Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
EMJ Online First, published on August 21, 2014 as 10.1136/emermed-2014-203932 Original article
One-handed chest compression technique for paediatric cardiopulmonary resuscitation: dominant versus non-dominant hand Je Hyeok Oh, Chan Woong Kim, Sung Eun Kim, Dong Hoon Lee, Sang Jin Lee Department of Emergency Medicine, College of Medicine, Chung-Ang University, Seoul, Republic of Korea Correspondence to Professor Chan Woong Kim, Department of Emergency Medicine, Chung-Ang University, College of Medicine, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756, Republic of Korea; [email protected] Received 21 April 2014 Revised 18 July 2014 Accepted 31 July 2014
ABSTRACT Background Pediatric resuscitation guidelines do not specify which hand to use for one-handed cardiopulmonary resuscitation (CPR). Objective To determine whether there is a difference in the quality of one-handed chest compressions (OHCCs) using the dominant versus non-dominant hand in simulated paediatric CPR. Materials and methods 41 doctors took part in the study. Chest compressions were alternately performed with the dominant (test 1) and non-dominant hand (test 2) in a random order at 30 min intervals. Experiments were carried out with a 5-year-old paediatric manikin without ventilation for 2 min. Data on average compression rate ( per min) and average compression depth (mm) were collected and compared. Results No significant differences were found in the average compression rate (118.0±14.3/min vs 117.3±14.5/ min, p=0.610) and average compression depth (41.3 ±5.6mm vs 41.9±4.1mm, p=0.327) between tests 1 and 2. Conclusions No significant difference was found in the quality of OHCCs using the dominant and non-dominant hand in simulated paediatric CPR. The study suggests there is no need for paediatric resuscitation guidelines to state a preferred hand for performing OHCC.
What is already known on this subject ▸ The 2010 European Resuscitation Council Guidelines recommend either two-handed chest compression or one-handed chest compression (OHCC) in cardiopulmonary resuscitation (CPR) for children over 1 year of age. Previous studies have provided contradictory evidence as to whether it is better to use the dominant or non-dominant hand for OHCC. What this study adds ▸ In this randomised crossover trial, no significant difference was found in the quality of OHCC using the dominant versus non-dominant hand in a 2 min simulated paediatric CPR. Therefore it seems unnecessary for the paediatric resuscitation guidelines to state a preferred hand for performing OHCC.
A randomised crossover trial was carried out, with chest compressions performed using the dominant (test 1) and non-dominant hand (test 2).
significant difference in compression depth between the two tests was set at 5 mm7 and the SD of compression depth was determined to be 5.8 mm,8 and a standardised difference was then calculated. The minimum sample size required was 10 for a two-tailed paired Student’s t test with a significance level of 0.05 and statistical power of 0.80. Forty-one doctors took part in the study. All participants enrolled voluntarily during regular CPR education at our institute. The CPR instruction lasted for 3 h and was provided by an instructor using video to guide practice. The participants in our study were limited to doctors who had successfully completed the basic life support course for healthcare providers proposed by the American Heart Association. All participants gave their informed consent. All experiments were carried out immediately after the CPR instruction. In this experiment, we used a 5-year-old Resusci Junior Basic and SkillGuide paediatric manikin (Laerdal Medical, Stavanger, Norway). Performance test data on chest compression, including average compression rate ( per min) and average compression depth (mm), were collected using the CPRmeter (Laerdal Medical) and the software Q-CPR Review V.3.1 (Laerdal Medical). This experiment was conducted in the simulation centre of a single medical school.
Study subjects
Study protocol
The study sample size was calculated using G*Power 3.1.6 In light of a previous study, the
This study was approved by the institutional review board of our university (C2014043). In test 1,
INTRODUCTION The 2010 International Consensus on Cardiopulmonary Resuscitation (CPR) states that chest compression can be conducted on children using one-handed chest compression (OHCC) or two-handed chest compression (THCC) techniques.1 A few studies have compared the two techniques, but no studies have determined which hand to use in OHCC.2–4 The 2010 European Resuscitation Council Guidelines provide a detailed description of the two techniques,5 but for OHCC do not state which hand should be used. Therefore, this study aimed at determining whether there is a significant difference in the quality of OHCCs using the dominant and nondominant hand in simulated paediatric CPR.
MATERIALS AND METHODS Study design To cite: Oh JH, Kim CW, Kim SE, et al. Emerg Med J Published Online First: [please include Day Month Year] doi:10.1136/emermed2014-203932
Key messages
Oh JH, etemployer) al. Emerg Med 2014. J 2014;0:1–3. doi:10.1136/emermed-2014-203932 Copyright Article author (or their Produced by BMJ Publishing Group Ltd under licence.
1
Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
Original article chest compression was conducted continuously using the dominant hand for 2 min and in test 2 it was conducted similarly using the non-dominant hand. The order of the two tests was randomised using a random number sequence produced by a web-based computer programme.9 The 30 min washout period between the tests was planned to relieve the participants’ fatigue. To evaluate the effect of handedness alone, chest compression was conducted without ventilation. The manikin was placed in the supine position on a hard floor without any mattress. In accordance with the 2010 European Resuscitation Council Guidelines,5 OHCC was conducted at a velocity of ≥100 compressions/min (but not exceeding 120 compressions/ min) to at least one-third of the depth of the chest, but the hand which was not being used could be placed in any position as no instruction was given in the guidelines. To prevent participants from receiving feedback, the CPR meter display was hidden and audiovisual feedback was not provided. At the completion of each experiment, the degree of difficulty in THCC conducted on an adult was assumed to be 5 points and the degree of difficulty in OHCC was estimated on a 10-point visual analogue scale (VAS).
Statistical analysis All statistical analyses were performed using IBM SPSS V.20 (IBM, Armonk, New York, USA). Data were analysed using a Shapiro–Wilk test to verify the normal distribution. For normal distribution, a paired t test was used and otherwise, a Wilcoxon signed-rank test was used. Data on average compression rate, average compression depth and VAS were analysed. Comparisons of average compression rate and average compression depth values between tests 1 and 2 were made. Data are presented as mean±SD. A p value of 5 (the assumed degree of difficulty in THCC in adults) in both tests 1 and 2, which suggests that all participants were unfamiliar with OHCC. Since there are insufficient data on effective OHCC techniques, participants might have not received standardised OHCC skills during their basic life support course. Second, the effectiveness of OHCC might have been affected by confounding factors in the rescuers—for example, the position of the hand not used to perform chest compression, the posture of the rescuers and their arms, need for arm straightening and the strength of the dominant arm. Our research has a number of implications. First, paediatric resuscitation guidelines do not have to change to state a preferred hand for performing OHCCs. Second, future strategies for paediatric CPR by a single rescuer might incorporate a switch of hands every 2 min to reduce the effects of fatigue and extend the period of chest compressions. Further investigation is needed to prove the effectiveness of these strategies. Finally, we conclude that hand dominance did not significantly influence the quality of OHCC. However, further studies on factors significantly influencing the effectiveness of OHCC are needed to establish a standardised OHCC technique. Oh JH, et al. Emerg Med J 2014;0:1–3. doi:10.1136/emermed-2014-203932
Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
Original article This study has some limitations. First, since a manikin was used, it might be difficult to apply the results to clinical practice. Second, the guidelines do not include a detailed description of possible confounding factors, such as the position of the hand which does not perform chest compressions and the posture of the rescuers. Third, if chest compression is conducted at a compression/ventilation ratio of 30:2 or 15:2, it may result in hand-off time. Although the hand-off time might affect rescuers’ fatigue, we conducted chest compression without ventilation because we could not adjust this factor. Therefore, in clinical practice different results might be obtained when CPR is performed at a compression/ventilation ratio of 30:2 or 15:2. Fourth, all the participants in our study were doctors and the results might be different if the rescuer were a layperson. Additionally, the small number of female participants might have influenced the results. Fifth, chest compressions were performed on the floor rather than on a high adjusted hospital bed and therefore our results cannot be applied to patients lying on a bed. Sixth, the small number of left-handed participants might have affected the results. Seventh, our study used 2 min chest compression and thus the results cannot be applied to the situation where a single rescuer performs OHCC for a long time.
Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCE 1
2 3
4
5
6
7
8
CONCLUSIONS No significant difference was found in the quality of OHCCs using the dominant and non-dominant hand in simulated paediatric CPR. Therefore, no change is needed in the paediatric resuscitation guidelines to state a preferred hand for performing OHCC. Acknowledgements We thank the healthcare providers for their participation in this study. Contributors JHO: conception and design of the study; analysis and interpretation of data. CWK, SEK, SJL, DHL: acquisition of data. JHO, CWK, SEK: drafting of the article or revising it critically for important intellectual content. CWK: final approval of the version submitted. Competing interests None. Ethics approval Institutional review board of the College of Medicine, Chung-Ang University (C2014043).
Oh JH, et al. Emerg Med J 2014;0:1–3. doi:10.1136/emermed-2014-203932
9 10 11
12
13
14 15
de Caen AR, Kleinman ME, Chameides L, et al. Part 10: paediatric basic and advanced life support: 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations. Resuscitation 2010;81(Suppl 1):e213–59. Stevenson AG, McGowan J, Evans AL, et al. CPR for children: one hand or two? Resuscitation 2005;64:205–8. Peska E, Kelly AM, Kerr D, et al. One-handed versus two-handed chest compressions in paediatric cardio-pulmonary resuscitation. Resuscitation 2006;71:65–9. Udassi JP, Udassi S, Theriaque DW, et al. Effect of alternative chest compression techniques in infant and child on rescuer performance. Pediatr Crit Care Med 2009;10:328–33. Biarent D, Bingham R, Eich C, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 6. Paediatric life support. Resuscitation 2010;81:1364–88. Faul F, Erdfelder E, Buchner A, et al. Statistical power analyses using G*Power 3.1: tests for correlation and regressi0n analyses. Behav Res Methods 2009;41:1149–60. Oh JH, Lee SJ, Kim SE, et al. Effects of audio tone guidance on performance of CPR in simulated cardiac arrest with an advanced airway. Resuscitation 2008;79:273–7. Oh JH, Kim CW, Kim SE, et al. Comparison of chest compressions in the standing position beside a bed at knee level and the kneeling position: a non-randomised, single-blind, cross-over trial. Emerg Med J 2014;31:533–5. http://www.random.org/ (accessed Jan 2014). Kundra P, Dey S, Ravishankar M. Role of dominant hand position during external cardiac compression. Br J Anaesth 2000;84:491–3. Nikandish R, Shahbazi S, Golabi S, et al. Role of dominant versus non-dominant hand position during uninterrupted chest compression CPR by novice rescuers: a randomized double-blind crossover study. Resuscitation 2008;76:256–60. Ozcan A, Tulum Z, Pinar L, et al. Comparison of pressure pain threshold, grip strength, dexterity and touch pressure of dominant and non-dominant hands within and between right-and left-handed subjects. J Korean Med Sci 2004;19:874–8. Murray MP, Gore DR, Gardner GM, et al. Shoulder motion and muscle strength of normal men and women in two age groups. Clin Orthop Relat Res 1985;192:268–73. Ellenbecker TS. A total arm strength isokinetic profile of highly skilled tennis players. Isokinet Exerc Sci 1991;1:9–21. Brown LP, Niehues SL, Harrah A, et al. Upper extremity range of motion and isokinetic strength of the internal and external shoulder rotators in major league baseball players. Am J Sports Med 1988;16:577–85.
3
Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
One-handed chest compression technique for paediatric cardiopulmonary resuscitation: dominant versus non-dominant hand Je Hyeok Oh, Chan Woong Kim, Sung Eun Kim, et al. Emerg Med J published online August 21, 2014
doi: 10.1136/emermed-2014-203932
Updated information and services can be found at: http://emj.bmj.com/content/early/2014/08/21/emermed-2014-203932.full.html
These include:
Data Supplement
"Abstract in Korean" http://emj.bmj.com/content/suppl/2014/08/20/emermed-2014-203932.DC1.html
References
This article cites 14 articles, 3 of which can be accessed free at: http://emj.bmj.com/content/early/2014/08/21/emermed-2014-203932.full.html#ref-list-1
P
EMJ Online First, published on August 21, 2014 as 10.1136/emermed-2014-203932 Original article
One-handed chest compression technique for paediatric cardiopulmonary resuscitation: dominant versus non-dominant hand Je Hyeok Oh, Chan Woong Kim, Sung Eun Kim, Dong Hoon Lee, Sang Jin Lee Department of Emergency Medicine, College of Medicine, Chung-Ang University, Seoul, Republic of Korea Correspondence to Professor Chan Woong Kim, Department of Emergency Medicine, Chung-Ang University, College of Medicine, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756, Republic of Korea; [email protected] Received 21 April 2014 Revised 18 July 2014 Accepted 31 July 2014
ABSTRACT Background Pediatric resuscitation guidelines do not specify which hand to use for one-handed cardiopulmonary resuscitation (CPR). Objective To determine whether there is a difference in the quality of one-handed chest compressions (OHCCs) using the dominant versus non-dominant hand in simulated paediatric CPR. Materials and methods 41 doctors took part in the study. Chest compressions were alternately performed with the dominant (test 1) and non-dominant hand (test 2) in a random order at 30 min intervals. Experiments were carried out with a 5-year-old paediatric manikin without ventilation for 2 min. Data on average compression rate ( per min) and average compression depth (mm) were collected and compared. Results No significant differences were found in the average compression rate (118.0±14.3/min vs 117.3±14.5/ min, p=0.610) and average compression depth (41.3 ±5.6mm vs 41.9±4.1mm, p=0.327) between tests 1 and 2. Conclusions No significant difference was found in the quality of OHCCs using the dominant and non-dominant hand in simulated paediatric CPR. The study suggests there is no need for paediatric resuscitation guidelines to state a preferred hand for performing OHCC.
What is already known on this subject ▸ The 2010 European Resuscitation Council Guidelines recommend either two-handed chest compression or one-handed chest compression (OHCC) in cardiopulmonary resuscitation (CPR) for children over 1 year of age. Previous studies have provided contradictory evidence as to whether it is better to use the dominant or non-dominant hand for OHCC. What this study adds ▸ In this randomised crossover trial, no significant difference was found in the quality of OHCC using the dominant versus non-dominant hand in a 2 min simulated paediatric CPR. Therefore it seems unnecessary for the paediatric resuscitation guidelines to state a preferred hand for performing OHCC.
A randomised crossover trial was carried out, with chest compressions performed using the dominant (test 1) and non-dominant hand (test 2).
significant difference in compression depth between the two tests was set at 5 mm7 and the SD of compression depth was determined to be 5.8 mm,8 and a standardised difference was then calculated. The minimum sample size required was 10 for a two-tailed paired Student’s t test with a significance level of 0.05 and statistical power of 0.80. Forty-one doctors took part in the study. All participants enrolled voluntarily during regular CPR education at our institute. The CPR instruction lasted for 3 h and was provided by an instructor using video to guide practice. The participants in our study were limited to doctors who had successfully completed the basic life support course for healthcare providers proposed by the American Heart Association. All participants gave their informed consent. All experiments were carried out immediately after the CPR instruction. In this experiment, we used a 5-year-old Resusci Junior Basic and SkillGuide paediatric manikin (Laerdal Medical, Stavanger, Norway). Performance test data on chest compression, including average compression rate ( per min) and average compression depth (mm), were collected using the CPRmeter (Laerdal Medical) and the software Q-CPR Review V.3.1 (Laerdal Medical). This experiment was conducted in the simulation centre of a single medical school.
Study subjects
Study protocol
The study sample size was calculated using G*Power 3.1.6 In light of a previous study, the
This study was approved by the institutional review board of our university (C2014043). In test 1,
INTRODUCTION The 2010 International Consensus on Cardiopulmonary Resuscitation (CPR) states that chest compression can be conducted on children using one-handed chest compression (OHCC) or two-handed chest compression (THCC) techniques.1 A few studies have compared the two techniques, but no studies have determined which hand to use in OHCC.2–4 The 2010 European Resuscitation Council Guidelines provide a detailed description of the two techniques,5 but for OHCC do not state which hand should be used. Therefore, this study aimed at determining whether there is a significant difference in the quality of OHCCs using the dominant and nondominant hand in simulated paediatric CPR.
MATERIALS AND METHODS Study design To cite: Oh JH, Kim CW, Kim SE, et al. Emerg Med J Published Online First: [please include Day Month Year] doi:10.1136/emermed2014-203932
Key messages
Oh JH, etemployer) al. Emerg Med 2014. J 2014;0:1–3. doi:10.1136/emermed-2014-203932 Copyright Article author (or their Produced by BMJ Publishing Group Ltd under licence.
1
Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
Original article chest compression was conducted continuously using the dominant hand for 2 min and in test 2 it was conducted similarly using the non-dominant hand. The order of the two tests was randomised using a random number sequence produced by a web-based computer programme.9 The 30 min washout period between the tests was planned to relieve the participants’ fatigue. To evaluate the effect of handedness alone, chest compression was conducted without ventilation. The manikin was placed in the supine position on a hard floor without any mattress. In accordance with the 2010 European Resuscitation Council Guidelines,5 OHCC was conducted at a velocity of ≥100 compressions/min (but not exceeding 120 compressions/ min) to at least one-third of the depth of the chest, but the hand which was not being used could be placed in any position as no instruction was given in the guidelines. To prevent participants from receiving feedback, the CPR meter display was hidden and audiovisual feedback was not provided. At the completion of each experiment, the degree of difficulty in THCC conducted on an adult was assumed to be 5 points and the degree of difficulty in OHCC was estimated on a 10-point visual analogue scale (VAS).
Statistical analysis All statistical analyses were performed using IBM SPSS V.20 (IBM, Armonk, New York, USA). Data were analysed using a Shapiro–Wilk test to verify the normal distribution. For normal distribution, a paired t test was used and otherwise, a Wilcoxon signed-rank test was used. Data on average compression rate, average compression depth and VAS were analysed. Comparisons of average compression rate and average compression depth values between tests 1 and 2 were made. Data are presented as mean±SD. A p value of 5 (the assumed degree of difficulty in THCC in adults) in both tests 1 and 2, which suggests that all participants were unfamiliar with OHCC. Since there are insufficient data on effective OHCC techniques, participants might have not received standardised OHCC skills during their basic life support course. Second, the effectiveness of OHCC might have been affected by confounding factors in the rescuers—for example, the position of the hand not used to perform chest compression, the posture of the rescuers and their arms, need for arm straightening and the strength of the dominant arm. Our research has a number of implications. First, paediatric resuscitation guidelines do not have to change to state a preferred hand for performing OHCCs. Second, future strategies for paediatric CPR by a single rescuer might incorporate a switch of hands every 2 min to reduce the effects of fatigue and extend the period of chest compressions. Further investigation is needed to prove the effectiveness of these strategies. Finally, we conclude that hand dominance did not significantly influence the quality of OHCC. However, further studies on factors significantly influencing the effectiveness of OHCC are needed to establish a standardised OHCC technique. Oh JH, et al. Emerg Med J 2014;0:1–3. doi:10.1136/emermed-2014-203932
Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
Original article This study has some limitations. First, since a manikin was used, it might be difficult to apply the results to clinical practice. Second, the guidelines do not include a detailed description of possible confounding factors, such as the position of the hand which does not perform chest compressions and the posture of the rescuers. Third, if chest compression is conducted at a compression/ventilation ratio of 30:2 or 15:2, it may result in hand-off time. Although the hand-off time might affect rescuers’ fatigue, we conducted chest compression without ventilation because we could not adjust this factor. Therefore, in clinical practice different results might be obtained when CPR is performed at a compression/ventilation ratio of 30:2 or 15:2. Fourth, all the participants in our study were doctors and the results might be different if the rescuer were a layperson. Additionally, the small number of female participants might have influenced the results. Fifth, chest compressions were performed on the floor rather than on a high adjusted hospital bed and therefore our results cannot be applied to patients lying on a bed. Sixth, the small number of left-handed participants might have affected the results. Seventh, our study used 2 min chest compression and thus the results cannot be applied to the situation where a single rescuer performs OHCC for a long time.
Provenance and peer review Not commissioned; externally peer reviewed.
REFERENCE 1
2 3
4
5
6
7
8
CONCLUSIONS No significant difference was found in the quality of OHCCs using the dominant and non-dominant hand in simulated paediatric CPR. Therefore, no change is needed in the paediatric resuscitation guidelines to state a preferred hand for performing OHCC. Acknowledgements We thank the healthcare providers for their participation in this study. Contributors JHO: conception and design of the study; analysis and interpretation of data. CWK, SEK, SJL, DHL: acquisition of data. JHO, CWK, SEK: drafting of the article or revising it critically for important intellectual content. CWK: final approval of the version submitted. Competing interests None. Ethics approval Institutional review board of the College of Medicine, Chung-Ang University (C2014043).
Oh JH, et al. Emerg Med J 2014;0:1–3. doi:10.1136/emermed-2014-203932
9 10 11
12
13
14 15
de Caen AR, Kleinman ME, Chameides L, et al. Part 10: paediatric basic and advanced life support: 2010 International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations. Resuscitation 2010;81(Suppl 1):e213–59. Stevenson AG, McGowan J, Evans AL, et al. CPR for children: one hand or two? Resuscitation 2005;64:205–8. Peska E, Kelly AM, Kerr D, et al. One-handed versus two-handed chest compressions in paediatric cardio-pulmonary resuscitation. Resuscitation 2006;71:65–9. Udassi JP, Udassi S, Theriaque DW, et al. Effect of alternative chest compression techniques in infant and child on rescuer performance. Pediatr Crit Care Med 2009;10:328–33. Biarent D, Bingham R, Eich C, et al. European Resuscitation Council Guidelines for Resuscitation 2010 Section 6. Paediatric life support. Resuscitation 2010;81:1364–88. Faul F, Erdfelder E, Buchner A, et al. Statistical power analyses using G*Power 3.1: tests for correlation and regressi0n analyses. Behav Res Methods 2009;41:1149–60. Oh JH, Lee SJ, Kim SE, et al. Effects of audio tone guidance on performance of CPR in simulated cardiac arrest with an advanced airway. Resuscitation 2008;79:273–7. Oh JH, Kim CW, Kim SE, et al. Comparison of chest compressions in the standing position beside a bed at knee level and the kneeling position: a non-randomised, single-blind, cross-over trial. Emerg Med J 2014;31:533–5. http://www.random.org/ (accessed Jan 2014). Kundra P, Dey S, Ravishankar M. Role of dominant hand position during external cardiac compression. Br J Anaesth 2000;84:491–3. Nikandish R, Shahbazi S, Golabi S, et al. Role of dominant versus non-dominant hand position during uninterrupted chest compression CPR by novice rescuers: a randomized double-blind crossover study. Resuscitation 2008;76:256–60. Ozcan A, Tulum Z, Pinar L, et al. Comparison of pressure pain threshold, grip strength, dexterity and touch pressure of dominant and non-dominant hands within and between right-and left-handed subjects. J Korean Med Sci 2004;19:874–8. Murray MP, Gore DR, Gardner GM, et al. Shoulder motion and muscle strength of normal men and women in two age groups. Clin Orthop Relat Res 1985;192:268–73. Ellenbecker TS. A total arm strength isokinetic profile of highly skilled tennis players. Isokinet Exerc Sci 1991;1:9–21. Brown LP, Niehues SL, Harrah A, et al. Upper extremity range of motion and isokinetic strength of the internal and external shoulder rotators in major league baseball players. Am J Sports Med 1988;16:577–85.
3
Downloaded from emj.bmj.com on October 11, 2014 - Published by group.bmj.com
One-handed chest compression technique for paediatric cardiopulmonary resuscitation: dominant versus non-dominant hand Je Hyeok Oh, Chan Woong Kim, Sung Eun Kim, et al. Emerg Med J published online August 21, 2014
doi: 10.1136/emermed-2014-203932
Updated information and services can be found at: http://emj.bmj.com/content/early/2014/08/21/emermed-2014-203932.full.html
These include:
Data Supplement
"Abstract in Korean" http://emj.bmj.com/content/suppl/2014/08/20/emermed-2014-203932.DC1.html
References
This article cites 14 articles, 3 of which can be accessed free at: http://emj.bmj.com/content/early/2014/08/21/emermed-2014-203932.full.html#ref-list-1
P
