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Wanna
freefall out into nothing
Gonna leave this world for a while
Now I'm free, freefalling --Tom Petty and the
Heartbreakers
July
10, 2009: We've all seen video of astronauts drifting
and gliding gracefully around inside the International Space
Station like fish in a fishbowl. It looks so relaxing. But
as enjoyable as it appears to be, there's a down side to all
that freefalling1.
 Right:
Astronaut Clay Anderson floats through the Unity node of the
International Space Station. [more]
"When
astronauts land back on Earth after a long time in space,
not only is their vestibular system mixed up and their kinesthetic
sense thrown off," says Dr. Benjamin Levine of the University
of Texas Southwestern Medical Center, "but also their
bones and muscles have deteriorated."
In
space, even more than on Earth, it's "use it or lose
it." The human body and all its parts need to work to
remain vital. Bones must bear weight to keep their density
and strength. Muscles need to push or pull against resistance
to stay in shape; without work they waste away.
Is
this also true of our most critical muscle – the human heart?
NASA is launching a new study called Integrated Cardiovascular2
to find out.
"We
know that astronauts lose heart mass and exercise capacity
when they're in microgravity for a long time," says Johnson
Space Center's Julie Robinson, ISS program scientist. "We
suspect that this could lead to impaired heart function, which
could cause low blood pressure and even fainting when astronauts
get back to gravity. But we need detailed information. In
the future, astronauts will spend longer and longer in space,
and even live and work on the moon and Mars. We want to know
exactly how space-living will affect their hearts and heart
function."
Dr.
Levine is a principal investigator for the experiment along
with Dr. Michael Bungo of the University of Texas Health Science
Center at Houston. They've enlisted the support of several
other cardiovascular experts3 to conduct this research
– the most comprehensive and advanced study of its kind to
date.
"We're
investigating how, how much, and how fast deterioration occurs
in the heart during long duration space travel," says
Levine.
Below:
A computer-generated diagram of the Integrated Cardiovascular
investigation onboard the ISS. Image courtesy of the Johnson
Space Center, Human Research Program.
The
space station crew, which has recently increased to six members,
will help Levine and his team find answers by serving as subjects
for Integrated Cardiovascular. The experiment will last for
more than 2 years -- long enough to gather plenty of data
on 12 different astronauts before, during, and after their
stints in space.
"We're
incorporating the most sophisticated tools4 ever
used in such an experiment to look at the heart and its chambers
and valves," says Levine. "This is the first investigation
ever to use advanced echo-Doppler techniques to follow the
structure and function of the heart during long periods in
space and confirm findings by using advanced magnetic resonance
imaging tools on the ground. For example, we're using an echocardiogram
to determine how heart muscle atrophy influences the way the
heart relaxes and fills, and an MRI to quantify this atrophy
precisely, and determine whether it scars or gets infiltrated
by fat."
An
echocardiogram uses high-pitched sound waves that are picked
up as they reflect off different portions of the heart. These
echoes are turned into a moving picture, allowing researchers
to watch a movie of the heart in action as blood flows through
the heart. By looking at such movies before, during, and after
spaceflight, the team can discern mechanical changes that
happen in a person's heart after he or she is away from Earth's
gravity for a long time. With the MRI, they can look at detailed
computer images of the heart tissues to pinpoint exactly what
kind of atrophy occurs.
 Right:
Astronaut Cady Coleman performs a remotely guided echocardiogram
on a test subject utilizing Integrated Cardiovascular protocols,
while Betty Chen, a training coordinator, observes. [larger
image]
"We're
answering questions like 'is the deterioration simply in size,
like Arnold Schwarzenegger's muscle loss if he stopped lifting
weights, or does the heart scar, do cells die?'"
The
team is also studying the effects of heart atrophy on crewmembers'
ability to exercise and on the likelihood of their developing
unusual heart rhythms both on the space station and after
returning to Earth. In addition, the researchers will look
closely at other cardiovascular issues, such as how blood
pressure responds to the reintroduction of gravity at the
levels experienced on Earth, the moon, and Mars.
"All
of the results will help us fine-tune exercise protocols for
the space station crew," says Robinson. "We'll also
learn what to look at in astronauts' hearts before we send
them to, say, Mars. We'll identify a set of risk factors that
can help flight surgeons determine the best candidates for
long space missions."
Levine
adds, "We may, however, show that the heart does just
fine in space, and that the strategies now used to keep astronauts
in shape are adequate to keep the heart functioning normally
and in good health. If so, flight surgeons can turn their
attention instead to other potentially critical problems such
as bone loss or radiation exposure."
Importantly,
this study's results will help researchers in developing preventive
and rehabilitative regimens for people on Earth.
"The
information we get from these experiments will be relevant
for patients after long-term bedrest or other physical activity
restrictions, as well as for patients with congestive heart
failure, heart disease, and even normal aging."
SEND
THIS STORY TO A FRIEND
Author: Dauna Coulter
| Editor:
Dr. Tony Phillips | Credit: Science@NASA
| end
notes |
|
(1)
Up on the space station
in Earth orbit, you're weightless. In fact, if you don't
fasten yourself onto or into something while you sleep,
there's no telling where in the space station compartment
you'll wake up. You may find yourself wedged next to
an air vent. But space station astronauts only appear
to be floating. They are actually in "freefall,"
which means the major force acting on them is from gravity.
On the station, the gravity pull comes from the Earth
because it is the closest large body. The space station
free-falls as it orbits the Earth. If there were no
forces acting on the space station, it would travel
in a straight line away from the Earth. Because the
Earth pulls the ISS towards it and is traveling 7900
meters per second (26,000 feet per second) parallel
to the Earth's surface, the ISS moves around the Earth
in a circle. The force of gravity on both the astronauts
in the ISS and the ISS itself is about nine-tenths of
what it is at the Earth's surface. Why do you think
NASA astronauts in the ISS feel weightless? You only
feel weight when something pushes against you. The ISS
can't push the astronauts because both the ISS and the
NASA astronauts free-fall at the same rate. (They are
traveling at the same speed and in the same direction.)
(2)
This experiment is supported entirely through
NASA funding mechanisms utilizing grants to the University
of Texas Southwestern Medical Center and the University
of Texas Health Science Center at Houston and onsite civil
service and contractor support at the Johnson Space Center.
The study's full name is Cardiac Atrophy and Diastolic
Dysfunction During and After Long Duration Spaceflight:
Functional Consequences for Orthostatic Intolerance, Exercise
Capability and Risk for Cardiac Arrhythmias (Integrated
Cardiovascular). More
information.
(3)
RESEARCH TEAM
Principal
Investigators:
Benjamin D. Levine, M.D., Institute for Exercise and
Environmental Medicine, Presbyterian Hospital and University
of Texas Southwestern Medical Center at Dallas, Dallas,
TX
Michael W. Bungo, M.D., University of Texas Medical
School, Houston, TX
Co-Investigator(s)/Collaborator(s):
Steven H. Platts, Ph.D. Johnson Space Center, Houston,
TX
Douglas R. Hamilton, M.D., Ph.D., Wyle Laboratories,
Houston, TX
Smith L. Johnston, M.D., Johnson Space Center, Houston,
TX
Payload
Developer: Johnson Space Center, Human Research Program,
Houston, TX
Sponsoring
Agency: National Aeronautics and Space Administration
(NASA)
(4)
Magnetic resonance imaging and echocardiography
will be used before and after spaceflight. Echocardiography
will also be used in flight.
A
special imaging technique called magnetic resonance
spectroscopy will also be used to quantify the amount
of fat in the subjects’ hearts.
Before
and after flight, subjects will be tilted on a table
at angles to approximate various levels of gravity (from
levels experienced on the moon up to those experienced
on Earth). During those tests, each subject’s heart
rate and blood pressure will be monitored and the blood
flow from their hearts will be measured by using an
echocardiogram.
The
reaction of the subjects’ bodies to exercise stress
will be determined before and after flight by having
them perform exercise while their heart rate, blood
pressure, and blood flow from their hearts are measured.
Electrocardiograms
will also be taken on several occasions during the study
and will last up to 48 hours at a time. These recordings
will be concurrent with continuous measurements of blood
pressure and activity (using Actiwatches worn at the
waist and ankle) to estimate the amount of work their
heart is doing daily on Earth and in space.
NASA's
Future: US
Space Exploration Policy |
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