In Tribute to Charlie Houston
2010; Elsevier BV; Volume: 21; Issue: 2 Linguagem: Inglês
10.1016/j.wem.2010.03.004
ISSN1545-1534
Autores Tópico(s)Cardiovascular and Diving-Related Complications
ResumoSCIENCE now has proved that flyers and mountain climbers can reach altitudes of almost six miles, remain normal and alert, and come away none the worse for wear—without supplemental oxygen … It is only necessary that they accustom themselves gradually to the decreasing pressures and dwindling oxygen … For this discovery, of much value in the planning of future upper air explorations, credit goes to a pair of venturesome young men of the U. S. Navy—Lieut, (jg) Walter S. McNutt, Jr., and Carlton R. Morris, Hospital Apprentice. Under the supervision of Lieut. Cmdr. Charles S. Houston, U.S.N.R., a flight surgeon and authority on mountain climbing, McNutt and Morris tested for an entire month, in Florida, an odd sea-level combination of mountain climbing and airplane flying called “Operation Everest.” The men lived in a compression chamber. They “flew” or “climbed” almost six miles without supplemental oxygen and suffered no ill effects. They reached a simulated altitude of 29,025 feet—23 feet higher than the unconquered peak of Mount Everest, the highest mountain in the world … The program's purpose was to study the adaptation of the human body to slowly increasing anoxia, or lack of oxygen. As a result of its findings it may be possible to reproduce artificially the necessary physiological changes in an aviator in order to “acclimatize” him quickly before he reaches the upper air … Morris and McNutt reached the “altitude” topping Mount Everest, remained there for almost 30 minutes and didn't lose consciousness … The test chamber was really something to see. It was of steel, about 20 feet long and perhaps 10 feet in diameter, with two doors about six feet apart in one end. Technicians and observers who entered the chamber did so by way of a small lock, remaining there until its air was reduced to the same pressure as that of the volunteers; and when they left the process was reversed. The chamber bristled with control appliances and was operated by a 14-man crew of experts … It was interesting to watch McNutt and Morris as they “climbed” to their record-breaking height of 29,025 feet on the next to the last day. When they reached this height their blue complexions turned to a rather deep purple. (If this sounds a bit wild, let me explain that men start to turn blue in the face after they've been exposed to heights of about 13,000 feet without supplemental oxygen.) At this point they were breathing heavily and looked definitely uncomfortable; but they stayed there without supplemental oxygen for four hours … Other high altitude physiological studies are sure to follow this initial effort … It is with great sadness that the Wilderness Medical Society (WMS) notes the death of Dr Charles (Charlie) Houston in 2009 at the age of 96. Charlie was one of the Founding Members of the WMS and remained actively involved with our organization until age slowed him down. What follows are a few remembrances of Charlie from persons who knew him well. Words never do justice fully to any man or woman, but as we suffer his loss, they can perhaps add a bit of color to his memory, both for those close to him and those who knew of him from afar. As Rob Roach so eloquently pointed out to me in a correspondence, “Charlie was much more than a founding member of the WMS. Before there were thousands of people going to WMS meetings, there were Charlie's meetings at the Yosemite Institute. Before there was a Journal of Wilderness Medicine, there was Charlie with his book Going Higher attempting to educate people about high altitude. Before any of us had ever heard of K2, Charlie was attempting to find a route to the top.” I agree with Rob—Charlie was in many ways an innovator, and definitely a force. To set the stage, the following facts and commentary are adapted from the reporting by Stephen Goodwin in the United Kingdom for the Independent Newspaper. Charlie was born in New York on August 24, 1913. He was introduced to the hills by his parents and at the age of 12 had walked with them from Geneva to Chamonix. While a medical student, he joined the Harvard Mountaineering Club, teaming up with 4 other enthusiasts to form the “Harvard Five.” In 1933, he was invited to climb on Mt Crillon, Alaska and a year later participated in an expedition led by his father, Oscar Houston, to make the first ascent of Mt Foraker. During subsequent expeditions, he participated in climbs on such mountains as Nanda Devi and in prospecting the approach to Mt Everest from the Nepal side. During a journey in 1950 he explored the Khumbu valley towards the southern flank of Everest. Prior to this time, expeditions to Everest had always approached from the north in Tibet. Charlie and others camped on the Khumbu glacier and viewed the intimidating icefall that cascades from the Western Cwm. They assessed the icefall to be too hazardous for laden porters and doubted that Everest could be climbed by this route. They were wrong, but they were there. As a mountaineer, Charlie is most famously associated with K2, giant of the Karakoram and arguably the most difficult of the world's 8000-m peaks. Charlie led 2 expeditions to K2. The first, in 1938, was an acclaimed reconnaissance during which he and Paul Petzoldt became the first climbers to reach “The Shoulder” on the Abruzzi Spur. It had required a supreme effort, wading in deep powder snow. “I felt that all my previous life had reached a climax in these last hours of intense struggle,” Houston wrote. Charlie made studies of “thin air” during the Second World War. Entering the Navy as lieutenant in 1941, after interning at the Presbyterian Hospital in New York, he trained pilots in the effects of hypoxia at combat altitudes. Immediately after the war, Houston persuaded the Navy to let him do further research on volunteers in a decompression chamber. Called Operation Everest, the tests were ostensibly about gaining air combat superiority but were ultimately more interesting to mountaineers, because they showed that with acclimatization, humans would be able to survive briefly at the top of the world. Twenty years later, Houston returned to the subject, directing physiology studies each year from 1967 to 1975 at a laboratory at 5300 m on Mt Logan in the Canadian Yukon, and re-running a more ambitious version of Operation Everest in 1985. War service over, Houston returned to K2 in 1953 with a team that included his close friend Bob Bates. Storm and struggle accompanied the team up the Abruzzi Spur; even so, by the beginning of August they were encamped just below The Shoulder and optimistic that the summit was within reach. Just 3 good days were needed. However, foul weather confined them to battered tents. In retrospect, Charlie was philosophical about the 10-day battering at Camp VIII. “Perhaps it is this conquest, conquest of one's self through survival of such an ordeal, that brings a man back to frontiers again and again.” On August 7, as the clouds lifted and the climbers crawled out of their tents, the young geologist Art Gilkey collapsed unconscious in the snow. He had developed phlebitis, with blood clots in his left leg. As both a doctor and climber, Charlie knew there was no chance of getting Gilkey back to Base Camp alive, but there was also no question about whether or not the team would try to save him. Avalanche risk and bad weather delayed them for 3 days, until, as Gilkey's condition worsened, descent became imperative. In a raging blizzard, with Gilkey wrapped in a sleeping bag and smashed tent, an exhausted and ice-encrusted team began inching him down the mountain. Gilkey had just been lowered over a cliff when one of the climbers, who suffered frostbitten feet, slipped, dragging his rope-mate with him, and dislodging others. Bates thought his end had come. Once off the ice slope, they would all drop hundreds of meters to the glacier below. Amazingly, the 5 hurtling climbers were halted on the lip of the abyss by the strength and superb belaying technique of another team member, who also held the weight of the suspended Gilkey. Many believe that the critical juncture in Charlie Houston's life came at that moment on August 10, 1953 as he lay unconscious on a narrow shelf high on the Abruzzi Spur. Charlie was coaxed back from the brink of death by Bob Bates, who awakened him and ordered him to climb 50 m to the shelter of a camp. Bates recalled it thus: “Charlie,” I said with the greatest of intensity, looking directly into his eyes, “if you ever want to see Dorcas and Penny (his wife and daughter) again, climb up there right now.” By accounts, Charlie then fairly swarmed up the snowy rocks of the cliff. After being urged back to life by Bates, Charlie had little idea where he was. “What are we doing here?” he kept repeating. Battered and bleeding, the party struggled to the nearby Camp VII, and then 3 of them went to fetch Gilkey, who had been left anchored by 2 ice axes. He had vanished, swept to certain death by an avalanche. It was another 4 days of nightmare descent before the team stumbled gaunt and hollow-eyed into the embrace of their porters. During the descent, Charlie was at times delirious. At a reunion 25 years later he revealed how close he had come to ending it all above a technically difficult “chimney” pitch. He feared he would knock his friends off the mountain if he fell. “Better jump off to one side and get it over with,” he'd thought. “I knelt in the snow and said the Lord's Prayer. Next thing I can remember is being grasped by strong arms and helped into Camp IV.” Charlie never again attempted a high mountain ascent. He ceased climbing and devoted himself to his family, medicine, and human good. A growing family and rural medical practice increasingly filled his time. The years 1957 to 1962 were spent working as an internist in Aspen. He then became Director of the United States Peace Corps for India, an ideal post for someone so devoted to the well-being of his fellow human beings. Charlie settled into teaching medicine at the University of Vermont and, as we all know, became one of the great authorities on high altitude–related medicine. During his life, he authored K2: The Savage Mountain;1Houston C.S. Bates J.H. K2: The Savage Mountain. The Lyons Press, Guilford, CT2008Google ScholarGoing High, The Story of Man and Altitude2Houston C.S. Going High, The Story of Man and Altitude. American Alpine Club, Burlington, VT1980Google Scholar (which became Going Higher: Oxygen, Man and Mountains3Houston C.S. Harris D.E. Zeeman E.J. Going Higher: Oxygen, Man, and Mountains.5th ed. The Mountaineers, Seattle, WA2005Google Scholar); and Five Miles High (with Robert Bates and Jim Wickwire).4Bates R.H. Houston C.S. Five Miles High: The Thrilling True Story of the First American Expedition to K2.2nd ed. The Lyons Press, Guilford, CT2000Google Scholar In his last decade, Houston's liberalism reasserted itself publicly and he would stand on a soapbox in Burlington city park railing against the warmongering of George W. Bush and the shameful absence of universal medical care in the United States. He was a man of complex emotions, as revealed in a fine biography by Bernadette McDonald, entitled Brotherhood of the Rope.5McDonald B. Brotherhood of the Rope: The Biography of Charles Houston. The Mountaineers, Seattle, WA2007Google Scholar In May 2006, Charlie received an honorary doctorate from the University of Colorado. At that time, fundraising was initiated to fully endow the Charles Houston Chair in High Altitude Medicine and Physiology. To date, more than $550,000 has been raised toward the long-term goal of a $2 million dollar endowment. For more information, and to contribute, please see: http://www.altituderesearch.org/about/csh. Now, let us hear directly from some of those who knew him. For nearly 40 years, I have had a photograph of Charlie in my office. I'm looking at him now. He's sitting in the radio shack beside the Arctic Institute's dirt strip at Kluane, in the Yukon, with an old dark blue baseball cap clamped on his grizzled short-cropped hair. He's calmly chatting with Phil Upton who is in the Heliocourier, 100 miles away over the huge massif of Mt Logan. Two days before Charlie died, I phoned him from my home in Oregon, some 3000 miles away. Robin, his elder son, answered and after Robin and I had spoken for a couple of minutes, he held the phone to Charlie's ear. I could hear Charlie trying to say something we decided later was about my articles on drug companies. “Charlie,” I shouted into the phone, “I want you to know you're very, very annoying. And I love you, I really do.” I thought I heard a laugh. In all sorts of ways, that sums it up. From the time I met him, in 1968, to the time he died, Charlie drew me in, encouraged, needled, bullied, cajoled, threatened, and inspired me. In hundreds of phone calls between Burlington and my home in Chicago, he'd have me banging my head against the wall in frustration, promising myself I'd never, ever work with him again. And then he'd turn around and, making good use of his scientific argument and shameless use of his charm, draw me into sometimes reluctant acquiescence. He would listen to my deepest worries about goals, feasibility, safety, and by sharing his own concerns, draw me into his web—a web made up of at least as much emotion as science. Back in 1968, at a conference in Aspen on low-oxygen, high altitude physiology, Charlie was recruiting for an exciting new project. A few months before, under Charlie's direction from the radio shack, Barry Bishop had led a group of climbers up Mt Logan to set up a temporary research lab at 17 600 ft on the summit plateau. They showed that despite the extreme conditions, the lab as a habitable structure was feasible. Now the question was whether research could be done there, and if so, what questions could best be answered. A week before the Aspen conference, I had returned from studying kidney oxygenation in miners in the central altiplano of Peru, and I was due to return to the Andes to work on long-term hypoxia. But here in Aspen was one of the world's great mountaineers and foremost altitude experimentalists, an icon as well as a hero, urging me to join him to do any number of studies. The project sounded inspired, bold, and thrilling. All I had to do was tell him what studies I wished to do, and help write the grant proposal. And, of course, the next year, 1969, make the project actually produce. So I signed on and began a relationship that changed my life. The Mt Logan project, both down by Lake Kluane and up at High Camp, combined all that was best about research and much of what I wanted from being in the mountains. Charlie took care of the daily worry of running a complex and widely spread operation, in difficult and potentially very dangerous terrain, under conditions where disparate scientific goals might clash as much as disparate personalities. It became one of the greatest experiences of my life, not merely because of the friends I made, or just because of the grandiose mountains and vast glaciers. It was wonderful because Charlie, the great leader that he was, made it so, because he set the tone: good-humored, efficient, tolerant, self-effacing, and affectionate. He managed the complex logistics and equally complex characters, with firm wit and steady purpose. One of the project's most productive studies came at the start with the observation that retinal hemorrhages occurred on sudden ascent. The subsequent careful hemodynamic studies on the retinal circulation were a triumph for Regina Frazer and for Charlie.6Frayser R. Houston C.S. Bryan A.C. et al.Retinal hemorrhage at high altitude.N Engl J Med. 1970; 282: 1183-1184Crossref PubMed Scopus (75) Google Scholar By the time the entire project closed, I had left, and many of the lead scientists had scattered. Charlie went on to other research projects, meanwhile being the genius who, with his colleagues, set up and maintained the Hypoxia Conferences. Over 3 years, Charlie and I tried to work together on a book, but eventually I dropped out, baffled by the distance between Chicago and Burlington, the very different phases of our lives, and above all by the disparate view we had of the book's aims and readership. Charlie was proved right by the book's subsequent success, but the split was painful for me, and, I believe, for Charlie. When Going High2Houston C.S. Going High, The Story of Man and Altitude. American Alpine Club, Burlington, VT1980Google Scholar came out, and I discovered he had dedicated it to me, I was deeply moved by his generosity. We sparred often. But he sparred with everyone with whom he worked closely, and perhaps I got on better with him than most. Many of us at some time or other swore blind they'd never work with Charlie again, because he could be so controlling, so unable to give over any imagined reins. But we still would have died for him. When, 10 years ago, Charlie was accused of having falsely claimed to have been the first to describe high altitude pulmonary edema, rather than Herb Hultgren of Stanford, I was delighted to be in a position to leap to his defense. I had been lent Herb Hultgren's diaries, and was able to prove that neither he nor Hultgren claimed to be first to describe the condition, nor the first to show high altitude pulmonary edema could not be due to an effect of altitude on the heart.7Rennie D. Herb Hultgren in Peru: What causes high altitude pulmonary edema?—Advances in experimental medicine and biology.in: Roach R.C. Wagner P.D. Hackett P.H. Hypoxia: Into the Next Millenium. Vol 474. Kluwer Academic/Plenum Publishers, New York1999: 1-22Google Scholar For years, as I went into medical editing and could no longer keep up the altitude work, we preserved a distance—perhaps a wary distance. But a year or so ago, Charlie and I had yet another entire day at his home in Burlington, where, 40 years ago, he had once played me a tape the members of his K2 expedition had recorded in a tent as they licked their wounds immediately after their descent. We went on into the late evening, he in his big chair, I picking my way between the stacks of books. Now, decades later, we hammered away at everything from the precise physical make-up of the Silk Road, Marco Polo's reliability, and Genghis Khan's attitude (right wing), all the way to nitric oxide and the microvasculature, through to the machinations of the pharmaceutical companies, and a single-payer healthcare system. Of course, we had quite a few conversations since, but each one more limited, and, most ominously, each one showing a more resigned, cheerier Charlie. Charlie and I had always liked to engage, and the slow disappearance of that engagement, and the taking on of a simpler, more grateful and less prickly personality was oddly painful. Now we must all get used to the fact that Charlie, this tremendous presence, this great man, is no longer around. There must be many others like myself who feel the void and wish they could tell Charlie how grateful we are. At least I was given the privilege of telling him, yet again, how annoying he could be, and how much I loved him. I know Charlie mostly as a mountain climber. From his leadership on the first ascent of Nanda Devi in 1936—the highest mountain ascended until Annapurna was climbed 14 years later—to his expeditions on K2 in 1938 and 1953, Charlie represented the best in climbing. The seminal moment of Charlie's climbing life came on K2 in 1953. He and his partners decided to put their entire effort into rescuing team member Art Gilkey, who was incapacitated by altitude sickness. They knew that the rescue was not only virtually impossible, but that it would also very likely cost them their lives. The men placed the contract of the belay—the “brotherhood of the rope,” as Charlie would so often refer to it—above concern for self. They failed to save Gilkey. But against great odds, they succeeded in bringing each other down alive. Reinhold Messner said, “I have great respect for the Italians who summitted K2 for the first time in 1954, but even greater respect for the Americans and the way they failed in 1953. They were decent. They were strong. And they failed in the most beautiful way you can imagine. This is the inspiration of a lifetime.” Their heroic dedication to one another, to staying together and bringing each other down safely, remains an example not only for all climbers, but for all people. Charlie's vision extended far beyond the mountains. His book Going Higher3Houston C.S. Harris D.E. Zeeman E.J. Going Higher: Oxygen, Man, and Mountains.5th ed. The Mountaineers, Seattle, WA2005Google Scholar was and is the bible of high altitude medicine for the lay reader. Charlie's research brought attention to understanding human adaptation to altitude, and is the underpinning of the acclimatization strategies and medical regimens employed today. Charlie was a tireless investigator. His high altitude research on Mt Logan from 1967 to 1979, the Operation Everest high altitude chamber studies in 1946 and 1985, and his founding of the International Hypoxia Symposia are just a few examples. He even tinkered in the family basement with the creation of an artificial heart. In 2006, I had the opportunity to spend an afternoon in the midst of the surviving members of the iconic expedition to K2. Our purpose was to sustain Charlie's work in high altitude medicine with the University of Colorado's Altitude Research Center and establishment of an endowed chair in Charlie's name. Mostly, however, we assembled to celebrate Charlie. As Streather, Bates, Craig, and Molenaar gathered around Charlie, I witnessed that what Charlie had observed was true. “We entered the mountains as strangers, but we left as brothers.” Many individuals make a difference in spite of themselves; others make a difference because of themselves. Charlie Houston made a difference to many people for both reasons. Charlie's near-century of a life has been recounted by many people more eloquent than I, so I will not repeat their laudatory recounting of a remarkable man, but I will offer a few reflections that have evolved over the 35 years that I knew him. As we all know, Charlie was an extremely bright and perceptive man who could be engaging and charming, as well as inscrutable and irascible. He had two uncanny talents that catalyzed his legend in the histories of both mountaineering and medicine. First, he had brilliant ideas. In fact, some of those ideas were genius. Second, he was able to attract and get commitments from teams of both climbers and scientists, all of whom had the “right stuff” to accomplish what he divined, sometimes in spite of him. Charlie made an immeasurable difference in my life. My early pursuit of a medical career and passion for climbing happened to overlap. Sometime in the mid-1970s, Charlie organized one of several mountain medicine seminars in Yosemite. For what more could I ask? It was there that I began to know and appreciate Charlie (I was too shy to introduce myself), as well as important others such as Noel Odell, Herb Hultgren, and Gil Roberts. I gained a sense that there was history and awe in the fellowship that mountains brought to people. My early academic career coincided with the inception of the Hypoxia Symposia, and the rest is history. I presented my first paper at “Hypoxia” with Charlie sitting right next to me, more pleased that I had finished perfectly at 10 minutes than with my science. I was thrilled to be there, and I owe much to his encouragement. Yet Charlie never kept things simple, and I began to see another side of this complex man. On the first day of Operation Everest II, as we 26 investigators descended on Natick, Charlie was ready to call it all off. In a very heated meeting, Jack Reeves and John Sutton on the spot resurrected what Charlie had been about to disassemble, and what Charlie then went on to lead brilliantly. Several years later, Charlie asked me to spend a sabbatical year as Research Director in Keystone at the Colorado Altitude Research Institute, an operation of his own creation. I was ecstatic to be offered this honor and opportunity. With my usual naive optimism, I threw myself into a dream job, only to find myself having differences with Charlie, who was 2000 miles away in Burlington. At a meeting in Chamonix that winter, I skied with John Sutton, who had worked for 20 years with Charlie. With some despair, I explained my conflicts with Charlie and asked John what he thought I was doing wrong. John said, “Mate, don't worry. He's always like that and has driven me nuts for years. But I love him anyway.” The subsequent years have caused me not to ponder my plights with Charlie, but to be grateful for the great differences he made to so many. Experiencing Charlie has made me appreciate how important it is for each of us to put aside our idiosyncrasies and realize how much influence we have on young, developing minds and spirits. Charlie challenged himself and was able to share much of his nurturing soul with many of us, inspiring a generation of young physicians, scientists, and mountaineers. I spoke with Charlie shortly before he died. He seemed glad to hear from me, and with his sharp memory asked how Bozeman was and how my wife, Kim, my older children, and our young child, Kira, were doing. So Charlie, I love you for all of the facets of your heart. You got me started on a professional and personal life linked to the thin air that has enchanted so many of my colleagues and friends, without whom my life would have been much less. In the spring of 1975, I was 27 years old and took care of trekkers and climbers who suffered altitude sickness on their way to Everest Base Camp, 2 day's journey above my earthen-floor yak hut at 14 000 feet in Pheriche, Nepal. I thought about Charlie Houston, who 25 years earlier had been in the first party allowed to explore the Khumbu region and south side of Mt Everest. I often wondered what it must have been like to be the first foreigner in the area. I knew that Charlie had mixed emotions about being the vanguard of the “intrusion of the West” into the Sherpa homeland. For decades, he chose not to return for fear of observing what “progress” had wrought in the land he wished to remember as undisturbed by modernity. The medical literature on altitude illness was scant, and I was more than curious. From what I could gather during visits to the Shanta Bhawan Hospital library in Kathmandu and with Dr John Dickinson, Charlie was the world's expert, so I wrote to him, detailing my experience with 66 cases of severe acute mountain sickness and HAPE. I received an enthusiastic and helpful reply, and we began a correspondence, and then a relationship akin to father and son, for the next 34 years. In 1977, I participated in the Mt Logan project. I was awed by the boldness of Charlie's vision. Flying subjects from sea level to the 17 500-ft summit plateau of Mt Logan was risky business. (Most scientists and support staff staged the ascent with a stay at King's Trench camp and then either climbed or flew to the plateau.) Weather was troublesome, flying was dangerous, and logistics were nearly unmanageable. HACE, airplane crashes, and stranded personnel kept Charlie busy and worried all summer. But the operation was successful. Despite the difficulties, Charlie showed that a lab devoted to high altitude medicine could be operated in an extreme environment and be productive. He helped set the stage for subsequent similar projects on Everest and Denali.8Houston C.S. High Altitude Physiology Study—Collected Papers. Queen City Press, Burlington, VT1980Google Scholar Charlie's leadership was inspiring; it was certainly one of his great talents. He chose his team very carefully; he was a master at appraising other's capabilities as well as potential problems, and the resulting group was like a family. No doubt, Charlie could sometimes be gruff, stubborn, and demanding, but the loyalty he inspired worked magic. Charlie finally returned to Nepal in 1981, and visited base camp during the American Medical Research Expedition to Everest. I received a note from him, sent from Base Camp, while I was at Camp III on my way to the summit. He advised me, “Don't be surprised if you find you don't have the reserves you thought you did” when up very high. I didn't quite know what to make of that. Was he worried about me, or challenging me? A few days later I endured a near-death experience with a fall on the Hillary Step on the way down from the top. Fortunately, his admonition was incorrect. In 1985, at the age of 72, Charlie headed-up a remarkable project—Operation Everest II. This was a sequel to the famous 1947 Operation Everest, in which he showed that humans could indeed survive a gradual ascent to the altitude of the summit of Mt Everest without supplemental oxygen. For Operation Everest II, he obtained funding, convinced the Army to provide the chamber, organized a talented and diverse crew of more than 20 scientists—featuring John Sutton, Jack Reeves, and Allen Cymerman—and oversaw every aspect of the operation. There were daily obstacles and problems, some of which he created himself. He and others emerged feeling like they had been through a war, but a successful one. This endeavor resulted in more than 35 scientific papers, as well as many book chapters, and was a true landmark in the field of high altitude physiology.9Houston C.S. Sutton J.R. Cymerman A. Reeves J.T. Operation Everest II: man at extreme altitude.J Appl Physiol. 1987; 63: 877-882PubMed Google Scholar, 10Houston C.S. Operation Everest I and II Studies of acclimatization to simulated high altitude.Respiration. 1997; 64: 398-406Crossref PubMed Scopus (13) Google Scholar For many of the participants, the interactions with
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