The Effects of Hypercapnea on Outcomes

There's observational study and I'll focus firstly on the one that Glenn mentioned that the group did. So they had three groups hypocapnea, normal capnea and mild hypercapnea. The result that Glenn focused on was this one down here showing that among survivors those with hypercapnea had better outcomes. But both are a statistical point of view but also a conceptual point of view that's in my mind the wrong group because you're conditioning on patients being survivors.