Techniques for automated feedback control of mechanical ventilation.

Mechanical ventilators have become more sophisticated with the advent of microprocessor control. Advances in monitoring have also improved our ability to harmonize patient-ventilator interaction. The next obvious step in this technologic progression is to turn over some decision making to the ventilator. In the jargon of today, we are "closing the loop.'' Ventilators have used closed-loop control for simple tasks for the last decade. Newer closed-loop processes include modes that increase or decrease support based on a single-monitored variable. An example is the automated control of pressure support to maintain a deired tidal volume. More sophisticated closed-loop techniques, such as proportional assist ventilation and adaptive support ventilation, not only monitor multiple input variables but also use closed-loop control of several variables. This article reviews the closed-loop ventilation modes currently available to clinicians.