Introduction The major components affecting high quality cardiopulmonary resuscitation (CPR) have been defined as the ability of the rescuer, hand position, position of the rescuer and victim, depth and rate of chest compressions, and fatigue. Until now, there have been no studies on dominant versus non-dominant hand position and the rescuer's side of approach. This study was designed to evaluate the effectiveness of hand position and approach side on the quality of CPR between right-handed (RH) and left-handed (LH) novice rescuers.
Material and methods 44 health science university students with no previous experience of basic life support (BLS) volunteered for the study. We divided volunteers into two groups by handedness. Adult BLS was performed on a manikin for 2 min in each session. The sequences were randomly performed on the manikin's left side of approach (Lap) with the rescuer's left hand in contact with the sternum (Lst), Lap/Rst, Rap/Lst and Rap/Rst.
Results We compared the quality of chest compressions between the RH and LH groups according to predetermined positions. A significant decrease in mean compression depth between the two groups was only observed when rescuers performed in the Rap/Lst scenario, regardless of hand dominance. The frequency of correct hand placement also significantly decreased in the Lap/Rst position for the LH group.
Conclusions The performance of novice rescuers during chest compressions is influenced by the position of the dominant hand and the rescuer's side of approach. In CPR training and real world situations, a novice rescuer, regardless of handedness, should consider hand positions for contacting the sternum identical to the side of approach after approaching from the nearest and most accessible side, for optimal CPR performance.
- Cardiopulmonary Resuscitation
- Chest Compression
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The 2010 European Resuscitation Council (ERC) and American Heart Association (AHA) cardiopulmonary resuscitation (CPR) guidelines have been optimised for high quality CPR.1 ,2 Early effective chest compression according to these guidelines is the most important factor that helps to restore spontaneous circulation and survival after cardiac arrest.1 ,2 The major components affecting the outcomes of CPR have been noted as the ability of the rescuers, the hand position of the rescuer, the position of the rescuer, the position of the victim, both the depth and rate of chest compressions, the degree of rescuer's fatigue and duty cycle.3 Some investigators have reported that among medical doctors, chest compressions are more effective when the dominant hand of the rescuer is in contact with the sternum.4 However, comparison of dominant and non-dominant hand effects between right-handed (RH) and left-handed (LH) novice rescuers has not been investigated.5
Previously, the 2005 International Liaison Committee on Resuscitation guidelines recommended that it is reasonable for the layperson and for healthcare professionals to be taught to position the heel of their dominant hand in the centre of the chest of an adult victim, with the non-dominant hand on top.6 However, the International Liaison Committee on Resuscitation, ERC and AHA guidelines do not define the relation of the dominant and non-dominant hand positions during chest compression.1 ,2 ,7 ,8 Furthermore, 66% of subjects preferred to approach from the right side of the patient. However, the rescuer's side of approach has been reported to have no impact on any aspect of CPR quality.9 Jones et al9 ,10 suggested that rescuers should approach from their nearest and most accessible side because this approach will limit hand-off time and allow for complete compressions to the best of the rescuer's ability.
To date, there have been no studies addressing the association between hand dominance position and the rescuer's side of approach. This manikin simulation study was designed to evaluate the effectiveness of dominant versus non-dominant hand position for a rescuer's side of approach on the quality of hand only CPR between RH and LH novice rescuers.
Materials and methods
The study protocol was reviewed and approved by the institutional review board of the study institution. Forty-four first year health science university students with no previous experience in basic life support (BLS) volunteered for the study. This study was explained to the participants, and written informed consent was obtained from all volunteers. All participants received CPR training in which adult BLS was taught according to the 8 h training course of the 2010 guidelines.
We divided volunteers into two groups (RH and LH, respectively). Single rescuer adult BLS was performed on the manikin for 2 min by all participants. Sequence selection for CPR performance was computer randomised. Skill assessment was performed according to the 2010 guidelines. A SkillReporter manikin (Laerdal Medical, Stavanger, Norway) was used for assessing CPR performance. Participants were directed to perform hand only CPR for 2 min in each session. The chest compression sequences were performed at random as follows: (1) on the manikin's left side with the rescuer's left hand in contact with the sternum (Lap/Lst); (2) on the manikin's left side with the rescuer's right hand in contact with the sternum (Lap/Rst); (3) on the manikin's right side with the rescuer's left hand in contact with the sternum (Rap/Lst); and (4) on the manikin's right side with the rescuer's right hand in contact with the sternum (Rap/Rst). During all CPR sessions, we ensured no feedback among participants. The volunteers had 30 min of rest between each session.
Data were recorded and evaluated for the rescuer's sex, age and specific characteristics. Compression rate and depth, total number of chest compressions and the percentage of compressions with correct hand placement were recorded with a SkillReporter manikin. Open questions were posed to all participants regarding hand position preference for contacting the sternum and rescuer position beside the victim.
Demographic and clinical data are presented as medians or proportions, as appropriate. The Kruskal–Wallis non-parametric one way analysis of variance was used for continuous variables in the case of non-normality. The χ2 test or Fisher's exact test was used to assess the associations between categorical variables. Statistical significance was set at p<0.05. We calculated the sample size required for a study involving four directions to detect a moderate difference (Cohen's effect size=0.25) at a 5% significance level with 80% power. Assuming a correlation (ρ) of 0.6 between each of the four directions, a sample size of 20 participants was sufficient (eg, 10 participants in the LH group and 10 participants in the RH group).11 The investigator recorded the total number of chest compressions, corrected hand placement (%), depth of chest compression (mm) and mean compression rate (compressions/min). A linear mixed model for a repeated measures covariance pattern model with unstructured covariance within participants was used. Two fixed effects were included: one addressing the between participant handedness effect (level: RH and LH) and one addressing the within participant direction effect (direction: Lap/Lst, Lap/Rst, Rap/Lst and Rap/Rst). Possible differences in handedness across directions were analysed according to handedness×direction interactions. The interaction between handedness and direction was tested at a significance level of 0.10. Hypothesis testing was two sided at a significance level of 0.05. All statistical analyses were performed using SAS V.9.2 (SAS Institute Inc, Cary, North Carolina, USA).
Characteristics of the participants
A total of 44 first year health science university students volunteered for the study. Only 10 volunteers were left handed. The recording data of the volunteers were divided into four scenarios (Rap/Rst, Rap/Lst, Lap/Rst and Lap/Lst) according to stacked hand position and rescuer's side of approach. There was no statistically significant difference in age between the RH and LH groups. Their demographic characteristics, including height, weight and body surface area, were not statistically significant (table 1). Four of the participants were ambidextrous, who were considered as RH at the time of the statistical analysis as they were more familiar with right hand usage. During testing, the number of compressions attempted was consistent with international recommendations.
Chest compression quality
A significant decrease was observed for mean chest compression rate (compressions/min) in the Rap/Lst scenario for the RH group (figure 1B). After we compared the quality of chest compressions between the RH and LH groups according to each method and position for chest compression, only the Rap/Lst group showed a significant decrease in mean compression depth between the two groups, regardless of hand dominance (figure 1A). The frequency of correct hand placement was significantly lower in the Lap/Rst scenario for the LH group (table 2, figure 1C). The preference for dominant hand position and position beside the victim was reported by open questions. These results indicate that RH novice rescuers preferred the Rap/Rst scenario (35.3%) and LH rescuers the Lap/Lst scenario (60.0%) (figure 2). Of the four ambidextrous participants, three preferred the Rap/Rst scenario and the other preferred the Rap/Lst scenario.
Handedness is an intriguing feature of human motor performance that is characterised by the tendency to favour one hand for skilled non-manual tasks.12 Handedness is often portrayed as a non-functional artefact of cerebral asymmetry. Recent studies have revealed that handedness reflects cerebral specialisation for specific control processes. During aimed movements, the dominant arm shows advantages for coordinating intersegmental dynamics, as required for specifying trajectory speed and direction, while the non-dominant arm shows advantages in controlling limb impedance, as required for accurate final position control. Each hemisphere/limb system is specialised for different but complementary functions.13 In terms of CPR for handedness, recent studies demonstrated that although there was an increased frequency of correct chest compressions with positioning the dominant hand in contact with the sternum, it did not reach statistical significance during uninterrupted chest compression CPR by novice rescuers for 5 min, and the side from which a rescuer approached a patient did not affect the quality of chest compressions.5 ,9 ,10 These findings have important implications for CPR performance. Nevertheless, the handedness and rescuer's side of approach should be considered simultaneously during CPR. To date, there have been no studies investigating handedness and the rescuer's side of approach simultaneously in relation to CPR performance by novice rescuers.
Well known to the public is the concept of the batter; a batter is a person whose turn it is to face the pitcher in baseball. There are differences for the home plate's side of approach—a RH batter box or LH batter box—and hand position for gripping the baseball bat. The differences in handedness can influence performance by changing the trajectory of the swing. Previous studies only compared chest compression quality during uninterrupted chest compression CPR after approaching from both their preferred and non-preferred sides without assessing the subject’s handedness and hand position in contact with the sternum.9 ,10 Compared with previous studies, our study has considered more stereoscopic and complex aspects than previous studies.
Our study also demonstrated that there are differences in compression depth and correct hand placement when considering the dominant hand in contact with the sternum and the rescuer's position beside the victim. Although a prospective study with a large number of patients treated by both novice and experienced rescuers is needed to investigate the mechanics and effectiveness of CPR distinguished by handedness and direction of approach, we postulate changes in visual–motor integration and angle for applied force direction by dominant hand position for contacting with the sternum and rescuer position beside the victim.
In real world CPR situations, resuscitation should be considered as a multifactorial approach, including judgments such as recognition, victim's status, performance errors, voice and visual instructions, and chest compressions. Stimulus saturation limits signal recognition during complex situations. This effect can lead to frustration, reduced performance and increased human error.14 In addition to this complex stimulus, chest compressions during CPR require fine and skilled coordination of the human body, where the hand which is in direct contact with the sternum is the main cause of the applied force.5 Nikandish et al assumed that the hand in contact with the sternum may be responsible for the magnitude of the applied force. The hand which is on the top of the other hand may be more responsible for the direction in which the force is applied during chest compressions.5
Our study revealed that RH novice rescuers preferred the Rap/Rst scenario and LH rescuers preferred the Lap/Lst scenario. In aimed movements by handedness, Wang et al13 showed that the dominant arm had advantages for coordinating trajectory speed and direction while the non-dominant arm showed advantages in controlling accurate final position. In contrast with expectations, compression depth significantly decreased in the Rap/Lst scenario for both RH and LH rescuers, regardless of hand dominance. Incorrect hand placement significantly increased in the Lap/Rst scenario for LH rescuers. Considering the direction for rescuer position beside a victim, novice rescuers during chest compressions may be influenced by visual–motor integration. Visual–motor integration is the ability of the eyes and hands to work together, which involves visual perception and eye–hand coordination.15 Previous studies showed that there are no significant differences in hand position and a rescuer's side of approach in experienced participants.
Although differences in CPR performance by hand position and rescuer's side of approach could be resolved by CPR training and experience, differences in CPR performance should be considered in CPR training and instructions given to a novice. Field et al found that a chest compression rate above 120/min reduces compression quality. They and the 2010 ERC guidelines recommended that a mean compression rate of 100–120 compressions/min for 2 min is feasible for maintaining adequate chest compression quality.2 ,16 ,17 In our study, the mean compression rate in the Lap/Lst scenario was relatively faster than in others. This may be a factor for the reduction of compression quality. However, the principles for approach from the patient’s nearest and most accessible side should be considered for reducing hands-off time in novice rescuers. Fortunately, our results indicate the Rap/Rst and Lap/Lst scenarios for both LH and RH novice rescuers. For optimal CPR performance, novice rescuers, regardless of handedness, can easily regulate hand position for contacting the sternum according to the side of approach after approaching from the nearest and most accessible side for optimal CPR performance. This may warrant greater consideration in CPR training and supplementation of new CPR guidelines.
There were some limitations in our present investigation. First, because we simulated a victim via a manikin, the data from our study cannot be directly extrapolated to a real world context. Second, each volunteer had different physical characteristics, and we used only one type of CPR manikin. However, there were no statistically significant differences between two groups for physical characteristics at baseline. Third, despite being CPR novices, assessment of baseline acquisition of CPR skills was not undertaken prior to the study. However, a recent study revealed that trainees over a 7 h training course demonstrated the best performance for acquisition of CPR in immediate tests after training. All subjects in the present study received CPR training according to the 8 h training course of the 2010 AHA, and participated in this study directly after completing the training course. Additionally, the study was conducted using compression only CPR without ventilation. Fourth, we also extrapolated only 2 min of CPR duration in each session. Thus fatigue was not an issue. However, more than 2 min of CPR increases the risk of improper technique. The protocol may minimise bias due to differences in age, sex and physical strength. Fifth, CPR performance mechanics may not be considered by measurement of angle and strength of applied force direction and changes in visual–motor integration by hand position for contact with the sternum and rescuer position beside the victim. Lastly, the number of LH participants was small, and ambidextrous participants were considered RH by subjective judgment.
For the future, a prospective study with a larger number of patients treated by novice and experienced rescuers is needed to investigate the mechanics and clinical effectiveness of CPR by handedness.
The performance of novice rescuers during chest compressions is influenced by the position of the dominant hand and the rescuer's side of approach. In CPR training and real world situations, novice rescuers, regardless of handedness, should consider hand position for contacting the sternum identical to the side of approach after approaching from the nearest and most accessible side for optimal CPR performance.
JSU and HK contributed equally to this study.
Contributors Guarantor of the integrity of the entire study: JSY, HK and SWK. Study concepts and design: JSY, HK, SWK and JSP. Literature research: JSY, HK, JSP, KMB, MSJ, HSL, SPC and SWK. Clinical studies: JSY, HK, JSP, KMB and MSJ. Experimental studies/data analysis: JSY, HK, HSL, SPC and SWK. Statistical analysis: JSY, HK, HSL and SWK. Manuscript preparation: JSY, HK and SWK. Manuscript editing: JSY, HK, JSP, KMB, MSJ, HSL, SPC and SWK.
Funding This work (NRF-2010-0009806) was supported by a National Research Foundation Korea grant funded by the MEST.
Competing interests None.
Ethics approval The study was approved by the institutional review board of Chungnam National University Hospital.
Provenance and peer review Not commissioned; externally peer reviewed.