resuscitation 2002;55:151–5. 9. Ochoa FJ, Ramalle-Gomara E, Lisa V, Saralegui I. The effect of rescuer fatigue on the quality of chest compressions. Resuscitation 1998;37:149–52. 10. Hightower D, Thomas SH, Stone CK, Dunn K, March JA. Decay in quality of closedchest compressions over time. Ann Emerg Med 1995;26:300–3. 11. Wik L. Automatic and manual mechanical external chest compression devices for cardiopulmonary resuscitation. Resuscitation 2000;47:7–25. 12. Timerman S, Cardoso LF, Ramires JA, Halperin H. Improved hemodynamic performance with a novel chest compression device during treatment of in-hospital cardiac arrest. Resuscitation 2004;61:273–80. 13. Handley AJ, Handley SA. Improving CPR performance using an audible feedback system suitable for incorporation into an automated external defibrillator. Resuscitation 2003;57:57–62.
14. Wik L, Thowsen J, Steen PA. An automated voice advisory manikin system for training in basic life support without an instructor: a novel approach to CPR training. Resuscitation 2001;50:167–72. 15. Abella BS, Edelson DP, Kim S, et al. CPR quality improvement during in-hospital cardiac arrest using a real-time audiovisual feedback system. Resuscitation 2007;73:54–61. 16. 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. 17. Kim JA, Vogel D, Guimond G, Hostler D, Wang HE, Menegazzi JJ. A randomised controlled comparison of cardiopulmonary resuscitation performed on the floor and on a moving ambulance stretcher. Prehosp Emerg Care 2006;10:68– 70. 18. Kramer-Johansen J, Edelson DP, Losert H, Köhler K, Abella BS. Uniform reporting of measured quality of cardiopulmonary resuscitation (CPR). Resuscitation 2007;74:406–17. 19. Chappell AS, Sander JW, Brodie MJ, et al. A crossover, add-on trial of talampanel in patients with refractory partial seizures. Neurology 2002;58:1680–2. 20. Leary M, Abella BS. The challenge of CPR quality: improvement in the real world. Resuscitation 2008;77:1–3. 21. Perkins GD, Boyle W, Bridgestock H, et al. Quality of CPR during advanced resuscitation training. Resuscitation 2008;77:69–74. 22. Krep H, Mamier M, Breil M, Heister U, Fischer M, Hoeft A. Out-of-hospital cardiopulmonary resuscitation with the AutoPulse system: a prospective observational study with a new load-distributing band chest compression device. Resuscitation 2007;73:86–95. 23. Beckers SK, Skorning MH, Fries M, et al. CPREzy improves performance of external chest compressions in simulated cardiac arrest. Resuscitation 2007;72:100–7.