Global mechanical power does not determine regional energy distribution in heterogeneous lungs

Introduction: Mechanical power (MP) integrates key determinants of ventilatory load and has been associated with ventilator-induced lung injury (VILI). However, because MP is typically derived from airway-opening measurements, it represents a global metric that may not reflect how energy is distributed within mechanically heterogeneous lungs. We aimed to investigate whether global MP uniquely determines regional energy partitioning under heterogeneous conditions. Methods: We conducted a deterministic in-silico study using a parallel two-compartment resistance-compliance model under volume-controlled ventilation. Systematic parameter sweeps over compliance and resistance ratios were performed, and a partition index (PI) was introduced to quantify preferential inspiratory energy delivery to the more compliant compartment. Results: Across the heterogeneity space, PI varied widely (0.352-0.800), while global MP ranged from 1.46 to 5.85 J/min. Importantly, iso-lines of MP overlapped regions with markedly different PI values, demonstrating that similar global MP can correspond to substantially different energy distributions. Among parameter sets matched within ±5% MP, the maximal difference in PI reached 0.39, indicating pronounced variability in preferential energetic loading despite comparable global energy delivery. Discussion: These findings demonstrate a structural non-identifiability: global mechanical power does not uniquely determine how inspiratory energy is partitioned in heterogeneous lungs. The proposed PI provides a compact descriptor of impedance-driven energetic routing and highlights conditions in which acceptable global MP may mask disproportionate regional energy exposure. Incorporating heterogeneity-aware information may therefore be necessary to interpret MP and guide safer ventilation strategies.