sentences:  Ed Hommer's prosthetist, Tom Halvorson, oversaw Nawang's fittings and coached him on how to hike and climb at extreme altitudes safely.This enabled Nawang to successfully trek across the high Himalayan Khumbu region of Nepal for days to reach Everest basecamp, climb steep snow and ice slopes during the many weeks of acclimatization ascents partially up the mountain and back, then make the final continuous push to the summit and back during a perfect "weather window" on the mountain.Each day he had to carry—in addition to his food, water, extra clothes, and other supplies—a spare prosthetic leg in case of problems.