Thanks for the comment. Yes, at about 5750 metres, your oxygen intake is half what it is at sea level (imagine climbing the stairs at sea level with just one lung of air), fortunately I had climbed Chacaltaya (5421 m) and Huayna Potosi (6088 m) beforehand so was fairly acclimatised. You also have high UV to contend with, twice as much at this altitude compared to sea level. Great views and worth the trek.