A 40 year old man started his trekking 4 days ago from Lukla (2800m) in the Everest region of Nepal. He reached Tengboche (3860 m) on third day where he was short of breath with moderate exertion and was easily fatigued. He ascended further ignoring his symptoms and reached Dingboche (4410m) on fourth day. https://seriouswatchers.shop/product-category/watches/