Today we are excited to welcome Fran Wilde to The Speculative Herald. She is here to tell us about all the fascinating (and potentially bad) things that can happen with altitude changes. Her latest book, Cloudbound, releases today, and unfortunate for her characters, they are faced with the altitude change from heading down to the clouds in this book. Into the Depths By Fran Wilde   While Updraft (Tor 2015) is a pretty level novel — flying-wise — Cloudbound (Tor 2016) does exactly what it says on the tin… by heading into the clouds. In this case, vertical worldbuilding became an important part of the characters’ plight, and very quickly, because: science!   How does a high-altitude culture experience a plunge into the depths? My research suggested a couple of potential reactions, and follow-up discussions with several physicians helped support this.   One reaction was a variation on over-oxygenation, hyperoxia, or oxygen intoxication, where the brain gets a rush of unexpected 02 – much more than it’s used to, and too quickly. Side effects can include: disorientation, breathing problems, and vision changes such as myopia. Other observed effects of more oxygen than normal can include elation, a natural high, and/or…