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.
Mechanical ventilation - closed-loop mechanical ventilation - dual control modes -
automatic tube compensation - pressure support - adaptive support ventilation
