Content uploaded by Lucas Rehnberg
Author content
All content in this area was uploaded by Lucas Rehnberg on May 26, 2014
Content may be subject to copyright.
Available via license: CC BY 2.0
Content may be subject to copyright.
RES E A R C H Open Access
A comparison between the 2010 and 2005 basic
life support guidelines during simulated
hypogravity and microgravity
Thais Russomano
1,2*
, Justin H Baers
1,2
, Rochelle Velho
1
, Ricardo B Cardoso
1
, Alexandra Ashcroft
1,2
,
Lucas Rehnberg
1
, Rodrigo D Gehrke
1
, Mariana K P Dias
1
and Rafael R Baptista
1
Abstract
Background: Current 2010 terrestrial (1G
z
) CPR guidelines have been advocated by space agencies for hypogravity
and microgravity environments, but may not be feasible. The aims of this study were to (1) evaluate rescuer
performance over 1.5 min of external chest compressions (ECCs) during simulated Martian hypogravi ty (0.38G
z
) and
microgravity (μG) in relation to 1G
z
and rest baseline and (2) compare the physiological costs of conducting ECCs in
accordance with the 2010 and 2005 CPR guidelines.
Methods: Thirty healthy male volunteers, ranging from 17 to 30 years, performed four sets of 30 ECCs for 1.5 min
using the 2010 and 2005 ECC guidelines during 1G
z
,0.38G
z
and μG simulations (Evetts-Russomano (ER) method),
achieved by the use of a body suspension device. ECC depth and rate, range of elbow flexion, post-ECC heart rate (HR),
minute ventilation (V
E
), peak oxygen consumption (VO
2
peak) and rate of perceived exertion (RPE) were measured.
Results: All volunteers completed the study. Mean ECC rate was achieved for all gravitational conditions, but true depth
during simulated microgravity was not sufficient for the 2005 (28.5 ± 7.0 mm) and 2010 (32.9 ± 8.7 mm) guidelines, even
with a mean range of elbow flexion of 15°. HR, V
E
and VO
2
peak increased to an average of 136 ± 22 bpm, 37.5 ± 10.3
L·min
−1
, 20.5 ± 7.6 mL·kg
−1
·min
−1
for 0.38G
z
and 161 ± 19 bpm, 58.1 ± 15.0 L·min
−1
,24.1±5.6mL·kg
−1
·min
−1
for μG
from a baseline of 84 ± 15 bpm, 11.4 ± 5.9 L·min
−1
, 3.2 ± 1.1 mL·kg
−1
·min
-1
, respectively. RPE was the only variable to
increase with the 2010 guidelines.
Conclusion: No additional physiological cost using the 2010 basic life support (BLS) guidelines was needed for healthy
males performing ECCs for 1.5 min, independent of gravitational environment. This cost, however, increased for each
condition tested when the two guidelines were compared. Effective ECCs were not achievable for both guidelines in
simulated μG using the ER BLS method. This suggests that future implementation of an ER BLS in a simulated μG
instruction programme as well as upper arm strength training is required to perform effective BLS in space.
Keywords: Basic life support, CPR guidelines, Hypogravity, Microgravity
Background
Human exploration of space is curtailed by the physio-
logical and technical impact of reduced gravity. Neverthe-
less, it has provoked a fascination in mankind as limitless
as the void of space itself. Aerospace medicine and physi-
ology are evolving in tandem with explorer -class missions
to accommodate the challenges associated with maintaining
the safety, health and optimum performance of astronauts
during spaceflights.
All organ systems are affected by exposure to extra-
terrestrial environments. Alterations to cardiovascular
physiology with reduced gravity manifest acutely and
chronically [1]. Reduced-gravity environments cause the
cardiovascular system to undergo adaptive functional and
structural changes. Microgravity induces a reduction in
hydrostatic pressure, causing a cephalic redistribution of
blood and body fluids. This headward shift is responsible
* Correspondence: trussomano@hotmail.com
1
Microgravity Centre, School of Engineering, PUCRS, Porto Alegre 90619-900,
Brazil
2
Centre of Human and Aerospace Physiological Sciences, School of
Biomedical Sciences, KCL, London WC2R 2LS, UK
© 2013 Russomano et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the
Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11
http://www.extremephysiolmed.com/content/2/1/11
for the ‘puffy-face & bird-leg’ appearance of astronauts in
space. The cardiovascular system adapts to microgravity
by reducing blood volume by approximately 20%, which is
in part responsible for the orthostatic intolerance com-
monly found post-spaceflight. A reduction in heart size
was also observed in microgravity [2]. However, based on
data from space missions, it is suggested that such cardio-
vascular alterations do not lead to important cardiac dys-
function or dysrrhythmias. Therefore, the possibility of
cardiac deconditioning developing into a life-threatening
condition, such as a cardiac arrest, during short to moder-
ate spaceflights is approximately 1% per year [3]. Never-
theless, with space agencies shifting their emphasis to
lunar return missions and the eventual human exploration
of Mars, the likelihood for cardiovascular issues to mani-
fest themselves will be further enhanced with increasing
space mission length.
An explorer-class mission to Mars will require approxi-
mately 2.4 years for completion: a 6-month flight to Mars,
an approximate 500-day surface stay, and a 6-month return
flight to Earth [4]. The cumulative and interactive effects of
physiological problems from a long-term spaceflight could
be potentially devastating for crewmembers. Prolonged ex-
posure to reduced gravity may result in altered heart con-
duction and repolarisation, predisposing astronauts to
cardiac dysrrhythmias [5]; electrical heart instability, in
conjunction with encountered biodynamic stressors, pre-
sents the disturbing possibility of cardiac arrest in astro-
nauts partaking in lengthy missions.
Further to exploration-class missions, the global private
sector is having a greater influence on space ventures. The
introduction of civilian tourist space travel broadens the
population who may be subjected to the pertinent aspects
of cardiovascular risks associated with spaceflight. Survey
data show the demographics expected for suborbital
spaceflight participants to be 70% male with an average of
57 years of age, 22% of which were older than 65 years [6].
This suggests that the expected population engaging in ci-
vilian spaceflight will be more likely to harbour subclinical
cardiovascular conditions, hence increasing the probability
of a cardiac event. Currently, international space institu-
tions are refraining from imposing safety regulations, stat-
ing that there are no medical requirements for space
tourism passengers and that only minimum training is re-
quired on how to respond to emergency situations [7].
Effective management of acute and chronic medical
emergencies, such as basic life support (BLS), is vital on
missions to ensure astronaut and tourist safety. External
chest compressions (ECCs) constitute the core of BLS and
must continue until advanced life support (ALS) can com-
mence to maintain adequate perfusion to vital organs. The
collaborative algorithm between the American Heart Asso-
ciation and the European Resuscitation Council for adult
BLS delineates key steps required for effective terrestrial
cardiopulmonary resuscitation (CPR) and was updated in
2010 [8]. These new guidelines place more emphasis on
ECCs than ventilation. The previous airways-breathing-cir-
culation ‘A-B-C’ algorithm has been altered to ‘C-A-B’.This
ensures rapid blood distribution to target areas whilst oxy-
gen saturation is sufficiently high. It is now essential to per -
form ECCs of adequate depth (minimum 50 mm) and rate
(100 compressions·min
−1
)[8].
Terrestrial (1G
z
) CPR guidelines have been advocated by
international space agencies for hypogravity and micro-
gravity environments. Nonetheless, performing ECCs dur-
ing spaceflight is more challenging due to reduced gravity
[9]. Previous studies have shown the 2005 CPR guidelines
to be feasible for simulated hypogravity and microgravity
conditions. However, current guidelines, which require
deeper ECCs, may not be feasible without compromising
the rescuer's health and may go beyond the rescuer's phys-
ical capability; therefore, a comparison between the 2005
and 2010 CPR guidelines in hypogravity and microgravity
environments is needed.
This investigation aimed to evaluate rescuer perform-
ance over 1.5 min of ECCs during simulated Martian
hypogravity and microgr avity in relation to 1G
z
and add-
itionally compare the physiological costs of conducting
ECCs in accordance with the 2005 and 2010 CPR guide-
lines. It was hypothesised that current ECC depth and
frequency guidelines should be achievable for all simu-
lated gravitational conditions. However, the 2010 ECC
guidelines were expected to be mor e physiologically
demanding in proportion to the reduction in simulated
gravity.
Methods
Study design
The protocol included performing four set s of 30 ECCs
over a period of 1.5 min in accordance to the 2005 and
2010 CPR guidelines during 1Gz, ground-based Martian
hypogravity (0.38G
z
)andmicrogravity(μG) simulations
at the John Ernsting Aerospace Physiology Laboratory,
Microgravity Centre, Pontif ícia Universidade Catolica
do Rio Grande do Sul (PUCRS), Brazil. The study
employed a w ithin-volunteer repeated measure s design,
with each volunteer being their own control. The order
of simulated gravitational conditions and CPR guidelines
were randomised. The study protocol was approved by the
Ethics and Research Committees of PUCRS.
Volunteers
A total of 30 healthy male volunteers, ranging from 17
to 30 years of age, served as rescuers performing CPR.
They were recruited on a voluntary basis and signed a
consent form prior to the beginning of the study.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 2 of 9
http://www.extremephysiolmed.com/content/2/1/11
Equipment and materials
A standard CPR mannequin (Resusci Anne Skill Reporter,
Laerdal Medical Ltd., Orpington, UK) was modified to in-
clude a linear displacement transducer capable of measur-
ing ECC depth and rate. The mannequin's chest steel
spring depressed 1 mm with every 1 kg of weight that was
applied to it. Real-time feedback of each ECC was provided
to the volunteers via a modified electronic guiding system
with a light-emitting diode (LED) display. The LED display
consisted of a series of coloured lights that indicated depth
of ECCs (red, 0–39 mm; yellow, 40–49 mm; green, 50–60
mm). An ECC rate of 100 compressions·min
−1
was
established using an electronic metronome. A 6-s interval
between each ECC set represented the time taken for two
mouth-to-mouth ventilations.
A custom-built body suspension device (BSD) was
used to simulate redu ced gravitational fields (de veloped
by the Microgravity Centre, PUCRS). It is pyramidal in
shape and consists of carbon steel bars of 6 cm × 3 cm
thickness (base area, 300 cm × 226 cm; height, 200 cm).
It comprises of a body harness and counterweight sys-
tem made of 20 bars of 5 kg each (Figure 1).
For simulated 0.38G
z
, the steel cable connected the
counterweights through a pulley system to the harness
worn by the volunteer. The necessary counterweight s
were calculated using Equations 1 and 2 [10]:
RM ¼
0:6BM SGF
1G
ð1Þ
CW ¼ 0:6BM RM ð2Þ
where RM is the relative mass (in kg), 0.6BM is the per-
centage of total body mass, SGF is the simulated
gravitational force (m·s
−2
), 1G = 9.81 m·s
−2
and CW is the
counterweight (in kg).
During the performance of ECCs, the mannequin was
placed supine on the floor with the volunteer adopting
the terrestrial CPR position.
For simulated μG, volunteers were suspended by the
body harness via the use of the steel cross bar (1205.0
mm × 27.5 mm). A static nylon rope was attached to the
steel wiring of the cross bar, with carabineers fastened at
each end. These were clipped to corresponding hip attach-
ments of the body harness. A safety carabineer was also
attached to the volunteer's back.
The mannequin was fully suspended to allow the per-
formance of the Evetts-Russomano (ER) BLS technique.
In order to perform the ER technique, the volunteer
places his left leg over the mannequin's right shoulder
and his right leg around the torso and across the back of
the mannequin. The left and right ankles cross in the
inter-scapula area of the mannequin for added stabili ty.
The application of force to the chest of the mannequin
will then be countered by the volunteer's legs and feet
and is achieved by the flexion and extension of the
volunteer's arms [11].
Angle of elbow flexion was measured using a custom-
built electrogoniometer on the volunteer's dominant arm
(developed by the Microgravity Centre, PUCRS). The
electrogoniometer consisted of two aluminium bars (200.0
mm × 20.0 mm × 3.0 mm) covered with rubber material
and was fastened over the volunteer's lateral epicondyle
via a series of straps; this allowed the change in flexion/ex-
tension (from 0° to 90°) to be accurately measured. The
device was connected with a linear 10 kΩ potentiometer
and powered by a 5-V power source.
Figure 1 Body suspension device with mannequin fully suspended simulated microgravity.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 3 of 9
http://www.extremephysiolmed.com/content/2/1/11
An Aerosport VO2000 analyser (MedGraph ics, Saint
Paul, MN, USA) recorded minute ventilation (V
E
) and
oxygen consumption per minute (VO
2
). VO
2
was
standardised, calculated and recorded directly by the
computerized ergospirometric system used (Aerograph
4.3, AeroSport Inc., Ann Arbor, MI, USA).
An Onyx 9500 fingertip pulse oximeter measured heart
rate (HR; Nonin Medical Inc., Plymouth, MN, USA). The
Borg scale measured rate of perceived exertion [12].
Protocol
Anthropometric characteristics (height in m, weight in kg)
were measured, and body mass index (BMI; kg·m
−2
) was
calculated from them. Volunteers were first familiarised
with the equipment, as well as both terrestrial CPR and
ER techniques; volunteers were required to demonstrate
that they had mastered both BLS methods.
Volunteers rested for 5 min prior to BLS to record
baseline values. They then performed four sets of ECCs
over a period of 1.5 min in accordance with the 2005
and 2010 ECC guidelines at 1G
z
followed by the two
gravitational simulations. A minimum of 10 min rest
was given to volunteers between each set of ECCs .
ECC frequency and depth, a s well as angle of elbow
flexion, were measured throughout the experiment. Ex-
haled gases were sampled continuously and analysed
every three breaths. Heart rate was recorded before
(resting heart rate) and immediately after the completion
of each protocol. After four sets of ECCs, subjective ap-
praisal of exertion using the Borg scale was noted.
The Aerosport VO2000 analyser used its own software
and was auto-calibrated prior to each protocol. The
mannequin's chest system was calibrated between volun-
teers using inputs of 0 and 60 mm. The elbow
electrogoniometer was calibrated prior to each protocol
using two points: full extension of the arm (0°) and mea-
sured 90° flexion.
A DataQ acquisition device with eight analogue and six
digital channels, 10 bits of measurement accuracy, rates up
to 14,400 samples·s
−1
and USB interface was used (DATA-
Q Instruments Inc., Akron, OH, USA). The device sup-
ported a full-scale range of ±10 V and a resolution of ±19.5
mV. WinDaq data acquisition software allowed for the
conversion of volts to the necessary units used. Two input
channels were used during data collection: one from the
chest system of the mannequin and the other from the
elbow electrogoniometer.
Data analysis
Data of physiological variables, which were determined
by either averaging the last 30 s of exercise or comparing
the last 30 s of exercise to baseline state and ECC depth,
rate and elbow flexion, were reported as mean values
(±SD). Percentage of maximum HR was calculated by
comparing post-ECC HR with theoretical maximum HR
(calculated using the 220-age equation) [13]. VO
2
peak
represents the highest recorded VO
2
during the four
ECC sets. Elbow flexion was calculated as a range from
the minimum to maximum angle of an individual ECC.
The ECC depth was analysed in two different ways:
maximum depth (D
Max
) achieved and true depth (D
T
),
which was calculated using Equation 3:
D
T
¼ D
Max
D
IRecoil
ð3Þ
where D
T
is the true depth of external chest compres-
sion, D
Max
is the maximum depth of external chest com-
pression and D
IRecoil
is the depth of inadequate recoil,
which is the distance not decompressed between subse-
quent external compressions.
The measures were derived post hoc from the data files
using GraphPad Prism v5.0a for analysis. Statistical com-
parisons were performed on physiological variables using
a one-way, non-parametric ANOVA test and on ECCs
and elbow flexion data using a two-way ANOVA. A 95%
confidence interval calculation around the mean was used.
The level of significance was set a priori as p ≤ 0.05.
Results
All 30 volunteers completed the protocol. Mean (±SD)
age, weight, height and BMI were 22.5 (±3.5) years, 78.2
(±13.1) kg, 1.80 (±0.07) m and 23.3 (±2.9) kg·m
−2
,
respectively.
The mean (±SD) D
Max
of all four sets for 1G
z
and the
simulated gravitational environments for the 2005 and
2010 ECC guidelines is presented in Figure 2A,B. All
volunteers were able to abide by the 2005 and 2010 ECC
guidelines at 1G
z
(47.1 (±3.0) and 57.0 (±2.3) mm) and
simulated 0.38G
z
(46.2 (±3.6) and 55.1 (±3.7) mm). For
simulated μG, the mean ECC D
Max
obtained using the
ER method fell 0.2 mm below the 2005 guidelines (39.8
(±8.3) mm), and there was considerable variation in the
range of ECC D
Max
. Eleven volunteers were able to ad-
here to the 2010 ECC guidelines in simulated μG, and
the mean D
Max
fell short of the 50-mm effective limit
(44.9 (±10.9) mm). However, not all volunteers allowed
full recoil of the mannequin's chest for the three gravita-
tional conditions. The mean (±SD) D
IRecoil
for 1G
z
,
0.38G
z
and μG were 6.7 (±4.9), 2.5 (±2.2) and 11.5
(±5.5) mm for 2005 ECC guidelines and 4.6 (±3.5), 1.6
(±1.8) and 11.9 (±5.7) mm for the 2010 ECC guidelines,
respectively. For both ECC guidelines, D
IRecoil
was less
during the Martian simulation and higher during simu-
lated μ G.
The mean (±SD) D
T
of the individual ECC sets per
condition, calculated from D
IRecoil
to D
Max
, is depicted
in Figure 3A,B and Table 1. Mean D
T
was within the ef-
fective limits set by the 2005 and 2010 ECC guidelines
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 4 of 9
http://www.extremephysiolmed.com/content/2/1/11
in the 1G
z
control environment for all four ECC sets. For
the 2005 ECC guidelines, the mean D
T
for the last three
ECC sets was above the effective lower limit for simulated
0.38G
z
compared to 1G
z
. In contrast, the mean D
T
of
ECCs was below the effective lower limit in simulated μG
compared to the 1G
z
control environment for both ECC
guidelines and for all four ECC sets.
The mean (±SD) ECC rate was successfully maintained
above 100 compressions·min
−1
for each set within each
gravitational condition, with reference to both ECC guide-
lines (Table 1).
The mean (±SD) ranges of elbow flexion of the
volunteer's dominant arm at 1G
z
during the 2005 and
2010 ECC guidelines were 3.4° (±2.0°) and 4.3° (±2.8°), re-
spectively. The range of elbow flexion increased to 10.6°
(±6.8°) during the 2005 ECC guidelines and to 14.0°
(±8.1°) during the 2010 ECC guidelines in simulated
0.38G
z
. When using the ER method in simulated μG,
ranges of elbow flexion of the volunteer's dominant arm
during the 2005 and 2010 ECC guidelines were 15.5°
(±8.7)° and 16.5° (±10.1)°. No difference in range of elbow
flexion was observed between ECC guidelines for either
simulated reduced gravity conditions (Figure 4).
The mean (±SD) rescuer HR at baseline, post-ECC, as
well as percent change and percentage of maximum HR
in all three gravitational conditions is illustrated in
Table 2. There was an increment in HR responses post-
ECC for simulated 0.38G
z
and μG. No differences be-
tween ECC guidelines were noted.
Mean (±SD) rescuer V
E
for 1G
z
, 0.38G
z
and μG in-
creased from 11.4 (±5.9) L·min
−1
at rest to 23.8 (±6.2),
34.4 (±10.4) and 55.1 (±15.6) L·min
−1
for the 2005 ECC
guidelines and 27.5 (±7.9), 40.6 (±10.2) and 61.1 (±14.4)
L·min
−1
for the 2010 ECC guidelines, respectively. With
respect to both ECC guidelines, there was no significant
difference in the increase in V
E
from rest for the three
gravitational conditions (Figure 5A). During the last 30 s
of ECCs, V
E
increased by 153.0%, 275.8% and 490.1% at
1G
z
, 0.38G
z
and μG for the 2005 ECC guidelines. An
increase of 194.8%, 334.9% and 568.1% was seen for the
2010 ECC guidelines, respectively.
During the performance of ECCs, the mean (±SD) res-
cuer VO
2
increased from 3.2 (±1.1) mL·kg
−1
·min
−1
at
rest to peak levels of 14.8 (±5.0) mL·kg
−1
·min
−1
at 1G
z
,
19.3 (±7.1) mL·kg
−1
·min
−1
at 0.38G
z
and 23.5 (±5.1)
mL·kg
−1
·min
−1
at μG for the 2005 ECC guidelines. For
the 2010 ECC guidelines, the increase was to 16.4 (±4.5)
mL·kg
−1
·min
−1
at 1G
z
, 21.8 (±8.1) mL·kg
−1
·min
−1
at
0.38G
z
and 24.7 (±6.2) mL·kg
−1
·min
−1
at μG (Figure 5B).
During the last 30 s of ECCs, VO
2
increased by 283.3%,
428.6% and 559.7% at 1G
z
, 0.38G
z
and μG for the 2005
ECC guidelines. An increase of 367.7%, 509.0% and
590.3% was seen for the 2010 ECC guidelines, respect-
ively. No difference wa s noted between ECC guidelines
for all three gravitational conditions.
The Borg scale showed there was an increase in the
mean (±SD) rate of perceived exertion intra- and inter-
conditions (Figure 6).
Discussion
Preparation for adverse cardiac events is vital to ensure the
safety of space explorers, thus potentiating the develop-
ment of the most effective protocol for BLS in simulated
0.38G
z
and μG.
This study was the first of its kind to investigate the ad-
ministration of effective ECCs using the 2010 ECC guide-
lines in comparison to the previous 2005 ECC guidelines
during simulated 0.38G
z
and μG, while looking at the
physiological impact on the rescuer.
Both ECC guidelines emphasise that effective ECCs have
two key components—adequate compression depth and
rate—to ensure sufficient haemodynamics from time of ar-
rest to application of ALS. When assessing the D
Max
achieved during ECCs, results from the 1G
z
and simulated
0.38G
z
sessions showed that all volunteers were able to
perform according to both the 2005 and 2010 ECC stan-
dards. In fact, the ability of volunteers to abide by the pre-
vious 2005 ECC guidelines at 1G
z
and during simulated
2005 ECC Guidelines
1G
z
0.38G
z
G
0
10
20
30
40
50
60
70
+
+
*
Condition
Depth (mm)
2010 ECC Guidelines
1G
z
0.38G
z
G
0
10
20
30
40
50
60
70
Recoil
Range
+
+
*
Condition
Depth (mm)
AB
Figure 2 Mean (±SD) maximum depth with depth of compressed chest post-inadequate recoil at 1G
z
, 0.38G
z
and μG. (A) The 2005 ECC
guidelines. (B) The 2010 ECC guidelines. The dashed line(s) depicts the effective limit(s) of depth for each respective guideline. n =30;asterisk denotes
significant difference in maximum depth to 1G
z
control, p < 0.05. The plus sign denotes significant difference in recoil to 1G
z
control, p <0.05.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 5 of 9
http://www.extremephysiolmed.com/content/2/1/11
0.38G
z
is in agreement with previous studies [10,14]. Al-
though mean D
Max
did not meet the 2005 ECC guidelines
during simulated μG,anegligibledifferenceof0.2mm
would probably be deemed effective during in vivo BLS.
However, the considerable inter-volunteer variability ob-
served questions the efficacy of the ER method, which con-
curred with the findings of Rehnberg et al. [14]. Mean D
Max
failed to abide by the 2010 ECC guidelines, which corre-
sponds with the findings of Kordi et al. [15] (Figure 2B).
Previous studies noted that volunteers were failing to
consistently allow full chest recoil using the ER method
during simulated μG (Figure 2) [14]. This can be detri-
mental to the effectiveness of BLS, as incomplete de-
compression decreases the change in thoracic pressure
and thereby reduces perfusion to vital organs. To ad-
dress this issue and a first for space CPR studies, ECC
D
T
was calculated by adjusting for D
IRecoil
(Figure 3
and Table 1).
When assessing ECC D
T
, all 30 volunteers failed to
abide by both ECC guidelines during simulated μG using
the ER method. This could be attributable to rescuers
inadequately decompressing between individual ECCs or
interruptions durin g ECCs when using the ER position
in simulated μG.
The inadequate decompressions between ECCs may
be due to rescuers focussing on achieving the 100
compressions·min
−1
rate set by guidelines during simu-
lated μG. This is supported by mean ECC rate in keeping
with both sets of ECC guidelines, whilst true depth of indi-
vidual ECC sets was not (Table 1). This is not in accord-
ance with a previous parabolic flight study using the ER
method that found ECC rate to be lower whilst ECC depth
remained adequate for the used ECC guidelines at that
time, which were the same as 2005. These findings, how-
ever, may represent a limitation of the BSD system. The
parabolic study had a sample size of 3 and was able to ad-
here to ECC guidelines even with such a small window of
freefall, approximately 20 s per parabola [11].
In addition, the high SD seen in Table 1, which repre-
sents the inter-volunteer variability for ECC rate,
2005 ECC Guidelines
1234
0
10
20
30
40
50
60
70
***
**** ** **
ECC Sets ECC Sets
Depth (mm)
Depth (mm)
2010 ECC Guidelines
1234
0
10
20
30
40
50
60
70
1G
z
0.38G
z
G
**
**
**
**
AB
Figure 3 Mean (±SD) true depth (D
T
) of ECC at 1G
z
, 0.38G
z
and μG. (A) The 2005 ECC guidelines. (B) The 2010 ECC guidelines. The dashed line
(s) depicts the effective limit(s) of depth for each respective guideline. n =30;single asterisk denotes p < 0.05, while double asterisk denotes p <0.001.
Table 1 Mean (±SD) true depth (D
T
) and rate of individual ECC sets at 1G
z
, 0.38G
z
and μG
Gravitational
condition
ECC
guidelines
ECC ECC sets
1234
1G
z
2005 Depth (mm) 40.9 (±5.0) 40.4 (±5.0) 40.6 (±4.9) 40.1 (±4.6)
Rate (comp·min
−1
) 104 (±5) 105 (±5) 105 (±6) 105 (±5)
2010 Depth (mm) 52.4 (±4.2) 52.1 (±4.6) 52.5 (±3.5) 52.6 (±3.9)
Rate (comp·min
−1
) 105 (±4) 104 (±4) 104 (±3) 104 (±3)
0.38G
z
2005 Depth (mm) 43.4 (±4.4) 44.1 (±4.2)* 43.7 (±4.3)* 43.7 (±4.4)*
Rate (comp·min
−1
) 103 (±6) 104 (±6) 104 (±5) 103 (±5)
2010 Depth (mm) 52.7 (±4.4) 53.7 (±4.0) 53.6 (±4.0) 53.6 (±4.9)
Rate (comp·min
−1
) 103 (±6) 103 (±5) 103 (±5) 103 (±5)
μG 2005 Depth (mm) 30.0 (±5.3)** 28.5 (±7.5)** 27.7 (±7.4)** 27.1 (±7.9)**
Rate (comp·min
−1
) 105 (±7) 106 (±5) 105 (±5) 106 (±5)
2010 Depth (mm) 34.7 (±9.8)** 34.8 (±8.7)** 31.5 (±9.4)** 31.1 (±8.5)**
Rate (comp·min
−1
) 104 (±7) 105 (±5) 106 (±8) 103 (±10)
n = 30; *p < 0.05 and **p < 0.01, significant difference from 1G
z
control.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 6 of 9
http://www.extremephysiolmed.com/content/2/1/11
increases with time in simulated μG. This suggests deg-
radation of ECC rate during the course of BLS.
Overall, the results of this investigation suggest that the
ECCs administered were ineffective in simulated μG, as
only mean ECC rate was adhered to, which would reduce
the benefit to the casualty due to inadequate vital organ
perfusion. This also indicates that the efficacy of the ER
method is deficient at producing true depth of ECCs in a
simulated μG environment, which contradicts previous
studies only analysing maximum depth of ECCs and that
did not account for D
IRecoil
of the mannequin [14].
The efficacy of ECCs is dependent on the physiological
impact of CPR on the rescuer. Increased HR, V
E
and
VO
2
peak were inversely correlated with the simulated
gravitational conditions studied, which indicates greater
physical effort during the performance of BLS (Table 2
and Figure 5). The HR results support those found by both
Dalmarco et al. [10] and Rehnberg et al. [14]. Further-
more, there was no difference in HR, V
E
and VO
2
peak be-
tween ECC guidelines, which may imply that current ECC
guidelines do not impose additional physical effort, unlike
the simulated gravitational environment.
In our study, it is important to note that VO
2
peak wa s
measured and used as an estimation of VO
2
max,
allowing comparisons with previous literature findings
to be drawn [16].
There are limited studies that evaluate VO
2
max during
or post-spaceflight, all of which are short-duration mis-
sions (<14 days) [17]. It has been hypothesised that appro-
priate exercise countermeasures may maintain VO
2
max
during long-duration explorer-class missions. Thus, the
additive effects of cardiac deconditioning would have less
influence on the rescuer's aerobic capabilities to perform
ECCs in μG, making the physical difficulty of the ER
method the key variable in performing effective ECCs.
Interestingly, decreases in VO
2
max arise following re-
entry. Levine et al. [18] noted that after the SLS-1 and
SLS-2 missions, six astronauts showed VO
2
max levels of
2.1–2.9 L·min
−1
. In addition, the extra-vehicular activity
(EVA) suit required for planetary surface exploration may
also determine the level of cardiovascular exercise cap-
acity. Studies at NASA's Johnson Space Center in simu-
lated 0.38G
z
showed an increase in VO
2
by an additional
20 mL·kg
−1
·min
−1
(40% of the volunteer's VO
2
max) while
wearing a Mark III prototype exploration EVA suit [19].
After a Martian landing, crewmembers will most likely
be required to begin work immediately without a sufficient
period for acclimatisation to 0.38G
z
[20]. This reduced
aerobic capacity, in conjunction with orthostatic intoler-
ance and impaired blood flow from long-term micrograv-
ity exposure, may significantly impact a crewmember's
capability during emergencies or while assisting an inca-
pacitated crewmate.
Although any attempt to administer CPR in an EVA
suit is unlikely to be achievable, the physiological aspect
would be interesting to consider. Therefore, the mean
VO
2
peak of a rescu er in an EVA suit would be 41.8
mL·kg
−1
·min
−1
in simulated 0.38G
z
, which accounts for
our 21.8 mL·kg
−1
·min
−1
(Figure 5B) and the expected
additional 20 mL·k g
−1
·min
−1
from wearing an EVA suit
[19]. For the average male weight (78.2 kg) in our study,
this would equate to 3.3 L·min
−1
after four sets of ECCs .
This exceeds the VO
2
max of 2.9 L·min
−1
found by
Figure 4 Mean (±SD) range of elbow flexion in dominant arm
at 1G
z
, 0.38G
z
and μG. n = 30; Asterisk denotes significant
difference to 1G
z
control, p < 0.05.
Table 2 Mean (±SD) heart rate responses at 1G
z
, 0.38G
z
and μG
Mean (±SD), bpm ECC
guidelines
Baseline Heart rate 1G
z
0.38G
z
μG
84 (±15) HR post-ECC 111 (±19) 132 (±23)* 159 (±19)* 2005
%Δ 33.8 (±18.4) 60.0 (±25.8)* 94.7 (±33.9)*
%Max 56.1 (±9.4) 66.9 (±11.6)* 80.7 (±9.9)*
HR post-ECC 117 (±21) 140 (±21)* 163 (±18)* 2010
%Δ 41.4 (±22.8) 71.2 (±30.5)* 98.8 (±35.4)*
%Max 59.2 (±10.9) 71.1 (±10.7)* 82.3 (±9.4)*
HR responses are depicte d as baseline and post-ECC values (bpm), percent change from baseline and percentage of maximum heart rate (maximum heart rate
was calculated using the 220-age equation). n = 30; *p < 0.05, significant difference from 1G
z
control.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 7 of 9
http://www.extremephysiolmed.com/content/2/1/11
Levine et al. [18]. This value may be an underestimation,
as the casualty would also be wearing an EVA suit and
the pressurisation of their suit would have to be over-
come as well.
Furthermore, this study looked at the range of elbow
flexion, while previous studies only took maximum elbow
flexion into account [10,14]. The greater range of elbow
flexion seen during simulated 0.38G
z
could be accredited
to the recruitment of upper arm muscle groups to com-
pensate for the reduction in upper body weight. The lack
of difference in the range of elbow flexion for either ECC
guidelines may indicate that the upper limb muscle groups
are recruited in the same manner (Figure 4).
An increase in elbow flexion range was also noted be-
tween simulated μGand1G
z
. Using the 2005 ECC guide-
lines during simulated μG, the mean increase of 15.5°
(±8.7°) in the volunteer's dominant arm was similar to the
approximate 11° (±8.3°) and 15° (±9.1°) of the right and left
arms, respectively, found by Rehnberg et al. [14]. However,
it is important to highlight that the change from the ter-
restrial to the ER BLS position might have contributed to
the recruitment of different muscle groups. Like simulated
0.38G
z
, the lack of difference in the range of elbow flexion
using the ER method for both ECC guidelines may indi-
cate that the upper limb muscle groups are recruited in
the same manner. This further suggests that guidelines are
equally difficult in simulated μG, as this correlates with
the inability to achieve effective true ECC depth and the
non-significant difference in physiological variables be-
tween guidelines (Figure 4).
Although the physiological variables measured were not
different between guidelines, volunteers perceived current
ECC guidelines to be more difficult (Figure 6). This might
have been influenced by the fact that volunteers had a pre-
conception that illuminating more LEDs for current ECC
guidelines could have been less attainable.
This study is not without limitations, since it is based
on the evaluation of healthy young males performing 1.5
min of BLS. The simulated gravitational environment,
using a BSD, may not replicate all physiological effects
secondary to reduced gravity exposure, apart from
weight reduction, which is essential for successful BLS.
This also applies to the mannequin when considering
that chest wall expansion would occur upon reduced
gravity exposure, affe cting chest compression depth.
Other psychological and physiological factors may differ
in a simulated study compared to an actual cardiac ar-
rest, such as stress. Furthermore, there are differences in
chest wall compliance between humans and manne-
quins, which do not take into account variations in body
anthropometrics, as well as EVA suits. In addition, the
sample may not be representative of the commercial
space passenger population in terms of demographics.
Conclusion
In summary, the physiological variables measured showed
no significant difference between the 2005 and 2010 BLS
1G
z
0.38G
z
G
0
20
40
60
80
*
*
*
*
Condition
VE(BTPS:Lmin-1)
AB
1G
z
0.38G
z
G
0
10
20
30
40
2005
2010
*
*
*
*
Condition
VO
2
peak (ml kg
-1
min
-1
)
Figure 5 Minute ventilation (V
E
) and peak oxygen consumption (VO
2
peak) at 1G
z
, 0.38G
z
and μG. (A) Mean (±SD) V
E
at 1G
z
, 0.38G
z
and
μG. Baseline was 11.4 (±5.9) L·min
−1
.(B) Mean (±SD) VO
2
peak normalised to weight at 1G
z
, 0.38G
z
and μG. Baseline was 3.2 (±1.1) mL·kg
−1
·min
−1
.
n = 30; Asterisk denotes significant difference to 1G
z
control, p < 0.05.
6
8
10
12
14
16
18
20
2005
2010
1G
z
0.38G
z
G
*
*
**
+
+
Figure 6 Mean (±SD) rate of perceived exertion for four sets of
ECCs at 1G
z
, 0.38G
z
and μG. n = 30; Asterisk denotes significant
difference to 1G
z
control, p<0.05. Plus sign denotes significant
difference between ECC guidelines, p < 0.05.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 8 of 9
http://www.extremephysiolmed.com/content/2/1/11
guidelines for all three gravitational conditions studied, al-
though the performance of ECCs during hypogravity and
microgravity simulations depicted an increase in physio-
logical cost compared to terrestrial BLS.
This investigation demonstrated that despite ECC D
T
and rate being in accordance to the 2005 and 2010
guidelines, accomplishing ECCs in a Martian environ-
ment might require a supra-maximal aerobic capacity.
Further research into BLS and EVA suits is required to
facilitate it on Mars.
Our study also showed that effective ECCs wer e not
attainable for both the ECC guidelines in simulated μG
using the ER BLS method. This indicates that future im-
plementation of BLS education using the ER method in
simulated μG and upper arm strength training are
required to perform effective BLS in space.
Space agencies, commercial space ventures and aca-
demic institutions need to collaborate to devise a suit-
able BLS protoco l for hypogravity and microgravity
environments, accounting for the difficulty in meeting
current terrestrial ECC guidelines in simulated reduced
gravity conditions. These findings are even more pertin-
ent with the dawn of commercial spaceflight.
Abbreviations
ALS: Advanced life support; A-B-C: Airways-breathing-circulation; BLS: Basic
life support; BMI: Body mass index; BSD: Body suspension device;
CPR: Cardiopulmonary resuscitation; D
IRecoil
: Depth of inadequate recoil;
ER: Evetts-Russomano; ECC: External chest compression; EVA: Extravehicular
activity; HR: Heart rate; 0.38G
z
: Martian hypogravity; D
Max
: Maximum depth;
μG: Microgravity; V
E
: Minute ventilation; VO2 peak: Peak oxygen
consumption; PUCRS: Pontifícia Universidade Catolica do Rio Grande do Sul;
1G
z
: Terrestrial; D
T
: True depth.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
TR participated in the design and coordination of the study. JHB participated
in the design and coordination of the study, data collection and analysis and
helped draft the manuscript. RV participated in the design and coordination
of the study, data collection and helped draft the manuscript. RCB
participated in data analysis of external chest compressions. AA participated
in the data collection and analysis and helped draft the manuscript. LR
participated in the data analysis of external chest compressions. RDG
recruited volunteers and participated in the data collection and analysis.
MKPD recruited volunteers and participated in the data collection and
analysis. RRB participated in the design and coordination of the study. All
authors read and approved the final manuscript.
Received: 24 July 2012 Accepted: 11 January 2013
Published: 1 April 2013
References
1. Aubert AE, Beckers F, Verheyden B: Cardiovascular function and basics of
physiology in microgravity. Acta Cardiol 2005, 60(2):129–51.
2. Sides MB, Vernikos J, Convertino VA, Stepanek J, Tripp LD, Draeger J,
Hargens AR, Kourtidou-Papadeli C, Pavy-LeTraon A: The Bellagio report:
cardiovascular risks of spaceflight: implications for the future of space
travel. Aviat Space Environ Med 2005, 76(9):877–895.
3. Johnston SL, Marshburn TH, Lindgren K: Predicted incidence of
evacuation-level illness/injury during space station operation. In 71st
Annual Scientific Meeting of the Aerospace Medical Association: May 2000.
Houston, Texas; 2000.
4. Bonin GR: Initiating piloted mars expeditions with medium-lift launch
systems. JBIS 2005, 58:302–309.
5. Grenon SM, Xiao X, Hurwitz S, Ramsdell CD, Sheynberg N, Kim C, Williams
GH, Cohen RJ: Simulated microgravity induces microvolt T wave
alternans. Am J Physiol Heart Circ Physiol 2005, 10(3):363–370.
6. Space tourism market study. http://www.futron.com/spacetourism/default.htm.
7. FAA: 14 CFR Part 417 Launch Safety: Lightning criteria for expendable
launch vehicles. Direct Final Rule 2011, 1:33139–33152.
8. Koster RW, Baubin MA, Bossaert LL, Caballero A, Cassan P, Castren M, Granja
C, Handley AJ, Monsieurs KG, Perkins GD, Raffay V, Sandroni C: European
Resuscitation Council Guidelines for Resuscitation 2010 Section 2. Adult
basic life support and use of automated external defibrillators.
Resuscitation 2010, 81(10):1277 – 1292.
9. Hurst V, West S, Austin P, Branson R, Beck G: Comparison of bystander
cardiopulmonary resuscitation (BCPR) performance in the absence and
presence of timing devices for coordinating delivery of ventilatory
breaths and cardiac compressions in a model of adult cardiopulmonary
arrest. http://ntrs.nasa.gov/search.jsp?R=20080003861.
10. Dalmarco G, Calder A, Falcão F, de Azevedo DFG, Sarkar S, Evetts S, Moniz S,
Russomano T: Evaluation of external cardiac massage performance
during hypogravity simulation. In Conf Proc IEEE Eng Med Biol Soc 2006,
1:2904–2907.
11. Evetts SN, Evetts LM, Russomano T, Castro CJ, Ernsting J: Basic life support
in microgravity: evaluation of a novel method during parabolic flight.
Aviat Space Environ Med 2004, 76:506–510.
12. Borg G: Perceived exertion as an indicator of somatic stress. Scand J
Rehabil Med 1970, 2:92–98.
13. Robergs RA, Landwehr R: The surprising history of The HRmax=220-age
equation.
J Exerc Physiol
2002, 5(2):1–10.
14. Rehnberg L, Russomano T, Falcão F, Campos F, Everts SN: Evaluation of a
novel basic life support method in simulated microgravity. Aviat Space
Environ Med 2011, 82(2):104–110.
15. Kordi M, Cardoso RB, Russomano T: A preliminary comparison between
methods of performing external chest compressions during microgravity
simulation. Aviat Space Environ Med 2011, 82(12):1161–1163.
16. Day JR, Rossiter HB, Coats EM, Skasick A, Whipp BJ: The maximally
attainable VO
2
during exercise in humans: the peak vs. maximum issue.
J Appl Physiol 2003, 95(5):1901–1907.
17. Moore AD, Lee SMC, Stenger MB, Platts SH: Cardiovascular exercise in the
U.S. space program: past, present and future. Acta Astronaut 2010,
66(7–8):974–988.
18. Levine BD, Lane LD, Watenpaugh DE, Gaffney FA, Buckey JC, Blomqvist CG:
Maximal exercise performance after adaptation to microgravity. J Appl
Physiol 1996, 81(2):686–694.
19. Norcross JR, Lee LR, Clowers KG, Morency RM, Desantis L: DeWitt JK, Jones
JA, Voss JR, Gernhardt ML: Feasibility of Performing a Suited 10-km Ambulation
on the Moon- Final Report of the EVA Walkback Test (EWT). Washington, DC:
NASA; 2009.
20. Katuntsev VP, Osipov YY, Filipenkov SN: Biomedical problems of EVA
support during manned space flight to Mars. Acta Astronaut 2009,
64(7–8):682–687.
doi:10.1186/2046-7648-2-11
Cite this article as: Russomano et al.: A comparison between the 2010
and 2005 basic life support guidelines during simulated hypogravity
and microgravity. Extreme Physiology & Medicine 2013 2:11.
Russomano et al. Extreme Physiology & Medicine 2013, 2:11 Page 9 of 9
http://www.extremephysiolmed.com/content/2/1/11
