view few others have seen. >> ladies and gentlemen, not only is my phone not dead, but that is adrian ballengerr: while both climbers made it to the top, only adrian did it without supplemental oxygen. high altitude sickness forced cory to turn back. >> the summit is just through the clouds. up above us. >> reporter: on his way down, cory met a group of climbers who supplied him with supplemental oxygen. the oxygen gave cory the energy to reach the summit first, from there he cheered on his friend as he made the final push. >> 8,995 feet right now. i've never seen anybody work so hard for anything in my life. my brother, we leave the summit behind. >> reporter: in 37 days, adrian logged nearly 140 miles while acclimating to the high altitude. he consumed 22,000 calories on a diet that allowed him to consume air at roughly 8% oxygen. safely back at advanced base camp, adrian reflected on the experience. >> i feel super emotional. i cried so hard yesterday on the summit. in the last ten meters to the summit. i would never want to climb everest without oxygen again, and i am so proud and happy. >>