Mechanical cardiopulmonary resuscitation in microgravity and hypergravity conditions: A manikin study during parabolic flight

Abstract

Introduction
Space travel is expected to grow in the near future, which could lead to a higher burden of sudden cardiac arrest (SCA) in astronauts. Current methods to perform cardiopulmonary resuscitation in microgravity perform below earth-based standards in terms of depth achieved and the ability to sustain chest compressions (CC). We hypothesised that an automated chest compression device (ACCD) delivers high-quality CC during simulated micro-and hypergravity conditions.

Methods
Data on CC depth, rate, release and position were collected continuously during a parabolic flight with alternating conditions of normogravity (1 G), hypergravity (1.8 G) and microgravity (0 G), performed on a training manikin fixed in place utilising an ACCD. Kruskal-Wallis and Mann-Withney U test were used for comparison purpose.

Results
Mechanical CC was performed continuously during the flight; no missed compressions or pauses were recorded. Mean depth of CC showed minimal but statistically significant variations in compression depth during the different phases of the parabolic flight (microgravity 49.9 ± 0.7, normogravity 49.9 ± 0.5 and hypergravity 50.1 ± 0.6 mm, p < 0.001).

Conclusion
The use of an ACCD allows continuous delivery of high-quality CC in micro- and hypergravity as experienced in parabolic flight. The decision to bring extra load for a high impact and low likelihood event should be based on specifics of its crew's mission and health status, and the establishment of standard operating procedures.

Full text

Mechanical cardiopulmonary resuscitation in microgravity
and hypergravity conditions: A manikin study during parabolic flight
Alessandro Forti
a
, Michiel Jan van Veelen
b
, Tommaso Squizzato
c
, Tomas Dal Cappello
b
,
Martin Palma
b
, Giacomo Strapazzon
b,
⁎
a
Anaesthesia and Intensive Care Surgery, AULS 3 Serenissima, Venice, Italy
b
Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
c
Department of Anesthesia and Intensive Care, IRCCS San Raffaele Scientific Institute, Milan, Italy
abstractarticle info
Article history:
Received 7 November 2 021
Received in revised form 5 December 2021
Accepted 19 December 2021
Available online xxxx
Introduction: Space travel is expected to grow in the near future, which could lead to a higher burden of sudden
cardiac arrest (SCA) in astronauts. Current methods to perform cardiopulmonary resuscitation in microgravity
perform below earth-based standards in terms of depth achieved and the ability to sustain chest compressions
(CC). We hypothesised that an automatedchest compression device (ACCD) delivers high-quality CC during sim-
ulated micro- and hypergravity conditions.
Methods: Data on CC depth,rate, release and position utilising an ACCDwere collected continuously during a par-
abolic flightwith alternating conditions of normogravity (1 G), hypergravity (1.8 G) and microgravity (0 G), per-
formed on a training manikin fixed in place. Kruskal-Wallis and Mann-WithneyUtest were used for comparison
purpose.
Results: Mechanical CC was performed continuously during the flight; no missed compressions or pauses were
recorded. Mean depth of CC showed minimal but statistically significant variations in compression depth during
the different phases of the parabolic flight (microgravity 49.9 ± 0.7, normogravity 49.9 ± 0.5 and hypergravity
50.1 ± 0.6 mm, p<0.001).
Conclusion: The use of an ACCD allows continuous delivery of high-quality CC in micro- and hypergravity as ex-
periencedin parabolic flight.The decision to bringextra load for a highimpact and low likelihood eventshould be
based on specifics of its crew's mission and health status, and the establishment of standard operating proce-
dures.
© 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords:
Resuscitation
Space
Mechanical devices
Microgravity
Hypergravity
Basic life support
Chest compression
1. Introduction
Growth in the space tourism sector and a shift toward long-duration
interplanetary missions to the Moon and Mars are expected in the near
future. These developments come with an increased risk of medical
emergencies to be managed in challenging logistical conditions, as lon-
ger missions with older and less healthy individuals may be expected
[1,2]. Space travel can affect the cardiovascular system during launch,
orbit entry and re-entry extravehicular activity, physical and autonomic
stress [1], as well as due to cardiovascular deconditioning in micrograv-
ity [3]. Radiation-induced cardiovascular disease can occur during long
duration space flight [4]. Although no astronaut has suffered a cardiac
arrest requiring cardiopulmonary resuscitation (CPR), there have been
several primary minor cardiac events that have self-resolved [5,6]as
well as near-drowning events due to technical failure in a spacesuit
that could have led to an asphyctic cardiac arrest [1]. Space tourism
could even bring people with cardiovascular risk factors in sub-orbital
and spaceflight, and the burden of emergencies (estimated as about
0.06 events per person-year in general population) and sudden cardiac
arrest (SCA) could increase [1,7].
Recent guidelines for CPRduring spaceflight advise approaching CPR
similarly to earth-based ones [8]. There are three main methods to per-
form chest compressions (CC) that can be used in microgravity: the
Handstand (HS), the Reverse Bear Hug (RBH), and the Evetts-
Russomano (ER) [9,10]. Guidelines suggest to start with the ER tech-
nique at the site of the emergency (as it allows transportation of the vic-
tim) and to shift to HS technique assoon as the victim is restrained and
the surface distance allows for its application [8]. However, all tested
methods perform below earth-based standards in terms of depth
achieved. Even in the most optimal situation where the HS technique
is used on a restrained patient, HS technique resulted in suboptimal
American Journal of Emergency Medicine 53 (2022) 54–58
⁎Corresponding author at: Institute of Mountain Emergency Medicine, Eurac Research,
Via Ipazia 2, 39100 Bolzano, Italy.
E-mail address: giacomo.strapazzon@eurac.edu (G. Strapazzon).
https://doi.org/10.1016/j.ajem.2021.12.056
0735-6757/© 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Contents lists available at ScienceDirect
American Journal of Emergency Medicine
journal homepage: www.elsevier.com/locate/ajem

compression depth (44.9 ± 3.3mm), where a compression depth of be-
tween 50 and 60 mm is advised in international guidelines [8-10]. Man-
ual chest compression quality deteriorates significantly within minutes
even in highly trained and fitrescuers[8,11].
Automated chest compression devices (ACCD) can guarantee high-
quality and uninterrupted CC. Although survival in a conventional pre-
hospital or clinical setting is similar to good quality manual CPR [12],
it seems likely that the performance gain in delivered CC by ACCD in
microgravity could be much higher than the alternative manual tech-
niques. The efficacy of using an ACCD in microgravity has never been
published, even if an abstract describing potential feasibility has been
reported [8]. In this study we investigated under repeatable conditions
the quality of mechanical CC (regarding compression depth, rate, pres-
sure point, and recoil) during all the phases of a parabolic flight (simu-
lating 1 G vs 1.8 G vs 0 G). We hypothesised that an ACCD delivershigh-
quality CC during all the phases of a parabolic flight.
Fig. 1. Panel A. Upper vision of LUCAS 3's floor attachment system: a) aircraft belts for LUCAS 3; b) aircraft belts for manikin; c) aeronautical belts for the head of the manikin; d) wired
LaerdalSimPad PLUS; e) LUCAS3; f) GoPro Hero5 Session camera; g) manikin; h) carabiners and connection tothe aircraft rails.Panel B. Front visionof LUCAS 3: a ) aircraft belts for LUCAS
3; b) aircraft belts for manikin; c) LUCAS 3 piston; d) wired Laerdal SimPad PLUS; e) watch for time-in-flightrecord; f) aircraft rails; g) carabiner and connection withthe pencil; h) data
sheet for in flight recording. Panel C. Test session during microgravity conditions.
A. Forti, M.J. van Veelen, T. Squizzato et al. American Journal of Emergency Medicine 53 (2022) 54–58
55

2. Methods
The study was performed during the 4th parabolic flight campaign
in Dübendorf, Zürich (Switzerland) with Skylab and the Swiss Aero-
space Agency on June 11, 2020. The review board of the flight campaign
approved the study protocol (protocol number VP-152).
2.1. Study setting
We employed the LUCAS 3 (Stryker, MI) ACCD and a training mani-
kin fitted with a standard compression spring (Laerdal Resusci Anne
QCPR, Stavanger, Norway) withthe capability to record the characteris-
tics of CC via a connected tablet (Laerdal SimPad PLUS, Stavanger,
Norway). The manikin was placed on the aircraft's floor and fixed
with certified aeronautical belts (Fig. 1). We positioned the ACCD on
the manikin, and after testing during the flight at 1 G, data were col-
lected during the parabolic flight.
2.2. Parabolic flight
The parabolic flight was carried out using a modified, two-engine
Airbus A310 type 304 “ZERO-G”aircraft specifically predisposed for
parabolic flights with a central experimental area where micro- and
hypergravity were experienced. During the steady flight, gravity expe-
rienced was 1 G (i.e. normogravity). During flight at 7,000 m, parab-
olas were initiated by gradual increase of the attitude to around 50°
from a steady horizontal flight. During this phase of approximately
20 s, the aircraft and crew experienced an acceleration of 1.8 G. The
aircraft then followed a free-fall trajectory forming a parabola lasting
approximately 20 s, during which there was a microgravity (0 G) pe-
riod. An exit phase at 1.8 G, symmetrical with the entry phase, was
performed on the descending part of the parabola to return the air-
craft to stabilised altitude level within about 20 s. Data were collected
during 16 hypergravity, 9 normogravity and 8 microgravity periods
(each of ~20 s).
2.3. Data collection
We collected data on quality of mechanical CC in term of compres-
sion rate, depth, release and position. Data were collected during the
chest compression with three different methods: a) the wired Laerdal
SimPad PLUS (Stavanger, Norway); b) the LUCAS 3 log files (Stryker,
MI); and c) the video recorded during all phases of the experiment by
GoPro Hero5 Session camera (Woodman Labs, Inc., CA) fixed as a
single-body with the ACDD-manikin system (Fig. 1). Specifically, video
data was analysed with custom software written in Phyton based on
the OpenCV 3.0 library. A region of interest channel and spatial reliabil-
ity tracker to track with high accuracy the movement of the LUCAS 3
piston was implemented to calculate compression rate and estimate
depth and release.
2.4. Statistical analysis
Kruskal-Wallis test was used to compare compression depth, re-
lease and rate during 0 G, 1 G and 1.8 G and Mann-Whitney Utest
was used for pairwise comparisons. The percentage of effective chest
compressions was analysed by means of Pearson's chi-squared test;
an effective chest compression was defined as a compression with a
depth of ≥50 mm at the correct position (mid-chest). P-values of
pairwise comparisons were adjusted by means of Holm-Bonferroni
correction. SPSS version 26 statistical software (IBM Corp., Armonk,
NY) was used. Tests were two-sided and p< 0.05 was considered
statistically significant. Values are reported as mean ± standard
deviation.
3. Results
Eight consecutive parabolas were done during a 26-min flight (see
video in the Supplementary Video 1). Each of the eight microgravity
phases of each parabola lasted from 22 to 26 s. Data from eight parab-
olas were analysed by LUCAS 3 log files and the video recorded; data
from the last four parabolas were analysed from the Laerdal SimPad
PLUS.
Mechanical chest compression was performed continuously during
the flight; the LUCAS 3 log file did not record any missed compression
or pause. No displacement or other technical problem of the device
were reported. Depth, release and rate during the last four parabolic
flights are shown in Fig. 2. There was a minimal but statistically signifi-
cant variation in compression depth during the different phases of the
parabolic flight (Table 1). Depth of CC in hypergravity conditions was
higher than in microgravity (50.1 ± 0.6 vs 49.9 ± 0.7, p= 0.047) and
normogravity conditions (50.1 ± 0.6 vs 49.9 ± 0.5,p< 0.001). CC re-
lease was lower in hypergravity than in normogravity (0.7 ± 0.6 vs
0.0 ± 0.1, p< 0.001) and microgravity conditions (0.7 ± 0.6 vs 0.2 ±
0.4, p< 0.001) (Table 1). The rate of CC recorded via the manikin during
the different phases of the flight remained stable (p= 0.939), similarly
to data fromthe LUCAS 3 log file. Effective CC differed during micrograv-
ity compared to hypergravity (73% vs 87%, p< 0.001) but not compared
to normogravity conditions (73% vs 79%, p=0.098).
Qualitative analysis of video recording data of the entire flight con-
firmed the absence of clinically relevant variations in the quality of CC
including all the eight parabolas (data not shown).
4. Discussion
This is the first study that report the feasibility and effectiveness in
terms of quality of chest compressions delivered with an ACDD during
microgravity and hypergravity conditions. Mechanical CC were per-
formed continuously during the entire flight without any missed CC,
pause or displacement of the ACDD from the manikin. Different phases
of the flight caused expected changes in the quality of mechanical CC
(regarding depth and release) that were not clinically relevant during
microgravity and hypergravity conditions compared to normogravity.
The mean range of depth, rate and recoil of CC recorded during all
phases of the parabolic flight can be considered within the one advised
by international guidelines [13], as the change in depth was in the range
of decimals of mm. We consider the minor deviation in mean depth of
CC below the threshold of 50 mm of no clinical significance. Our results
were better than the values obtained with the three main methods to
perform manual CC in microgravity, thatall performed below guidelines
set standards in terms of CC depth achieved and the ability to sustain
compressions [13]. The HS method resulted in a mean CC depth of
47.3 ± 1.2 mm, the RBH of 41.7 ± 6.2 mm [9] and the ER showed incon-
sistent results ranging from 27.1 ± 7.9mm to 42.3 ± 5.6 mm [14,15].
The use of an ACCD allowed to continuously deliver high-quality CC.
The monitoring system did not show any missed compression, pause,
displacement or other technical problem even in a complex scenario
of rapid changes of gravity. This is in line with the experiences of pre-
hospital emergency medical service providers, where ACCD are em-
ployed especially when the access to the patient is limited, or transfers
have to be made while guaranteeing correct continuous CC, with the
ability to maintain CC for longer periods, such as in the helicopter emer-
gency medical services [16].
The treatment of cardiac arrest consistsof early, good quality CC and
defibrillation. Defibrillation in microgravity has been tested successfully
[17], and a defibrillator is available in the International Space Station
[18]. With the addition of an ACCD astronauts could have the chance
to provide high quality CC also for prolonged time, potentially improv-
ing outcome in case of a SCA in a situation with limited resources and
spaces as well as with challenging conditions (i.e., microgravity).The re-
cent guidelines for CPR during spaceflight heve already suggested the
A. Forti, M.J. van Veelen, T. Squizzato et al. American Journal of Emergency Medicine 53 (2022) 54–58
56

use of an ACCD as an option t[8]. However, time to first CC and defibril-
lation may be prolonged by the use of ACCD in space as it was shown in
helicopters [16]. One of the most challenging points would be to
develop a specific standard operating procedure (SOP) to allow not
only a rapid application of a defibrillator but also a swift and effective
deployment of the ACCD to minimise compromised perfusion time.
Fig. 2. Compression depth,release and rate duringthe last four parabolas. Each parabola is depictedwith grey and pink colours.Grey colour represents the hypergrav ity phases (1. 8 G) and
pink the microgravity phase (0 G). White background represents the steady flight (normogravity, 0 G). (For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
Table 1
Compression depth, release and rate and percentage of effective chest compressions during microgravity, normogravity and hypergravity.
Microgravity (0 G) Normogravity (1 G) Hypergravity (1.8 G) p-value
Compression depth (mm), mean ± SD 49.9 ± 0.7 49.9 ± 0.5 50.1 ± 0.6 <0.001
Compression release (mm), mean ± SD 0.2 ± 0.4 0.0 ± 0.1 0.7 ± 0.6 <0.001
Compression rate per minute, mean ± SD 101.4 ± 0.5 101.3 ± 0.5 101.3 ± 0.5 0.939
Effective chest compressions⁎, % 73% 79% 87% <0.001
⁎Chest compression with depth ≥50 mm on a mid-chest level.
A. Forti, M.J. van Veelen, T. Squizzato et al. American Journal of Emergency Medicine 53 (2022) 54–58
57

Optimal cardiac arrest response manoeuvres in microgravity already
differ on the phase of the CPR [8] and the integration of the use of an
ACCD could substitute one of the different manual techniques based
on the usage situation. Optimal transfer, as well as restraining methods
and fitting devices should be determined through practising complete
cardiac arrest response scenarios in a follow up study and in a scenario
that allows the simulation of longer microgravity periods.
Cons of an ACCD in spaceflights are the added weight (approxi-
mately 8 kg for the current device but down to 3.5 kg for others, that
could better justify the estimated cost of 20,000 $/kg to put in orbit
extra load [1]), despite that an ACCD could remain in service for several
years and has to be transported only once in its lifecycle (e.g. to the In-
ternational Space Station). Other disadvantages could be the potential
adverse effects on structural integrity of the spacecraft caused by
ACCD vibrations and the additional training required to restrain
effecively the ACCD and the victim in microgravity [7].
4.1. Limitations
Parabolic flights mimic microgravity during spaceflight but are lim-
ited in time, and therefore it was not possible to record longer sessions
of chest compressions. Our study did not include the process of deliver-
ing next to the victim, restraining and fitting an ACCD because the alter-
nating gravity phases experienced during a parabolic flight do not make
that feasible (every phase of each parabola last from 20 to 26 s) and
safety regulation does not allow for it.
5. Conclusions
The use of an ACCD allows to continuously deliver high-quality CC
and, even in a complex scenario of rapid changes of gravity, the moni-
toring system did not show any missed compression, pause, displace-
ment or other technical problem. Specific SOP and training should be
developed for the practical application of ACCD in case of SCA during
spaceflight. Its deployment should not delay the delivery of manual
CC, and the decision to bring one-time extra load for a high impact
and low likelihood event (i.e. SCA) should be based on the specifics of
the mission and health status of its crew.
Authors' contributions
AF and GS contributed to conceptualisation and development of the
study design. AF, MvV, TS, TDC, MP and GS participated in data collec-
tion and analysis. TDC performed the statistical analysis. AF, MvV, TDC
and GS oversaw the interpretation of results. AF, MvV, TS, TDC and GS
did the literature review and wrote the manuscript. All authors critically
reviewed the final draft of the manuscript and have given approval for
the version submitted.
Funding
This study was supported by internal funding only.
Availability of data and materials
The datasets during and/or analysed during the current study avail-
able from the corresponding author on reasonable request.
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Declaration of Competing Interest
The authors declare that they have no competing interests.
Acknowledgements
We thank Laerdal Italia Srl (Bologna, Italy) and Croce Bianca (Bol-
zano, Italy) for lending the equipment for the study. The authors thank
the Department of Innovation, Research, Universityand Museums of the
Autonomous Province of Bozen/Bolzano, Italy for covering the Open Ac-
cess publication costs.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.ajem.2021.12.056.
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