He's the person who can make the difference between life and death in the remote jungles of the Amazon or on the slopes of Everest. He was the only doctor on the mountain in 1996 when eight mountaineers, including New Zealander Rob Hall, died in the disaster that is told in the movie Everest. Dr Kamler treated surviving climbers at 21,000 feet including Beck Weathers who had been left for dead on the mountain but managed to get to a camp for help. Dr Kamler talks about survival in the extremes.