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- mechanical power
- adaptive support ventilation
- adaptive pressure ventilation
- pressure control-mechanical power
- volume control-mechanical power
Introduction
Mechanical power (MP) estimates the energy delivered to the lungs during mechanical ventilation and integrates multiple ventilator parameters including tidal volume (VT), pressure, and breathing frequency.1 Higher levels of MP have been associated with ventilator-induced lung injury (VILI),2 postoperative respiratory complications,3 and higher mortality rates in the ICU.4 Studies have suggested that MP is a superior predictor of VILI risk compared to approaches targeting the individual components.5 It has also been suggested that high MP levels could generate VILI independently of its single parameters.6
The standard calculation of MP is derived from continuous pressure-volume waveforms as the integral of pressure and volume change (waveform-MP) including 3 main areas: the elastic static, elastic dynamic, and resistive components of the energy applied to lungs during mechanical ventilation. The elastic static represents the energy delivered when PEEP is applied, whereas elastic dynamic represents the energy delivered with each tidal breath required to distend the elastic structures of the lung. The resistive component of MP is the energy component required to generate flow through the airways.
Multiple alternative formulas have been suggested for MP calculation.7,8 A simplified formula has been utilized to estimate MP during pressure controlled ventilation (PC-MP):
Where ΔPinsp is the “applied or set pressure” during inspiration by the ventilator.
Additionally, an alternate formula was derived for volume-controlled modes (VC-MP):
Where Ppeak represents the peak pressure and the ΔP represents the static driving pressure.
The optimal simplified formula to use in patients receiving pressure-regulated, volume-targeted modes such as adaptive pressure ventilation (APV), a mode similar to pressure-regulated volume control (PRVC) and partially automated hybrid modes such as adaptive support ventilation (ASV), remain unclear. As MP is becoming extensively used in research and as a bedside tool integrated into ventilators, it …
Correspondence: Elias N Baedorf Kassis MD. E-mail: enbaedor{at}bidmc.harvard.edu
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