Control theories in critical illness and critical care

Summary form only given, as follows. Critical care is a triumph of the last half-century. Today, devices (such as mechanical ventilators and kidney dialysis machines) and drugs (such as synthetic antimicrobials) can sustain life through illnesses that were lethal just decades ago. Yet despite successful stabilization and reversal of the process that triggered their critical illness, many patients still fail to recover and regain physiologic independence from their multiple supports. In this lecture, we will explore the way in which therapeutic failures and a specific therapeutic success -- tight control of blood sugar-- have been interpreted by biomedical scientists in the context of three leading theories of physiologic controI: homeostasis, network theory and allostasis. The ambiguities and conflicts will illuminate opportunities for decision and control theorists and engineers in the emerging field of systems biology and its application to critical clinical medicine.