Extraterrestrial CPR and Its Applications in Terrestrial Medicine

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Chapter 8
Extraterrestrial CPR and Its Applications in Terrestrial
Medicine
Thais Russomano and Lucas Rehnberg
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/intechopen.70221
Provisional chapter
© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,
and reproduction in any medium, provided the original work is properly cited.
DOI: 10.5772/intechopen.70221
Extraterrestrial CPR and Its Applications in Terrestrial
Medicine
Thais Russomano and Lucas Rehnberg
Additional information is available at the end of the chapter
Abstract
Cardiopulmonary resuscitation (CPR) is a well-established part of basic life support
(BLS), saving countless lives since its rst development in the 1960s. Recently, work has
been undertaken to develop methods of basic and advanced life support (ALS) in micro-
gravity and hypogravity. Although the likelihood of a dangerous cardiac event occurring
during space mission is rare, the possibility exists. The selection process for space mis-
sions nowadays considers individuals at ages and with health standards that would have
precluded their selection in the past. The advent of space tourism may even enhance this
possibility. This chapter presents a synthesis of the results obtained in studies conducted
at the MicroG-PUCRS, Brazil, examining extraterrestrial CPR during ground-based
microgravity and hypogravity simulations and during parabolic ights and sustained
microgravity. It outlines the extraterrestrial BLS guidelines for both low-orbit and deep-
space missions. The former are based on a combination of factors, unique for the envi-
ronment of space. In a seing like this, increased physiological stress due to gravitational
adaptation and the isolated nature of the environmental demands can aect the outcome
of resuscitation procedure.
Keywords: extraterrestrial CPR, microgravity, hypogravity, medical emergencies,
cardiac arrest, BLS, space tourism, space missions, space medicine, space physiology
1. Introduction
Cardiopulmonary resuscitation (CPR) is a well-established part of basic life support (BLS)
and has saved tens of thousands of lives [1] since its development by Peter Safar in the 1960s
[2]. Terrestrial BLS guidelines are developed by national organisations, such as the American
Heart Association (AHA), the European Resuscitation Council (ERC) and the International
Liaison Commiee on Resuscitation (ILCOR). The terrestrial method of performing CPR has
© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.

not changed signicantly since it was rst implemented, the locked straight-arm method
with the rescuer accelerating their chest to generate the force needed to compress the victim’s
chest. Other aspects of the BLS guidelines often change and evolve as new evidence emerges,
one example being the Chain of Survival, which has recently been updated [3]: (1) immediate
recognition of cardiac arrest and activation of the emergency response system, (2) early CPR
with an emphasis on chest compressions, (3) rapid debrillation, (4) eective advanced life
support and (5) integrated post-cardiac arrest care [4–6].
Changes in gravitational elds, such as those found in the microgravity of space and hypo-
gravity of Mars or the Moon, pose several practical and logistical problems that will impact on
the eectiveness of the CPR administered and aect the outcome for any patient who experi-
ences a cardiac arrest in a space mission. In recent years, several studies have been undertaken
to develop methods of basic and advanced life support (ALS) in microgravity and hypograv-
ity, using ground-based simulations, parabolic ights or training for medical emergencies in
actual space missions.
It is important rstly to understand some of the physics behind space life sciences. The grav-
itational force of the Earth, which produces an acceleration of approximately 9.81 m/s2 at
mean sea level and is indicated by the symbol ‘g’ (small leer), has shaped the anatomy and
physiology of human beings over millions of years. The concept of human body G vectors
uses an axial nomenclature system that has been the basis for studies related to acceleration
physiology since its introduction [7]. The three major axes are longitudinal (Z), lateral (Y) and
horizontal (X). The direction of acceleration forces along the axes is called (+) or (−), but in
general the positive sign is omied. The inertial forces are opposite to the acceleration forces,
as indicated in Figure 1. Therefore, when considering the eects of the G force on human
physiology, it is important to indicate the axis and the direction of the acceleration force along
it. For example, when a volunteer is performing terrestrial CPR manoeuvres, it is said that
they are under the inuence of 1 Gz.
It is a common misconception that gravity does not exist in space, either aboard space ships
or space stations in lower earth orbit (LEO). Typical LEO ranges from between 120 and 360
miles above the Earth, and the gravitational eld at this distance is still quite strong, roughly
88% of that felt at the Earth’s surface. Therefore, what is often referred to as ‘zero gravity’ is
in fact microgravity, an important dierence to note, and the objects or astronauts seen to be
‘oating’ in space are in reality in a constant state of free fall. This means they are actually
falling around the Earth at the same rate as the orbital speed of their spacecraft, which is
approximately 17,500 miles/h (28,000 km/h), providing the same eect that would be given
by real microgravity [9].
The prex micro (μ) derives from the original Greek mikros (μικρός), meaning small.
A microgravity environment is one that imparts to an object a net acceleration that is
extremely small compared with that produced by Earth at its surface, which can be achieved
using various methods, including Earth-based drop towers, parabolic aircraft ights and
Earth-orbiting laboratories. Exposure to microgravity has been shown to aect every single
body system, and the resultant physiological changes can lead to undesirable health conse-
quences [9, 10].
Resuscitation Aspects116

The acceleration due to gravity at the surface of a planet varies directly as the mass and
inversely as the square of the radius. The Moon is 384,403 km distant from the Earth, and
it has a diameter of 3476 km. The acceleration due to gravity is 1.62 m/s2 (1/6 of the Earth)
because the Moon has less mass than the Earth. Mars and Earth have diameters of 6775 km
and 12,775 km, respectively. The mass of Mars is 0.107 times that of the Earth. This makes the
gravitational acceleration on Mars 3.73 m/s2, as expressed in Eq. (1):
gm = 9.8 × 0.107 ×
(
12775 / 6775
)
2 = 3.73m / s
2 (1)
Therefore, if a body weighs 200 N on Earth, it is possible to calculate how much it would
weigh on Mars. Knowing that the weight of an object is its mass (m) times the acceleration of
gravity, we can have W = m × g, 200 = 9.8 × m and m = 20.41 kg. This mass is the same on Mars,
so the weight on Mars is WMars = 3.73 × 20.41 = 76.1 N and mMars = 7.61 kg.
Some of the physical principles of microgravity and hypogravity have been explained above
to clarify some of the common terminology and misconceptions. Throughout this chapter, we
will use the terms microgravity and hypogravity. When discussing microgravity, commonly
referred to as ‘weightlessness’ by laypersons, we are referring to being in space either aboard
Figure 1. Standard acceleration nomenclature. Note that the arrows indicate the direction of the inertial reaction to an
equal and opposite acceleration [7, 8].
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a space craft or aboard a space station and not on the surface of any extraterrestrial body.
When talking about hypogravity, this relates to being on the surface of another extraterres-
trial body (i.e. Mars, Moon) as these surfaces do have a gravitational eld; however, they are
weaker than that of Earth’s.
This chapter will rst present the eects of a space mission on human physiology, con-
sidering in particular cardiovascular and pulmonary function and their adaptation to the
hostile environment of space. It will then discuss more than a decade of research involving
a series of studies examining extraterrestrial CPR during ground-based microgravity and
hypogravity simulations and during parabolic ights. It will also outline the essential CPR
steps, in the form of extraterrestrial CPR guidelines, to be applied for both low-orbit and
deep-space missions, such as a trip to Mars. The rationale behind the creation of specic
guidelines for microgravity and hypogravity BLS and CPR is based on a combination of
factors that render current traditional methods inappropriate for use in the unique envi-
ronment of space, a seing in which the human body must adapt to altered gravitational
conditions that lead to increased physiological stress, and where the isolated nature of the
environment demands greater self-reliance, all of which may hinder a successful outcome
when resuscitating a patient.
2. The eects of microgravity on human physiology and its impact on
the cardiopulmonary system
Physiological alterations suered by astronauts during space missions have been observed,
reported and studied from the beginning of manned space ight. The microgravity of space
appears to aect every single organ and body system of the astronauts, in dierent intensi-
ties and manner, both during short- and long-term missions. The rst men to remain in space
longer than 24 h were Soviet cosmonauts Titov and Nikolayev in the 1960s. Postight data
collection revealed that the cardiovascular systems of the cosmonauts presented problems in
readapting to the gravity of the Earth, with both exhibiting diculties in maintaining arterial
blood pressure levels when standing [9].
During the initial phases of the American space programme, NASA astronauts from the
Gemini, Apollo and Skylab missions also showed deleterious signs and symptoms related
to exposure to microgravity. Although these early ventures into the space environment were
shorter than the missions nowadays, with the longest being a 3-month Skylab ight, it was
already evident that the eects of microgravity on the human body would be very challeng-
ing. For example, astronauts presented decreases in plasma volume (around 10–20%); red
blood cells (space anaemia); bone calcium levels (bone demineralisation); skeletal muscle
size and strength (muscle atrophy), especially those that support posture (anti-gravitational
muscles and bones); intestinal mobility; immune responses; and sleeping hours [10–13]. Most
astronauts also suered from space motion sickness, which is a common condition, aecting
around 70% of astronauts during the rst 72 h of a space mission, causing nausea, vomiting,
dizziness and light-headedness and consequently decreasing physical and mental perfor-
mance and overall well-being [14].
Resuscitation Aspects118

Moreover, very early in the manned space ight era, it became clear that the harmful eects
on human physiology and anatomy would not be restricted solely to the time spent in micro-
gravity. Important postight alterations were also apparent after the return of astronauts to
Earth’s gravity, such as neurovestibular disturbances, orthostatic intolerance and reduced
aerobic capacity [15].
2.1. Space cardiovascular physiology
A progressive shift of body uids and blood from the lower extremities to the upper body
occurs in the absence of Earth’s gravitational force [16, 17]. Initially, this upward shift increases
the central uid volume, cardiac size (around 20%) and cardiac output. It then leads to a nega-
tive uid balance and reduction of 12–20% in the circulating blood volume [17], which causes
a decreased resting stroke volume of 10–20% and a reduced cardiac output with an average of
1.5 L min−1 lower than preight values [18, 19]. These changes are secondary to the reduction
in circulating blood volume [20].
This condition has been nicknamed the ‘puy-face and bird-legs syndrome’, as the face of the
astronaut becomes rounded, redder and more swollen, while the legs become thinner, due to
the redistribution of uids and blood from the lower to upper body. The situation is reversed
when the astronaut is once more subject to the gravitational force of the Earth, which distributes
the uid and blood back to its original position [16, 21]. These stages of cardiovascular adaption
to microgravity and subsequent readaptation upon return to Earth are represented in Figure 2.
Arterial blood pressure and heart rate are more dicult to evaluate during a space mission.
While some studies have demonstrated that microgravity can decrease both arterial blood
pressure and heart rate [20, 22], others have shown that heart rate, for example, remains
unchanged in microgravity [23]. Research is reporting average decrease of 15 bpmin ight
resting heart rate and an average decrease of 6 mmHg in mean arterial pressure. These car-
diovascular changes were observed when compared with preight standing values and not
supine [22]. In addition, the arterial blood pressure reduction occurred in diastolic values,
while systolic blood pressure remained unchanged from that of preight.
More recently, visual impairment intracranial pressure (VIIP) syndrome has been identied as a
health issue occurring in astronauts who have stayed in microgravity for at least 6 months. This
syndrome was rst reported in 2005, when a refractive change in visual acuity (mainly hypero-
pia) was detected after a long-term space mission. This nding was further conrmed through
evaluations conducted by means of a series of questionnaires applied to astronauts who took part
in long space ight missions on the ISS [24]. Very lile is known regarding the risk factors and
pathophysiological mechanisms involved in space VIIP syndrome. The current consensus within
the space ight community is that visual changes and eye alterations (papilloedema, posterior
globe aening, hyperopic shift, choroidal folds) are a consequence of raised intracranial pres-
sures resulting in optic nerve sheath distension. This increase in optic nerve sheath diameter can
readily be measured using a simple, non-invasive and low-cost ophthalmic procedure, resulting
in an easy way to diagnose this medical condition [25]. However, other factors, such as increased
levels of carbon dioxide in the spacecraft, genetic predisposition and ocular and/or brain struc-
tural changes secondary to microgravity could also be involved in the aetiology of this syndrome.
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Although no serious cardiac events in space have required resuscitation to date, the over-
all risk of potential cardiac deconditioning developing into a life-threatening illness is
approximately 1% per year [26, 27]. Despite this low gure, some documented cases of
astronauts presenting disturbances in cardiac rhythm have been observed, such as ven-
tricular tachycardia and prolonged QTc interval after short- and long-duration ights.
However, there is lile compelling evidence from ight data that space causes cardiac
dysfunction or life-threatening dysrhythmias [28, 29]. Ventricular arrhythmias were also
reported during the second month aboard the MIR space station [30], and a loss of left ven-
tricular mass was seen during the exposure to microgravity [31]. These factors combined
could pose extra stress to the cardiovascular system and, in a worst-case scenario, lead to
cardiac arrest [32].
Figure 2. Schematic view of the blood and uid distribution on Earth (1), after insertion into microgravity (2), during
space adaptation (3) and upon return to Earth (4). Note that the puy-face and bird-legs syndrome occurs in numbers
2 and 3 [16, 21].
Resuscitation Aspects120

2.2. Space respiratory physiology
Short- and long-term exposure to microgravity produces several eects on lung volumes,
capacities and function, which have been assessed during space missions and parabolic
ights, as well as in ground-based studies.
Evidence has shown that there is a 4 mm increase in the anteroposterior (AP) dimension of
the chest wall at the level of the fth intercostal space during microgravity exposure. This
expansion can be explained by a decrease in weight of the abdominal wall, which allows
the sternum to move in a cranial direction. As well as expanding the ribcage, this induces
subsequent relaxation of parasternal intercostal muscles, further increasing the AP distance
[33]. The eect of microgravity on chest anatomy was also observed during parabolic ights,
whereby a displacement of the sternum in the cranial direction was found in microgravity,
accompanied by an increase in diameter of the lower rib cage. This change in position of the
chest wall was predicted to cause the volume-pressure curve to lie between the standing-
upright and the supine-position curves, with the net result of a reduction in lung volumes. In
ve subjects studied in a KC-135 aircraft during parabolic ight, functional residual capacity
decreased by 432 ml during exposure to the acute microgravity phase. Vital capacity also
reduced from a mean value of 4.72 L at 1 G to 4.35 L at 0 G. Forced vital capacity and forced
expiratory volume in 1 s were also decreased by an average of 2.5% in the 20 s of microgravity
per parabola in a parabolic ight [34].
During the 9-day-long Space Life Sciences-1 space mission, forced vital capacity and forced
expiratory volume in 1s were signicantly reduced on ight day 2 due to the eect of sus-
tained microgravity but were greater than preight values at day 9. In comparison with
standing preight values, tidal volume was decreased by 15% (110 ml) in microgravity, and
this reduction remained during the entire space ight. Functional residual capacity and expi-
ratory reserve volume decreased signicantly in-ight by 520 and 370 ml, respectively, when
compared with preight standing values. Residual volume was less during ight by 350 ml,
when compared with standing control values. This 20% reduction in the residual volume was
unexpected as it is normally fairly resistant to change. It is believed that lung volumes are
aected by the changes in intrathoracic blood volume that occurs throughout a mission and
by the alterations in respiratory mechanics and cranial displacement of the diaphragm and
abdominal content that happens in the absence of gravity [35].
The gravitational gradient aects the distribution of ventilation and perfusion in the upright
human lung. This uneven distribution of ventilation and blood ow within the lungs leads to
variations in ventilation-perfusion ratios. Cardiogenic oscillations of CO2 decreased to approx-
imately 60% in amplitude in microgravity [36], and there was also a signicant reduction in
cardiogenic oscillations of nitrogen (to 44%) and argon (to 24%) in comparison to preight
standing values [37]. Possible causes of the residual inhomogeneity of ventilation include
regional dierences in lung compliance, airway resistance and the motion of the chest wall and
diaphragm. Microgravity was expected to completely abolish apicobasal dierences in perfu-
sion, and its persistence is possibly related to other mechanisms not aected by gravity, such
as central-peripheral dierences in blood ow and interregional dierences in conductance.
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The diusion capacity of the lung has been shown to increase by 62% in a parabolic ight
study and by 28% in sustained microgravity when values were compared with preight
standing values [36, 38]. The standing-to-supine transition pre- and postight caused a sig-
nicant elevation in blood volume in pulmonary capillaries. Diusing capacity of the mem-
brane was unchanged preight in the standing-to-supine transition and signicantly elevated
in-ight in comparison to standing (27%) and supine (21%). In microgravity, the capillary
lling is uniform, which is associated with a large increase in the surface area of the blood-gas
barrier. Consequently, the membrane-diusing capacity is substantially raised. This suggests
an absence of subclinical interstitial pulmonary oedema in microgravity, as had been previ-
ously speculated [38, 39].
The overall eect of acute and sustained exposure to microgravity, although aecting the respi-
ratory system, does not cause any deleterious eects to gas exchange in the lungs. However,
there is no current suitable method of accessing arterial blood in space. Consequently, at pres-
ent, values for blood-gas tensions are usually derived from measurements of respiratory gas
partial pressures. To this end, the earlobe arterialised blood technique for collecting blood-gas
tensions has been considered for use in space [40]. Access to arterial blood analysis would
allow beer physiological evaluations and the management of clinical emergencies during
space missions, resulting in increased safety for crewmembers.
3. Current cardiopulmonary resuscitation (CPR) practice in microgravity
and hypogravity and its simulations on Earth
Although the likelihood of a dangerous cardiac event occurring in a space mission at present
is rare, the possibility exists. The selection process for space missions nowadays considers
individuals at ages and with health standards that would have precluded their selection in
the past. With increased age, less stringent health requirements, longer duration missions
and increased physical labour, due to a rise in orbital extravehicular activity, the risk of an
acute life-threatening condition occurring in space has become of greater concern. The advent
of space tourism may even enhance this possibility, with its popularity set to rise over the
coming years as private companies test their new technology. Therefore, space scientists and
physicians will have a greater responsibility to ensure space travellers, whether professional
astronauts or space tourists, are adequately trained and familiarised with extraterrestrial BLS
and CPR methods.
It is currently estimated that the time between the occurrence of cardiac arrest and the per-
formance of ALS on a secured patient during a space mission ranges between 2 and 4 min
[41]. However, BLS guidelines highlight that failure of the circulation for 3 min will lead
to cerebral damage and that delay, even within this time frame, will lessen the chances of
a successful outcome. Therefore, the rate of decline of a patient who has suered cardiac
arrest is dependent, amongst other things, upon the immediate initiation of CPR and the
provision and adequacy of such prior to the return of spontaneous circulation, should this
be achieved [3].
Resuscitation Aspects122

3.1. Extraterrestrial CPR simulations
The main dierence in CPR in hypogravity and microgravity compared to terrestrial CPR is
the strength of the gravitational eld. In microgravity, patient and rescuer are both essentially
weightless. When thinking about the technique of terrestrial CPR, with the rescuer acceler-
ating their chest and upper body to generate a force to compress the patient’s chest, it is
obvious that this cannot work in microgravity without signicant aids. To this end, several
microgravity CPR techniques have been developed and tested in parabolic ights [4, 42, 43]
and during ground simulations, such as when using a body suspension device system, to test
their ecacy [5, 44, 45].
3.1.1. Body suspension device system
Many partial-gravity suspension systems have been designed and used since the Apollo pro-
gram. The cable suspension method typically uses vertical cables to suspend the major seg-
ments of the body and relieve some of the weight exerted by the subject on the ground, thus
simulating partial gravity. A body suspension device (BSD) system used to simulate both
hypogravity and microgravity was developed by the Aerospace Engineering Laboratory,
MicroG Centre, PUCRS, Porto Alegre, Brazil. It consists of carbon steel bars, 0.6 mm × 0.3 mm
in thickness, which are shaped into a prism frame. It has a height of 2000 mm, with a base of
3000 mm × 2260 mm [46].
This BSD has been used to simulate microgravity by fully suspending a volunteer and CPR
mannequin. A steel cross bar (1205 mm × 27.5 mm) was hung using reinforced steel wiring
that gave it the ability to withstand up to 600 kg. A static nylon rope was aached to the steel
wiring of the cross bar, with carabineers fastened at each end, which were clipped to the cor-
responding hip aachments of the body harness worn by the volunteer. A safety carabineer
was also aached to the volunteer’s back. Figure 3(A) and (B) illustrates how CPR methods
can be studied during microgravity simulations on Earth [5].
Figure 3. (a) The body suspension device system of the MicroG Centre, with the volunteer perpendicular and the
CPR mannequin parallel to the oor, both being fully suspended, simulating microgravity. (b) The body suspension
device system of the MicroG Centre, with both the fully suspended volunteer and CPR mannequin parallel to the oor,
simulating microgravity.
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Another way to simulate microgravity for the performance of CPR is placing the mannequin
in the vertical position supported by a wall, which avoids the use of the rescuer body weight
during the external chest compressions, as represented in Figure 4.
The BSD comprises of a body harness and counterweight system made of 20 bars of 5 kg
each. Counterweights were used to simulate hypogravity by partially oseing the eects of
the +1 Gz environment in order to simulate Mars (0.35 Gz) or the Moon (0.16 Gz) gravities.
Reinforced steel wire was used in a pulley system that connects the weights at the end of the
body suspension device to the volunteer. A carabineer connects the steel wire to the aach-
ment point on the back of the body harness (Fesp P100PGP). The manikin was positioned on
the oor during the hypogravity simulation and +1 Gz [6, 46, 47]. Figure 5 presents a sche-
matic view of CPR being performed during ground-based hypogravity simulation.
The amount of counterweight used to simulate the hypogravity conditions, such as Mars or
the Moon, was calculated for each volunteer based on their body weight, as presented in Eqs.
(2) and (3) [46].
RM =
(
0.6BM × SGF
)
/ 1G (2)
CW = 0.6BM − RM (3)
Using Eq. (2), the relative mass of a subject in a simulated gravitational eld can be calculated,
where RM = relative mass (kg), BM = body mass on Earth (kg), SGF = simulated gravitational
force (m/s2) and 1G = 9.81 m/s2. Eq. (3) gives the counterweight (CW, in kg) necessary to simu-
late body mass at a preset hypogravity level. The 0.6 refers to the 60% of the weight of the
upper body, as the legs are supported on the oor.
Figure 4. Microgravity simulation for CPR performance with the mannequin supported by a wall, in the vertical position,
perpendicular to the oor. The volunteer is performing external chest compressions by exing and extending his legs
and therefore moving his body back and forth on top of a wheeled trolley.
Resuscitation Aspects124

For these ground-based hypogravity simulation studies, a standard CPR manikin (Resusci
Anne Skill Reporter, Laerdal Medical Ltd., Orpington, UK) was modied to include a linear
displacement transducer capable of measuring external chest compression (ECC) depth and
rate. The steel spring located in the mannequin’s chest depressed 1 mm with every 1 kg of
weight applied to it. A real-time feedback of each ECC was provided to the volunteers via
a modied electronic guiding system with an LED display. The LED display consisted of a
series of coloured lights that indicated depth in mm of ECCs (red and yellow, too shallow;
green, ideal). An ECC rate of 100–110 compressions/min−1 was established using an audio
metronome. A 6 s interval between each ECC set represented the time taken for two mouth-
to-mouth ventilations. Although not true to real life, by adding in these aids, it allowed stan-
dardisation of the volunteers as their experience and training in CPR varied.
3.1.2. Parabolic ights
Reduced gravity can be achieved with a number of technologies, each depending upon the
act of free fall, such as drop towers, small rockets and parabolic ights. The laer is the only
way to allow human subjects to be studied under conditions of microgravity or hypogravity.
Therefore, many physiological and operational studies have been conducted by space agen-
cies around the world in parabolic ights.
In parabolic ights, adapted airplanes execute a series of manoeuvres (parabolas), each pro-
viding around 20 s of reduced gravity (hypogravity) or weightlessness (microgravity), during
which experiments can be performed and data collected. A typical NASA parabolic ight lasts
3 h and carries experiments and crewmembers. It climbs from an altitude of 7 km above sea
level at a 45° (pull up) angle, traces a parabola (pushover) and then descends at 45° (pull out).
Microgravity by means of free fall is experienced during the pushover phase. In the pull-up and
pull-out segments, crew and experiments are subjected to hypergravity that ranges between 2
and 2.5 Gz [9].
Figure 5. The body suspension device system of the MicroG Centre, with the CPR mannequin on the oor and volunteer
assuming the terrestrial CPR position, being partially suspended through the counterweight system, simulating
hypogravity.
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During a European Space Agency (ESA) campaign, there are typically 3 days of ights with
31 parabolas per ight. For each parabola, there are also two periods of increased gravity
(approximately 1.8 Gz), which last for 20 s immediately before and after the 20 s of reduced
gravity, as shown in Figure 6.
4. Extraterrestrial CPR methods
Some of the challenges faced in this unique environment have already been presented, includ-
ing the practical, logistical and physical. The physiological changes and increased physical
demands that occur in an extraterrestrial environment make the performance of CPR already
dicult, but add to this, the limited storage and parameters found on any spacecraft or orbiting
station, such as the ISS, and the task become all the more daunting, especially if ill prepared. To
this end, several methods of CPR have been developed to bridge the gap between the time of
occurrence of a cardiac arrest and the time when further resuscitation equipment can be avail-
able. These methods focus in particular on the ability of a single person to apply CPR, in par-
ticular the Eves-Russomano (ER), reverse bear hug (RBH) and handstand (HS) CPR methods.
The rationale for the development of these single-person methods is that in microgravity,
whether in a spacecraft or space station, all equipment is stored away as cabin space is limited
and equipment oating freely is hazardous. Thus, the time to elapse between a fellow crew-
member recognising the need for retrieval and deployment of life support equipment could
range anywhere from 2 to 4 min [41]. This time period is obviously a critical window that
will aect patient survival, and therefore, to maximise the chances of a successful outcome, a
single-person method of microgravity CPR is needed so chest compressions can begin while
advanced life support equipment is retrieved.
Figure 6. ESA parabolic ight prole, in which each parabola provides 20 s of microgravity that is preceded and
succeeded by 20 s of hypergravity.
Resuscitation Aspects126

Evidence regarding the applicability and suitability of the three single-person rescuer methods
discussed in the next section is scarce and varies for several reasons. Parabolic ights have been
used to research these methods [4, 42, 43], and although these ights provide an excellent micro-
gravity analogue, the short periods of actual microgravity provided mean the data collected
and the conclusions drawn from the results have limitations. The majority of the scientic data
comes from ground-based analogues, wherein these unique CPR methods can be studied over
longer periods of time. Nonetheless, it is dicult with these analogues to fully reproduce the
microgravity environment and physiological changes usually seen in microgravity. As with all
analogues, they are good but never a perfect replication of the actual environment.
4.1. Eves-Russomano CPR method
The ER technique is the newest of the three methods to be discussed and perhaps the most
technically dicult, potentially requiring more training of the individual than other methods
to ensure its procient application. The rescuer places their left leg over the right shoulder of
the patient and their right leg around the patient’s torso, allowing their ankles to be crossed
approximately in the centre of the patient’s back; this is to provide stability and a solid plat-
form against which to deliver force, without the patient being pushed away (Figure 7(A)).
From this position, chest compressions can be performed while still retaining easy access to
perform ventilation. When adopting the ER method, the rescuer must be situated in a manner
that also allows sucient space on the patient’s chest for the correct positioning of their hands
to deliver the chest compressions.
It is important to note that the rescuer simply wrapping their legs around the patient’s waist
is not an adequate position; this will not provide a rm enough base, and the chest compres-
sions applied will extend the patient’s back and reduce the actual depth of the compressions.
The advantage of the ER position over other methods is that by being face-to-face with the
patient, single-person ventilation is easier. Initial parabolic ight and ground-based simula-
tion data showed the ER method as delivering an adequate rate and depth of chest compres-
sions, although this was according to the 2005 resuscitation guidelines [5, 42]. More recent
data from ground-based simulations, using the updated 2010 guidelines, demonstrated that
rescuers using the ER method fell slightly below par in terms of depth of compression but
were able to maintain an adequate rate [45, 47].
A disadvantage of the ER method lies in its being technically more dicult and potentially
requiring the most amount of training in order to be eective. In addition, the ER method is
fatiguing after 2 min of chest compressions following the current guidelines, being consid-
ered more tiring than the HS method, although less so than the RBH technique. It has been
found that rescuer fatigue leads to a failure to decompress the chest completely. This is a com-
mon problem across all three methods as fatigue takes eect, but it is more pronounced with
the ER method, and this may be in part due to the positioning of the rescuer [48].
Although there is no statistical data to support the idea, it has been observed and surmised
by researchers that height and anthropometric measurements may not be a predetermining
factor for successful chest compressions using the ER method. This signies that a rescuer
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with short legs who may not be able to cross their ankles behind the patient’s back may still
be capable of performing CPR to an adequate standard using the ER method [5].
4.2. Reverse bear hug CPR method
The RBH method is possibly the simplest of the three single-person methods presented and
is essentially similar to the Heimlich manoeuvre. The rescuer needs no additional equipment
or to be wary of their surroundings as the RBH method is independent of capsule parameters.
Figure 7. Three single-person microgravity CPR methods in ground-based microgravity simulations at the MicroG
Centre and in parabolic ights: (A) Eves-Russomano, (B) reverse bear hug and (C) handstand.
Resuscitation Aspects128

The rescuer takes up position behind the patient to easily wrap their arms around the patient
and lock their hands across the patient’s chest. Arm exion is primarily used to produce the
force needed for chest compressions. The rescuer can use their legs to stabilise both them-
selves and the patient (Figure 7(B)).
The advantage of the RBH method lies in its simplicity to learn and apply. The rescuer can
easily assume a position behind the patient, nd the correct spot on the patient’s chest and
begin chest compressions. Parabolic ight data has shown the RBH method to be an eective
method of CPR in simulated microgravity [4]. However, when assessed during a ground-
based analogue over a prolonged period of time, such as 2 min, the RBH fell dramatically
short of the current resuscitation guidelines [45]. Despite the relative simplicity of the method,
ground-based studies suggest that it is an ineective and inecient method when performed
over time. CPR using the RBH was seen to initially provide an adequate depth and rate of
chest compression, in accordance with the most recent guidelines. Nonetheless, as early as
the second cycle of chest compressions, rescuers rapidly tired—resulting in a decline in the
depth of chest compressions and overall drop in the quality of CPR [44, 45]. Logistically, this
method also presents a problem in ventilating as the rescuer is positioned to the rear of the
patient. Assuming the rescuer is alone, they would need to rotate the patient so they are face
to face in order to provide ventilations, before rotating the patient back again in order to con-
tinue compressions. This manoeuvring would delay the resumption of chest compressions
and ultimately aect the quality of the CPR applied.
4.3. The handstand CPR method
Performance of the HS method also requires no equipment, but the patient does need
to be placed against the inner side of the capsule or spacecraft in which they are located.
Importantly, this must be a solid surface that is capable of withstanding the force and vibra-
tion generated by the application of the CPR. Once a suitable site to position the patient has
been identied, the rescuer must then place their feet on the surface opposite to the patient,
having their arms stretched out above their head, as demonstrated in Figure 7(C).
From this position, the rescuer can ex/extend their hips while keeping their arms straight
and locked on the patient’s chest in the traditional spot, to generate the force needed for chest
compressions. Parabolic ights [4] and ground-based simulations [45] have found the HS
method to be the least fatiguing of the three single-person CPR methods, with rescuers able
to provide an adequate depth and rate of chest compressions, in accordance with the latest
guidelines [4, 44, 45].
The major limiting factor of this technique is its reliance on the physical parameters of the
vessel itself. The HS method is dependent on a capsule that is between a range of diameters in
order to have sucient space for the patient and rescuer, as well as enough distance between
the two to allow sucient hip and knee movement in order to generate enough force for chest
compressions. Furthermore, the height of the rescuer is crucial with this method; a shorter
rescuer may not be able to achieve good placement of the feet on the surface opposite to
the patient, thereby being unable to generate enough force and resulting in inadequate chest
compressions.
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4.4. Restrained CPR method: standard position
The restrained CPR method using the standard position is identical to that of terrestrial CPR but
requires the use of equipment to restrain both the rescuer and the patient to prevent both from oat-
ing away from each other after the delivery of force. The restraint system currently used aboard the
ISS is known as the crew medical restraint system (CMRS). The patient rests on the CMRS, which
is used to strap the patient into a supine position. The standard technique, as the name suggests,
is the same conventional CPR technique used on Earth. The dierence lies in the rescuer having
straps around their waist and a restraint cord across their lower legs (Figure 8). Researchers con-
ducted in parabolic ights have shown this method to require a great deal of eort on the part of
the rescuer, as they must counteract the force of the chest compressions. Thus, this method was
seen to fatigue the rescuer quickly, even more so than the single-person HS method [4, 43].
4.5. Restrained CPR method: straddling position
In the straddling manoeuvre, the rescuer performs chest compressions by kneeling across the
patient’s waist but uses the same retraining equipment as with the standard technique. The
delivery of the chest compressions is the same as that of terrestrial CPR, in that arms are kept
straight and placed on the chest. The advantage of this position over the standard technique
is that it requires less space. The standard position requires an area large enough for both the
CMRS and rescuer to t side by side, whereas the rescuer is positioned above the patient in the
straddling technique, thereby reducing the total space in use. This could be an important factor
to consider, given the limited dimensions of a spacecraft or the ISS. Despite the familiarity and
Figure 8. Crew medical restraint system (CMRS) being tested in a parabolic ight (A) and at the international space
station (B) [43].
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relative ease of use of these techniques, parabolic ight data has indicated that CPR performed
using both restraint methods fall below current AHA guidelines, suggesting they may not be
the most appropriate method to use in the event of a cardiac arrest scenario on board [43].
4.6. Hypogravity CPR methods
4.6.1. Terrestrial-style hypogravity CPR
In hypogravity, sucient gravitational eld is present on most celestial bodies that humans
could encounter (Moon or Mars), meaning that CPR could begin without any adjuncts or
equipment. Unlike the conditions for administering CPR in microgravity, the presence of at
least some gravity in these environments makes CPR feasible with traditional terrestrial CPR.
However, the technique of CPR may need adjustment to counter the negative impact of the
reduced gravitational eld. Traditional CPR instruction advises the use of straight, rigid arms
placed on the patient’s chest to perform compressions. However, a reduction in the upper body
weight of the rescuer due to a reduced gravitational eld will lead to a decreased ability to
generate force through acceleration of the upper body and the subsequent transfer of that force
through the straight arms. Research has shown that a natural tendency to adapt takes place,
seeking to generate more force by exing/extending the upper limbs in order to augment accel-
eration of the upper body [46]. In instances where traditional CPR in hypogravity is not suf-
cient to generate enough force to achieve the necessary depth of chest compressions, rescuers
are encouraged to have a combined technique of accelerating their upper body and extending
their upper limbs to generate enough force to compress the chest to 50–60 mm [45, 47].
4.6.2. The seated arm-lock (SeAL) method
The seated arm-lock (SeAL) method is a new concept but has many similarities to the tra-
ditional CPR technique used for hypogravity [49]. It was devised as a means of combaing
the potential negative issues caused by performing CPR in hypogravity. The SeAL method
involves the rescuer straddling the patient, with the patient’s arms being locked in behind
the rescuers’ knees. The rescuers knees should be positioned in the shoulder area of the
patient and their toes by the patient’s hips (Figure 9). When used in a low-gravitational-eld
environment, the position prevents the rescuer from being pushed away from the patient by
using the arms as a secure and comfortable pivot point. No residual tone is required in the
patient’s arms.
A small preliminary study found that rescuers were able to produce adequate depth of
chest compression across a range of gravity conditions, Earth (1 Gz), Moon (0.38 Gz) and
Mars (0.16 Gz). Additionally, the authors suggest that the SeAL method will allow the res-
cuer to be beer secured to the patient and therefore prevent the two from being pushed
apart from each other [49]. A preliminary study has recently been conducted at the MicroG-
PUCRS, Brazil, testing a variation of this technique, called the Mackaill-Russomano hypoG
CPR method. This adaptation of the SeAL technique sees the rescuer straddling the man-
nequin (CPR victim) and using their legs to embrace the legs of the dummy to act as an
anchor. The weight of the mannequin legs were calculated and adapted to be in accor-
dance with the gravitational force of the hypoG environment being simulated.
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5. Summary of ground-based space analogue studies
5.1. Microgravity CPR studies
Research into extraterrestrial CPR, particularly CPR in microgravity, has been ongoing for
more than a decade. Several parabolic ight campaigns [4, 42, 43] have investigated the feasi-
bility of the main CPR methods. As previously mentioned, although parabolic ights provide
an excellent analogue of microgravity, their short duration (about 20 s per parabola) limits
the amount of data that can be collected and interpreted. Accordingly, most of the available
evidence investigating the dierent CPR methods has come from ground-based simulation
studies, using such devices as the BSD. Although still with limitations, ground-based simula-
tion studies do provide additional insight into the eectiveness and feasibility of microgravity
CPR methods, particularly over prolonged time periods. Resuscitation guidelines are in gen-
eral updated every 5 years, with adaptations made based on current evidence. This requires
that CPR research in simulated extraterrestrial environments be periodically re-evaluated to
determine if the various methods continue to meet current guidelines.
Earlier studies examining the ER method showed it could be administered and comply with
the 2010 CPR guidelines while also correlating with parabolic ight data, indicating its use
could provide eective CPR in microgravity. In addition, the research aimed to evaluate the
physiological impact of performing the ER method, using subjective (Borg scale) and objec-
tive measurements (heart rate). Although found to be very tiring in comparison to terrestrial
CPR, the ER method could be sustained eectively for up to 2 min [5]. Building on this work,
comparative studies were conducted of the three main single-person CPR techniques, the ER,
RBH and HS methods. A preliminary study comparing these methods proved the suitability
of the BSD for conducting this type of research, which then led to a larger study. Results from
Figure 9. The seat arm-lock method in simulated hypogravity at the European Astronaut Centre.
Resuscitation Aspects132

the larger comparative study, carried out using the 2010 guidelines, found the HS method
to be the most eective in terms of depth (also called ‘true depth’ to account for adequate
decompression of the chest during ECC) and rate of administered ECCs, closely followed
by the ER method, while the RBH gave the worst clinical results, as well as being extremely
fatiguing (Figures 10 and 11). These studies also assessed the physiological cost of performing
these methods, compared to terrestrial CPR. Using more objective measures, such as oxy-
gen uptake (VO2), these studies demonstrated that all three methods had a greater VO2 than
terrestrial CPR, with the HS being the least aerobically demanding and the RBH the most
demanding [44, 48].
The physiological challenge of these methods is potentially a very important issue, as a well-
documented decline in VO2max occurs when in microgravity for a prolonged period, even
when using countermeasures. These ground-based studies, which aim for 50–60 mm com-
pression depth in accordance with both the 2010 and 2015 resuscitation guidelines, highlight
the signicant increase in VO2 that takes place, when compared to the 2005 guidelines. These
ndings emphasise the importance of maintaining aerobic capacity in case the need to per-
form CPR in microgravity should arise [47, 50].
A series of studies have considered muscle activation, via supercial electromyography
(EMG), while performing CPR in micro- and hypogravity, in order to understand the muscle
groups used in comparison to terrestrial CPR. The rationale behind this was to potentially
identify the responsible muscle groups so as to tailor exercise programs to ensure these mus-
cle groups are maintained [6, 51, 52]. EMG data showed the triceps, pectoralis major and rec-
tus abdominis muscles to be more active when conducting microgravity CPR, particularly for
the ER method, when compared to 1 Gz and hypogravity CPR. This data adds to the evidence
found in other studies indicating that astronauts need to maintain their muscle endurance in
these particular muscle groups, as well as preserve their cardiorespiratory capacity to be able
to adequately perform CPR should they need to in an emergency [52].
5.2. Hypogravity CPR studies
The BSD has also been successfully used in a series of studies evaluating CPR in simulated
hypogravity. These studies have focused on the feasibility of performing CPR using the terres-
trial method in hypogravity, as well as assessing the alterations in technique in hypogravity,
physiological impact and weight as a pivotal factor in performing CPR in these environments.
Initial hypogravity studies showed that CPR in hypogravity, particularly Lunar and Martian
environments, was feasible using traditional terrestrial CPR. Furthermore, they highlighted
the occurrence of an increase in the arm exion angle of the rescuer [46]. Traditional teach-
ing of BLS and CPR advocates that arms should be kept rigid in order to transfer the force of
acceleration of the rescuers’ upper body to the chest of the patient. These studies show that
for CPR to be eective, and achieve guideline recommendations, the rescuer needs to ex and
extend their arms, up to 14° (±8.1°), and use their upper limb musculature to generate force
to compress the chest to a sucient depth. This was even greater in microgravity using the
ER method, up to 16.5° (±10.1°); however, as the technique used is markedly dierent to ter-
restrial CPR, a direct comparison between the two is dicult [46, 47, 50] (Figure 12).
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Similar to the microgravity studies, the physiological cost was measured subjectively and objec-
tively, using the Borg scale and VO2, respectively. Compared to terrestrial CPR, hypogravity
CPR is more tiring and requires a greater VO2, but not to the same extent as the microgravity
CPR methods [47] (Figure 13). EMG hypogravity CPR studies have shown the occurrence of
more muscle activation in the rectus abdominis compared to +1 Gz CPR, as the rescuer needs
to accelerate their upper body faster to generate the same force as would be found at +1 Gz.
Considering Newton’s second law of motion, F = m × a, a reduction in mass will require an
increase in acceleration to maintain the same force.
Figure 10. Mean true depth of ECC over 1.5 min for terrestrial and microgravity CPR using the three methods. Dashed
line represents greater than 50 mm of depth set by the ILCOR 2010 guidelines; n = 23. Adapted from Ref. [48].
Figure 11. Mean rate of external chest compression (6 SEM) over 1.5 min for terrestrial and microgravity CPR using the
three methods. Dashed line represents the lower limit of 100 compressions/min set by the ILCOR 2010 guidelines; n = 23.
* Signicantly dierent from +1 Gz, ER and RBH. Adapted from Ref. [48].
Resuscitation Aspects134

Hypogravity studies have considered weight and gender and their importance in performing
CPR in these reduced gravitational elds. As the data shows, the more you eectively reduce
the rescuers’ body weight or possibly muscle mass, the harder it is to generate force for ECC,
and therefore the more tiring it becomes. As greater numbers of females join the astronaut
corp, it is important to address the dierences in weight and muscle mass to determine how
pivotal they are in performing CPR in hypogravity. These studies demonstrated the possible
existence of a gender dierence in the eectiveness of BLS when delivering ECCs, according
to the 2010 guidelines.
Female subjects were more likely to perform inadequate ECCs, as they tended to be shorter,
weigh less and possibly have a smaller muscle mass than the males. Moreover, they were
Figure 12. Mean (±SD) range of elbow exion in the dominant arm at +1 Gz, 0.38 Gz and microgravity. Adapted from
Ref. [47].
Figure 13. Peak oxygen consumption (VO2peak) at +1 Gz, +0.38 Gz and microgravity.
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shown to have a higher physiological demand when performing ECCs. This was compared to
males when performing CPR in hypogravity. Even when males had an eective reduction in
their weight, they were still able to generate enough force to produce adequate depth and rate
of ECC. This indicates that weight is not the only factor in eective ECC and that muscle mass
may play an important role that counterbalances low-weight situations. Therefore, female
rescuers may require additional strength training and alternative CPR techniques to over-
come their lower bodyweight and muscle mass to ensure they can perform adequate ECCs in
accordance with the current CPR guidelines [47, 50].
6. Extraterrestrial CPR guidelines
The extraterrestrial CPR guidelines presented in this chapter are based on the experience of
the authors who conducted several studies at the MicroG-PUCRS, Brazil, and an extensive
revision of the literature related to this topic. Therefore, the rationale behind specic guide-
lines for microgravity and hypogravity BLS and CPR is a combination of the novelty of the
environment, increased physiological stress and isolated nature of these environments, all
of which can aect the success of resuscitating a patient. However, familiarity and training
of the appropriate BLS protocols and novel CPR methods for these environments will be a
great benet for both rescuer and patient. Furthermore, with the popularity of space tourism
set to increase over the coming years, as private companies test new technology, there is a
responsibility of space scientists and physicians to make sure that participants are familiar
with and adequately trained in these novel BLS and CPR methods. Laypersons on Earth,
such as schoolteachers and civil servants, learn BLS and CPR for a variety of reasons, and this
custom should also apply to space tourists, who should be encouraged to become familiar
with extraterrestrial resuscitation techniques. Therefore, extraterrestrial CPR guidelines have
been developed and designed for all adults who will, for example, experience microgravity or
hypogravity as part of their professional careers when participating in parabolic ights and
space missions or who are involved in the training of astronauts.
Once cardiac arrest has been recognised, external chest compressions and ventilations need
to be started immediately to maximise chances of survival. The best evidence for depth and
rate of chest compressions come from international guidelines that are updated every 5 years
by the International Liaison Commiee on Resuscitation (ILCOR), who suggest changes to
the European Resuscitation Council (ERC) and American Heart Association (AHA) based on
the best possible evidence. Despite the well-documented altered physiology of astronauts in
microgravity, there is insucient evidence to suggest altering any of the parameters set by
these international guidelines.
Summary of terrestrial ERC Guidelines for resuscitation (2015):
• Ratio of 30:2 (compression/ventilation).
• Rate of chest compression of 100 min−1 (but not exceeding 120 min−1).
• Depth of chest compression between 5 and 6 cm.
Resuscitation Aspects136

• Ventilation should be 500–600 ml during CPR and given over 1 s; both breaths should take
NO longer than 5 s to prevent interruptions to chest compressions.
• If there are more than one rescuer or ventilation equipment available, 10–12 breaths should
be given every minute or one breath every 5 or 6 s, each delivered over 1 s. Observe for
visible chest rise.
The specic guidelines for chest compressions in microgravity and hypogravity remain the
same on Earth:
1. Compress the chest at a rate of 100–120 min−1.
2. Each time compressions are resumed, place your hands without delay in the centre of the
chest.
3. Pay aention to achieving the full compression depth of 5–6 cm (for an adult).
4. Allow the chest to recoil completely after each compression.
5. Take approximately the same amount of time for compression and relaxation.
6. Minimise interruptions in chest compressions.
7. Do not rely on a palpable carotid or femoral pulse as a gauge of eective arterial ow.
8. ‘Compression rate’ refers to the speed at which compressions are given, not the total num-
ber delivered in each minute. The number delivered is determined not only by the rate but
also by the number of interruptions to open the airway, deliver rescue breaths and allow
automatic external debrillator (AED) analysis.
Chest compression-only CPR is important during resuscitation as it will benet those who
are not fully trained or are unwilling to perform mouth-to-mouth rescue breaths; this applies
more to those who are entering hypogravity or microgravity as space tourists because all
astronauts receive suitable BLS training. Under no circumstances should chest compressions
be sacriced for ventilations. Evidence suggests that compressions are more essential than
ventilations during CPR and thus should be favoured during resuscitation [53]. There is no
evidence to suggest that a change in ratio would be of benet in hypogravity or micrograv-
ity. Therefore, rescuers should still aim for a ratio of 30:2 with a rate of compressions at 100
compressions min−1 and a depth of 5–6 cm, as stated above.
With regard to the depth of chest compression, it can be aected by the expansion of the chest
in microgravity. There is no specic evidence to support changes to the terrestrial guidelines;
however, it is theorised that a change in the chest wall dimensions of a patient in microgravity
may alter the requirements for eective delivery of CPR, meaning that 5–6 cm may not be a
sucient depth of compression and a depth of >6 cm may need to be considered. However,
more evidence is needed before contemplating any important change in these guidelines.
Currently, there is lile supporting evidence for the best practice of ventilation in either hypo-
gravity or microgravity. There is no reason to suppose that this would be dierent in a hypo-
gravity environment, compared to terrestrial CPR. As the technique of CPR is essentially the
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same for both conditions, the rescuer should be equally capable of providing ventilations to
the patient. The only caveat to this is if the patient and rescuer are in spacesuits, either while
performing an extravehicular activity or walking on the surface of a planetary body, as the suit
will obviously prevent them from giving mouth-to-mouth ventilation or administering CPR.
However, future research into hypogravity BLS should evaluate the practicality of providing
ventilations. With respect to microgravity, some research involving parabolic ight studies
[4, 42] has evaluated ventilation, as well as chest compression depth and rate of these CPR
methods. Findings have shown that rescuers using the Eves-Russomano method were able
to provide adequate ventilations of 491 ± 50.4 ml, in accordance to the 1998 ERC guidelines
that applied at the time [42]. Other research focusing on the use of ventilation adjuncts, which
required the mannequin to be intubated with a Kendall CardioVent device, showed that a lone
rescuer could provide adequate chest compressions with the ventilation adjunct. However,
seing up this equipment as a lone rescuer would delay the beginning of chest compressions
and would go against the new guidelines, C-A-B, where compressions take priority [4].
Throughout these guidelines the patient refers to the individual who has a suspected cardiac
arrest, and the rescuer refers to the person who is immediately responsible for their resuscita-
tion. The initial sequence in determining if the patient is responsive remains very similar to
the ERC 2015 CPR guidelines but takes into account the communication and resource limita-
tions whenwnments (Figure 14):
• Check if you and other crewmembers are safe. If environmental factors are likely to be the
precipitating factor (failure of life support systems, toxin build-up, trauma from projectile),
make sure these are no longer a threat to you and other crewmembers before aempting
to rescue the patient.
• Check for response—gently shake shoulders, and ask loudly in each ear, ‘Can you hear
me?’ or ‘Are you all right?’
• If patient does respond:
• Find a suitable place to secure the patient to avoid risk of oating and suering further
trauma or leave them in their present position if no alternative is available.
• Seek help from crewmembers, and aempt to determine what is wrong with the patient.
• Reassess regularly until help arrives or communication is established with mission con-
trol/ight surgeon.
• If patient does not respond:
• Shout for help immediately; when help arrives instruct them to nd resuscitation equip-
ment and more help. However, do not wait until they return; you must immediately
begin chest compressions.
• Follow the C-A-B sequence (compressions, airway, breathing).
• Start chest compressions, selecting the appropriate CPR method depending on the en-
vironment you are in.
Resuscitation Aspects138

• The lone rescuer should begin CPR with compressions rather than two ventilations to
prevent any delay in giving the rst compressions.
• Emphasis is placed on the lone rescuer beginning compressions before checking the air-
way, again to prevent any delay in chest compressions.
• If the patient is responsive and breathing normally:
• Place in a safe position.
• Send or call for help—call crewmembers or mission control.
• Reassess the patient regularly.
• If they are not breathing:
• Seek someone for further help, and establish communication with mission control. Fur-
ther resuscitation and AED are required.
Figure 14. Microgravity and hypogravity adult basic life support algorithm, adapted from ERC 2010 guidelines.
Reect on the updated sequence of steps from airway, breathing and compressions (ABC) to compressions, airway and
breathing (CAB).
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• Start chest compressions, selecting the appropriate method depending on the environment
you are in.
There is insucient evidence, especially for the SeAL technique, to say which method is supe-
rior in hypogravity. However, it is recommended that the traditional terrestrial CPR method
should be implemented rst, as it produces adequate depth of compression with low levels
of fatigue, suggesting that traditional CPR with an increased elbow exion is an eective
method of CPR [47]. Figure 15 presents the algorithm for CPR to be applied in hypogravity
environments.
6.1. Risks to rescuers
Altered physiology in microgravity and greater susceptibility to fatigue due to decon-
ditioning could potentially aect the quality of CPR. The main factors that need to be con-
sidered are:
• Reduced gravitational eld requires greater amount of force to be generated by the rescuer,
resulting in increased muscle strain and shortness of breath in comparison to Earth.
• Deconditioning due to prolonged exposure to microgravity and/or hypogravity can place
rescuers in a suboptimal physiological state when aempting to perform CPR. This could
result in both a poor CPR performance and signicant and rapid onset of fatigue.
Research examining CPR performance in simulated microgravity has shown all methods to
be more fatiguing compared to terrestrial CPR [48]. CPR in hypogravity is also found to be
more tiring than CPR on Earth, however, not to the same degree as in microgravity [47].
Current ERC guidelines recommend rotating rescuers every 2 min to prevent a drop in qual-
ity of chest compressions. A similar or possibly shorter window, such as 90 s, would be rec-
ommended for CPR in hypogravity. For microgravity, if enough crewmembers are present,
an even shorter window for rotating is recommended, such as 60 s, to preserve the quality of
chest compressions.
It is also important to consider that microgravity is a novel environment in itself and can
be disorientating, which could be a potential hazard in an emergency scenario. The internal
environment of a spacecraft or the ISS is also small, with conned spaces that can limit the
ability of the rescuer and patient to manoeuvre and transfer during CPR or any emergency.
Specically for the HS method, particular consideration must be given to placement of the
patient and positioning of the rescuer’s feet, as lots of equipment are found within the capsule
and there is the potential for damage to be caused to walls or partitions if they are not strong
enough to withstand the force applied for performance of the CPR chest compressions. For
the RBH and ER methods, there is always the danger of oating and hiing the sides of the
internal environment of the capsule/spacecraft when performing CPR.
The use of an AED also imposes risks. Its use must be controlled and applied only by those
trained to handle the equipment. Evidence shows that there have been few injuries due to
poor AED use; however, the isolated and unique environment of microgravity in particular
Resuscitation Aspects140

Figure 15. Algorithm for CPR in hypogravity.
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141

can provide additional challenges in terms of making sure that rescuers are safe and clear
when an AED is discharged.
7. Conclusion: extraterrestrial CPR—applications in space and on earth
As the space tourism industry commences and looks to expand over the following years,
greater numbers of individuals will undertake suborbital ights and enter the microgravity
environment. Before space tourism becomes a viable industry with regular ights, its tech-
nology will be tried and tested to the highest standards. The rapid rise in numbers of people
who enter microgravity will pose a potentially signicant increase in health problems, many
of which participants will be unaware. Growing numbers of individuals will enter the space
environment who will not have been subject to a strict preselection screening, such as that
undergone by people preparing to join the astronaut corp [54]. This scenario could lead to
potential diculties: individuals will be at greater risk of a life-threatening cardiac event if
they have not been screened for such health issues beforehand, and/or the physiological stress
of launching and remaining in microgravity could exacerbate any underlying cardiovascu-
lar condition. This scenario could be further compounded by a shortage of individuals who
have undertaken emergency training. This is a similar problem to that faced on Earth, with
a varying uptake of BLS/CPR training across countries. However, the novelty factor of the
microgravity environment combined with a serious medical emergency could create a highly
stressful situation in which these bystanders are likely to be ill prepared and lacking the
appropriate training necessary to carry out CPR techniques for the performance of adequate
BLS. To this end, it is recommended that such individuals undergo appropriate training prior
to a ight that would take them into an altered gravity environment. Healthcare profession-
als, schoolteachers and other civil servants who work with the public are currently given rst
aid and CPR training, and this exposure to basic BLS and CPR methods should be extended
to all travellers into space. It is unrealistic to expect these individuals to be fully trained in
all methods prior to launch, but familiarity with all methods, in accordance with ERC/AHA
guidelines for CPR depth and rate of chest compressions, could beer prepare them for the
possibility of a serious cardiac event occurring that requires CPR.
Individuals who do nd themselves in a situation of needing to administer BLS/CPR should
initially follow the steps in Figure 14, making sure that a crewmember or ground control is
aware that there is a medical emergency in progress. When commencing CPR, laypersons
familiar with all three methods should be encouraged to perform the technique with which
they feel the most comfortable and are consequently beer able to deliver eective external
chest compressions. As with the ERC/AHA guidelines, eective chest compressions should
be favoured over ventilations.
Training and familiarisation with the novel CPR methods used in microgravity can enable
laypersons to provide chest compressions and therefore maintain cardiac output and organ
perfusion, until either a more qualied crewmember can takeover the procedure or until the
craft ends its suborbital trajectory and returns to a normal gravitational environment where
terrestrial CPR can commence. These steps will improve the chances of the patient having a
favourable outcome.
Resuscitation Aspects142

Research into terrestrial CPR has shown that height and weight of the rescuer are correlated
to eectiveness of chest compressions, and therefore, extraterrestrial CPR research could be
used to improve terrestrial CPR, especially when physical disparities are encountered, such as
when a rescuer is of smaller stature or lacks sucient upper body weight. Examples of these
scenarios include a child aempting to resuscitate an adult outside of a hospital situation or a
small nurse resuscitating a large adult in hospital, who may also be obese or have signicant
lung pathology, such as pulmonary brosis or chronic obstructive pulmonary diseases, thus
restricting further compliance of the chest.
Using the traditional straight-arm CPR technique, there reaches a point of critical mass when a
rescuer is unable to overcome the resistance of the patient’s chest to achieve the required 50–60
mm depth of chest compression. Without sucient depth, not enough of a pressure gradient
is created to circulate blood and perfuse organs. In these scenarios, the authors suggest a foot-
note to the CPR guidelines, concluding that extension of the upper limbs (triceps extension)
can help augment the traditional straight-arm method with a synergistic acceleration of the
body and extension of upper body to generate the force required to compress the chest.
Author details
Thais Russomano1,2,3,4* and Lucas Rehnberg1,5
*Address all correspondence to: thais.russomano@innovaspace.org
1 Centre of Human and Aerospace Physiological Sciences, Faculty of Life Sciences &
Medicine, King’s College, London, UK
2 International Space Medicine Consortium Inc., Washington, DC, USA
3 InnovaSpace Consultancy, London, UK
4 Human Spaceight Capitalisation Oce, Harwell, UK
5 University Hospital Southampton NHS Foundation Trust, UK
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