Huh. So that means, when the doctor decides to intervene based on what the continuous monitor comes up with, the interventions have negative expected value? Which means the doctors are making bad decisions about what interventions to make based on the data they have? I'll believe this is possible, but I want to ask to be sure.

I also would wonder about other explanations. You say "a nurse installs it, takes a reading, and removes it about once an hour"; presumably the nurse also glances at the patient and, if anything seems off, might ask the patient questions or take other appropriate actions. Could that be a significant effect? (In other words, to eliminate this potential difference, the better comparison for "continuous monitoring" would be for a nurse to come by once per hour and give the patient the same level of attention, perhaps going through the same motions that are involved in the monitor process.) Incidentally, as I read your comment, I expected it to conclude that the monitor itself or the process of repeatedly installing it and removing it was harmful (although that would point in the opposite direction).