Mechanical Power: Using Ideal Body Weight to Identify Injurious Mechanical Ventilation Thresholds

Identifying the mechanisms of ventilator/ventilation-induced lung injury requires an understanding of the pulmonary physiology involved in the mechanical properties of the lung along with the involvement of the inflammatory cascade. Accurately measuring parameters that represent physiologic lung stress and lung strain at the bedside can be clinically challenging. Although surrogates for lung stress and strain have been proposed, such as plateau pressure and driving pressure, these values only represent a static variable in the ventilator breath. It has been proposed that a single variable could be used as a unifying parameter to identify a threshold for the safe application of mechanical ventilation. The concept of "mechanical power" applies an energy load transfer designation to the ventilator settings and output of tidal volume, airway pressures, and flow. However, there is a potential disconnect between the use of "absolute" mechanical power and the variability of body weight throughout a mixed medical population. Using ideal body weight as an influential factor to express mechanical power can potentially allow for a more accurate depiction of energy applied to the lungs and a potentially reliable injurious mechanical ventilation threshold indicator.