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Copyright: Aerospace Medical Association
Aviation, Space, and Environmental Medicine x Vol. 83, No. 7 x July 2012 643
RESEARCH ARTICLE
K ORDI M, K LUGE N, K LOECKNER M, R USSOMANO T. Gender infl uence
on the performance of chest compressions in simulated hypogravity
and microgravity. Aviat Space Environ Med 2012; 83: 643 – 8 .
Introduction: In the event of a cardiac arrest during microgravity
exposure, external chest compressions (ECCs) which form the main part
of basic life support should be carried out while the advanced life support
equipment is being deployed. This study was aimed to determine if there
was any gender difference in the effectiveness of performing ECCs using
a body suspension device to simulate lunar and Martian hypogravity and
microgravity. Methods: The volunteers performed ECCs during simu-
lated microgravity (using the Evetts-Russomano method): lunar, Martian,
and Earth/Control. Each volunteer performed 3 sets of 30 compressions
with 6 s rest in between. The volunteers had their increase in heart rate
measured and used the Borg scale to rate the intensity of work after each
protocol. Results: The mean depth compressions for men during all grav-
itational simulations were higher than the women, but both sexes per-
formed effective ECCs during the two tested hypogravity states. During
simulated microgravity, men performed signifi cantly deeper ECCs (mean 6
SD of 45.07 6 4.75 mm) than women (mean 6 SD of 30.37 6 4.75 mm).
None of the women achieved the required mean depth of ECCs. Though
the increase in heart rate was higher in women, no signifi cant difference
was seen in the Borg scale scores between genders during or after the
performance of ECCs in microgravity. Discussion: The results suggest
both genders can perform effective ECCs during simulated hypogravity.
Women, however, cannot perform effective ECCs during microgravity
simulation. These fi ndings suggest that there is a gender difference when
performing the Evetts-Russomano method.
Keywords: CPR , Evetts-Russomano , basic life support , BLS .
A CARDIAC ARREST IS defi ned as the cessation or
stoppage of the heart, as of a function or a disease
process, resulting in loss of effective circulation ( 1 ). As-
tronauts are continually assessed medically, are in good
general health, and the probability of an astronaut having
a cardiac arrest during a space mission is around 1% ( 12 ).
With plans for a manned space mission to Mars poten-
tially as early as 2030, the amount of time spent in space-
fl ights for astronauts is likely to increase; for instance, if
traveling to Mars in the future, astronauts may eventu-
ally be exposed to up to 500 d of spacefl ight ( 8 ). With
this comes the increased possibility of exposure to dif-
ferent extraterrestrial gravitational environments, such
as the Moon and Mars.
The microgravity environment encountered during
spacefl ight results in extreme physiological changes
in all mammals, most notably the deconditioning of
the cardiovascular, muscular, and skeletal systems ( 17 ).
Different countermeasures are used in order to offset
any negative effects caused by microgravity exposure.
However, current countermeasures are only able to at-
tenuate some of the negative effects caused by space-
fl ight ( 9 ). Furthermore, with the likelihood of space
tourism becoming more available and affordable, the
number of space tourists is expected to increase ( 4 ). The
effects of microgravity on the majority of medical condi-
tions are currently unknown ( 11 ) and potential future
commercial spacefl ight participants are likely to have a
broader age range and their medical history will play a
much less signifi cant part of their selection in compari-
son to astronauts ( 2 ).
From the current data gathered from human space-
fl ight, Sides et al. ( 15 ) concluded no signifi cant ‘ evidence
for the existence of serious cardiac dysrhythmias, mani-
festation of asymptomatic cardiovascular disease, or clin-
ically signifi cant reduction in cardiac systolic function ’
with exposure to microgravity ( 15 ). Currently, the lon-
gest period within a microgravity environment is 438 d,
achieved by the Russian cosmonaut Valery Poliakov and,
therefore, the data gathered on the long-term effects of
microgravity exposure is very limited. There is also a
lack of data from interplanetary missions ( 2 ).
Basic life support (BLS) is the immediate medical care
administered to treat a cardiac arrest. It aims to maintain
open airways and to support the breathing and circula-
tion without the use of any equipment or medication
until advanced life support can be carried out ( 1 ). Exter-
nal chest compressions (ECCs) form the main part of
BLS and are also used in advanced life support. They are
used to help prolong the window of opportunity for
successful resuscitation by maintaining some degree of
oxygenation to the brain and heart ( 5 ).
The American Heart Association (AHA) states the
minimum depth of the ECCs should be between 40-50
mm and of a rate of at least 100 compressions per minute
and trained rescuers should also provide ventilations in
From the Centre of Human and Aerospace Physiological Sciences,
School of Biomedical Sciences, King ’ s College London, London, UK.
This manuscript was received for review in August 2011 . It was
accepted for publication in March 2012 .
Address correspondence and reprint requests to: Mehdi Kordi, 13
Harebell Close, Cambridge CB1 9YL, UK; mehdikordi@hotmail.co.uk .
Reprint & Copyright © by the Aerospace Medical Association,
Alexandria, VA.
DOI: 10.3357/ASEM.3171.2012
Gender Infl uence on the Performance of Chest
Compressions in Simulated Hypogravity
and Microgravity
Mehdi Kordi , Nicholas Kluge , Mariana Kloeckner ,
and Thais Russomano
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Copyright: Aerospace Medical Association
644 Aviation, Space, and Environmental Medicine x Vol. 83, No. 7 x July 2012
GENDER DIFFERENCE IN BLS — KORDI ET AL.
a compression-ventilation ratio of 30:2 ( 1 ). During mi-
crogravity, the current cardiopulmonary resuscitation
(CPR) protocol aims to commence advanced life sup-
port to patients (using a medical restraint system) within
2-4 min of the event ( 7 ). This means BLS needs to be
carried out for at least that amount of time. There are
three main ECCs techniques that have been researched
to be potentially used during microgravity: the hand-
stand maneuver, the reverse bear hug, and the Evetts-
Russomano (ER) method ( 7 , 10 , 14 ).
The handstand maneuver is currently taught to as-
tronauts to perform ECCs during weightlessness. This
technique is performed with the rescuer’s feet on the
fl ight deck ceiling, using the quadriceps muscle group
extensions to provide chest compressions. The second
method is the reverse bear hug/modifi ed Heimlich
maneuver. This is where the rescuer performs ECCs by
wrapping and locking their arms around from behind
the patient ’ s body and solely using elbow fl exion to cre-
ate the ECCs. The ER method involves the rescuer plac-
ing their left leg over the right shoulder of the victim
and their right leg around the torso, allowing ankles to
be crossed to aid muscular stability. From this position,
ECCs can be performed. The same terrestrial, 1 1-G z
ECC position is used during ground-based hypogravity
simulations, in which the rescuer kneels down by the
side of the manikin in order to perform BLS.
The effectiveness of each BLS method to be used in
microgravity has been reviewed and it has been sug-
gested that the reverse bear hug method could not
achieve the frequency or depth of compressions in accor-
dance with AHA standards of the time of publication
( 10 ). It was also suggested that the handstand technique
could obtain the depth and frequency of ECCs within
the standard set by the AHA ( 1 , 10 ). There are two
main disadvantages to the handstand method, however.
Firstly, valuable time is used by the rescuer trying to fi x
the victim to the ground of the spacecraft or space sta-
tion. Secondly, the performance of ECCs can cause some
vibrations that can potentially cause structural damage
to the space vehicle or put in risk the safety of the mis-
sion. In addition, both the volunteer and rescuer need to
be situated and braced against opposite walls of the
space vehicle, making the method completely reliant on
the rescuer’s height and length of lower limbs to be able
to reach the victim and have their feet on the fl ight deck
at same time.
Evetts et al. ( 7 ) introduced the ER technique and initial
examination showed that the depth and frequency of
the ECCs were within the 1998 AHA BLS standards of 80
ECCs per minute ( 7 ). Since then the AHA standards have
increased the minimum frequency to at least 100 com-
pressions per minute ( 1 ). The main advantage of the ER
technique is that it allows a fast transition from perform-
ing the ECCs to giving mouth-to-mouth ventilations.
A search of the literature showed that the ER tech-
nique was the only BLS method that had used a ground-
based model to evaluate its effectiveness ( 14 ). All other
studies have examined the three different BLS methods
in question during parabolic fl ights, which are a more
ideal test setting, but only produces 22 s of weightless-
ness per parabola ( 10 ). It can be argued that parabolic
fl ights are the best method for studying weightlessness,
but it has been stated that the environment does have
its limitations ( 9 , 10 ) for numerous reasons, such as the
short time span per parabola, the novelty of the environ-
ment, and the hypergravity state before and after each
microgravity phase of a parabola.
This study aimed to determine if there was a gender
difference in the effectiveness of performing ECC basic
life support during simulated lunar ( 1 0.16 G z ), Martian
( 1 0.35 G z ), and microgravity using the ER method, for 3
sets of 30 ECCs. This is the fi rst study designed to look
at the infl uence of gender in the performance of ECCs
during ground-based simulation of different gravita-
tional states by means of a body suspension device.
METHODS
Subjects
The study protocol was approved by the Pontifícia
Universidade do Rio Grande do Sul (PUCRS) Ethics and
Research Committees. Each volunteer signed a written
informed consent form before the beginning of the experi-
ment. All volunteers declared themselves fi t and healthy
by answering a basic medical questionnaire form.
There were 20 male and 12 female volunteers used in
this study. The male volunteers were 21.7 yr old 6 3.06,
with an average height of 176 6 6.73 cm, weight 73.4 6
12.6 kg. The female volunteers were 21.5 yr old 6 3.06,
with an average height of 163 6 7.98 cm and weight
60.73 6 10.6 kg.
The exclusion criteria included any volunteer who
presented cardiovascular, bone, or muscle disease or was
taking any medication that would affect the experiment.
All of the experiments were carried out in the John Ernsting
Aerospace Physiology Laboratory, Microgravity Centre,
PUCRS, Brazil. Volunteers had to visit the laboratory
on four different occasions separated by at least a 24-h
interval, with each session lasting no more than 1 h.
Equipment
The body suspension device was used to simulate
both hypogravity and microgravity. This was developed
by the Aerospace Biomedical Engineering Laboratory,
Microgravity Centre, PUCRS, Brazil. The body suspen-
sion device consists of carbon steel bars 0.6 3 0.3 mm in
thickness that is shaped as a prism frame. It has a height
of 200 cm with a base of 300 cm 3 226 cm. Counterweights
were used to simulate hypogravity simulation to par-
tially offset the effects of the 1 1-G z environment to
simulate Martian or lunar gravity. 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 attachment
point on the back of the body harness. The manikin was
positioned on the fl oor during the hypogravity simula-
tion and 1 1 G z . The volunteer was asked to kneel down
by the side of the manikin, assuming the BLS position
currently used on Earth.
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Aviation, Space, and Environmental Medicine x Vol. 83, No. 7 x July 2012 645
GENDER DIFFERENCE IN BLS — KORDI ET AL.
The amount of counterweight used to simulate the
hypogravity conditions was calculated for each volun-
teer by working out their relative mass in the simulated
gravitational fi eld and then using this answer to calcu-
late the amount of counterweight needed based on his/
her bodyweight, as presented in Eqs. 1 and 2 below.
RM = (0.6BM SGF)/1Gu Eq. 1
CW = 0.6BM RM Eq. 2
Using Eq. 1 , the relative mass of a subject in a simulated
gravitational fi eld can be calculated, where RM 5 relative
mass (kg), BM 5 body mass on Earth (kg), SGF 5 simu-
lated gravitational force (m z s 2 2 ), and 1G 5 9.81 m z s 2 2 .
Eq. 2 gives the counterweight (CW, in kg) necessary to
simulate the body mass to be used in a preset hypograv-
ity level.
The body suspension device was also used to simu-
late microgravity by fully suspending the volunteers.
A steel cross bar (1205 3 27.5 mm) was hung using rein-
forced steel wiring that gave it the ability to withstand
up to 600 kg. A static nylon rope was attached to the
steel wiring of the cross bar, had carabineers fastened
at each end, which were clipped to the corresponding
hip attachments of the body harness. A safety carabi-
neer was also attached to the volunteers back. If the
volunteers wanted to stop, they can do so safely, by
unwrapping their legs and suspending in the body
harness and stabilize themselves by planting their feet
on the ground.
The ER method involves the volunteer and manikin
being fully suspended and perpendicular to each other
using the body suspension device. The volunteer placed
his left leg over the right shoulder of the manikin and
his right leg around the manikin ’ s torso, allowing an-
kles to be crossed to aid muscular stability. From this
position, ECCs were performed. The body position for
the performance of the ECCs at 1 1 G z was the same as the
one described for hypogravity simulations, with the
only difference being that the volunteers were not
attached to the body suspension device and, therefore,
there was no decrease in their upper body weight dur-
ing the ECCs.
The specially adapted CPR manikin (ResusciAnne
Skill Reporter, Laerdal Medical Ltd, Orpington, UK)
was able to measure the chest compression depth by
using a linear displacement transducer, which was
fi xed inside the manikin. A steel spring was also fi tted
inside the chest, which depressed 1 mm with every 1 kg
of weight that was applied to it. Real-time feedback of
the displacement of the chest was provided by the elec-
tronic guiding system (EGS), which had a LED visual
display.
Different colored LEDs showed various voltage out-
puts depending on the depth of the ECCs, ranging from
0 mm to 60 mm. An audio metronome was also provided
by the EGS, which was set at 100 bpm. The EGS also had
a visual display that counted down from 30 to 0 and
then 10 to 0 alternatively to represent the number of
compressions and rest (representing two ventilations), re-
spectively, to match the 30:2 compression-ventilation
ratio, as set by the BLS guidelines. The chest compres-
sions which ranged between 40-50 mm were qualifi ed as
a ‘ good quality ’ ECC and the rate set by the metronome
complies with the AHA Guidelines ( 1 ). The EGS also
provided visual real-time feedback using the LED dis-
play. This allowed the volunteers to ensure that the cor-
rect depth of chest compression was achieved with each
individual chest compression.
Heart rate was measured immediately after each
protocol by using a heart rate monitor (Polar FT-1, Po-
lar Electro Oy, Kempele, Finland) which was worn
around the chest just below the pectoral muscles. The
receiver was strapped to the wrist for easy monitor-
ing. The Borg scale was used to rate the perceived ex-
ertion ( 3 ).
A DataQ (DataQ Instruments, Akron, OH) acquisition
device was used which had 8 analog and 6 digital chan-
nels, 10 bits of measurement accuracy, and rates up to
14,400 samples per second. It supports a full scale range
of 6 10 V and a resolution of 6 19.5 mV. WinDaq data
acquisition software (DataQ Instruments) allowed for
conversion of volts to the desired units. The DataQ had
input channels from the EGS, which had a continuous
analog signal.
Procedure
The volunteers were required to visit the laboratory
four times. To eliminate any learning effects or fatigue,
the order of simulated gravitational states at which
ECCs were performed was randomized. During each
visit, the volunteers had to perform the corresponding
ECCs method during either 1 1 G z (control), 1 0.16 G z
(lunar), or 1 0.35 G z (Martian) hypogravity simulations
and a 0 G (microgravity) simulation. Before each proto-
col, the volunteers had their resting heart rate measured
after being seated for a period of 10 min. Following this,
each volunteer familiarized themselves with the equip-
ment for a further 10 min. Regardless of the number of
ECCs completed, it was the investigators’ responsibil-
ity to instruct the volunteers to stop and break when
the EGS had fi nished its countdown. Both the frequency
and depth of the ECCs were continuously recorded
throughout the three sets of ECCs. The volunteers
were asked to continue for the full three sets unless
they were prevented by any discomfort or fatigue. The
heart rate was measured immediately at the end of each
protocol. After the completion of the three sets of ECCs,
the volunteers were asked to score their perceived exer-
tion using the Borg scale.
Statistical Analysis
The results were shown as mean 6 SEM. The statistical
software (Minitab, version 16.0) was used to carry out a
2-way ANOVA test for the intergender and intra- gender
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646 Aviation, Space, and Environmental Medicine x Vol. 83, No. 7 x July 2012
GENDER DIFFERENCE IN BLS — KORDI ET AL.
differences between different gravitational states as-
suming equal variance and a Tukey HSD post hoc test
was performed were applicable. A confi dence level of
P ⱕ 0.05 was used.
RESULTS
The results suggests that gender and the simulated
gravitational state does signifi cantly contribute to the
quality of ECCs [F(2, 120) 5 45.32; P , 0.0001]. No sig-
nifi cant difference was observed between male and fe-
male mean depth of ECCs at 1 1 G z ( P 5 0.487) and
1 0.35 G z ( P 5 0.372) and all volunteers were able to
achieve the mean minimum depth compression. During
the 1 0.16 G z and 0 G
z conditions, a signifi cant difference
between genders was seen ( Fig. 1 ). Though female mean
values of ECCs at 1 0.16 G z were lower than the corre-
sponding male values, both genders performed good
quality ECCs during the simulated hypogravitational
states.
During microgravity simulation the mean ECC depth
of the female volunteers was lower than the male volun-
teers ( P , 0.0001) and did not achieve the minimum
required depth compression of 40 mm. The frequency of
the ECCs ( Fig. 2 ) was shown to have no signifi cant dif-
ference between genders, regardless of the simulated
gravitational state. All groups managed to maintain the
minimum frequency of 100 ECCs/min, as set by the
AHA ( 1 ).
Observing intragender differences between each sim-
ulated gravitational state, a signifi cant difference was seen
among the male volunteers [F(2, 76) 5 6.195; P 5 0.001].
Further analysis showed no signifi cant difference in ECC
depth between 1 1 G z , 1 0.35 G z , and 1 0.16 G z . How-
ever, a signifi cant decrease was observed between men
performing the ECCs at simulated 0 G
z compared to all
other simulated states ( P , 0.01).
A 2-way ANOVA showed a signifi cant difference in
the female volunteers [F(2, 44) 5 39.23; P , 0.0001]. No
signifi cant differences were seen with female volunteers’
ECC depth in 1 1 G z and 1 0.35 G z . In addition, the female
volunteers showed no difference in the depth of ECCs
between 1 0.35 G z and 1 0.16 G z . The depth of the 0 G
z
ECCs were signifi cantly lower ( P , 0.0001) than all
other gravitational states.
The mean Borg scale scores of the volunteers ’ per-
ceived rate of exertion is shown in Fig. 3 . No signifi cant
difference between men and women was observed at
any simulated gravitational state. However, an increase
in the mean Borg score was observed for both male and
female volunteers as the simulated gravitational state
reduced progressively toward 0 G.
Despite no statistical difference between either gen-
der ’ s rate of perceived exertion during each gravitational
simulation, women had a signifi cantly larger increase in
heart rate after performing the ECCs at each gravita-
tional state. Both genders had an increase in their mean
heart rate as the simulated gravitational state was re-
duced. All the information gathered from heart rate is
shown in Table I .
The only simulated gravitational state that did not reach
the minimum threshold of a ‘ good ’ quality compression
Fig. 1. The mean depth of external chest compressions (ECC) between
male and female volunteers during different simulated gravitational states.
The dotted lines represent the range of a good quality chest compression;
† represents a signifi cant difference from 0 G (both intra- and intergen-
der); € denotes a signifi cant difference from 0.16 G
z for female volun-
teers only; ¥ denotes a signifi cant difference from 1 G
z and 0.35 G
z for
female volunteers only; and ‡ denotes a signifi cant difference from 1 G
z ,
0.35 G
z , and 0.16 G
z in both male and female volunteers.
Fig. 2. The mean frequency of external chest compressions (ECC)
of male and female volunteers during different simulated gravitational
states. The dotted lines represent the range of a ‘ good ’ quality ECC.
Fig. 3. The average Borg scale scores for both men and women when
performing external chest compressions (ECC) during different gravity
simulations. No signifi cant differences between genders during the same
gravitational simulation were seen; † indicates signifi cantly different to
0 G ;¥ indicates signifi cantly different from 1 G
z ; € indicates signifi cantly
different from 0.16 G
z ; and ‡ indicates signifi cantly different from 1 G
z ,
0.35 G
z , and 0.16 G
z .
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Aviation, Space, and Environmental Medicine x Vol. 83, No. 7 x July 2012 647
GENDER DIFFERENCE IN BLS — KORDI ET AL.
as was the mean female ECC depth during simulated
microgravity. Further analysis of each set of 30 ECCs
( Fig. 4 ) shows that all three individual sets are both sig-
nifi cantly lower than the corresponding male mean ECC
depth and do not reach the effective minimum ECC
depth required. The difference in the ECC depth be-
tween each sex after the fi rst set was 11.41 mm, 13.47
mm after the second set, and 14.4 mm after completion
of the fi nal and third set. Though both sexes decreased
the depth of the ECCs performed, the female volunteers
reduced more than the male volunteers.
DISCUSSION
The men ’ s mean ECC depth ( Fig. 1 ) was signifi cantly
higher in comparison to female volunteers’ mean values
during the simulated lunar and microgravity states. No
difference between the sexes was seen at 1 1 G z and
1 0.35 G z . Despite this, both sexes managed to score
within the range of a “ good quality ” ECC during both
hypogravity simulations. No signifi cant difference in
the frequency of the ECCs was seen regardless of the
simulated gravitational state or gender ( Fig. 2 ). Both
genders also managed to perform above the minimum
effective rate of 100 ECCs/min during all gravitational
states. This suggests that both genders can perform ef-
fective ECCs during lunar and Martian hypogravity
simulations.
However, the female volunteers could not reach the
minimum mean of 40 mm depth during microgravity.
Further analysis of the individual results shows that no
female volunteer managed to reach an average ECC
depth of 40 mm or more over the 3 sets of 30 compres-
sions. Only two (17%) of the female volunteers managed
to scored the minimum depth of “ a good quality ” ECC
for at least one set during any time in the experiment.
Out of the male volunteers, 16 (80%) achieved the mini-
mum threshold during simulated microgravity for 2
of the 3 sets. Only two (10%) male volunteers did not
reach the 40 mm of chest compression during any of
the sets. This suggests that there is a gender difference
when performing ECCs using the ER method during
simulated microgravity, with the male volunteers, un-
like their female counterparts, able to perform “ good
quality ” ECCs.
This initial experiment used 3 sets of 30 ECCs which
lasted approximately 65 s. However, it is believed that
the target time to deploy and start advanced life support
can be as long as 4 min during a space mission ( 9 ).
Future experiments should evaluate gender differences
in performing ECCs at simulated microgravity, lunar,
and Martian hypogravity states over the full target time
(4 min), which will consist of approximately 12 sets of 30
ECCs, especially in relation to the decrement of mean
depth and frequency of ECCs. This might give a stronger
indication to other potential factors which may be associ-
ated with gender that could infl uence the quality of the
ECCs, such as fi tness, strength, and poor technique.
In addition, there are limitations in simulating micro-
gravity and hypogravity using a body suspension de-
vice. Firstly, volunteers could use the bungee cords to
generate momentum between each ECC, which would
make it easier to reach the target depth compression that
could potentially give misleading results. Ideally, in fu-
ture experiments, the possible impact of the bungee
cords on the performance of ECCs can be adjusted for
each subject. Furthermore, the plane of work in per-
forming the ER technique is parallel to the direction of
gravity and, therefore, it might assist the elbow fl exion
and can add an extra resistance against the legs when try-
ing to maintain a stable platform to perform the ECCs.
No gender difference was seen when the volunteers
were asked to rate their perceived exertion ( Fig. 3 ), but
male volunteers performed ECCs more effectively. This,
again, implies that both sexes perceived equal exertion,
but female volunteers ’ performance of ECCs during
microgravity simulation was not effective. Borg scale
scores are subjective and it has been suggested that the
scores become more accurate to actual physiological
Fig. 4. The comparison of the Evetts-Russomano (ER) external chest
compressions (ECC) method during microgravity simulation. All 3 sets
of 30 compressions are signifi cantly different between men and women.
The difference between mean male and female depth compressions in-
creases with each set; * denotes a signifi cant difference between genders
at the same gravitational state.
TABLE I. A SUMMARY OF THE MEAN ( 6 SE) OF MALE AND FEMALE VOLUNTEERS ’ HEART RATE AT REST AND DURING THE PERFORMANCE
OF ECCS AT 1 1 G
z , 1 0.35 G
z , 1 0.16 G
z , AND 0 G
z .
Resting HR HR at 1 1 G
z HR at 1 0.35 G
z HR at 1 0.16 G
z HR at 0 G
z
Men Mean 73.6
‡
§¥ †
99.15
† ¥ €
113.55
† €
126.05
‡
† €
145.7
‡
§¥ €
SE 6 14.09 6 17.57 6 17.49 6 28.73 6 24.73
Women Mean 84.67
‡
§¥ †
125.5
† ¥ €
142.25
† €
158.58
‡
€
174
‡
§ €
SE 6 11.13 6 25.05 6 20.96 6 18.73 6 10.1
‡ Signifi cantly different from 1 G
z ;
† signifi cantly different from 0 G
z ; ¥ signifi cantly different from 0.16 G
z ; § signifi cantly different from 0.35 G
z ; and
€ signifi cantly
different from resting heart rate.
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648 Aviation, Space, and Environmental Medicine x Vol. 83, No. 7 x July 2012
GENDER DIFFERENCE IN BLS — KORDI ET AL.
fatigue when a volunteer ’ s scores are closer to complete
failure, regardless of gender ( 13 ). Electromyography
analysis of the arm, back, chest, and hamstring muscles
should be assessed to see the infl uence of strength and
muscle group in performance of ECCs during micro-
gravity and hypogravity simulations. This would evalu-
ate the role muscle strength plays in performing ECCs at
microgravity when the ER method is used. In addition,
future experiments could assess the effect of fi tness and
strength within the gender group and to what extent
technique or the learning effect infl uence performance
of the ER method.
The difference between post-experiment and resting
heart rate was higher in the female volunteers at each
gravitational simulation, suggesting that they were ex-
erting themselves more than the male volunteers when
performing the ECCs. Despite the signifi cant increase in
heart rate, the ECCs carried out during both hypogravi-
tational states showed that the women were still able to
do them to a suffi cient standard. A more effective way to
gauge physical exertion would be to measure lactate
levels immediately after performing each protocol. Lac-
tate levels are shown to have a greater correlation with
actual body fatigue ( 16 ), having a much narrower range.
Unlike the data gathered in this experiment, it has been
previously suggested that women cannot perform effec-
tive ECCs during simulations of Martian and lunar hy-
pogravity ( 6 ). This study looked at ECCs over a 3-min
period without rest, which is not compliant to the AHA
ratio of 30 compressions followed by 2 mouth-to-mouth
ventilations ( 1 ), in this case simulated with 6 s rest in
between each set.
Though the handstand and reverse bear hug have
been compared in a parabolic fl ight ( 10 ), when it was
reported that the handstand method could perform
ECCs which were ‘ good ’ quality and at least 100 bpm,
the study was limited by only being able to have 22 s of
microgravity exposure and by only using male volun-
teers. A review of the literature shows that no validated
ground-based models of the handstand and reverse
bear hug exist. An important future experiment would
be to develop ground based models for all the micro-
gravity BLS methods and evaluate the one that is the
most effective overall, taking into account any gender
difference and the ability to perform mouth-to-mouth
ventilations between sets in accordance to AHA stan-
dards ( 1 ). However, with the ECCs for basic life support
needing to be performed as quickly as possible, the ER
technique has been shown to be the only method that
can be performed immediately and the transition from
ECCs to ventilations can be done instantaneously. The
handstand method completely relies on the height and
reach of the rescuer and the transition from ECCs to
ventilations wastes valuable time.
In conclusion, this initial evaluation of the perfor-
mance of ECCs and gender found that the male volun-
teers were better at performing ECCs during simulated
microgravity using the ER method than the female
volunteers. However, female volunteers, like the male
volunteers, could perform effective ECCs at every
simulated gravitational state apart from microgravity
simulation.
ACKNOWLEDGMENT
Authors and affi liations: Mehdi Kordi, M.Sc., B.Sc., and Thais
Russomano, M.D., Ph.D., Centre of Human & Aerospace Physiological
Sciences, Kings College, London, UK; and Nicholas K. Correa,
Mariana K. P. Dias, and Thais Russomano, M.D., Ph.D., Aerospace
Biomechanical Lab, Microgravity Centre/PUCRS-Brazil, Porto Alegre,
Brazil.
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