Dynamic mechanical power at the bedside: A validation study in volume-controlled and pressure-controlled ventilation modes.

BACKGROUND

Mechanical power (MP) integrates the contributors to ventilator-induced lung injury and relates to mortality, yet bedside calculation remains challenging. The dynamic mechanical power equation (MPdyn) offers a simple approach but requires validation against the geometric gold standard (MPgeo).

OBJECTIVES

To validate MPdyn against MPgeo in volume-controlled (VCV) and pressure-controlled ventilation (PCV) across I:E ratios of 1:2 and 1:1.

METHODS

Prospective observational study in a tertiary ICU. Adults with ARDS (n = 36) underwent standardized measurements in VCV and PCV at I:E 1:2 and 1:1. For each setting, three complete pressure-volume (P-V) loop screenshots were captured. MPgeo (J/min) was derived using a Python-based image-processing tool (OpenCV/NumPy/PIL) employing grayscale conversion, thresholding, morphological closing, flood-fill segmentation, and area-ratio computation. MPdyn was computed as MV × [WOBv + (PEEP × 0.098)]. Agreement was assessed with univariable linear regression and Bland-Altman analyses.

RESULTS

MPdyn correlated strongly with MPgeo in all modes and I:E ratios (R2 ≥ 0.97). Biases (MPdyn - MPgeo) were 0.15 J/min (0.8 %) for VCV 1:2, 0.32 J/min (2.1 %) for VCV 1:1, 0.28 J/min (1.9 %) for PCV 1:2, and 0.52 J/min (3.4 %) for PCV 1:1. The standard deviation of the bias remained <0.5 J/min across analyses.

CONCLUSIONS

MPdyn demonstrates high agreement with MPgeo in both VCV and PCV modes, supporting its use as a simple, reliable, and bedside-applicable tool for calculating mechanical power in ARDS patients.