Space, the Final (Medical) Frontier
PHYSICIANS FIND THEIR PLACE AMONG THE STARS.
The New Physician January-February 2001
by Jennifer ZeiglerVolume 51, Issue 1
During the frenetic days of the space race’s 1960s Apollo missions, Dr. Joe Kerwin had won a place in the National Aeronautics and Space Administration’s (NASA) astronaut corps, but he had yet to secure a ticket into orbit. For years, he had been sitting in on the Monday morning pilots’ meeting at NASA’s Johnson Space Center, but to no avail. “I kept raising my hand for Apollo missions, and Al Shepard would say, ‘Put your hand down. You’re not going to the moon.’”
Shepard was right—Kerwin wasn’t going to the moon. Eight years out of medical school, the physician–astronaut had landed his position by way of a National Academy of Sciences (NAS) recommendation for NASA to recruit scientists as well as the fearless test pilots whose “right stuff” made them the cornerstone of early manned space flight. The NAS saw space exploration as more than just an environment for the daring to test their nerves: Space was a boundless laboratory, and physicians and scientists alike should have their place in it.
Of the first five scientists NASA recruited into the astronaut corps in 1965, Kerwin was the only physician. He had already logged in hundreds of flying hours as a navy flight surgeon, but this NASA selection allowed him to chase a bigger dream.
“When I was a kid, I would sit in the kitchen and eat…sandwiches and read science-fiction books. And my brothers would come in and say, ‘Ah, little Joe. He’s going to the moon someday,’” he says. And while he never did get to the moon, in 1973 Kerwin made one giant leap for the role of physicians in space.
“Now, here comes Skylab whose purpose was, among other things, was to determine whether humans can withstand long-term space flight,” he says of the U.S. space station that orbited Earth from 1973 to 1979. “So it suddenly became a biomedical mission, and it was what I was waiting for.” When he raised his hand to volunteer this time, no one told him to put it back down.
And so, on May 25, 1973, Kerwin became the second physician in space—he missed being the first, because a Russian cosmonaut launched into orbit just a few days ahead of him—and began NASA’s first serious study of zero gravity’s effects on the human body, work that continues today on the International Space Station. (See how space affects the human body, p. 13.)
DOCS IN SPACE
So, welcome to the space doctor’s world—one that fluctuates between Earth and sky. Your job is to determine how to permanently put humans in a zero-gravity environment—a world where up is down and down is left or right. Confusing, huh? Well get this—even the organs you dissected as a first-year medical student are not where they should be as a result of this weightlessness.
It’s challenging work but easily linked to the practice of medicine. “The body was probably never meant to travel in space,” says Dr. Jeffrey Sutton, director of the National Space Biomedical Research Institute (NSBRI). “[But], medicine is all about physiology pushed too far. [Space medicine is] a really cool area because you have to think outside the box.”
In Kerwin’s day, there was barely a box to think outside of. “We were guided by the fragmentary, but interesting, data [about the human body] that had been gathered on astronaut flights from the beginning,” Kerwin says. But due to the brevity of early manned space flights, little was known about zero gravity’s long-term effects, and this knowledge was essential for NASA to have as it made plans to populate space and conduct interplanetary missions.
So when Kerwin and his two crew mates went to Skylab in 1973, it was to spend a month conducting research in life sciences, astronomy and other areas. While Americans were celebrating Memorial Day and pulling the lawn mower out of winter storage, Kerwin was using his medical background to study the weight loss, motion sickness and bone density reduction astronauts suffer. The crew performed aerobic exercises and measured changes in cardiovascular fitness; examined nutrition, creating a complete intake/output analysis for each crew member; conducted dental examinations; and investigated muscular capabilities.
Skylab reinforced NASA’s ability to conduct valid science in space, Kerwin says. “Suddenly we had a very sophisticated data set—still the best we’ve got.” Because the three Skylab missions were the last long-term, American-controlled space research missions, data gathered since then on numerous shuttle missions can only be applied to short-term flights, he says. “My personal experience in Skylab makes me proud of the good work we did. Since then we’ve been waiting—we’ve been doing a lot [of research], but we’ve been waiting [for another long-term research opportunity].”
Skylab wet the biomedical research whistle and established a role for physicians in space. Since then, 16 American physicians have made the trip on shuttle missions, trying to find answers to medical questions both 200 miles up and down here on Earth.
Dr. Drew Gaffney had been an associate professor at the University of Texas Southwestern Medical Center when he was recruited to be a payload specialist on Columbia’s 1991 mission, which was the first to be dedicated solely to life science research. Responsible for studying venous pressure in zero gravity, Gaffney became both scientist and subject on the mission, launching into space with a central venous catheter inserted near his heart so he could measure his blood pressure changes during the mission.
Circulation is a serious concern for astronauts because zero gravity prevents blood from flowing easily back into the extremities. “The blood hangs out in the head and chest and not in the abdomen and legs,” Gaffney says. Researchers expected that blood pressure would go up because of this, and Gaffney was surprised when the data indicated his pressure went down. “Quite honestly, I thought the system had failed,” he says, adding that he was so sure the data was incorrect, he reset the experiment’s entire system and checked it again. But the results were correct, and Gaffney says he finds satisfaction in the fact that he played a part in altering researchers’ thinking about blood pressure changes in space. “Having worked so long and so hard to get there, and then, by-in-large, having [the experiment] work was really satisfying.”
Just learning about the changes the body undergoes in space is not the sole challenge to physicians, says Dr. Bernard Harris, a physician–astronaut who journeyed into space in 1993 and 1995. “It’s going to be really important that physicians can [compensate for] these changes,” Harris says.
His work helped NASA get closer to the point where physicians can do just that. He didn’t fall into this business by accident; Harris says he had wanted to be an astronaut since childhood and chose medicine as his best way to get there.
His plan worked. In 1993 NASA sent Harris on a two-week mission to further study how living systems function in space. Harris spent time watching fish and tadpoles swim in circles—fish, like humans, have no concept of up or down in space, so they can’t swim in straight lines. He also served as the seven-member crew’s medical officer. NASA usually medically trains two crew members to tend to basic medical needs in space, but when physicians are on board, “we make the calls,” Harris says. (Crews are also supported by an on-ground flight surgeon. See “Physicians Without Wings,” p. 18.) “Every day is just like going to the doctor’s office,” Harris says. “You see common ailments—colds, muscle strains, headaches, diarrhea,” which, he adds, is even more uncomfortable in space than on Earth.
Kerwin had a similar experience with Skylab. “We had a general practitioner’s office capability in space. I couldn’t remove an appendix, but I could remove a tooth,” he says. “We could get back in 24 hours” if something more serious arose. “It’s sort of like camping in the Sierras,” he says—but at a much higher altitude, of course.
Harris spent more time in his high-flying exam room during his 1995 mission, which rendezvoused with the Russian space station Mir. Of the mission’s roughly 25 medical experiments, many focused on operational medicine. “In space, we don’t know what normal examinations are,” Harris says. “All of the windows for examining the organs are different.” For example, it doesn’t take a medical student to know that the heart is located down and to the left inside the chest cavity, so that’s where a physician would look for it on Earth. But physicians in space know that to find a crew member’s heart in zero gravity, they’ve got to steer their stethoscopes up and to the center because weightless organs float up.
But while in space, physician–astronauts don’t just examine crew members and conduct medical experiments; they also perform duties as astronauts. Both Harris and Kerwin went on space walks; Kerwin repaired a damaged Skylab heat shield during his.
RESEARCH PARTNERSHIPS
Research related to space medicine isn’t only conducted in outer space, however. The NSBRI’s Sutton says NASA recognizes how the wealth of talent at U.S. medical schools can enhance its space program.
“As the International Space Station [ISS] became a reality, it became enormously urgent not only to solve the motion sickness problem but others as well,” says Dr. Bobby Alford, the NSBRI’s chairman. At 240 miles above Earth, the ISS operates in zero gravity, and astronauts staff the facility for four to six months, making the long-term effects of weightlessness a serious concern. “And NASA, having realized that, saw they needed to go about research in a new way,” Alford says.
NASA realized the results of some Earth-based life science research could be directed to aid the agency’s search for countermeasures, or solutions, to the physical and psychological effects of long-term space flight. So, in 1997, well before the ISS launched, the space agency established the NSBRI—a consortium of 12 schools engaging in NASA-sponsored research—to tap into and help direct the wealth of life science research already being conducted. The NSBRI is based at Baylor College of Medicine.
“The real influence and power in terms of the research institute is all of the researchers across the country,” Alford says. “If [NASA were] to try to establish or create the resources that all these research institutions have, they couldn’t possibly do it. It’d be too expensive.”
It makes for a great bargain for NASA. The NSBRI researchers have secured National Institutes of Health (NIH) and private foundation funding in addition to some of NASA’s financial resources. These outside funding sources are lured to the work because of the potential Earth benefits. (See “Down to Earth” p. 25.) “This is a bold, new era, and [the research] is absolutely essential if the human space program is to go forward,” Sutton says.
NASA also works with Vanderbilt University’s Center for Space Physiology and Medicine, whose biomedical researchers try to solve the physical ramifications of space travel.
Some of the countermeasures being researched could include a system to deal with the high-power bands of radiation astronauts are exposed to once they leave the Earth’s orbit. Gaffney, who now serves as the space physiology center’s associate director, says that in addition to the radiation concern, the bone and muscle atrophy that is inevitable in zero gravity and the psychological challenges of being physically isolated with a few other people for years at a time are the biggest problems requiring solutions from researchers.
Dr. Sam Pool, the assistant director of Johnson Space Center’s Space Medicine and Life Sciences Directorate, echoes Gaffney’s top priorities and adds several more. “We’d like a breakthrough in better being able to deal with the bone loss, which is one of the most serious problems. We’d like a breakthrough in the area of neurophysiology…; we’d like to have some surgical techniques which could be used in microgravity.”
The need for more extensive medical treatments comes from the fact that travel beyond Earth’s orbit promises to be years long. “When you go to Mars, you’re a long way from the nearest hospital,” Kerwin says. “You could be three years from the nearest hospital.” So researchers are working on medical technologies that are lightweight and can be used to treat any problem that might arise.
“We are at a threshold of having a suite of new technologies,” Sutton says. Sutton’s research focuses on generating on-going, passive monitoring systems that will help physicians on the ground treat medical problems a world or two away. “We’re interested in doing completely noninvasive treatments based on computerized models of individuals,” he says. One example is finding a way to monitor blood without ever using a needle, since having blood drawn in space is very uncomfortable for astronauts.
TO MARS AND BEYOND
Many say the progression of countermeasure research is essential mainly because the future is here. The ISS maintains a continual human presence in space that we’ve never before had—in November, NASA celebrated its first anniversary of permanent space habitation. “Space will never have a time when humans are not there,” Harris says.
Space medicine has come a long way since Kerwin’s groundbreaking foray beyond our atmosphere. But the ISS is only a jumping-off point in NASA’s attempt to grab the golden ring: a successful manned mission to Mars. And to do that, many unanswered questions must have solutions in order to ensure the crew’s safety.
“We still don’t have a set of accurate countermeasures for people who spend a long period of time in that environment, and that makes the Mars mission rather difficult at best,” Pool says. “The development of countermeasures is very, very important.”
The ISS has always been considered the test environment for countermeasures, but with the station billions of dollars over budget and Congress weary of footing the bill, the station’s viability as a research laboratory is threatened. Plans for entire sections of the station have been scrubbed, and future crews have been scaled back from six to three people, which many experts say is barely enough manpower to keep up with routine maintenance. “Skylab was much simpler of a craft to fly,” Kerwin says, and he adds that the ISS should have a continual staff of at least six to complete the volume of research the station needs to conduct.
Many NASA officials and astronauts also express concerns over the Bush administration’s appointment of Sean O’Keefe to replace NASA’s former administrator, Dan Goldin. O’Keefe is better known as a management guru rather than as a space visionary. He served as the secretary of the Navy under the first Bush administration and, according to NASA flight surgeon Terry Taddeo, was known as “the Grim Reaper.” The current President Bush tapped O’Keefe for NASA while he was serving as the deputy director of the White House’s Office of Management and Budget.
“I’m worried right now based on the lack of knowledge [we have] about what Mr. O’Keefe is going to do,” Kerwin says. Many astronauts with whom The New Physician spoke are taking a wait-and-see approach. They say the potential for research cutbacks worries them, but there’s not much they can do about it. Kerwin says if O’Keefe can pull up NASA by its bootstraps into a better management plan, then “that’s great”—but other space experts have said the agency should not expect the wide-reaching, let’s-get-to-Mars-at-any-cost vision for which Goldin was famous.
Congress is also reining in its enthusiasm for the space agency as the ISS becomes increasingly expensive. “You can’t use the M-word in Congress right now,” Taddeo says of a Mars mission. “[NASA is] just like any other government agency. You’re there at the whim of the Congress and the president.”
But not everyone thinks NASA’s problem lies in expensive ideas and not enough money to pay for them. “The bottleneck, in my opinion, is not money, it is risk,” Sutton says. “Since [the] Challenger [explosion], we have been in a risk-averse culture. As a society, we have an expectation that we’re going to go up, and everything will be fine.” But this is impossible, he says, because NASA can’t screen astronauts for every potential medical problem, given the years needed for interplanetary travel. No matter where people go, they will get sick, Sutton says. “If you put seven people in their 40s and put them away for a year, people will become ill. There will be things that arise. That is just the human condition.” So, he says, we’ll never be able to avoid all of the risks of long-term space travel, a fear NASA—and society—will have to overcome if the space program is to continue on its current path.
However, for those who work in space medicine, the future is still starlight bright. “If you’re a space nut like me, the most exciting thing there is…is putting people in systems to go to Mars,” Kerwin says. “The challenge is out there, and we know we can do it.”
The Trouble With Space TravelYour body swells, you’re nauseous, you lose more bone mass than osteoporotic women do. Buzz Lightyear may look like the picture of action-hero health, but trust us: Infinity and beyond is no picnic for the human body.
With the 1-G gravitational pull we’re used to on Earth no longer tugging on us in space, the human body uses its defense mechanisms as best it can to adjust. “The body is very resilient,” says Dr. Bernard Harris, a physician–astronaut who has made two trips into space. But the problem often lies in how the body changes—adjustments to space’s zero gravity make coming back down to Earth all the more difficult. Here are some examples:
Bone loss — Without the need to hold the body straight against a constant downward pull, bones become less dense in space, mostly in the hips, spine and lower extremities. Bone density decreases at a rate of about 1 percent to 2 percent per month, and it never stops, making the prospect for long-term travel dangerous upon Earthly return, when the bones suddenly need to start doing their job again. This constant calcium purging in the bones is also believed to increase the chance of developing kidney stones in space.
Muscle atrophy — Muscle loss can be as great as 25 percent of the original mass, although research has shown that regular and lengthy periods of exercise while in a weightless environment can reduce this effect.
Fluid redistribution — Weightlessness causes bodily fluids to fill the sinuses, so astronauts tend to feel as if they have a head cold for much of the trip. Studies have found the sensation is relieved during exercise sessions, which force the fluids back to where they belong. Fluids also swell in the hands and chest, and researchers are concerned that long-term fluid buildup in the head could cause brain damage.
Cardiovascular changes — The body, sensing the fluid shifts, believes it to be suffering a fluid overload. This causes the brain to downgrade the cardiovascular system, lowering blood pressure and slowing the heart rate. While lower blood pressure and slower heart rates are the goal of every Earthly aerobic workout, eventually the slowdown causes a decrease in red blood cell production, which makes astronauts anemic.
Nausea — Because weightlessness plays tricks on the senses—astronauts have a difficult time discerning up from down and left from right—about 60 percent of space travelers suffer from motion sickness, although the body’s internal adjustments usually control it after a few days.
Radiation exposure — Beyond the Earth’s atmosphere lie the Van Allen radiation belts, which can be very damaging to long-term space travelers. Researchers are trying to develop shielded areas in spacecrafts for human travelers to seek shelter from the potentially cancer-causing rays.
Psychological challenges — Extended periods of isolation are a concern for long-term space travelers. A trip to Mars is expected to take three years, and researchers realize that is a long time to be locked up in a tiny vehicle with maybe six other people. The 16 sunrises and sunsets and the 45-minute day Earth-orbiting astronauts experience also play with the body’s circadian rhythms, and Mars travelers would potentially be screened for adaptation abilities to that planet’s 25-hour day.
Orthostatic disorders — Without the need to stand up straight, astronauts tend to develop orthostatic problems and for several days after their return to Earth have difficulty standing without fainting. This becomes a problem in re-entry into Earth’s atmosphere, as astronauts, who have adjusted to space’s zero gravity, actually feel a force greater than Earth’s 1-G on the way back down, causing them to faint at times, a potentially hazardous situation if they are piloting the space shuttle.
All of these changes make astronauts a little awkward and uncoordinated on Earth’s return, says Dr. Drew Gaffney, a physician–astronaut who flew on the space shuttle in 1991. “It’s probably a good week until you’re back to normal. If you want to beat someone at Ping-Pong, play them after they’ve been in space.”
—J.Z.
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EDUCATIONAL RESOURCES----------------------
PROGRAMMABLE PACEMAKERSOne of the first medical breakthroughs derived from NASA research occurred in the late 1970s when a California-based company used technology from the space program to introduce a bi-directional telemetry pacemaker system, which allows a physician to gather information about a pacemaker’s function and to reprogram it based on the patient’s needs—all without requiring surgery.
Researchers created the innovative pacemaker by using two-way communication originally developed by NASA to talk with satellites. The pacemaker’s single microchip and rechargeable, long-life battery are also products of the agency’s research. The end result is a state-of-the-art pacemaker that closely matches the natural rhythm of the heart.
BONE DENSITY MEASUREMENTSFor years, NASA has been concerned with the dramatic bone loss astronauts suffer during extended time in orbit. Astronauts lose approximately 1 percent to 2 percent of their bone density in a month; compared to postmenopausal women on Earth, who average 1 percent bone loss per year.
To more accurately measure this bone loss, the NSBRI has developed the advanced multiple-projection, dual-energy, X-ray absorptiometer—a compact instrument designed to take precise bone and tissue measurements. The current measurement method uses a single-projection X-ray process and fails to take in account patient positioning or the natural density within the structure of a bone. “Bones are not symmetric; they are asymmetric. If there was more bone in the path of the X-ray, then I would say your bone density was higher,” says Harry Charles, the NSBRI’s associate team leader for technology development, who led the research and testing of the new device. The instrument resolves this problem by taking multiple, angularly spaced projections to provide a more precise measurement of bone density. This allows NASA to determine whether countermeasures are effective.
But before the instrument begins evaluating astronauts for bone loss, it may already be in use on Earth. “Obviously, it has great potential with osteoporosis. It can ultimately be portable. It can ultimately be in a physician’s office. It can be in clinical settings of all types,” Charles says. The device is undergoing accuracy studies on human subjects and soon could be in commercial use.
ROBOTIC SURGERYWhen astronauts float thousands of miles above the Earth, every task is complicated, and completing intricate and precise repairs on a satellite is almost impossible. Therefore, NASA has long been at the cutting edge of robotics, using mechanisms to perform work in space. Now, some of that robotic technology is making its way into the operating room, allowing surgeons to conduct noninvasive, endoscopic procedures.
Endoscopic surgery is performed by inserting a slender camera into an incision to access a part of the patient’s body. Before using robotics, the surgical staff had to hold the camera while the surgeon used it to monitor the operation. With the new system, the surgeon sits in front of a monitor and uses hand-controllers to manage robotic arms performing the surgeries. Voice-recognition software controls the camera movement. The robotic arm provides steadiness and accuracy that simply isn’t possible with the human hand.
Electrical Disturbances in the Heart
In the early 1980s, Dr. Richard Cohen—intrigued by the relationship between minute disturbances in a patient’s heart rhythm and the risk of sudden cardiac arrest—sought NASA support to study microvolt T-wave alternans, which are minor fluctuations in the heart’s electrical activity. Cohen, a professor of biomedical engineering at Harvard–MIT Division of Health Sciences and Technology, believed T-wave alternans could help explain why some people suffer sudden cardiac arrest without any prior evidence of heart disease. Electrocardiograms are not sensitive enough to pick up the changes in T-wave alternans and, at the time, no other technology
was available to study them.
Cohen knew NASA would be interested in this work because some astronauts had noted changes in their heart activity during space travel. His research could provide the agency with a better understanding of the behavior of the heart in zero gravity.
So with NASA support, Cohen, who has since been appointed leader of the NSBRI’s cardiovascular alterations team, led the development of the T-wave alternans test, which when performed during a standard stress test, can detect the subtlest beat-to-beat variations of the heart. In April 1999, the test received clearance from the Food and Drug Administration (FDA) and has since found widespread acceptance in the medical community.
BREAST CANCER DETECTIONWhen NASA’s Jet Propulsion Laboratory began working on an ultrasensitive infrared photo sensor in the early 1980s, researchers figured the final product would someday be used to target launched missiles as part of President Reagan’s futuristic Space Defense Initiative, better known as the “Star Wars” program. But upon completion of the Quantum Well Infrared Photo (QWIP) detector a decade later, researchers found the Cold War had thawed, and they were left to find new uses for the technology.
That was when a small New York technology company stepped in and negotiated with the NASA technology transfer program to obtain the licensing rights to QWIP’s biomedical applications. Company officials believed the technology, which is sensitive enough to identify differences in temperature of less than 0.01 degrees Celsius, could be used to recognize cancerous breast lesions by detecting a tumor’s attempt to acquire a new blood supply, a common characteristic of malignant lesions. In order to acquire the supply, the tumor exudes nitric oxide, altering the blood flow and temperature of tissue around the cancer.
The company’s cancer detection system, which received FDA approval in 1999, has become widely accepted as breakthrough technology in the fight against breast cancer. It is considered a dramatic improvement over mammography, which detects the calcification of cancer cells only after they develop.
IMPLANTABLE INSULIN DELIVERYNASA’s Viking lander missions launched in the mid-1970s provided the agency with invaluable images of the surface of Mars. And it has also provided much needed relief to insulin-dependent diabetics who rely on daily injections.
The Programmable Insulation Medication System, an implantable computerized pump that acts as an artificial pancreas, delivers insulin to the body at a controlled rate. The pumping mechanism is taken directly from a component of the Viking lander, while the remainder of the device—a refillable reservoir, a tube to the diabetic’s intestine, a microcomputer and a battery, all of which are encased in a titanium shell—was devised by Johns Hopkins University’s Applied Physics Laboratory in
collaboration with NASA.
The microcomputer is the key to delivering the insulin to the abdominal cavity in short pulses, with the rate programmed through a small transmitter placed over the implanted device. The same transmitter can also be used to obtain information from the pump’s stored memory and can generate performance records. Patients avoid further surgery by refilling their insulin reservoirs with special hypodermic needles approximately four times a year.
MUSCLE STIMULATION TECHNOLOGYIn order to get work done in zero gravity, astronauts rely on the Remote Manipulator System (RMS), the space shuttle’s six-axis, 50-foot mechanical arm used to move payloads and satellites weighing up to 65,000 pounds. As part of astronaut training, NASA’s Goddard Space Center developed an RMS simulator to allow astronauts to a get a feel for the powerful mechanism.
The computerized control systems for that simulator have since contributed to the advancement of functional electronic stimulation (FES)—a therapeutic treatment method for neuromuscular illnesses that uses electrical currents to initiate muscle contraction, which relaxes muscle spasms, prevents muscle atrophy due to disuse, increases blood circulation and range of motion, and reinforces muscle memory.
An Ohio-based company used the RMS control systems to develop an FES computer-controlled stationary bicycle, which sends low-level electric pulses to the user’s leg muscles, empowering the legs to pedal in a natural motion at 50 revolutions per minute. The equipment garnered national attention for its role in the therapy of actor Christopher Reeve, who suffers from paralysis after having fallen from a horse in 1995.
VENTRICULAR ASSIST DEVICESometimes the inspiration to transfer NASA technology into the medical field can be very personal. This was the case for Johnson Space Center engineer David Saucier. After undergoing a heart transplant in 1984, Saucier worked with his physicians, Michael DeBakey and George Noon from Baylor College of Medicine, to develop a better heart pump.
This led to the development of a miniaturized and implantable ventricular assist device (VAD) that employs NASA’s turbopump design, which maintains the performance of the space shuttle’s engines. The VAD is one-tenth the size and approximately one-quarter the cost of current heart pumps on the market and provides a weak heart much needed rest by pumping more than 10 liters of blood per minute. Additionally, the heart pump weighs less than 4 ounces and operates on only 8 watts of power. In 2000, the new VAD was implanted in a 31-year-old woman. The device received approval from the FDA last year to begin multicenter clinical trials. —S.S.
Jennifer Zeigler is a senior writer with The New Physician.
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