Cardiopulmonary resuscitation (CPR) during spaceflight -a guideline for CPR in microgravity from the German Society of Aerospace Medicine (DGLRM) and the European Society of Aerospace Medicine Space Medicine Group (ESAM-SMG)

Abstract

Background: With the "Artemis"-mission mankind will return to the Moon by 2024. Prolonged periods in space will not only present physical and psychological challenges to the astronauts, but also pose risks concerning the medical treatment capabilities of the crew. So far, no guideline exists for the treatment of severe medical emergencies in microgravity. We, as a international group of researchers related to the field of aerospace medicine and critical care, took on the challenge and developed a an evidence-based guideline for the arguably most severe medical emergency-cardiac arrest. Methods: After the creation of said international group, PICO questions regarding the topic cardiopulmonary resuscitation in microgravity were developed to guide the systematic literature research. Afterwards a precise search strategy was compiled which was then applied to "MEDLINE". Four thousand one hundred sixty-five findings were retrieved and consecutively screened by at least 2 reviewers. This led to 88 original publications that were acquired in full-text version and then critically appraised using the GRADE methodology. Those studies formed to basis for

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G U I D E L I N E Open Access
Cardiopulmonary resuscitation (CPR) during
spaceflight - a guideline for CPR in
microgravity from the German Society of
Aerospace Medicine (DGLRM) and the
European Society of Aerospace Medicine
Space Medicine Group (ESAM-SMG)
Jochen Hinkelbein
1,2,3*†
, Steffen Kerkhoff
1,2,3†
, Christoph Adler
4,5
, Anton Ahlbäck
3,6
, Stefan Braunecker
3,7
,
Daniel Burgard
8
, Fabrizio Cirillo
9
, Edoardo De Robertis
10
, Eckard Glaser
1,3,11
, Theresa K. Haidl
12
, Pete Hodkinson
3,13
,
Ivan Zefiro Iovino
9
, Stefanie Jansen
14
, Kolaparambil Varghese Lydia Johnson
3,15
, Saskia Jünger
16
,
Matthieu Komorowski
3,17
, Marion Leary
18
, Christina Mackaill
3,19
, Alexander Nagrebetsky
20
, Christopher Neuhaus
1,3,21
,
Lucas Rehnberg
22
, Giovanni Marco Romano
23
, Thais Russomano
24
, Jan Schmitz
1,2,3
, Oliver Spelten
25
,
Clément Starck
3,26
, Seamus Thierry
3,27,28,29
, Rochelle Velho
30
and Tobias Warnecke
31
Abstract
Background: With the “Artemis”-mission mankind will return to the Moon by 2024. Prolonged periods in space will
not only present physical and psychological challenges to the astronauts, but also pose risks concerning the
medical treatment capabilities of the crew. So far, no guideline exists for the treatment of severe medical
emergencies in microgravity. We, as a international group of researchers related to the field of aerospace medicine
and critical care, took on the challenge and developed a an evidence-based guideline for the arguably most severe
medical emergency –cardiac arrest.
Methods: After the creation of said international group, PICO questions regarding the topic cardiopulmonary
resuscitation in microgravity were developed to guide the systematic literature research. Afterwards a precise search
strategy was compiled which was then applied to “MEDLINE”. Four thousand one hundred sixty-five findings were
retrieved and consecutively screened by at least 2 reviewers. This led to 88 original publications that were acquired
in full-text version and then critically appraised using the GRADE methodology. Those studies formed to basis for
(Continued on next page)
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data made available in this article, unless otherwise stated in a credit line to the data.
* Correspondence: jochen.hinkelbein@gmail.com
Jochen Hinkelbein and Steffen Kerkhoff shared first authorship.
1
German Society of Aviation and Space Medicine (DGLRM), Munich, Germany
2
Department of Anaesthesiology and Intensive Care Medicine, University
Hospital of Cologne, 50937 Cologne, Germany
Full list of author information is available at the end of the article
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine
(2020) 28:108
https://doi.org/10.1186/s13049-020-00793-y

(Continued from previous page)
the guideline recommendations that were designed by at least 2 experts on the given field. Afterwards those
recommendations were subject to a consensus finding process according to the DELPHI-methodology.
Results: We recommend a differentiated approach to CPR in microgravity with a division into basic life support
(BLS) and advanced life support (ALS) similar to the Earth-based guidelines. In immediate BLS, the chest
compression method of choice is the Evetts-Russomano method (ER), whereas in an ALS scenario, with the patient
being restrained on the Crew Medical Restraint System, the handstand method (HS) should be applied. Airway
management should only be performed if at least two rescuers are present and the patient has been restrained. A
supraglottic airway device should be used for airway management where crew members untrained in tracheal
intubation (TI) are involved.
Discussion: CPR in microgravity is feasible and should be applied according to the Earth-based guidelines of the
AHA/ERC in relation to fundamental statements, like urgent recognition and action, focus on high-quality chest
compressions, compression depth and compression-ventilation ratio. However, the special circumstances presented
by microgravity and spaceflight must be considered concerning central points such as rescuer position and
methods for the performance of chest compressions, airway management and defibrillation.
Introduction
Manned spaceflight to the Moon or Mars [1] may be-
come reality in the near future. In these exploration mis-
sions, both duration and medical requirements differ
significantly from spaceflight in low earth orbit (LEO)
[2,3] and dictate the need for extensive planning for the
management of life-threatening medical conditions. In
contrast to LEO missions, evacuation during flights to
the Moon or Mars will be challenging if not impossible
[2,4]. Although every crew member receives basic
medical training and each crew has at least one Crew
Medical Officer (CMO) with extended medical skills, the
crew’s most medically trained member might become in-
capacitated. This will significantly limit the crew’s med-
ical emergency treatment capabilities.
Given that a single medical emergency could endanger
the whole mission, it is of utmost importance to develop
medical procedures and guidelines to facilitate medical
treatment in the remote environment. Based on an inci-
dence of medical emergencies in the general population
of 0.06 events per person per year, an astronaut crew of
six having a flight duration of 2.74 years (or 900 days, the
expected duration of a mission to Mars) may encounter
an estimated 0.99 medical emergencies [5]. However,
new calculations adopting the Integrated Medical Model
estimate the incidence of crewmember incapacitation re-
quiring evacuation during LEO mission as low as 0.017
events per person per year [6].
Cardiac arrest is a critical medical condition with high
expected morbidity and mortality. It can have a variety
of causes (e.g., cardiac event or injury, hypoxia, circula-
tory shock, toxic exposure, electric shock, or trauma) all
of which remain possible during spaceflight [7]. Without
immediate and effective cardiopulmonary resuscitation
(CPR), cardiac arrest will result in the death of the
crewmember. Since immediate, advanced and highly in-
tensive management is required, cardiac arrest is likely
to have profound effects on crew and has the potential
to endanger the whole mission.
With its beginning in the 1950s and 60s with Kouwen-
hoven, Jude, and Knickerbocker [8,9], research activities
for CPR on Earth have been extensive. CPR guidelines
from the American Heart Assosciation (AHA) and the
European Resuscitation Council (ERC) are updated regu-
larly with evolving evidence and have been adapted to a
variety of provider and patient populations over the
years. Although the current guidelines include a section
on CPR in special circumstances [10], they do not ad-
dress cardiac arrest management in microgravity. Fur-
thermore, while CPR on Earth is a common occurence
[11], it has, so far, never been practiced in reality on a
human during spaceflight.
CPR represents a significant challenge even to trained
health care professionals on Earth [12]. However, micro-
gravity, limited physical space, and limitations in man-
power and equipment are likely to complicate CPR
during space missions. Adaptation of CPR guidelines to
a microgravity environment exemplifies the fundamental
challenges of CPR.
Aims and scope of the guideline
The microgravity environment significantly complicates
the delivery of CPR. Therefore, terrestrial guidelines can-
not be used during spaceflight without several modifica-
tions and specifications. The aim of this guideline is to
address the unique challenges of CPR in microgravity by
reviewing, analyzing, and rating available scientific evi-
dence. For specific topics where no or minimal previous
research is available, expert opinion and consensus were
used to generate recommendations.
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 2 of 18

Material and methods
Literature search strategy
A task force with 27 members was created by the
ESAM-SMG and the DGLRM and consisted of a broad
range of both medical and scientific experts that in-
cluded Aerospace Medicine, pre-hospital and in-hospital
Emergency Medicine, General Surgery, Cardiology,
Anesthesiology, Intensive Care Medicine, and Physics.
This task force then prepared a first list consisting of the
essential steps of CPR that would need to be addressed
in a guideline for the special environment of micrograv-
ity or spaceflight.
In total, there were 15 key-words which formed the
basis for the creation of specific questions to guide the
systematic literature research (Table 1). Those questions
were then drafted utilizing the PICO-structure (Popula-
tion, Intervention, Comparison, Outcome) [13,14].
Every member was able to draft and propose keywords
and PICO-questions and a consensus was built. Subse-
quently, the generated keywords and questions were
reviewed and, if necessary, modified by the other task
force members. Altogether, 134 questions were defined.
Additional questions could not be structured using the
PICO format (e.g., ethical questions).
For each of the 134 questions, a specific search-
strategy for PubMed (“MEDLINE”;https://www.ncbi.
nlm.nih.gov/pubmed/) was then created. In 75 cases, the
questions did not differ in their search-strategy which
led to a total of 59 different search strings, all listed in
Additional file 1. The search strategy resulted in 4165
articles in PubMed.
The identified abstracts were inserted into the
browser-based program “abstrackr”(http://abstrackr.
cebm.brown.edu) to enable a time-effective screening
process of the abstracts [15]. “Abstrackr”allows the re-
viewer to read the abstract and decide whether it seems
relevant, irrelevant or of unknown relevance. Subse-
quently, every abstract was screened independently by
two blinded reviewers.
In cases without conflicts, the abstract was either cate-
gorized as relevant or irrelevant. Conflicts were solved
by the Chairperson after the review of the full-length
paper. After the screening process, 432 abstracts were
left of which 269 remained after removal of duplicates.
Subsequently, the original papers were acquired using
primarily “MEDLINE”and “Google Scholar”. This led to
88 available original papers, as the remaining 181 articles
were either not written in the English language or, des-
pite all efforts, not accessible.
Quality of evidence
All 88 publications were analyzed using the GRADE
methodology (The Grading of Recommendations
Assessment, Development and Evaluation) to assess the
quality of the retrieved literature based on study design
limitations (selection, performance, detection, attrition
and reporting bias), effect consistency and size, direct-
ness, precision, publication bias, dose-response effect
and presence of antagonistic bias [16–19]. Quality of evi-
dence was rated as either “high”,“moderate”,“low”,or
“very low”.
Subsequently, the task force members were split into
teams of two to tackle one of the 15 main topics. Every
task force member was part of two teams in total and
was asked to use the original scientific papers, acquired
through the systematic literature search, to develop the
recommendations for the guideline. Everyone had access
to the original research questions, the literature that
passed selection and the results of the grading process.
After each member finished their part, the parts were
merged together and then presented to the whole task-
force for verification and feedback.
Consensus
Twenty-seven proposed recommendations were included
in the consensus finding process via the DELPHI
method [20]. This method is used to generate consensus
among a group of researchers addressing potentially
controversial questions [21]. In this case, all task force
members received a list with the proposed recommenda-
tions. They were asked via e-voting to state if they agree
or disagree and add a comment or a suggested correc-
tion. As a result, the list was sent back to the chairper-
son to collect all comments and evaluate the rate of
agreement.
Then, the results of this first round were sent back to
the task force members with the rate of agreement and
the anonymized comments and suggested corrections.
The members were asked a second time to state their
agreement/disagreement on the 27 recommendations
and add comments. After this second round, every
Table 1 Relevant topics for the development of a guideline for CPR during spaceflight
1. Chest compressions 2. Automated chest compression devices 3. Airway management
4. Ventilation 5. Suction 6. Defibrillation
7.Intravenous access 8. Medication 9. Medical Training
10. ROSC 11. Death 12. Telemedicine
13. Reversible causes of cardiac arrest 14.Technical limitations of spaceflight 15. Ethics
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 3 of 18

recommendation had received a clear vote for either
agreement or disagreement.
In total, 23 of the 27 proposed recommendations were
accepted of which 22 reached a strong consensus. There
were no recommendations supported by an intermediate
consensus (70–90% agreement) and only 1 recommen-
dation with a weak consensus (50–70% agreement). For
3 of the proposed recommendations no consensus could
be achieved (< 50% agreement).
Strength of recommendation
The strength of recommendation was determined by the
task force members as either strong or weak [18].
Scientific background for CPR in microgravity
Modern resuscitation techniques originate from the re-
search projects of Kouwenhoven, Jude, and Knicker-
bocker in the 1950s and 1960s [8] and have been an
active area for medical research [22,23].
With humankind starting the exploration of space in
1961, medical emergencies during spaceflight have been
a possibility, leading to space agencies actively preparing
and training their crews for such events [24]. The first
available reference to CPR in space dates back to 1968
when Busby published his report about medical prob-
lems for future space missions [25]. Busby suggested the
application of rescue breaths or mask ventilation com-
plemented with chest compressions for astronauts suf-
fering acute hypoxia, but did not elaborate on his
suggestion [25]. In addition to that, Frey et al. proposed
an emergency room for future space stations in which
chest compressions could be performed [26]. NASA
took on the challenge and performed experiments with
different positions to perform chest compressions in
1992 and even tested a mechanical chest compression
device [27]. The Crew Medical Restraint System (CMRS)
was first introduced during Space Shuttle mission STS-
81 in 1997 and enabled a fairly quick and secure fixation
of a patient and the provider [28].
In the following years, several experiments were con-
ducted during parabolic flight [29–31] or in simulated
microgravity [32–36] in order to identify the ideal tech-
nique of performing chest compressions.
Until today, no cardiac arrest ever happened in space
that was not associated with a catastrophic accident and
consecutive loss of the whole spacecraft and crew.
Microgravity CPR methods
So far, five different techniques for CPR in space have
been described and evaluated. Certainly, the restrained
CPR method in the standard position represents the
most apparent approach to performing chest compres-
sions in microgravity, as it is simply the application of
the earth-based standard technique. It requires the
rescuer and the patient to be fastened to the CMRS. The
rescuer utilizes one strap around the waist and one strap
across the lower legs to keep their position at the side of
the patient’s torso [37]. It was one of the first techniques
to be investigated during parabolic flight [30].
In the straddling position of the restrained CPR
method, patient and rescuer are again both attached to
the CMRS. The difference lies in the rescuer kneeling
across the patient’s waist and performing chest compres-
sions on top of the patient. This leads to a significant re-
duction in the required space and could represent an
advantage in a spacecraft where space is limited [37].
The reverse bear hug method (RBH) represents a modi-
fied version of the Heimlich-maneuver with the rescuer
enclosing the patient’s chest from behind. This technique
lends itself for CPR immediately at the site of the cardiac
arrest, as it does not require the patient and rescuer to be
restrained. Obviously, this technique cannot be performed
with a patient restrained on the CMRS [30].
Like the RBH method, the handstand (HS) method
does not require the patient to be restrained on the
CMRS, although it can be performed, however, on a re-
strained patient. The patient is placed with their back on
a solid surface of the spacecraft. The rescuer then places
their feet on an adequate surface on the opposite wall,
arms stretched out above the head. With both hands
placed in the correct position on the patient’s sternum,
the rescuer flexes and extends their hips and knees to
generate the force for compressing the patient’s chest.
This technique comes with the advantage of using
the rescuer’s lower extremity muscles, which enables
higher exercise endurance. Nevertheless, the major
disadvantage is represented by the dependence on the
distance between the patient and the opposing surface
as well as the actual height of the rescuer. Those fac-
tors make the HS method a very uncertain technique
in an emergency [37].
The newest technique is the Evetts-Russomano (ER)
CPR method. Like the HS and RBH methods, it does not
require a restrained patient and is suitable as a first-aid
instrument at the site of the emergency. The rescuer
places their left leg over the patient’s right shoulder and
the right leg around the patient’s torso. By interlocking
their ankles in the center of the patient’s back, the res-
cuer attaches himself to the patient and can now gener-
ate force onto the patient’s chest without being pushed
away [32,37].
The technique’s advantages are quick application, in-
dependence from spatial circumstances, and easy access
to the patient’s airway. However, without restraint res-
cuer and patient could drift and collide with the sides of
the spacecraft and, thus, pose a potential risk.
Besides the microgravity CPR techniques mentioned
above, other chest compression techniques, like the
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 4 of 18

Mackaill-Russomano-technique, have been suggested for
the special envirnonment of hypogravity [38].
Results and recommendations
Should CPR in microgravity be divided in different
phases?
Recommendation 1: CPR in microgravity SHOULD be di-
vided into a chain of survival consisting of Basic Life
Support (BLS) and Advanced Life Support (ALS).
Evidence summary
Several studies investigated the feasibility, course of ac-
tion, and effectiveness of CPR in microgravity [29–36,
39,40]. It consists of early recognition and the call for
help, early and effective chest compressions, early ad-
vanced life support with the use of a defibrillator if ap-
plicable and high quality post resuscitation care [11,41].
The chain of survival is a central part of the terrestrial
CPR guidelines [11,42].
Rationale for the recommendation
Emergencies can happen anywhere - this includes also
any place of a spacecraft. To guarantee effective and im-
mediate CPR during spaceflight, we recommend a two-
step approach similar to the earth-based CPR guidelines
with a first-aid component (BLS) and a second compo-
nent once additional help arrives (ALS) [11,41]. This in-
cludes the recommendation of a chest compression
technique for BLS that does not require patient or res-
cuer to be restrained or is dependent on the distance be-
tween two surfaces (such as the HS-method) and can
therefore be initiated, immediately and without any
equipment. Another advantage of this approach is that
once help arrives, transport of patient and rescuer under
ongoing chest compressions by the additional crew
members is possible.
What is the best initial chest compression technique at
the site of the emergency?
Recommendation 2: For initial BLS at the site of emer-
gency, the Evetts-Russomano method (ER) SHOULD be
applied initially. If the rescuer cannot perform adequate
chest compressions with the ER method, the rescuer
should switch to the Reverse-Bear-Hug method (RBH).
Evidence summary
Several controlled trials analyzed which chest compres-
sion technique is the most effective in microgravity [40,
43]. For initial BLS at the site of the emergency, only a
technique that does not require patient or rescuer to be
restrained can be considered. This limits the possible
techniques per se to the Handstand-method, the
Reverse-Bear-Hug method and the Evetts-Russomano
method. Only one controlled trial compared those three
methods [33], whereas other studies concentrated on
one or two of the techniques [29,30,32,36] or analyzed
the effectiveness mathematically [40].
Concerning the compression rate, the ER technique is
superior to the RBH method (compression rate, 104.6 ±
5.4 bpm vs. 94.7 ± 5.4 bpm) [40]. The HS method re-
sulted in compression rates of more than 120 bpm (ap-
plying the 2010 ERC guidelines) [33] and in one instance
of just below 100 bpm [30].
With regard to compression depth, the HS method
demonstrated the highest depth (47.4 ± 2.4 mm) [33]of
all the compared techniques, although it still not reached
the recommended 50–60 mm of the current ERC guide-
lines [44]. The ER method showed inconsistent results
concerning compression depth, ranging from 45.7 ± 2.4
mm [32] to 27.1 ± 7.9 mm [36]. Finally in the RBH
method, compression depths with a maximum of only
41.7 ± 6.2 mm [33] were achieved.
Rationale for the recommendation
Although the HS method proved to deliver the most ef-
fective chest compressions with regards to the 2010/
2015 ERC guidelines [36,40], we recommend the ER
method as the primary technique for basic life support
in microgravity. The decision is based on advantages of
the ER method which clearly outweigh its disadvantages.
In contrast to the HS method, the ER method is not
dependent on a specific spacecraft diameter. Another
advantage of the ER method is that it allows the patient
and rescuer to be transported under ongoing chest com-
pressions by a third person. The focus lies on the trans-
portation aspect, as in a spacecraft the emergency
equipment would be generally stored near the crew
medical restraint system.
Consequently, it would be more effective to transport
the patient to the equipment and a restraint system thus
creating the best treatment environment possible. This
is the reason for the recommendation to apply the RBH
method in case of a failure of the ER method.
What is the best chest compression technique at the
designated emergency treatment site?
Recommendation 3: As soon as the patient has been re-
strained on the Crew Medical Restraint System chest
compressions SHOULD be applied using the Handstand-
method (HS) if favored by the dimensions of the space-
craft and provider height.
Evidence summary
As mentioned above, the HS method has proved to de-
liver the highest quality manual chest compressions in
microgravity [34,40]. With HS, both compression depth
(44.9 ± 3.3 mm) and compression rate (115.4 ± 12.1 bpm)
were superior to all the other manual chest compression
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 5 of 18

techniques [40]. Furthermore, it has been demonstrated
to be the least strenuous technique, with a lower minute
ventilation for the rescuer (HS 39.89 ± 2.01 l/min vs ER
58.38 ± 2.90 l/min vs RBH 48.24 ± 2.32 l/min) [34].
Rationale for the recommendation
As the HS method represents the most effective chest
compression technique in microgravity [40], it should be
regarded as the current gold standard. Thus, it should
be applied as soon as the situation allows, once patient
has been transported to the emergency equipment and
restrained to the CMRS. This implies that the CMRS is
installed at a site of the spacecraft where the distance
from the CMRS to the opposing wall enables the
crewmembers to perform chest compressions in the HS-
method.
Theoretically, the HS method could be applied any-
where in the spacecraft if the surface distance allows its
application. Furthermore, transportation of the patient
and rescuer to the CMRS and emergency equipment
under ongoing HS chest compressions is impossible.
This justifies our recommendation to only use the HS
method once the patient has been restrained to the
CMRS.
Which chest compression technique should be used at
the designated emergency treatment site if the HS
method cannot be used?
Recommendation 4: If the application of the HS method
seems impossible either the restrained CPR method using
the standard OR straddling position SHOULD be
applied.
Evidence summary
There were only two studies that investigated the use of
the standard or straddling position for CPR in
microgravity with the rescuer and patient being re-
strained [30,31]. Both studies were performed during
parabolic flight, one using a mannequin [30], the other a
using a swine model [31]. Overall, the performance of
chest compressions in those standard or straddling posi-
tions was inferior to the HS method (compression depth
HS 4.01 ± 0.51 cm vs. standard 1.98 ± 1.12 cm vs.
straddling 3.07 ± 1.19 cm) [30] However, the achieved
compression rate for all mentioned techniques was
equally good [30].
Rationale for the recommendation
If limitations in space or other factors prevent the res-
cuer from applying chest compressions in a restrained
patient using the HS method, it is necessary to apply
chest compressions in either the restrained standard or
restrained straddling position. Although the findings
suggest an advantage of the straddling over the standard
position [30,40], we intentionally do not recommend
one technique over the other.
In a situation where the HS method cannot be applied,
there will possibly be other factors affecting the applica-
tion of chest compressions to the patient. Those factors
could include limitations in available space, wall-to-
CMRS distance and human physiological limitations
(e.g. height of the rescuer). In those cases, the rescuer
must decide which of the two techniques can be applied
and will provide the most clinically effective chest com-
pressions [37].
Automated Chest Compression Devices (ACCD)
In recent years, the invention of ACCDs has brought an
innovative aspect for the application of cardiopulmonary
resuscitation [45,46]. This invention was mainly driven
by the fact that quality of manual chest compressions is
one of the major contributors to good patient outcome
in CPR [47]. However, the quality of manual CPR is in-
fluenced by many factors (height, weight, training) and
deteriorates significantly within minutes even in highly
trained and fit rescuers [48–50]. To overcome those lim-
itations, ACCDs were developed by various companies
to improve the delivery of consistent high-quality chest
compressions over longer periods. Nevertheless, no
study was able to show an advantage of ACCDs over
manual chest compressions [51].
Should an automated chest compression device be used
on a patient in cardiac arrest in microgravity?
Recommendation 5: An automated chest compression
device COULD be used on a restrained patient (if avail-
able). Its installation, however, should not delay high
quality chest compressions.
Evidence summary
Several studies investigated the safety and effectiveness
of ACCDs in earth-based clinical and preclinical use
during CPR [52,53]. Unfortunately, no ACCD has ever
been tested under actual microgravity conditions during
spaceflight. Only one abstract reports the testing of a
LUCAS-II ACCD during parabolic flight, although no
full-length publication could be retrieved [54]. In this
study, the ACCD was already fastened to CPR manikin
when microgravity was reached. There was no signifi-
cant difference in compression depth and rate found
while comparing microgravity with 1G conditions. This
indicates that an ACCD could potentially operate effect-
ively in microgravity.
Rationale for the recommendation
The authors recognize the potential benefits of ACCDs
in microgravity with special consideration of the challen-
ging application of manual chest compressions. Fatigue,
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 6 of 18

suboptimal spatial conditions and limitations in the
number of rescuers can limit the effectiveness of manual
chest compressions even under optimal conditions in
microgravity. Therefore, ACCDs represent a potential
solution to overcome those human limitations.
The reason behind the weak recommendation is based
on the lack of high-quality studies for the use of those
devices in microgravity. Another factor is vibrations
being caused by those devices whose effects on the
structural integrity of a spacecraft are challenging to ex-
trapolate without further investigations. Moreover, the
crew training to apply these devices must be extensive
and the process of fastening the patient to such a device
is likely to be time-consuming, especially in micrograv-
ity. Furthermore, the weight and size of ACCDs repre-
sent a likely limitation for the inclusion of those devices
to the medical kit.
Although cardiac arrest remains a possibility during
spaceflight, its estimated occurrence is very low. This ar-
gues against embarking the load of > 8 kg during a space
mission for an ACCD that might never be used. In doing
so, other medical or mission-relevant equipment might
be left behind. This question cannot finally be answered
by this research group but will need to be addressed for
future space exploration missions.
Airway management and ventilation
Another crucial part in the delivery of successful CPR is
ventilation [55,56]. Besides effective chest compressions
and defibrillation, it constitutes the central skill of Basic
and Advanced Cardiac Life Support [23]. Therefore, it
seems reasonable to encompass the topic of airway man-
agement and ventilation in these guidelines.
As future space missions might not include trained an-
esthesiologists, nurse anesthetists, emergency physicians,
or paramedics, who have sufficient skills in airway man-
agement during emergencies, a reasonable strategy for
CMOs and regular crewmembers is needed.
Which airway device should be used to ventilate a patient
during CPR in microgravity?
Recommendation 6: If no rescuer with extensive training
in tracheal intubation is present, a second generation
supraglottic airway device SHOULD be used for airway
management.
Evidence summary
We have identified three studies investigating airway
management in microgravity [57–60]. Of those three
studies, two are covering supraglottic airway devices as
well [59,60]. In particular, the laryngeal mask (LMA), as
a representative of the supraglottic airway devices (SGA/
SAD), showed a high successful insertion rate in
simulated microgravity of 100% in a restraint position
and 97.5% in a free-floating position [60].
Although the study subjects of Keller et al. were
trained anesthesiologists, their success rate for tracheal
tube (TT) intubation in a free-floating condition was low
in some situations (15%). Even under restrained condi-
tions several intubation attempts were needed (success-
ful insertion rate: 92.5%) [60].
Rationale for the recommendation
SGAs are an accepted and widely used airway device
during CPR [42]. Although the CPR guidelines of the
ERC recognize the tracheal intubation as the optimal
method for airway management, they acknowledge the
difficulty and dangers of ETT intubation by
inexperienced providers. Therefore, SGAs represent a
valid and safe alternative that can be effectively applied
by inexperienced providers with minimal training under
CPR conditions [61].
This recommendation was made intentionally al-
though no study investigated a second generation SGA.
However, we believe that the differences in handling and
effectiveness of first- and second-generation SGAs are
minimal and the experiences with the first generation
devices are sufficient to make this recommendation.
Which airway device should be used if a provider
experienced in tracheal intubation is present?
Recommendation 7: The tracheal intubation remains the
gold standard for securing the airway if performed by a
skilled provider and SHOULD be performed in that case.
Evidence summary
In total, three studies investigated the feasibility and
success rate of TT intubation in microgravity [58–60].
Another study was published during the process of
guideline development [62,63]. Although all studies
were performed with limited subject numbers, it could
be shown that TT intubation in microgravity is possible,
but the success rates differed in the studies.
Starck et al. is the first study to investigate the use
of a video laryngoscope [62]. They measured an 80%
success rate for oro-tracheal intubation by novice op-
erators with a video laryngoscope in microgravity,
compared to a 40% for conventional laryngoscopy.
Experts performed similarly well with conventional
and video laryngoscopes.
Three older studies investigated conventional laryngo-
scopes. Whereas Keller et al. reported of an TT
intubation success rate of 92.5% under constraint condi-
tions in simulated microgravity [60], Groemer et al. only
found a 33% success rate for TT intubation under
constraint conditions [58]. This difference could be ex-
plained by comparing the study designs: Groemer et al.
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 7 of 18

researched TT intubation during parabolic flight - with
a limited microgravity time of 23 s [58], whether Keller
et al. performed TT intubation in a submerged scenario
with no time limit in simulated microgravity and an
average time to successful intubation of 36 s [60].
Rabitsch et al. found a 86% success rate for TT intub-
ation in a restraint setting under microgravity conditions
by paramedics [59].
Rationale for the recommendation
Tracheal intubation represents the gold standard in the
international guidelines concerning airway management
during cardiopulmonary resuscitation [42]. However,
crew-training to guarantee high success rates for TT in-
tubation needs to be extensive and requires at least 50
tracheal intubations in humans to reach a 90% success
rate [64]. Therefore, if a crewmember possesses the ne-
cessary training and experience, he or she should at-
tempt to perform TT intubation in a patient in cardiac
arrest.
However, the authors realize that such an instance will
be unlikely, and SGAs represent a viable alternative in
lack of a crewmember trained in TT intubation and the
required equipment.
Should patient and rescuer during an intubation attempt
be restrained or free-floating?
Recommendation 8: When tracheal intubation is
attempted patient and rescuer should be restrained using
the Crew Medical Restraint System.
Evidence summary
Of the four conducted studies, two compared the appli-
cation of TT intubation under free-floating and re-
strained conditions in microgravity [57,58,60]. Keller
et al. showed a clear superiority of the restrained method
(88% success rate) compared to the free-floating method
(15% success rate) [60]. Groemer et al. reported about a
slightly reduced success rate for the restrained method
(33%) compared to the free-floating method (41%).
Starck et al. only investigated TT intubation in a setup
with both patient and rescuer being restrained, but
showed a high success rate for video laryngoscopy in
novices and experts (80% vs. 95%) [62]. Also experts
achieved a high success rate with direct laryngoscopy
(96%), whereas novices had a significantly lower success
rate with direct laryngoscopy (40%) [62].
Rationale for the recommendation
Given the high success rate for TT intubation under re-
strained conditions in the studies of Starck [62] and Kel-
ler [60] et al. and the low success rate in free-floating
conditions, it seems reasonable to recommend the
restrained position to perform ETT intubation in
microgravity.
Should a suction device be available during airway
management?
Recommendation 9: A manual suction device SHOULD
be included in the emergency kit and be readily available
during CPR, especially during airway management.
Evidence summary
Thus far, no study has investigated the use of a suction
device during airway management in microgravity. How-
ever, several studies investigated surgical procedures and
bleeding control in microgravity [65–68]. In some of
those studies, suction devices were successfully used.
McCuaig et al. investigated the feasibility of blood re-
moval in microgravity during parabolic flight and effect-
ively used a commercial Laerdal® suction device [66]. In
a different study, McCuaig et al. tested an experimental
suction machine incorporating a centrifugal mechanism
successfully during microgravity in parabolic flight [67].
Rationale for the recommendation
The ability to remove fluids from a patient during airway
management represents a crucial skill in emergency
medicine [42,69]. Although no studies have been
performed to test suction devices during airway manage-
ment in microgravity, the effectiveness of suction devices
in other experimental settings during microgravity has
been tested. We, therefore, recommend keeping a micro-
gravity compatible suction device readily available during
emergency airway management in microgravity.
Defibrillation
When should a defibrillator be used? Recommenda-
tion 10: A defibrillator SHOULD only be used on a pa-
tient that is restrained to an electrically isolated and safe
surface.
Evidence summary No study specifically investigated
the use of a defibrillator on a patient in cardiac arrest in
microgravity. However, a defibrillator has been included
in one study that concentrated primarily on the
provision of chest compression [31]. In this study, a
commercially available defibrillator (Physio-Control,
Lifepack 10, Redmond, WA) was reliably used in the
swine model. The subjects were fastened on the electric-
ally isolated surface of the CMRS [31].
Rationale for the recommendation Defibrillation rep-
resents a crucial step in the treatment of a patient in car-
diac arrest suffering from ventricular fibrillation (VF) or
pulseless ventricular tachycardia (pVT) [42,70,71]. A
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defibrillator was first introduced on a Space Shuttle mis-
sion with STS-90 in 1998 [31] and is part of the crew
health care system (CHeCS) on the ISS [28]. Although
defibrillation offers great advantages in patient care and
is a potentially a lifesaving procedure, it also represents a
hazard for the rescuer and other crewmembers [72–74].
Therefore, it is necessary to reduce the risk of an acci-
dental shock for the other crewmembers and potential
damage to the electrical systems of the spacecraft. For
this reason, we recommend the use of a defibrillator only
on a patient that has been restrained on an electrical iso-
lated surface such as the CMRS [28].
What kind of defibrillator and electrodes should be
used on a patient in cardiac arrest in microgravity?
Recommendation 11: An automated external defibrilla-
tor (AED), with long duration batteries and long shelf-life
self-adhesive pads, SHOULD be stored with the emer-
gency equipment.
Evidence summary No study has been published that
has investigated the use of an AED for CPR in micro-
gravity. However, as already mentioned above a defibril-
lator has been reliably tested during parabolic flight [31].
Rationale for the recommendation A defibrillator is an
integral part of the emergency equipment during space-
flight. Therefore, it should be stored with the rest of the
emergency equipment to guarantee quick deployment of
this device. We recommend the use of self-adhesive de-
fibrillation pads as they offer the advantage of better
handling especially in microgravity since they require no
contact pressure (vs. conventional paddles) so the res-
cuer can keep their hands free for other tasks.
What features should the AED contain? Recommen-
dation 12: The AED SHOULD have a user-friendly inter-
face, a step-by-step instruction voice for correct pads
positioning and electrical shock delivery and a timing de-
vice for correct chest compressions/ventilation rate.
Evidence summary As already mentioned above, evi-
dence for defibrillator use in microgravity is scarce.
However, a study has been conducted investigating the
use and effectiveness of a timing device for CPR by ISS
astronaut CMO analogues [39]. Although this study was
performed in normogravity, it showed that CMOs with
only a short medical training would highly profit in their
performance of CPR through the application of a timing
device like a metronome for chest compressions and
ventilation [39].
Rationale for the recommendation As it is not
mandatory for the crew of a spacecraft to include a
health care provider skilled in emergency medicine,
the current standard for medical care during space
missions is represented by the CMO [28]. Those
CMOs receive a minimum of 80 h medical training
with only a small part being focused on CPR. There-
fore, it seems reasonable to include an AED in the
medical kit of a spacecraft. The AED guides the
CMO (or other crewmembers) with visual and acous-
tic instructions through the process of CPR.
How should crewmembers be trained for AED use?
Recommendation 13: All crewmembers SHOULD be
trained in the use of the specific AED provided during
the mission.
Evidence summary To this day, no study has been per-
formed to investigate training issues for defibrillation
during spaceflight.
Rationale for the recommendation There are different
models of AEDs available on the market. It seems only
logical to include the very same AED model in the pre-
flight training that is issued on the actual mission. For
laypersons short training sessions of around half an hour
with AEDs have been showing good results for long-
term skill retention [75].
Should CPR be attempted in the absence of a
defibrillator? Recommendation 14: Even if survival is
highly unlikely without defibrillation, CPR SHOULD
start when a defibrillator is unavailable in the space ve-
hicle, in patients who appear to be in cardiac arrest.
Evidence summary Studies concerning defibrillator use
in microgravity in particular are almost not available. As
no cardiac arrest ever happened during spaceflight, no
outcome investigations are possible.
Rationale for the recommendation There might be
different situations in which the on-board defibrillator
might not be available, e.g. a technical defect. Even in
the absence of a defibrillator the other crewmembers
should nevertheless perform CPR with the available
equipment. On the one hand, the cardiac arrest could
potentially be caused by an asystole or a pulseless elec-
tric activity (PEA) and consequently will not be eligible
for defibrillation therapy.
On the other hand, a different potentially reversible
cause for the cardiac arrest could be present. After suc-
cessful therapy of this reversible cause it could be pos-
sible to establish a Return of Spontaneous Circulation
(ROSC) even without a defibrillator.
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Should defibrillation be attempted, even if survival is
unlikely? Recommendation 15: Although the survival
rate is likely to be reduced in the absence of medical
skills and/or equipment for on-going medical support in
the event of ROSC in microgravity, defibrillation
SHOULD take place when appropriate.
Evidence summary So far, most studies on CPR in
microgravity have been designed towards the actual skill
performance. No study investigated adjunct measures or
post resuscitation care during spaceflight. One study
concentrated on a statistical approach to estimate
outcomes of astronauts with myocardial infarction and
subsequent cardiac arrest during spaceflight [76]. The
authors estimate the survival rate of an astronaut suffer-
ing from sudden cardiac arrest to be lower than 5% [76].
Rationale for the recommendation The context of a
space mission represents a highly remote setting. The
crew might comprise only of members with limited
medical training and medical equipment and medica-
tions are scarce with no option for resupply. Further-
more, external help and evacuation is unavailable or
difficult. These factors impair the prognosis of a patient
in ROSC as no further treatment in an advanced medical
facility is available.
As the cause of the arrest is sometimes not obvious in
the emergency treatment, we recommend delivering full
ALS therapy for a patient in cardiac arrest in micrograv-
ity whenever possible, acknowledging that post resuscita-
tion care will be suboptimal.
Intravenous access/ drug administration
When should venous access be attempted? Recom-
mendation 16: Venous access SHOULD ONLY be per-
formed if more than two rescuers are present during a
cardiac arrest and high-quality CPR is performed.
Evidence summary Intravenous access in microgravity
has never been investigated specifically, but it was
included in different studies as a consequence of the pri-
mary intervention [65,67]. It was shown that intraven-
ous access could be successfully obtained [67].
Rationale for the recommendation Venous access and
drug therapy are integral parts of the ACLS algorithm
[42]. However, these steps are less critical then chest
compressions, defibrillation and ventilation. We, there-
fore, recommend only attempting venous access once ef-
fective CPR is ongoing.
Which drug administration route should be
attempted first? Recommendation 17: As a first choice
for the application of medication a peripheral venous
cannulation SHOULD be used.
Evidence summary Intravenous access in microgravity
has never been investigated specifically, but it was in-
cluded in different studies as a byproduct [65,67].
Rationale for the recommendation The current CPR
guidelines incorporate the recommendation to attempt
intravenous access as a first route for drug administra-
tion [42]. As it has been proven, that intravenous access
in microgravity can be established we recommend
choosing it as a first route for drug administration in
microgravity.
Which alternative should be used for venous access?
Recommendation 18: When a peripheral venous access
cannot be established in a patient in cardiac arrest in
microgravity, the intraosseous tibial route SHOULD be
used.
Evidence summary There has been no study conducted
which investigates the performance of intraosseous ac-
cess during cardiac arrest in microgravity.
Rationale for the recommendation The current CPR
guidelines incorporate the recommendation to establish
an intraosseous access in a patient in cardiac arrest
when the intravenous cannulation fails. The intraosseous
route achieved similar plasma drug concentrations as
the intravenous route in a comparable time [77]. Also,
the training to learn and retain skills for intraosseous ac-
cess is moderate [78] and equipment for its application
is readily available. We, therefore, recommend the appli-
cation of intraosseous access as a second line for failed
intravenous access attempt on a patient in cardiac arrest
in microgravity, although it has never been tested in
microgravity.
How should an infusion be administered? Recommen-
dation 19: For intravenous and intraosseous infusion, a
degassed infusion bag encased in a pressure bag
SHOULD be used.
Evidence summary No study specifically investigated
the best way to administer intravenous fluids in a patient
in cardiac arrest. However, they were tested in an ATLS
study in microgravity during parabolic flights [65]. In
this study, degassed infusion bags encased in a pressure
bag were effectively used to administer crystalloid fluids
[65]. In a different study, an electric infusion pump was
successfully used to administer intravenous fluids in a
mannequin model [67].
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 10 of 18

Rationale for the recommendation Different options
are available for continuous infusion of intravenous
fluids. One is utilization of an infusion pump to adminis-
ter intravenous fluids. Another option would be the de-
gassed infusion bag encased in a pressure bag. The
advantage of the pressure bag lies in its simplicity. As it
does not rely on electrical power and an electrical
motor, it offers fewer failure possibilities. Also, the appli-
cation time of a simple pressure bag is probably shorter
than the time to prepare and start an advanced infusion
pump. We therefore recommend the use of a degassed
infusion bag encased in a pressure bag for quick admin-
istration of intravenous fluids in the emergency situation
of a cardiac arrest in microgravity.
Telemedicine
Should telemedicine support be consulted in LEO?
Recommendation 20: In low earth orbit telemedicine sup-
port SHOULD be consulted in the event of a cardiac ar-
rest, when it seems feasible and the manpower for its
application is present.
Evidence summary No study directly investigated the
use of telemedicine support during CPR in a patient in
cardiac arrest in microgravity. However, telemedicine
support in the performance of emergency medical pro-
cedures such as chest drain insertion has been success-
fully tested [65].
Rationale for the recommendation In the terrestrial
setting, telemedicine is an accepted addition for emer-
gency therapy in critically ill patients [79,80]. However,
CPR requires immediate action of all available crew-
members and emphasis should be put on the onboard
best quality treatment of the patient. In the first minutes
of a cardiac arrest the crew will be fully engaged to per-
form the CPR algorithm and the skills necessary to do
so.
Also, telemedicine support will probably not be able to
positively influence the application of these crucial first
CPR steps. Therefore, we believe, that the focus should
lie on the autonomous application of CPR by the crew-
members. Only if CPR can be performed without endan-
gering quality, one member of the crew should try and
seek telemedicine support.
Should telemedicine support be consulted during
space exploration missions? Recommendation 21:
During space exploration missions to Mars telemedicine
support will be impractical during CPR due to the com-
municational time-delay (3–23 min) and SHOULD only
be attempted, when additional crewmembers, not in-
volved in treating the patient, are present.
Evidence summary Communication delay from Mars to
Earth is estimated to range between 3 and 23 min each
way [81–83].
Rationale for the recommendation Because of the long
time delay no relevant benefit from telemedicine support
in the initial phase of CPR is expected. A response from
Mission Control would subsequently take 6 to 46 min.
As successful resuscitation attempts often last less than
15 min until ROSC [84,85], it is highly unlikely that
telemedicine support will have a beneficial impact in the
initial phase of CPR treatment. However, the crew will
be obliged to inform Mission Control of an ongoing
medical emergency.
Who should make the decision to terminate CPR if
necessary? Recommendation 22: The decision to termin-
ate resuscitation SHOULD be made by the crewmember
with the highest medical qualification after consultation
with telemedicine support. Only if telemedicine support is
unavailable or time delay prevents prompt feedback the
decision has to be made by the crewmember with the
highest medical qualification alone.
Evidence summary There are no studies investigating
the termination of CPR in a patient in cardiac arrest
during spaceflight. In addition, this topic remains highly
controversial even in the terrestrial setting.
Rationale for the recommendation The topic of ter-
mination of CPR remains a highly controversial one,
even in the terrestrial setting [86–88]. Especially for a
crew in spaceflight, the decision to terminate a CPR at-
tempt will be extraordinary challenging because of the
close personal relation to the patient and the remote set-
ting. As a physician might not be part of the crew, either
another crew member with special medical training
(nurse, paramedic, etc.) or a CMO will oversee resuscita-
tion. It is subsequently their duty to terminate the treat-
ment if the situation is deemed futile.
This decision surely requires communication with the
crewmembers involved in the treatment. Furthermore, it
should be attempted to consult the telemedicine support
on this decision. If telemedicine support is unavailable
or communication delay appears to be inadequate to the
medical leader, the decision to terminate CPR should be
made, nonetheless. It is their obligation to the crew to
prevent ongoing CPR in a futile situation and to preserve
the medical equipment and drugs for future possible
emergencies.
Ethics
Next to recommendations concerning the best clinical
practice for successful CPR during spaceflight, ethical
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 11 of 18

and psychological / psychiatric issues deserve attention
in this context; particularly since peculiarities of CPR are
entangled with specific characteristics of space flight.
While there is some evidence regarding psychological,
neuro-behavioural aspects [89] and ethical issues of
space flight [90], there is no guidance available to date
about specific considerations in the context of CPR. The
issues raised in this section are therefore not intended as
recommendations, but rather as questions for reflection,
and as future research directions.
Ethical questions related to CPR
Futility is a major ethical issue discussed in the context
of CPR on Earth –i.e. if an intervention is considered to
be futile in terms of its benefit for length and quality of
life, its ethical justification is questionable. However,
there are no clear boundaries for futility; this may even
be aggravated in the context of space flight since the
death of one crew member may jeopardise the whole
mission, resulting in potential conflicts of interest be-
tween the crew and the person at risk of death. More-
over, decision-making is complicated by the fact that it
will be virtually impossible to involve proxies (e.g. family
members) due to remote communication with the
ground.
The AHA recommends considering the values of pa-
tients, healthcare providers and local society in deter-
mining the appropriateness of CPR for an individual
patient [91]. Given the particular normative, cultural,
and spatial conditions of space flight, a context-specific
ethical framework is needed to support ethically respon-
sible decision-making concerning the application and
continuation of CPR during space flight. This requires
discussing acceptable and sustainable values regarding
CPR, including questions of futility, dignity, information
of the family, and proactive strategies such as advance
directives / “Do Not Attempt CPR”(DNACPR) orders.
An ethical framework also involves strategies to antici-
pate or assess the presumed will of the person in need of
CPR, as well as measures to be taken for crew members
in order to be prepared for the challenges related to
such a decision, and to cope with the decision and its
outcomes both as individuals and as a ‘community of
destiny’. In addition, pre-mission training should include
reflection on diverse scenarios (e.g., survival of the crew
member, survival with impairment, or death).
Another ethical question regards the adequate and
respectful dealing with the newly dead in case of un-
successful CPR. This includes the challenge of in-
formed consent with the use of newly dead patients
for research and training, and the balancing of inter-
ests between the protection of medical confidentiality
and the interest in gaining better insight in medical
issues in space through disclosure of information and
systematic collection of data [90].
Perceptual, cognitive, and psychomotor performance
For CPR on Earth, as is true for every emergency situ-
ation, a number of highly specific conditions, skills, and
psychophysiological prerequisites are essential. Next to
semantic and episodic knowledge on how to perform
CPR, its application demands (a) sympathetic function
such as attention, focused concentration, and quick re-
sponse capacity; (b) effective motor function, in particu-
lar fine motor skills; and (c) cognitive function in terms
of interpersonal interaction and decision-making. In the
remote microgravity environment, several factors are
complicating psychophysiological, cognitive, and motor
function.
For example, it was reported that the effects of micro-
gravity in addition to the working and living conditions
of space can induce stress states in astronauts that also
can lead to degradations of cognitive and psychomotor
performance [92]. Research on earth has shown that the
perceptual motor performance deteriorates under stress
[93–95], particularly with regard to control processes
such as the perception of time [96,97], the relationship
between automatic and controlled processes (inhibitory
processes), and the categorization of incoming informa-
tion [98,99]. A similar decrease of the perceptual motor
performances in the stressful environment of a space
mission could be confirmed [100–109], but it remains
unclear to what extend these observed deficits will
change during long- term space missions. Moreover,
findings suggest that increased feelings of loneliness and
abandonment may interfere with the cognitive perform-
ance [110] and that executive functions [111–114] and
decision making [115] are impaired in space missions.
Furthermore, the effect of microgravity is related to
mechanical and proprioceptive changes during the exe-
cution of movements, leading to a disruption of the
usual relationships among efferent and afferent signals
that has been referred to as a state of “sensorimotor dis-
cordance”[103]. With regards to CPR, the question
could be stressed whether these limitations also signifi-
cantly affect cognitive and psychomotor skills during re-
suscitation. However, the question also arises as to how
significant these limitations are and that, of course, re-
suscitation under the above-mentioned limitations is
better than no resuscitation at all. Considering situ-
ational restrictions concerning decision-making, struc-
tured guidelines for emergency situations like CPR are
urgently needed.
Intercultural issues
As a specific aspect of group dynamics, the international
and intercultural nature of space flight needs to be
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considered. Crews are diverse in terms of ethical and
cultural norms, e.g. regarding the broad ethical princi-
ples of beneficence, non-malevolence, autonomy, and
justice. For example, there may differences in emphasis
on patient autonomy or informed decision-making.
There may also be culturally diverse values and beliefs
concerning end-of-life, dealing with deceased persons,
handling emotions, spirituality, rituals of bereavement,
social behaviour norms [116]. More specifically with re-
spect to CPR, this may have implications for questions
concerning the beginning and ending of CPR [91].
Moreover, there may be different manifestations of emo-
tional reactions to distressing situations [116] which may
pose a challenge in terms of interpersonal communica-
tion and group dynamics.
Possible prevention and treatment approaches
During long-duration expeditions, where higher crew au-
tonomy and communication delays with the Earth will be
unavoidable, the ability to deal with psychiatric problems
on board becomes especially important. There will be no
possibility to evacuate an ill crewmember and the commu-
nication delays will make real-time conversation with spe-
cialists back home impossible. As a consequence, support
will depend on crew members being trained in psycho-
logical counselling and the use of psychoactive medications.
This person should have a knowledge of [1]: individual psy-
chopathology and small group behaviour [2]; the individual
and interpersonal effects of stressors to be expected during
the mission [3]; crisis intervention techniques and the facili-
tation of group awareness, cohesion, and teambuilding; and
[4] the appropriate use of tranquilizers and other psycho-
active medications, including their usefulness and side
effects under conditions of microgravity [117,118]. Studies
suggested that computer-based intervention programs ap-
plying cognitive-behavioural and self-help instruction may
be as effective as face-to-face intervention for dealing with
mild types of psychopathology [119–121]. Pre-mission
trainings should be implemented by each space agency
based on international agreements and focus on further de-
velopment of coping abilities of individual crewmembers
and crews [89].
According to evidence from space and other isolated
and confined settings, intra crew tension, leadership
styles, and group dynamics are key factors responsible
for exacerbating or ameliorating stress, or facilitating
coping and adaptation [118,122] and should be included
in these training programs, as well as self-care and self-
management and cross-cultural aspects in the prepar-
ation for long-term missions.
Conclusion and future research directions
We argue that for an adequate consideration of ethical
and psychological issues surrounding CPR during space
flight, a multi-level approach is needed. An important
systemic prerequisite will be a general ethical and psy-
chological framework that allows for a culture of con-
structively dealing with fragility and finiteness in a
context where fitness, strength, and controllability are
key requisites. This already starts with the mission selec-
tion process, when fear of disqualification may result in
underreporting of medical problems [90]. Pre-mission
trainings should address ethical issues and psychological
coping strategies in emergency situations. Moreover,
context-specific prevention and treatment approaches
need to be ensured, as well as the presence of crew
members trained in counselling and the use of psycho-
active medication. Future research should address these
ethical and psychological tension fields in order to eluci-
date expedient starting points for intervention. Herein,
participatory approaches involving key stakeholders may
be fruitful to initiate and maintain dialogue with respect
to the conditions that are needed to create an ethically
and psychologically sustainable environment of care in
the case of CPR.
Summary and conclusions
This guideline is intended to summarize the available
evidence for the application of CPR in a patient in car-
diac arrest in microgravity. It is an early attempt at im-
proving CPR performance in this special setting. The
authors acknowledge that a cardiac arrest during space-
flight is a highly unlikely scenario at the moment. As it
has never happened, real life experience is missing. But,
with the future rise of space tourism and the increase of
missions to the Moon and potentially to Mars, cardiac
arrest onboard a spacecraft is a real possibility.
Several studies have assessed CPR techniques in
microgravity. However, most of those studies concen-
trated on the application of chest compressions. In con-
trast, there are only four studies investigating airway
management in microgravity. The evidence for many
other aspects of CPR such as defibrillation, drug therapy
or post resuscitation care remains minimal to non-
existent. Therefore, this guideline faces also some im-
portant limitations.
Furthermore, the available studies were either per-
formed in microgravity during parabolic flights, during
simulated microgravity in a body suspension device or
underwater. All of those settings pose their own limita-
tions. Parabolic flight only allows for 20–22 s of micro-
gravity and, thus, many experiments are unable to
investigate the application chest compressions over real-
istic periods of time (2-min duration of a standard chest
compression cycle).
Body suspension devices allow the observation during
longer periods, but only simulate an imperfect micro-
gravity since the subjects are still affected by Earth’s
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 13 of 18

gravity. Underwater scenarios are also used to simulate
microgravity. If neutral buoyancy in the experimental
setup is achieved, microgravity can be simulated. But the
necessary preparations concerning equipment (buoyancy
control device, regulator, diving goggles, etc.) and hand-
ling limit the transferability of such a scenario to actual
spaceflight.
CPR in microgravity is feasible. However, it requires
modifications of the terrestrial guidelines to consider the
unique challenges of microgravity and long duration
spaceflight. Not only does the lack of gravity dictate spe-
cial techniques for chest compressions, the clinical re-
sources are extremely limited. This is primarily caused
by the unavailability of imminent support and evacu-
ation capabilities. Furthermore, limitations concerning
equipment and training restrict the availability of proper
post resuscitation care in form of an intensive care unit.
Therefore, and in the absence of any scientific evidence
for intensive care in microgravity, no explicit recommen-
dations concerning post-resuscitation care were made in
this guideline.
One additional factor is that the main task of the crew
is the mission, and medical training and preparations
only make up a small part of astronaut training. They
therefore have limited opportunity to develop clinical
confidence required for successful CPR. A future crew
for space exploration missions might not include a phys-
ician experienced in emergency medicine, or the phys-
ician might become incapacitated, which further
decreases the medical capabilities of the whole crew.
This guideline represents a first step to lay an evidence-
based foundation for CPR in microgravity during
spaceflight.
Further studies are necessary, but this guideline forms
a framework for future research priority setting in emer-
gency space medicine. However, the upcoming Moon
missions and the medical experiments that will be per-
formed during those missions will hopefully enrich our
knowledge on emergency medicine in microgravity. Al-
though no one would ever hope for real-life medical
emergencies, it is only a matter of time until the first
cardiac arrest during spaceflight happens. It can only be
our task to equip our crews with the best techniques
and treatment strategies.
Supplementary information
Supplementary information accompanies this paper at https://doi.org/10.
1186/s13049-020-00793-y.
Additional file 1. PICO-questions, literature search strings for PUBMED
and retrieved hits as of 31
st
July 2017.
Abbreviations
ACCD: Automated Chest Compression Devices; AED: Automated external
defibrillator; AHA: American Heart Association; ALS: Advanced life support;
BLS: Basic life support; CHeCS: Crew health care system; CMO: Crew Medical
Officer; CMRS: Crew medical restraint system; CPR: Cardiopulmonary
resuscitation; DGLRM: Deutsche Gesellschaft für Luft- und Raumfahrtmedizin,
German Society of Aviation and Space Medicine; ER: Evetts-Russomano;
ERC: European Resuscitation Council; ESAM: European Society of Aerospace
Medicine; ESAM-SMG: Space Medicine Group, European Society of Aerospace
Medicine; GRADE: The Grading of Recommendations Assessment,
Development and Evaluation; HS: Handstand; ILCOR: International Liaison
Committee on Resuscitation; LEO: Low earth orbit; LMA: Laryngeal mask;
NASA: National Aeronautics and Space Administration; PEA: Pulseless electric
activity; PICO: Population, Intervention, Comparison, Outcome; pVT: Pulseless
ventricular tachycardia; RBH: Reverse bear hug; ROSC: Return of spontaneous
circulation; SAD: Supraglottic airway device; SGA: Supraglottic airway;
TI: Tracheal intubation; TT: Tracheal tube; VF: Ventricular fibrillation
Acknowledgements
Not applicable
Authors’contributions
JH acted as the chairperson of the research group, JH and SK planned the
guideline, SK drafted the literature search, all authors corrected and
improved the literature search, SK applied the search strategy, JH, SK, MK
and CN lead the literature review process, JH solved conflicting screening
decisions, SK obtained the full length papers, JH, JS and SK performed the
GRADE, SK scheduled the teams for separate section recommendations, all
authors prepared and drafted recommendations based on the available
evidence, SK moderated the DELPHI-process, JH and SK defined the strength
of recommendations, JH and SK drafted the manuscript with support of all
authors, especially JS; TR, LR, AN, MK and CA. All authors read and approved
the final manuscript.
Funding
This guideline did not receive any funding. Open Access funding enabled
and organized by Projekt DEAL.
Availability of data and materials
Not applicable
Ethics approval and consent to participate
Not applicabale
Consent for publication
Not applicable
Competing interests
The authors declare that they have no competing interests.
Author details
1
German Society of Aviation and Space Medicine (DGLRM), Munich,
Germany.
2
Department of Anaesthesiology and Intensive Care Medicine,
University Hospital of Cologne, 50937 Cologne, Germany.
3
Space Medicine
Group, European Society of Aerospace Medicine (ESAM), Cologne, Germany.
4
Department of Internal Medicine III, Heart Centre of the University of
Cologne, Cologne, Germany.
5
Fire Department City of Cologne, Institute for
Security Science and Rescue Technology, Cologne, Germany.
6
Department of
Anaesthesia and Intensive Care, Örebro University Hospital, Örebro, Sweden.
7
Department of Anesthesiology, University of Florida College of Medicine,
Jacksonville, FL, USA.
8
Department of Cardiology and Angiology, Heart
Center Duisburg, Evangelisches Klinikum Niederrhein, Duisburg, Germany.
9
Department of Anaesthesia and Intensive Care, Santa Maria delle Grazie
Hospital, Pozzuoli, Naples, Italy.
10
Division of Anaesthesia, Analgesia, and
Intensive Care, Department of Surgical and Biomedical Sciences, University of
Perugia, Perugia, Italy.
11
Gerbrunn, Germany.
12
Department of Psychiatry and
Psychotherapy, Faculty of Medicine and University Hospital Cologne,
University of Cologne, 50937 Cologne, Germany.
13
Aerospace Medicine,
Centre of Human and Applied Physiological Sciences, King’s College,
London, UK.
14
Department of Otorhinolaryngology, Head and Neck Surgery,
University of Cologne, 50937 Cologne, Germany.
15
University of
Perugia-Terni, Perugia-Terni, Italy.
16
Cologne Center for Ethics, Rights,
Economics, and Social Sciences of Health (CERES), University of Cologne and
University Hospital of Cologne, Cologne, Germany.
17
Department of Surgery
Hinkelbein et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2020) 28:108 Page 14 of 18

and Cancer, Faculty of Medicine, Imperial College London, Exhibition road,
London SW7 2AZ, UK.
18
School of Nursing, University of Pennsylvania,
Philadelphia, PA, USA.
19
Accident and Emergency Department, Queen
Elizabeth University Hospital, Glasgow, Scotland.
20
Department of Anesthesia,
Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard
Medical School, Boston, USA.
21
Department of Anesthesiology, Heidelberg
University Hospital, Heidelberg, Germany.
22
University Hospital Southampton
NHS Foundation Trust, Anaesthetic Department, Southampton, UK.
23
Anesthesia and Postoperative Intensive Care Unit, AORN Cardarelli, Naples,
Italy.
24
Centre of Human and Applied Physiological Sciences, Kings College
London, London, UK.
25
Department of Anaesthesiology and Intensive Care
Medicine, Schön Klinik Düsseldorf, Am Heerdter Krankenhaus 2, 40549
Düsseldorf, Germany.
26
Anesthesiology Department, Brest University Hospital,
Brest, France.
27
Anesthesiology Department, Bretagne Sud General Hospital,
Lorient, France.
28
Medical and Maritime Simulation Center, Lorient, France.
29
Laboratory of Psychology, Cognition, Communication and Behavior,
University of Bretagne Sud, Vannes, France.
30
Academic Department of
Anaesthesia, Critical Care, Pain and Resuscitation, University Hospitals
Birmingham, Heart of England NHS Foundation Trust, Birmingham, UK.
31
University Department for Anesthesia, Intensive and Emergency Medicine
and Pain Management, Hospital Oldenburg, Oldenburg, Germany.
Received: 22 July 2020 Accepted: 7 October 2020
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