Accepted Manuscript

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Regular article
Comparison of quality of chest compression in different postures using a female patientmanikin
Author names
Kaoru Kobayashi1*, Yuri Ishida1, Shota Ichikawa1, Hiroto Ito1, Asahi Kobayashi1,Yukinobu Hiiragi1

Affiliations and mailing addresses
1

Department of Physical Therapy, School of Health Sciences, International University

of Health and Welfare, 2600-1 Kitakanemaru, Otawara, Tochigi, 324-8501, Japan*Corresponding author: Kaoru Kobayashi; kkobayashi@iuhw.ac.jp

Number of figures and tables: 2 (1 figures, 1 table)
Running title: Quality of chest compressions for female patients

2Abstract
Early cardiopulmonary resuscitation (CPR) intervention is critical for saving
individuals experiencing sudden cardiac arrest. Manikins are considered useful for CPR
training, but their level of realism is low, given the visible structural differences in thechests of biological men and women. However, to our knowledge, no study has examined
whether a patient’s sex has an impact on the performance of chest compression. Therefore,
this study aimed to investigate the quality of chest compressions in female patients, inrelation to the rescuers’ posture. This single-center cross-sectional study was conductedfrom July to October 2023 on 34 healthcare professional university students. Two
postures for chest compression were analyzed: 1) kneeling beside the patient’s chest(conventional compression) and 2) straddling the patient (straddle compression). The
mean age of the 34 participants (18 men and 16 women) was 21.2±0.6 years. Significant
differences were found in mean compression depth (p = 0.005) and appropriatecompression ratio (p = 0.013) between the conventional and straddle compression but notin other parameters. In conclusion, the rescuers’ posture during chest compression infemale patients affects the compression depth and depth ratio. The straddle compression
may facilitate the provision of well-balanced compressions of appropriate depth anddepth ratio. These findings can be applied to CPR training and provide guidance for3administering chest compressions to female patients.
Keywords: Chest compression, Straddle compression, Manikin, Female patient, Silicone

4

女性患者マネキンを用いた胸骨圧迫の姿勢による質の比較
小林1薰 1＊、石田侑里 1、市川翔大 1、伊藤大翔 1、小林朝陽 1、柊 幸伸 1

国際医療福祉大学保健医療学部理学療法学科

要旨：突然の心停止に対して、早期の心肺蘇生介入が重要である。訓練用マネキンは教育上有用であると考えられているが、リアルさのレベルが低い。その理由には、生物学的な男女の胸部の人体構造の違いが挙げられる。しかし、我々の知る限り、患者の性別が胸骨圧迫の質に影響を与えるという推測を支持または反証する研究はない。そこで、本研究では女性患者マネキンに対する胸骨圧迫の質について、胸骨圧迫の姿勢に着目して検討した。本研究は単一施設横断研究であり、2023 年 7 月から 10 月にかけて 34 名の医療専門職大学生を対象に実施した。
胸部圧迫の姿勢として、1）患者の胸の横に膝をついた姿勢（従来圧迫法）、2）患者をまたいだ姿勢（またぎ圧迫法）の 2 つを分析した。対象者 34 名（男性 18名、女性 16 名）の平均年齢は 21.2±0.6 歳であった。平均圧迫深度（p = 0.005）および圧迫深度適正率（p = 0.013）において、従来圧迫法とまたぎ圧迫法の間に有意差が認められたが、その他のパラメーターには有意差は認められなかった。
またぎ圧迫法は、適正な圧迫深度と深度適正率のバランスのとれた圧迫を提供することを容易にする可能性がある。これらの知見は CPR トレーニングに応用でき、女性患者への胸骨圧迫のエビデンスとなり得ることが示唆された。

51Introduction

2Sudden cardiac death is a potentially fatal event that can occur at any time. Early high-3

quality cardiopulmonary resuscitation (CPR) intervention is critical for saving the lives

4of individuals experiencing sudden cardiac arrest. Chest compression-only CPR has been5

associated with increased survival and favorable neurological outcomes after out-of-

6

hospital cardiac arrest1). Therefore, in emergency situations, bystanders should promptly

7

perform chest compression as a first aid measure.

8

Traditionally, CPR training is performed with manikins2,3). However, although9manikins are considered useful for training because they are “realistic representations of

10

actual human patients”4), some argue that their level of realism is low, given the11differences in the anatomical structure of the chest between biological men and women.

12

In a study that used digital photographs of men's and women's chests to identify the13correct hand placement for chest compression, laypersons tended to identify areas farther

14

away from the recommended position they were instructed; further, the range of15

misplacement was found to be greater in the digital photographs of women5).

16

However, to our knowledge, no study has examined whether a patient’s sex has an

17

impact on the performance of chest compression. The only study that utilized a female

18

patient manikin reported that rescuers tend to place their hands improperly when6

19

performing chest compression on a female simulated patient, because they try to avoid

20

touching the nipples6). The change in hand placement when performing chest

21

compression on female patients may indicate that the rescuer is consciously or

22

unconsciously trying to avoid touching the female’s breasts as much as possible.

23

Therefore, in such cases, well-balanced chest compressions cannot be delivered, and the24hand placement and posture during chest compression in female patients should be25

reconsidered.

26

Chest compressions performed in the straddle posture (i.e., sitting on the pelvis of the27patient) have been found to be qualitatively equivalent to those performed in the28

conventional posture (i.e., kneeling beside the patient)7,8). Moreover, in the straddle chest

29

compression techniques (straddle compression), the hand placement is aligned with the30sternum during compression, thus allowing the first-aid provider to avoid touching the31breasts. However, since no previous study has focused on chest compression quality in

32female patients, this assumption is not corroborated by scientific data. Therefore, this33

study aimed to investigate the quality of chest compressions in female patients, in relation34

to the rescuers’ posture.

3536

Materials and methods

737

Study design38This study was a single-center cross-sectional study. Power analysis using the free39

software G*Power9) yielded a target sample size of 34, given an effect size of 0.5, α-error

40

of 0.05, and power of 0.8.

4142Participants

43

The study lasted from July to October 2023. Participants were recruited from among44

healthcare professional university students. The inclusion criteria were as follows: having

45

attended CPR training within the past 5 years and no current disease that would interfere

46

with measurements (e.g., orthopedic disorder of the upper limbs, neurological and cardiac

47

diseases, etc.). Participants whose chest compression depth was <5 cm and those who48

were unable to maintain a compression pace of 100–120 compressions per minute (cpm)49during the preliminary training were excluded. The study was approved by the Research

50

Ethics Committee of the International University of Health and Welfare (approval

51

number: 22-Io-16). Written informed consent was obtained after all the participants were52

fully informed of the research purpose. In all, 34 participants were included.

5354

Setting up of the simulated patients

855

We used two Resusci Anne QCPR manikins (manufactured by Laerdal): the first was56

used for training, with no modifications to the manikin body, and the second was used for57

final measurements, following modifications to represent a female patient (Fig. 1), with58

the addition of silicone breasts and a bra. As regards breast size, we took the C cup size

59

as a reference as it is fairly common among Japanese women10), and, considering the60

overall age, we went down one size and used a B cup size (difference between the female

61patient's bust and underbust was approximately 12 cm).

62

Two postures for chest compression were analyzed: the first was the conventional chest

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compression techniques (conventional compression) of kneeling beside the patient’s chest

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and the second was the straddle compression (straddling the patient). The experimental

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protocol began with a 30-s training session using the training manikin, in which

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participants performed chest compression with a depth of about 5 cm (no more than 667cm), compression pace of 100–120 cpm, and full chest recoil, followed by a 5-min

68

interval. The order in which chest compressions were performed in the two postures by

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the same participant was randomized.

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Parameter measurements and data were recorded using SimPad PLUS with

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SkillReporter (manufactured by Laerdal). Data on the following measures of chest

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compression quality were collected: mean compression depth (mm), appropriate

973

compression depth ratio (%), appropriate recoil ratio (%), mean compression tempo

74(cpm), and appropriate compression tempo ratio (%).

75

Fig. 1 Preparation of the female patient simulator (left: outerwear view; right: underwear76view)

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Statistical analysis

79

The Shapiro–Wilk test was performed to ensure the normality of data, followed by80

either a paired t-test or a Wilcoxon signed-rank test, with a significance level of 5%. All81

statistical analyses were performed using IBM SPSS Statistics 29.0 (IBM Corp., Armonk,82NY, USA).

83
84

Results

85

The mean age of the 34 participants (18 men and 16 women) was 21.2±0.6 years. Table86

1 shows each parameter based on the rescuers’ posture during chest compression. The87

mean compression depth was significantly higher in the straddle compression than in the88

conventional compression (p = 0.005). The appropriate compression depth ratio was89

significantly higher in the straddle compression than in the conventional compression (p90= 0.013). No significant differences were observed in other parameters between the10

91

conventional and straddle compression.

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Table 1. Comparison of each parameter of chest compression (n = 34)9394

Discussion

95

Several studies examining the quality of chest compressions in relation to rescuers' sex

96

and different postures have been conducted; however, none have been performed with97

female patients. Thus, male examinees were reported to show a more proper compression

98

depth and appropriate compression depth ratio in the conventional compression compared99

to female examinees11), while in another study the same parameters for the straddle

100

compression were reported to be adequate regardless of the examinees' sex12). However,101

the straddle compression study focused on chest compressions performed on a stretcher,102

not on the floor. Although simple comparison is difficult, it may be inferred from the103

above results that, because of more robust physical features such as weight and muscular104

strength, male examinees were able to provide higher chest compression quality

105

regardless of posture.

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In this study, all the parameters for chest compression in the female patient simulator

107

modified with silicone breasts and a bra were compared in relation to the rescuers’ posture.

108

The results showed that the mean compression depth was 49.0 mm for the conventional

11109compression and 52.5 mm for the straddle compression. As per the American Heart110

Association guidelines 202013), which recommends a compression depth of about 5 cm,

111

the above results indicate that, when performing chest compression on a female patient,112

the straddle compression may facilitate appropriate compression depth, closer to the113

recommended value. However, a study examining the relationship between chest

114

compression depth and survival to hospital discharge rates14) reported that the appropriate

115

compression depth ranges from 40.3 to 55.3 mm, with the optimal depth being 45.6 mm.

116

Considering our findings, it can be said that even in the conventional compression, the117

chest compression depth was not too shallow to affect the results negatively. On the other118

hand, the appropriate compression depth ratio between the conventional and straddle

119

compression showed a difference of 26.5 percentage points, possibly because of specific120

factors related to the rescuers’ posture during chest compression. In our study, silicone

121

breasts and a bra were added to the manikin’s body to mimic the anatomical structure of122

the female chest, giving the manikin substantial thickness and elasticity. When123

performing chest compression using the conventional compression, the rescuers placed

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their hands across the silicone breasts with the fingertips placed towards the nipples. This125

may have resulted in less-than-adequate adherence of the hands to the sternum, making

126

the delivery of well-balanced compressions difficult, as the deeper the compression is,12127the more the fingers come into contact with the breast. On the contrary, in the straddle

128

compression, the placement of hands between the silicone breasts (aligned with the129

sternum during compression) not only allowed the rescuer to avoid touching the breasts

130

but also facilitated appropriate compression depth and depth ratio. The results of the study131

support our hypothesis that the straddle compression allows rescuers to perform higher-

132

quality chest compressions than the conventional compression.

133

A limitation of this study is that it utilized a manikin, albeit one that mimicked the134

realistic anatomy of a female patient. Although the silicone breast form used in the study135

was representative of the breasts of adult women, it is not clear whether the size, shape,

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and sagging of breasts caused by aging affect the quality of chest compression. Women’s

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cup sizes can vary in different countries worldwide. Generally, they are larger in North

138

America and Europe but smaller in Asia than in the rest of the world. Therefore,

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considering cup size in the assessment of chest compression quality holds significance.

140

In view of these important limitations, caution should be exercised in generalizing these141

results. Moreover, although the straddle compression improved the quality of chest

142

compression, there are concerns that it may exert a compressive force on the patient’s

143

abdomen and that the act of straddling a person, even a patient who is experiencing

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cardiac arrest, may be socially unacceptable. For instance, a severely obese individual

13

145

may have difficulty in maintaining the correct posture during chest compression, and for146

a pregnant patient, the effect of straddling on the mother and fetus must also be considered.

147

Therefore, the effectiveness of the straddle compression for female patients should be

148further investigated so that a public consensus can be reached. It should also be noted that149

rescuer’s sex may also affect the quality of chest compression. However, since this study150

was not designed to examine sex differences, we were unable to determine sex differences151

in chest compression quality in relation to different postures.

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In conclusion, our findings suggest that the rescuers’ posture during chest compression

153

in female patients affects the compression depth and depth ratio. The straddle

154

compression may facilitate the provision of well-balanced compressions of appropriate

155

depth and depth ratio. The results of this study can be applied to the current field of CPR

156

training and provide guidance for administering chest compressions to female patients.

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160

Acknowledgments
This study was supported by the JSPS Grant-in-Aid 22K10660. We would like to thank
Editage (www.editage.jp) for English language editing.

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162

Conflicts of Interest14

163

The authors have no conflicts of interest to disclose.

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165

Contributions

166

KK and YH conceptualized the study design and protocol and selected the research167

institution. IS, IH, KA, and IY were responsible for data collection and organization. KK,

168

IS, IH, KA, and IY were responsible for data analysis and interpretation. KK and YH

169

were responsible for drafting the manuscript. The manuscript submitted was critically170

reviewed, revised, and approved by all the authors.

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172

Availability of data and materials

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Raw data were generated at International University of Health and Welfare. Derived

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data supporting the findings of this study are available from the corresponding author KK

175

on request.

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Kaoru Kobayashi / 1

Table 1. Comparison of each parameter of chest compression (n = 34)

Mean compression depth

ConventionalStraddle

p-value

49.0 (41.8–54.0)

52.5 (47.8–55.3)

0.005a)56.0 (8.0–95.8)

82.5 (26.0–100.0)

0.017a)99.5 (67.8–100.0)

98.0 (80.8–100.0)

0.622a)114.5 (111.8–119.0)

116.0 (111.8–118.3)

0.610a)93.0 (50.0–99.0)

90.0 (56.5–99.3)

0.302a)(mm)
Appropriate compression
depth ratio (%)
Appropriate recoil ratio(%)
Mean compression tempo(cpm)
Appropriate compression
tempo ratio (%)
The data are expressed as the median (25th–75th percentile)a)Wilcoxon signed-rank test

Kaoru Kobayashi / 1