a b s t r a c t

Objective: There are no specific guidelines regarding the exact hand placement location for effective chest com- pressions. This study was designed to identify the optimal hand placement site over the chest during cardiopul- monary resuscitation (CPR).

Methods: The sternal length (SL) of young Korean adults was measured as the distance from the suprasternal notch to the lower end of the sternum. In addition, the heel width of the hand (H) was measured 1 cm (H1) and 2 cm (H2) distal to the proximal end of the carpal bones.

Results: A total of 300 men and 300 women were enrolled. SL positively correlated with height (R²=14.2), weight (R²=15.3), BMI (R²=10.3), H1 (R² =3.4), and H2 (R² = 5.0). Mean H2 and half of the SL (SL/2) for the subgroups were M 8.4 and 10.1 cm, M? 8.3 and 9.7 cm, W 7.6 and 10.1 cm, and W? 7.4 and 9.5 cm, respectively (M, men taller than the mean; M?, men shorter than the mean; W, women taller than the mean; W?, women shorter than the mean). Mean H2 in men was 1.1 to 1.6 cm shorter than SL/2, whereas mean H2 in women was 2.2 to 2.9 cm shorter than SL/2.

Conclusions: To find the most optimal chest compression point, from the patients’ left side, CPR providers need to palpate the SN using the right little finger and placing the left heel one heel width (H2) from the SN. From the patient’s right side, CPR providers should use the left little finger to palpate the SN and place the right heel one heel width (H2) from the SN.

(C) 2015

1. Introduction

Chest compressions during cardiopulmonary resuscitation (CPR) in- crease the internal pressure in the thoracic cavity and provide circulation by direct pressure on the chest. In 2000, the European Resuscitation Coun- cil published guidelines recommending identification of proper hand placement by placing the middle finger on the point where the ribs join the sternum and then placing the index finger on the sternum [1]. In 2005, the American Heart Association (AHA) published its CPR guidelines suggesting that chest compressions should be performed by placing the heel of the hand over the middle of the sternum along the internipple line (INL) [2]. In 2010, the AHA made a slight change in its recommenda-

? Informed consent was obtained for experimentation with human subjects.

?? Conflict of interest: None.

? There was no role of the funding sources.

?? Author contribution: Kim HJ developed the study concept and design; Kim HJ ac-

quired the data; Choi H and Kim HJ analyzed and interpreted the data; Choi H and Kim HJ drafted the manuscript; Kim HJ, Lee C, and Singer A critically reviewed the manuscript.

* Corresponding author at: Department of Emergency Medicine, Bucheon Hospital of Soonchunhyang University, 170 jomaru-ro, Wonmi-gu, Bucheon City, Gyenggi-do, 420- 767, South Korea.

E-mail address: [email protected] (H.J. Kim).

tions indicating that one should perform chest compressions over the cen- ter of the chest (CoC) by pushing hard on the lower part of the sternum [3]. However, Lee et al [4] found that people without proper training had a hard time finding the CoC during chest compressions. A study done by Oh et al [5] also found that chest compressions over the INL were safer than chest compressions over the CoC. In addition, a survey of Korean emergency rescue members found that they do not precisely push on the lower part of the sternum [6].

Few studies have actually measured the length of the sternum (SL) and the width of the heel of the hand (H) in an effort to identify the most appropriate site for chest compressions. Shin et al [7] who assessed whether the INL was the correct hand position for effective chest com- pression in adult CPR measured the SL using computed tomographic im- aging. Kusunoki et al [8] assessed the safety of the INL hand position landmark for chest compression by calculating the ratio between the length of the heel of the hand and the distance from the xiphisternal junction to the INL. However, there are few studies that have specifically measured both SL and H, although one would expect that there would be variability in the location of chest compressions depending on differ- ences in extrathoracic anatomy and heel widths. Therefore, we previ- ously designed a study to identify the most appropriate location for hand placement during chest compressions by objectively defining

http://dx.doi.org/10.1016/j.ajem.2015.11.008

0735-6757/(C) 2015

Fig. 1. (Copyright (C) 2014 by Korean Society of Emergency Medicine All Right Reserved) Measuring the SL with a measuring tape. This length was defined as the distance from the sternal notch to the lower end of the sternum based on palpation with the finger [9].

and measuring SL and H and measuring the difference between the H and half the SL [9]. In the current study, we expanded the number of subjects following the same protocol from the previous study in order to verify the optimal point of compression and establish the simplest guideline by analyzing physical characteristics of young Korean adults [9].

1. Methods
   1. Study design and subjects

We conducted a prospective observational study of hospital staff and students attending a CPR class ages 20 to 40 years. All subjects gave in- formed consent, and the study was approved by the institutional review board.

Study interventions

The height and weight of the study subjects were collected by verbal report, and body mass indices (BMIs) were calculated from these data. Sternal length was measured with a measuring tape from the lowest end of the sternum to the suprasternal notch (SN) (Fig. 1). The lowest end of sternum was defined as the junction between the lower margin of ribs and the sternum. To better define the heel of the hand, ink was placed on the hands of 1 male and 1 female subject, and an impression of their hands was made by “stamping” their hands onto a white piece of paper. We defined the heel of the hand as the darkest point of the print from the reference point, which was the lower or distal end of the carpal bones. Because the defined area was 1 to 2 cm from the

reference point, we measured the width of the heel of the hand 1 cm (H1) and 2 cm (H2) distal to the reference point (Fig. 2). One emergency medicine resident measured SL and H of all male subjects, whereas 1 certified paramedic measured SL and H of all female subjects. Study sub- jects were instructed to wear thin uniforms to allow accurate measure- ment of SL. The width of the distal interphalangeal joint of the study subjects’ index finger was also measured to use it as a quick length ref- erence for urgent situations. The primary outcome was the difference between H (both H1 and H2) and half the SL.

Data analysis

SPSS for Windows version 18.0 (IBM SPSS, Inc, Chicago, IL) was used for data analysis, and the general characteristics of the study subjects were described using means and SDs. sex differences were analyzed with the nonparametric Mann-Whitney U test. Pearson correlation co- efficients were used to determine the correlation between SL and other variables and between SL and H. P b .05 was considered statis- tically significant.

1. Results
   1. General study subjeCT characteristics

There were 600 participants in total, including 300 men and 300 women. The mean age of male subjects was 26 years. Mean height, weight, BMI, and SL of male subjects were 173.7 cm, 72.7 kg, 24.5 kg/ m², and 19.7 cm, respectively. The mean age of female subjects was 25 years. Mean height, weight, BMI, and SL of female subjects were 162.3 cm, 52.8 kg, 18.9 kg/m², and 19.2 cm, respectively (Table 1). Mean values for H1 and H2 of male subjects were 7.44 and 8.29 cm, respec- tively. Mean values for H1 and H2 of female subjects were 6.45 and

7.29 cm (Table 1). There were no significant differences between sexes (P N .05), except for mean height and weight (P b .05) (Table 1). In particular, mean measurements of SL were 19.7 +- 1.9 cm in men and 19.2 +- 1.9 cm in women, which were not significantly different (P = .280) (Table 1).

Correlation between SL/2 and height, weight, and BMI

Analysis of the correlation between half of the SL and all other vari- ables (height, weight, and BMI) showed positive correlation with all of the three variables. R² values from highest to lowest were weight (R²=15.3), height (R²=14.2), and BMI (R²=10.3) (Fig. 3).

Correlation between SL and H

Analysis of the relationship between SL and H (H1 and H2) demon- strated a weakly positive correlation. The R² value for H2 (5.0) was higher than that for H1 (3.4) (Table 2).

Fig. 2. (Copyright (C) 2014 by Korean Society of Emergency Medicine All Right Reserved) The heel of the hand was covered with ink and the hand was “stamped” onto a piece of white paper to measure the length of the heel at 2 points (H1 and H2). The darkest portion of the imprint of the heel of the hand was defined as H1 and H2 [9].

Table 1

General characteristics of study participants

Table 2

Association of heel length with SL

r

Male (n = 300)		Female (n = 300)	P			P		R2
Age, y	26 +- 5.1	25 +- 4.2	.422	H1		0.184	.009	3.4
Weight, kg	72.7 +- 8.8	52.8 +- 5.1	.000	H2		0.200	.004	5.0

H1, width of the heel of the hand 1 cm distal to the proximal end of the carpal bones; H2, width of the heel of the hand 2 cm distal to the proximal end of the carpal bones.

Height, cm	173.7 +- 4.2	162.3 +- 4.0	.000
BMI, kg/m2	24.5 +- 2.9	18.9 +- 2.2	.254
SL, cm	19.7 +- 1.9	19.2 +- 1.9	.280
H1,a cm	7.44 +- 0.3	6.45 +- 0.5	.083
H2,b cm	8.29 +- 0.6	7.29 +- 0.4	.097
Second finger DIP width	1.8 +- 0.4	1.6 +- 0.4	.201

Abbreviation: DIP, distal interphalangeal joint.

^a Width of the heel of the hand 1 cm distal to the proximal end of the carpal bones.

^b Width of the heel of the hand 2 cm distal to the proximall end of the carpal bones.

Fig. 3. Correlation between half of sternal length and variables (height, weight, and BMI;

R² value: BMI, 10.3; height, 14.2; weight, 15.3).

Comparison of H2 and SL/2 based on sex and mean height

Study participants were divided into 4 groups based on sex and height, and groups were compared to each other (Table 3). Mean values for SL/2 and H2 were compared (Table 3). H2 and SL/2 in group M (men taller than the mean) were 8.4 and 10.1 cm, respectively. H2 and SL/2 in group M? (men shorter than the mean) were 8.3 and 9.7 cm, respective- ly. H2 and SL/2 in group W (women taller than the mean) were 7.6 and

10.1 cm, respectively. H2 and SL/2 in group W? (women shorter than the mean) were 7.4 and 9.5 cm, respectively.

Mean difference between H2 and SL/2 based on sex and mean height

The mean differences between H2 and SL/2 were calculated (Table 4). The difference in length between H2 of group M and SL/2 of all other groups (M, M?, W, and W?) ranged from 1.1 to 1.6 cm. The difference in length between H2 of group M? and SL/2 of all other groups (M, M?, W, and W?) ranged from 1.1 to 1.6 cm. The difference in length between H2 of group W and SL/2 of all groups (M, M?, W, and W?) ranged from

2.2 to 2.5 cm. The difference in length between H2 of group W? and SL/ 2 of all groups (M, M?, W, and W?) ranged from 2.4 to 2.9 cm.

1. Discussion

Chest compressions on cardiac arrest patients can be performed by anybody including people without any medical background. Chest com- pression is considered to be the most important component of CPR be- cause coronary perfusion pressure drops substantially with any 4- to 5- second delay in chest compressions [10,11]. Studies suggest that maxi- mal force of compression can be achieved by placing the hypothenar part of the heel of the dominant hand in contact with the chest over the lower half of the sternum [12,13]. Therefore, when possible, right- handed providers should place the heel of their right hand in contact with the sternum when kneeling down at the right side of the adult pa- tient and left-handed providers should do the opposite. When not pos- sible, if the provider kneels on the right side of the patient, their right hand should be in contact with the sternum, and if they kneel on the left side, their left hand should be in contact. Furthermore, there are also studies regarding potential hemodynamic differences between the more cephalad compression point of female rescuers vs the more caudal compression point of male rescuers, which results from using this method of proper hand placement [14,15]. In addition, Rotenberg

Table 3

Comparison of H2 and SL/2 by group

	H2,a cm				SL/2,b cm
	Mean	SD	SE		Mean	SD	SE
M	8.4	0.588	0.065		10.1	1.856	0.292
M?	8.3	0.497	0.089		9.7	1.258	0.155
W	7.6	0.429	0.086		10.1	1.430	0.163
W?	7.4	0.393	0.069		9.5	1.181	0.122

M, men taller than the mean height; M?, men shorter than the mean height; W, women taller than the mean height; W?, women shorter than the mean height.

^a Width of heel 2 cm distal to the proximal end of the carpal bones.

^b Length of sternum/2.

Table 4

Mean difference in the length of the heel to SL/2

SL/2^b

cm

M

M’

W

W’

H2^a, cm

M	1.6	1.2	1.6	1.1
M’	1.6	1.2	1.5	1.1
W	2.5	2.2	2.4	2.2
W’	2.9	2.4	2.8	2.4

M, men taller than the mean height; M?, men shorter than the mean height; W, women taller than the mean height; W?, women shorter than the mean height.

^aWidth of heel 2 cm distal to the distal to the proximal end of the carpal bones.

^bLength of sternum/2.

[16] recently showed that there are potential hemodynamic differences in compression points.

However, there are few studies that have evaluated the optimal chest location for hand placement during compression by measuring SL [17-19]. Taking into consideration the results of these studies and data from our study, we developed a simple method of hand placement that could increase proper positioning by untrained providers and max- imize chest compression performance. In the current study, we greatly expanded the number of subjects from 200 to 600 compared with the previous study that also measured the SL of young Korean adults in their analysis of the placement of the chest compression site [9], which was too small to represent the general Korean population. As we found previously, H2 was more strongly correlated with SL than H1 [9]. In summary, most of the important results in the current study were similar to those in the previous study [9]. However, we were able to increase the reliability of the data with a larger sample size. In addition, the current study aimed at simplifying the guidelines for effec- tive chest compressions. Previously, the reference landmark for locating the lower half of the sternum was the xiphoid process (XP). However, based on the current study results, the reference point should be the SN because it is more objective and easier to find to locate the optimal site for chest compressions.

Generally, it is advised to place the heel of the hand over the lower portion of the sternum. However, the definition of the heel of the hand is ambiguous. Both the Korean Association of Cardiopulmonary Resuscitation and the AHA have indicated that the heel of the hand is the part of the hand between the lower portion of the palm and the upper portion of the wrist [20]. Baubin et al [12] reported that hypothenar part of heel should be placed to achieve maximal force dur- ing compression. We found that the heel of the hand was objectively de- fined by the “hand stamp method” that found the darkest point 2 cm distal to the lower end of the carpal bones (H2), which was more strongly correlated with SL than H1.

Shin et al [8] measured sternal length by computed tomographic im- aging and found statistically significant differences in sternal length be- tween Males and females. Interestingly, we found similar sternal length among males and females, and this is possibly due to the fact that the measurement reflects the curved shape of the chest. We also found that height, weight, and BMI are positively correlated with SL. In com- parison with the previous study [9], R² values of the 3 variables were all higher in the larger sample size, improving the reliability of the re- sults. In particular, weight showed the strongest correlation with SL. However, as we previously discussed [9], given that the R² values for weight and height were similar, height seems to be a more practical and useful predictor of SL than weight during actual chest compression because weight cannot be easily estimated in an emergency situation.

When subjects were divided into 4 groups (M, M?, W, and W?) based on sex and height, there was no significant difference in H2

between men and women. The groups of subjects (M and W) that were taller than the mean height had slightly longer (0.5 cm) ster- nums. In all groups (M, M?, W, and W?), the mean H2 was shorter than mean SL/2. In men, H2 was roughly 1.1 to 1.6 cm shorter than SL/2, whereas, in women, H2 was roughly 2.2 to 2.9 cm shorter than SL/2. The width of the distal interphalangeal joint of the index finger can be used as a quick reference for approximating a length of 1.5 to 2 cm (Table 1).

To deliver the most effective chest compressions, providers are rec- ommended to place the hypothenar part of their heel adequately above the XP [7,12,13]. In the previous study, we also recommended that the compression point for women rescuers is approximately one fingerbreadth above the point where men would place their hands be- cause the width of the heel of the hand in women is shorter than in men based on the previous study [9]. In either case, however, the com- pression point is over the lower half of the sternum adequately above the XP. However, rescuers without enough experience may not be able to correctly locate the lower half of the sternum correctly if instructed to compress the chest above the XP. On the other hand, be- cause SL/2 is slightly longer than H2, rescuers can rapidly estimate the midpoint of the sternum if they place their H2 based on the SN. After this step, we concluded that rescuers can reliably locate the lower half of the sternum. Therefore, the simplest guideline, regardless of CPR provider’s sex, is as follows: From the patients’ left side, CPR providers need to palpate the SN using the right little finger (LF) and place the heel of the left hand one heel width (H2) from the SN so that the heel is positioned at the CoC centered on the sternum. From the patient’s right side, CPR providers should use the left LF in palpation of the SN and then place the right heel one heel width (H2) from the SN.

Limitations

The following limitations should be considered while interpreting the results of the current study. First, the study subjects were relatively young adults and may not be representative of general patients who re- quire CPR. However, younger subjects, who have less variability in body shape, were also chosen in a prior study [9]. Future studies should be done on different age groups, such as older adults or young children. Second, reference points for measuring SL were identified by palpation, which could give inconsistent results. However, this method for identi- fying the sternum reflects actual practice in emergent situations, in which one needs to palpate the patient’s chest to identify the end of the sternum. Third, the heel of the hand was defined arbitrarily. Because there are no clear definitions in the AHA CPR guidelines, the current study assumed that the darkest portion of the hand stamp on a white piece of paper was the heel of hand. However, because the hand was stamped onto a flat paper rather than on one’s sternum, which is not flat, the defined area might not be accurate during actual chest com- pressions. Further study should be done on the ideal physical definition of the heel of the hand. Fourth, there may be hemodynamic changes de- pending on the exact location of hand placement during compression; however, the current study focused on establishing the easiest CPR guideline to follow in an emergent situation.

1. Conclusions

To achieve proper hand placement that maximizes the compression force that each rescuer is able to exert over the lower half of the ster- num, the rescuer should use the SN as a reference point and H2 as a ref- erence width of one heel. When kneeling next to the patients’ left side, CPR providers need to palpate the SN using the right LF and place the heel of the left hand one heel width from the SN so that the heel is po- sitioned at the CoC centered on the sternum. From the patient’s right side, CPR providers should use the left LF in palpation of the SN and then place the right heel one heel width from the SN.

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