Mechanical Ventilation: Understanding Key Terms and Concepts

​The material in this list of mechanical ventilation terms was provided to ECRI Institute by Robert Chatburn. It is derived from Chatburn's standardized vocabulary for mechanical ventilation (V 1.7.16) and definitions of terms used in what we refer to elsewhere as the Chatburn Taxonomy. (For more information about the Chatburn Taxonomy, see Mechanical Ventilation: Manufacturer-Specific Terminology for Ventilation Modes and Features. ) This material is ©2015 by Mandu Press, Ltd., and is used with permission.

Adaptive targeting scheme. A control system that allows the ventilator to automatically set some (or conceivably all) of the targets between breaths to achieve other preset targets. One common example is adaptive pressure targeting (e.g., Pressure Regulated Volume Control mode on the Maquet Servo-i ventilator), wherein a static inspiratory pressure is targeted within a breath (i.e., pressure-controlled inspiration) but this target is automatically adjusted by the ventilator between breaths to achieve an operator set tidal volume target (also known as volume-targeted pressure control).

Airway Pressure Release Ventilation (APRV). A form of pressure-control intermittent mandatory ventilation that is designed to allow unrestricted spontaneous breathing throughout the breath cycle. APRV is applied using inspiratory:expiratory (I:E) ratios much greater than 1:1 and usually relying on short expiratory times and gas trapping to maintain end-expiratory lung volume rather than a preset PEEP. This is in contrast to Bilevel Positive Airway Pressure (BIPAP), which is also pressure-control intermittent mandatory ventilation but with I:E ratios closer to 1:1, expiratory times that do not create significant gas trapping, and preset PEEP levels above zero.

Asynchrony (dyssynchrony). Regarding the timing of a breath, asynchrony means triggering or cycling of an assisted breath that either leads or lags the patient's inspiratory effort. Regarding the size of a breath, asynchrony means the inspiratory flow or tidal volume does not match the patient's demand. Also, some ventilators allow a patient to inhale freely during a pressure-controlled mandatory breath but not to exhale, thus inducing asynchrony. Asynchrony may lead to increased...