Comparison of Dynamic Mechanical Power Formula With Geometric Method in Pressure- and Volume-Controlled Ventilation: A Validation Study

This prospective observational study aims to validate the dynamic mechanical power (MPdyn) formula by comparing it with the gold-standard geometric method (MPgeo) in patients with acute respiratory distress syndrome (ARDS) who are mechanically ventilated in volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) modes. Mechanical power (MP) is a composite parameter that integrates multiple components of ventilator-induced lung injury (VILI) and has shown strong associations with mortality in ARDS. While several formulas exist for calculating MP in VCV and PCV modes, most require inspiratory resistance, which is not readily available at the bedside. The MPdyn formula, introduced by Asar et al., allows for bedside calculation without inspiratory resistance and has shown good agreement with established formulas such as MPrs and MPLM. However, it has never been validated against the geometric method, which calculates mechanical power based on the area of the pressure-volume (P-V) loop and is considered the most accurate standard. In this single-center study, 37 deeply sedated ARDS patients were ventilated with a Servo-U ventilator using both VCV and PCV modes. For each mode, two different I:E ratios (1:2 and 1:1) were applied, and 12 screenshots of full P-V loops were captured per patient, totaling 444 images. Geometric MP (MPgeo) was calculated using Python-based image processing with OpenCV and NumPy libraries. Dynamic mechanical power (MPdyn) was computed using ventilator-recorded values of minute volume (MVe), work of breathing per liter (WOBv), and PEEP. The primary outcome was the agreement between MPdyn and MPgeo values under different ventilator modes and I:E ratios. Secondary outcomes included regression correlation (R²) and Bland-Altman analysis of bias and limits of agreement. This study seeks to determine whether MPdyn is a valid and reliable surrogate for geometric mechanical power, particularly in clinical settings where bedside calculation is needed and inspiratory resistance cannot be easily measured.