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RESEARCH ARTICLE
Development of an automatic device
performing chest compression and external
defibrillation: An animal-based pilot study
Young-Il RohID, Woo Jin Jung, Hyeon Young Im, Yujin Lee, Dahye Im, Kyoung-
Chul ChaID*, Sung Oh Hwang ID*
Department of Emergency Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea
*chaemp@yonsei.ac.kr (KCC); shwang@yonsei.ac.kr (SOH)
Abstract
Background
Automatic chest compression devices (ACCDs) can promote high-quality cardiopulmonary
resuscitation (CPR) and are widely used worldwide. Early application of automated external
defibrillators (AEDs) along with high-quality CPR is crucial for favorable outcomes in
patients with cardiac arrest. Here, we developed an automated CPR (A-CPR) apparatus
that combines ACCD and AED and evaluated its performance in a pilot animal-based study.
Methods
Eleven pigs (n = 5, A-CPR group; n = 6, ACCD CPR and AED [conventional CPR (C-CPR)]
group) were enrolled in this study. After 2 min observation without any treatment following
ventricular fibrillation induction, CPR with a 30:2 compression/ventilation ratio was per-
formed for 6 min, mimicking basic life support (BLS). A-CPR or C-CPR was applied immedi-
ately after BLS, and resuscitation including chest compression and defibrillation, was
performed following a voice prompt from the A-CPR device or AED. Hemodynamic parame-
ters, including aortic pressure, right atrial pressure, coronary perfusion pressure, carotid
blood flow, and end-tidal carbon dioxide, were monitored during resuscitation. Time vari-
ables, including time to start rhythm analysis, time to charge, time to defibrillate, and time to
subsequent chest compression, were also measured.
Results
There were no differences in baseline characteristics, except for arterial carbon dioxide
pressure (39 in A-CPR vs. 33 in C-CPR, p = 0.034), between the two groups. There were no
differences in hemodynamic parameters between the groups. However, time to charge
(28.9 ±5.6 s, A-CPR group; 47.2 ±12.4 s, C-CPR group), time to defibrillate (29.1 ±7.2 s,
A-CPR group; 50.5 ±12.3 s, C-CPR group), and time to subsequent chest compression
(32.4 ±6.3 s, A-CPR group; 56.3 ±10.7 s, C-CPR group) were shorter in the A-CPR group
than in the C-CPR group (p = 0.015, 0.034 and 0.02 respectively).
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OPEN ACCESS
Citation: Roh Y-I, Jung WJ, Im HY, Lee Y, Im D,
Cha K-C, et al. (2023) Development of an automatic
device performing chest compression and external
defibrillation: An animal-based pilot study. PLoS
ONE 18(7): e0288688. https://doi.org/10.1371/
journal.pone.0288688
Editor: Luigi La Via, AOU Policlinico ’Rodolico -
San Marco’, ITALY
Received: March 16, 2023
Accepted: June 30, 2023
Published: July 26, 2023
Copyright: ©2023 Roh et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the paper.
Funding: This work was supported by the Korea
Medical Device Development Fund grant funded by
the Korea government (the Ministry of Science and
ICT, the Ministry of Trade, Industry and Energy, the
Ministry of Health & Welfare, the Ministry of Food
and Drug Safety) (Project Number: 1465032025;
1465032980;1465036172). There was no
additional external funding received for this study.
Conclusions
A-CPR can provide effective chest compressions and defibrillation, thereby shortening the
time required for defibrillation.
Introduction
Cardiopulmonary resuscitation (CPR) and defibrillation are important for survival of patients
with sudden cardiac arrest [1] and an effective, high-quality CPR increases the survival rate of
patients with cardiac arrest [2,3]. Although the rate of bystander CPR is gradually increasing,
the quality of CPR has been questioned. In many cases, CPR performed by ordinary individu-
als or even medical personnel may be insufficient [4,5]. Automatic chest compression devices
(ACCDs) can provide more uniform chest compression compared with manual chest com-
pression [6]. As chest compressions may generate aerosols from patients with cardiac arrest,
ACCDs are recommended for prolonged CPR during outbreaks of infectious disease, such as
coronavirus disease 2019 pandemic [7]. Accordingly, the application of ACCDs has expanded
significantly. The survival rate of patients with cardiac arrest due to ventricular fibrillation
(VF)/pulseless ventricular tachycardia (pVT) is inversely proportional to the time from VF/
pVT occurrence to defibrillation [8,9]. Electrical defibrillation is the only way to terminate
VF/pVT. The introduction of automated external defibrillators (AEDs) improves the survival
rate of patients with cardiac arrest due to VF by enabling early defibrillation [10,11]. Thus,
ACCDs and AEDs have become essential emergency care equipment. However, carrying two
equipment or treating patients with cardiac arrest may not always be feasible. In addition,
because each device operates separately, it may take time to perform a series of CPR proce-
dures. Integrating ACCD and AED can increase equipment mobility and application.
Recently, we developed an automated CPR (A-CPR) apparatus that combines ACCD and
AED. In this study, we evaluated the performance of the A-CPR in a pilot animal-based
experiment.
Methods
Device description
A-CPR consists of a functional part and a supporting frame (Fig 1). The functional part is
mounted on the supporting frame, which is composed of a compression-performing appara-
tus, an AED, and a control panel. The compression-performing apparatus is composed of a
piston and an actuator and is used to compress the chest. The piston is a round bar connected
to the actuator operated by a battery. The compression depth and rate of compression range
from 0 to 6 cm and 0 to 120 compressions per minute, respectively, and can be adjusted. An
AED is integrated with the compression-performing apparatus. The defibrillation electrodes
are stored in the designated pocket. The control panel controls chest compression and auto-
mated defibrillation. The operator can control the start or stop of chest compression, compres-
sion depth, compression rate, and shock delivery. The support frame consists of a backboard
and a supporting structure on which the compression-performing apparatus and AED are
mounted. The sequence of chest compression and defibrillation is based on the basic life sup-
port (BLS) algorithm and is installed into the A-CPR [3,12]. Once the A-CPR is initiated, it
first analyzes the rhythm. If a shockable rhythm is detected, the A-CPR starts chest compres-
sion and recommends performing defibrillation by pressing the shock button while continuing
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Competing interests: The authors have declared
that no competing interests exist.
chest compression. If a non-shockable rhythm is detected, the A-CPR immediately performs
mechanical chest compressions (Fig 2).
Pilot animal study
This study was designed to evaluate A-CPR performance and compare it with that of conven-
tional CPR (C-CPR) performed using an ACCD and an AED in a swine model of cardiac
arrest. This study was approved by the Institutional Animal Care and Use Committee of Yon-
sei University Wonju College of Medicine, Wonju, Republic of Korea (YWC-210517-1).
Animal preparation
Twelve Yorkshire pigs (weight, 35–43 kg; six females) were used in this study. The pigs were
allowed full access to water and food until the day before the experiment and were fasted from
midnight. After sedating the animals with intramuscular ketamine (15 mg/kg) and xylazine (2
mg/kg) followed by inhalation of 3% isoflurane, endotracheal intubation was performed with a
cuffed endotracheal tube. The animals were ventilated with oxygen and nitrous oxide via a vol-
ume-controlled ventilator (Draeger Fabius GS, Draeger Medical Inc., Telford, PA) with a tidal
volume of 10 mL/kg and a ventilation rate of 18 breaths/min adjusted to maintain normal arte-
rial oxygen saturation (94–98%) and end-tidal carbon dioxide (ETCO
2
) (35–45 mmHg).
Under aseptic conditions, the right femoral artery was cannulated, and aortic blood pressure
was continuously recorded using a 5-F micromanometer-tipped catheter. Right atrial pressure
was recorded using a 5-F micromanometer-tipped catheter inserted through the right external
Fig 1. Automated cardiopulmonary resuscitation apparatus.
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jugular vein. A vascular flowmeter (Transonic Systems, Inc., Ithaca, NY, USA) was placed on
the right internal carotid artery to monitor carotid blood flow (CBF). A 5-F pacing catheter
was introduced through the right internal jugular vein to induce VF. Once the catheters were
in place, a 1,000 unit intravenous (IV) heparin bolus was administered to prevent thrombosis,
and baseline arterial blood gas analyses were performed using a blood gas analyzer (i-STAT1,
Abbott Laboratories, Abbott Park, IL).
Study protocol
The pigs were randomized into two groups using randomization envelopes containing differ-
ent CPR methods (A-CPR or C-CPR group). An ACCD or A-CPR was positioned before the
experiment to minimize the risk of catheter or the monitoring apparatus dislodging. AED
(AED Plus
1
, Zoll, Chelmsford, Mass, USA) and pads were also applied before the start of the
experiment to reduce the bias from any delay in applying AED pads.
After the baseline data measurement, VF was induced by delivering an alternating electrical
current of 60 Hz to the endocardium, which was confirmed by the electrocardiogram (ECG)
waveform and a decrease in aortic pressure. After 2 minutes of untreated VF, basic BLS was
performed for 6 minutes to mimic a BLS situation in which a bystander recognizes cardiac
arrest and calls for help. Mechanical chest compressions with a depth of 5 cm using an ACCD
(LUCAS2, Stryker Medical, Kalamazoo, MI, USA) or A-CPR were performed at a rate of 100
chest compressions/min and a compression/ventilation ratio of 30:2 was maintained. Positive
pressure ventilation with a room air at a tidal volume of approximately 300 mL was delivered
using a resuscitator bag (Silicone resuscitator 87005133, Laerdal Medical, Stavanger, Norway).
Fig 2. Algorithm of an automated cardiopulmonary resuscitation sequence.
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After 6 min of BLS, defibrillation was performed according to the instructions (voice prompt)
from the AED for the C-CPR group and the A-CPR device for the A-CPR group. After defi-
brillation, chest compression administered continuously while single ventilation with 100%
oxygen were performed every 6 s, mimicking advanced life support (ALS) (Fig 3).
The experiment was terminated immediately after 2 min of ALS. Once a pig achieved
return of spontaneous circulation (ROSC), the animal was euthanized by IV potassium chlo-
ride injection.
Data measurements
Data were digitized using a digital recording system (PowerLab, AD Instruments, Colorado
Springs, CO, USA). Aortic and RAP, ETCO
2
, and CBF were continuously recorded. Coronary
perfusion pressure (CPP) was calculated as the difference between the aortic and right atrial
pressures in the end-diastolic phase. Outcome measures included chest compression fraction
(CCF), rate of successful defibrillation, and ROSC. Time variables, including time to start
rhythm analysis, time to charge, time to defibrillation, and time to subsequent chest compres-
sion, were measured.
Fig 3. Algorithms of automated cardiopulmonary resuscitation (CPR) and conventional CPR.
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Data analysis
Continuous variables are presented as mean ±standard deviation or medians and interquartile
ranges according to the normality of distribution. Student’s t-test or the Mann–Whitney U test
was used to compare the continuous variables between the A-CPR and C-CPR groups, as
appropriate. The nominal variables are reported as counts and percentages and were com-
pared using the chi-square or Fisher exact test, as appropriate. A linear mixed-model analysis
was used to compare hemodynamic parameters, including aortic systolic pressure, aortic dia-
stolic pressure, mean RAP, CBF, CPP, and ETCO
2
between the two groups. The statistical
results are presented as group-time interaction. Results with P <0.05 were considered statisti-
cally significant. Data were analyzed using the Statistical Package for the Social Sciences Statis-
tics version 23.0 for Windows (IBM Corp., Chicago, IL, USA).
Results
Baseline characteristics
Initially, six pigs were enrolled in each group; however, one in the A-CPR group was excluded
because of AED malfunction. Thus, five pigs in the A-CPR group and six pigs in the C-CPR
group were included in the final analysis. There were no significant differences, except PaCO
2
,
in baseline characteristics between the groups (Table 1).
Hemodynamic parameters during cardiopulmonary resuscitation
There were no significant differences between the groups in the group-time interaction analy-
ses of hemodynamic variables (Fig 4).
Table 1. Baseline characteristics.
A-CPR (n = 5) C-CPR (n = 6) P value
Weight (kg) 39 ±1.5 39 ±3.2 0.722
Female, n (%) 2 (40) 3 (50) 1.000
AoS (mmHg) 109 (103–121) 110 (95–121) 0.931
AoD (mmHg) 74 (70–80) 78 (59–86) 0.856
MAP (mmHg) 86 (85–101) 90 (71–97) 0.421
RAS (mmHg) 7.9 (5.3–8.5) 7.0 (5.8–9.1) 0.931
RAD (mmHg) 2 (0–3) 1 (-1–3) 0.841
CPP (mmHg) 81 (76–85) 88 (74–99) 0.269
CBF (mL/min) 191 (154–253) 263 (142–422) 0.383
ETCO
2
(mmHg) 47 (44–52) 45 (42–48) 0.257
pH 7.487 (7.433–7.541) 7.532 (7.522–7.545) 0.114
PaCO
2
(mmHg) 39 (35–40) 33 (31–36) 0.034
PaO
2
(mmHg) 120 (105–161) 145 (117–167) 0.539
HCO
3-
(mmol/L) 28 (27–31) 29 (26–32) 0.649
SaO
2
(%) 99 (98–100) 99 (99–100) 0.527
Lactate (mmol/L) 2.1 (1.0–2.9) 1.8 (1.2–2.6) 0.843
Variables are presented as medians (interquartile ranges) or frequencies (percentages).
A-CPR, automatic cardiopulmonary resuscitation; C-CPR, conventional cardiopulmonary resuscitation; AoS, aortic
systole; AoD, aortic diastole; RAS, right atrial systole; RAD, right atrial diastole; MAP, mean arterial pressure; CPP,
coronary perfusion pressure; ETCO
2
, end-tidal carbon dioxide; CBF, carotid blood flow; ROSC, return of
spontaneous circulation; PaCO
2
, arterial pressure of arterial carbon dioxide; PaO
2
, arterial pressure of arterial
oxygen; HCO
3-
, bicarbonate; SaO2, arterial oxygen saturation
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Outcomes
There was no significant difference in CCF between the groups (81.7 ±1.1%, A-CPR group;
81.1 ±1.4, C-CPR group; p = 0.418). There were no differences in ROSC and successful defi-
brillation because spontaneous circulation was restored in all animals after the first defibrilla-
tion and after 2 min of ALS.
Fig 4. Comparison of hemodynamic parameters during cardiopulmonary resuscitation.
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Comparison of time variables
Time to charge (28.9 ±5.6 s in the A-CPR group vs. 47.2 ±12.4 s in the C-CPR group), time to
defibrillation (29.1 ±7.2 s in the A-CPR group vs. 50.5 ±12.3 s in the C-CPR group), and time
to subsequent chest compression (32.4 ±6.3 s in the A-CPR group vs. 56.3 ±10.7 s in the
C-CPR group) were shorter in the A-CPR group than in the C-CPR group (p = 0.015, 0.034,
and 0.02, respectively) (Table 2).
Discussions
The A-CPR developed in this study demonstrated that it is feasible to integrate an AED with
an ACCD. Furthermore, we showed that A-CPR was more efficient to reduce the time to
charge, defibrillation and subsequent chest compression in an animal model of cardiac arrest
than that obtained using the two equipment individually.
In animals with VF, cessation of chest compressions for >15 s before defibrillation com-
promised CPR outcomes [13]. In clinical observations, the duration of the single longest pause
in chest compression is associated with unfavorable outcomes in patients with out-of-hospital
cardiac arrest (OHCA) [14]. When the pulse is assessed after defibrillation, subsequent chest
compression can be delayed by up to 29 s [15]. Accordingly, the CPR guidelines recommend
starting chest compression immediately after defibrillation and minimizing interruptions in
chest compressions during CPR [3,12]. However, pause in chest compressions before and
after electrical shock delivery in patients with cardiac arrest negatively impacts patient survival
rate [16]. Chest compressions are frequently interrupted during endotracheal intubation to
analyze the rhythm, charge the defibrillator, perform defibrillation, check the pulse, move the
patient, initiate CPR devices, shift compressors, and take over by healthcare providers [17–20].
Using a device that integrates an ACCD with an AED may reduce interruptions in chest com-
pressions. A-CPR is designed to resume chest compressions immediately after ECG analysis
and continuous chest compressions during defibrillation so that chest compressions are not
interrupted during CPR, except for the time required for the ECG analysis. In this pilot study,
when A-CPR was used, the time to defibrillation was shortened by approximately 11 s and the
time to subsequent chest compression was shortened by approximately 14 s compared to
when an AED and an ACCD were used separately. In patients with OHCA from VF, the likeli-
hood of ROSC increases when the pre-shock interval is <3 s and the post-shock interval
is <6 s [16]. Time to defibrillator charge was also shortened by 20 s with A-CPR compared to
that with C-CPR. Therefore, decreased interruptions in chest compression using A-CPR may
have a favorable effect on the outcome of cardiac arrest.
Table 2. Comparison of chest compression fraction and time variables between the groups.
A-CPR (n = 5) C-CPR (n = 6) P value
CCF (%) 81.7 ±1.1 81.1 ±1.4 0.418
Time to start rhythm analysis (s) 23.7 ±4.9 32.5 ±11.9 0.161
Time to charge 28.9 ±5.6 47.2 ±12.4 0.015
Time to defibrillation 29.1 ±7.2 50.0 ±12.3 0.034
Time to subsequent chest compression 32.4 ±6.3 56.3 ±10.7 0.002
Variables are presented as mean ±standard deviation.
A-CPR, automatic cardiopulmonary resuscitation; C-CPR, conventional cardiopulmonary resuscitation; CCF, chest
compression fraction
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Healthcare providers have to carry several equipment for resuscitation to the scene of car-
diac arrest, including AEDs and ACCDs, and perform several resuscitation steps including
intubation, ventilation, chest compressions, and defibrillation. A-CPR may increase proce-
dural efficiency and patient outcomes by integrating the functionalities of an ACCD and an
AED in a single device.
Transthoracic impedance is affected by shock waveforms, coupling devices, electrode size
and position, respiration, lung volume, and respiration phase [21]. High transthoracic imped-
ance necessitates multiple shocks and greater energy delivery for successful defibrillation [22].
Higher lung volume during inspiration may cause longer current paths, resulting in an
increase in transthoracic impedance [23]. Transthoracic impedance is 9% lower at the end of
expiration than at the end of inspiration [24]. Thus, delivering shock during inspiration signif-
icantly lowers the defibrillation success rate compared with delivering the shock during expira-
tion [25]. A-CPR delivers defibrillation energy without interrupting chest compressions and
delivers shock at the end of the compression phase. Lung volume is smaller during the com-
pression phase than that during the relaxation phase. Hence, shock delivery by A-CPR may
favorably influence defibrillation success.
Limitations
As the A-CPR used in this experiment was manufactured on the premise of its use in humans,
there were some limitations in its application to animals. This pilot study evaluated the in vivo
operation of A-CPR and compared the temporal benefit between the use of A-CPR and the
separate use of an AED and an ACCD in a small number of animals. Therefore, there were
limitations in comparing resuscitation outcomes between the two groups. To prevent the cath-
eter inserted into the experimental animal from dislodging, the experiment was conducted
with A-CPR or ACCD placed on the animal in advance. Hence, these results may not be
completely generalized to humans and may need further validation before this device can be
used in clinical settings.
Conclusions
An automatic CPR device developed in this study integrates the functions of mechanical chest
compressions and defibrillation to achieve significant hemodynamic outcomes. A-CPR can
provide continuous chest compressions during defibrillation, thereby shortening the time
required for defibrillation and improving treatment outcomes.
Supporting information
S1 Checklist. The ARRIVE guidelines 2.0: Author checklist.
(PDF)
Author Contributions
Conceptualization: Kyoung-Chul Cha, Sung Oh Hwang.
Data curation: Young-Il Roh, Woo Jin Jung, Hyeon Young Im, Yujin Lee, Dahye Im,
Kyoung-Chul Cha.
Funding acquisition: Sung Oh Hwang.
Investigation: Young-Il Roh, Woo Jin Jung, Hyeon Young Im, Yujin Lee, Dahye Im, Kyoung-
Chul Cha, Sung Oh Hwang.
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Resources: Woo Jin Jung, Hyeon Young Im, Yujin Lee, Dahye Im.
Supervision: Kyoung-Chul Cha, Sung Oh Hwang.
Writing – original draft: Young-Il Roh, Kyoung-Chul Cha, Sung Oh Hwang.
Writing – review & editing: Woo Jin Jung, Kyoung-Chul Cha, Sung Oh Hwang.
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PLOS ONE
Automated cardiopulmonary resuscitation apparatus
PLOS ONE | https://doi.org/10.1371/journal.pone.0288688 July 26, 2023 11 / 11
