EVALUATION OF SIMPLIFIED MECHANICAL POWER AND DISSIPATED ENERGY CALCULATIONS IN PHYSICAL RESPIRATORY MODELS WITH TISSUE AND AIRWAY RESISTANCE
DOI:
https://doi.org/10.14311/CTJ.2025.1.03Abstract
Mechanical power (MP) calculation is a promising predictor of ventilator-induced lung injury, yet simplified bedside equations rely on airway opening pressure, potentially missing key information about tissue-level stresses, and involve unclear contributions of PEEP and airway flow resistance. This study compared simplified MP equations in physical models of the respiratory system with either tissue viscoelastic (Rt) or airway flow (Raw) resistance, evaluating how pressure measurement location affects delivered and dissipated energy estimates. Six physical models (No-resistance, Tissue resistance, Flow resistance, and three combinations of Rt with different Raw) were ventilated with the same volume-controlled parameters. Pressure was measured at the airway opening and at an artificial lung level with vital signs monitor, sampled at 100 Hz. Mechanical energy was calculated using both simplified equations and a geometric method based on the pressure-volume loops. Simplified MP equations produced similar mechanical energy estimates for Tissue resistance model and Flow resistance model (Raw = 5 cmH2O·s·L-1) when pressure was measured at the airway opening. However, measurements at the artificial lung level revealed marked differences in delivered and dissipated energy. Simplified MP equations may misrepresent tissue-level energy, particularly when Raw dominates. Future studies should focus on refining energy estimation methods, considering driving transpulmonary pressures, inspiratory hold duration, and tissue versus flow resistance.
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Copyright (c) 2025 Šimon Walzel, Karel Roubik
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