Astrodocs: For these physicians, space is their workplace

Surrounded by the uninterrupted darkness of outer space, orthopedic surgeon Robert "Bobby" Satcher Jr., MD, PhD, peered down at Earth, a sphere of vivid blues, whites and greens.

Except for the view, his two spacewalks as an astronaut with the space shuttle Atlantis were similar to surgeries he performed at Chicago hospitals. There was the same high-stress environment, comparable tools and a need to think a few steps ahead. "The main thing that's different," he said with a laugh, "is that you're in space."

Dr. Satcher rocketed 5 million miles to the International Space Station in November 2009 on an 11-day mission -- becoming the most recent physician to replace a white coat with a space suit. Since 1973, 22 other U.S. physician-astronauts have participated in 49 space missions, conducting dozens of spacewalks and experiments to advance space exploration and the understanding of how space affects the human body. They take care of the health needs of fellow astronauts, and, through their research, have helped further medicine on Earth.

They have made history: the first black person to walk in space was Bernard Harris Jr., MD, in 1995. In 1997 J.M. Linenger, MD, PhD, MPH, set the record for the longest duration flight for a U.S. man -- 132 days, 4 hours and 1 minute in space. (That mark has since been broken.)

They also have died on missions: David Brown, MD, and Laurel Blair Salton Clark, MD, were on the shuttle Columbia when it broke apart while re-entering Earth's atmosphere on Feb. 1, 2003.

"The role of the physician-astronaut is a very vital one to NASA's mission," said Jeffrey Sutton, MD, PhD, president and director of the Texas-based National Space Biomedical Research Institute, which works with NASA to sponsor research at universities nationwide.

"Doctors, in addition to many being excellent scientists, bring a clinical perspective of taking care of individuals. NASA sends humans into very harsh, austere environments, and doctors bring an environment of prevention, of wanting to ensure health and safety," Dr. Sutton said.

The path to becoming an astronaut typically begins with a dream.

As a child, David Wolf, MD, watched on television as astronaut Ed White conducted the first American spacewalk in June 1965, and knew that one day he, too, would rocket to outer space. For Tom Marshburn, MD, the vision crystallized in high school with hopes of building rockets for NASA.

Both men went on to earn degrees in engineering and medicine. Dr. Wolf served as a flight surgeon for the U.S. Air National Guard. Dr. Marshburn practiced emergency medicine in Seattle.

In 1983, Dr. Wolf was hired as a physician-engineer at NASA. Dr. Marshburn joined the space agency as a flight surgeon in 1994 after receiving a space medicine fellowship through NASA and the University of Texas Medical Branch at Galveston. Both applied for and were accepted into NASA's astronaut program.

Potential rocket men and women who pass preliminary screening undergo two years of training and evaluation at the Johnson Space Center in Houston. They acquire skills that prepare them for spacewalks, and they fly aboard a C-9 jet aircraft that performs maneuvers to produce periods of weightlessness.

Those who are selected to become astronauts train at least another year for their missions. The length of training and types of exercises performed depend on each astronaut's flight assignment. For example, astronauts chosen to be crew members on the International Space Station train at least three years.

Once astronauts go into space, they want to go back.

"It never gets old. It's one of the most intense and captivating experiences that a human may have," said Dr. Wolf, who now lives in Texas. He took part in a handful of missions, including a visit to the Russian MIR space station in 1997.

When Dr. Marshburn returned from his 15-day mission in July 2009, he stepped off the shuttle Endeavour in Florida with wobbly legs and a spinning head -- and a thirst for more space travel. "It's so much more than you ever imagined it's going to be. ... It's an enormous amount of fun," he said, quickly adding, "but you're not allowed to pay too much attention to that."

Staying healthy in orbit

With any mission, the most critical periods for an astronaut's health are launch and re-entry to Earth's atmosphere.

It takes about 8½ minutes for a shuttle to rocket to space, forcing the astronauts' bodies to abruptly transition from a lifetime spent in Earth's gravity to being in no gravity at all, said NASA flight surgeon Richard Scheuring, DO.

Almost immediately, 75% to 95% of astronauts become nauseated and may vomit as their vestibular systems adapt to weightlessness. Blood and fluids redistribute to the upper parts of their bodies, which causes the heart to enlarge. They become less thirsty, and the kidneys increase output of urine, causing fluid and electrolyte levels to drop. Eventually, the heart shrinks due to the lack of gravity and fluid.

As days in space become weeks, an astronaut's muscles begin deteriorating, and load-bearing bones demineralize at a rate of approximately 1% per month.

When Dr. Wolf returned to Earth in January 1998, after 128 days in space, he thought he had ruined his body. The avid athlete had lost 40% of his lean body mass. His wrist felt as heavy as a bowling ball. His balance was destroyed.

After several years of rehabilitative medicine, Dr. Wolf returned to good health. But some people never fully recover, he said.

In addition to dealing with the physical effects of space, physician-astronauts must address health problems experienced by the crew.

For example, some astronauts have had urinary retention problems and needed catheterization. Others have been incapacitated by severe nausea or needed treatment for minor illnesses while on the shuttle, according to Dr. Scheuring.

"First and foremost, the role of a physician [astronaut] is to take care of people in space just like you take care of them on the ground," Dr. Satcher said.

Physician-astronauts treat and monitor health problems, assuring that the mission continues uninterrupted. But there is no NASA directive that a doctor be on each flight.

For missions without doctors, a crew member receives about 40 hours of medical training, including basic skills such as how to use a stethoscope.

When health problems arise, astronauts rely on a checklist of medical conditions, an ultrasound available on the space station to aid in diagnoses and NASA flight surgeons on Earth who closely monitor crew health via regular e-mails and daily phone conferences.

Surgery is not an option, due largely to the challenges of operating in zero gravity, where nearly every medical procedure needs to be modified and has a greater degree of difficulty.

"If we get to a point where we feel this [medical problem] is something we can't handle in space, they would have to come back," said Dr. Scheuring, adding that no astronaut has returned early for health reasons.

Beyond medical care

Physicians in space play an integral role designing and conducting experiments to find solutions for health concerns not only facing astronauts in space but also the public on Earth. Researchers are examining connections between the health risks of dust on the moon and asthma on Earth, sleep problems of astronauts and shift workers, and emergency medical care in space and war zones.

Experts say the role of physicians will expand when missions move beyond the space station and astronauts remain in space for more than two years, risking severe muscle atrophy, bone loss and radiation exposure. But such long-duration missions are not expected anytime soon.

President Obama's 2011 budget proposal calls for eliminating NASA's Constellation program, which aimed to return astronauts to the moon by 2020 and, eventually, to Mars.

The president's plan instead would look to commercial companies to transport astronauts to the International Space Station and to invest in new space technologies, which eventually would allow astronauts to explore the solar system. Crew members have been selected for NASA's four remaining shuttle missions, with the last one scheduled in September.

Dr. Marshburn hopes to return to space sometime. Until then, he is offering his medical expertise to NASA on the ground, helping to ensure that future missions are safe for humans. Doctors, he said, are needed to help design medical kits for astronauts, as well as spacecrafts, suits and other equipment that will protect crews from radiation, freezing temperatures and other risks inherent to space travel.

In Texas, Dr. Satcher is contemplating his future with NASA and a return to medical practice. For now, he is helping the agency prepare for upcoming missions.

But if an opportunity arises for him to return to space, there's no need to ask if he will suit up again.

He's ready for liftoff.