The absolute number of molecules of drug required to elicit a response
High clouds include cirrus, cirrocumulus, and cirrostratus clouds. These clouds are made up of either ice or water droplets, but they are usually made up of ice crystals. Water clouds tend to have sharp edges, and ice clouds are more wispy.
Not sure if this helps, but check this link.
https://www.windows2universe.org/earth/Atmosphere/clouds/cloud_heights.html
oxygen flow is low and his lungs do not have a lot of capacity
