Conventional protective ventilation with elevated mechanical power: Migration to safer values with small ventilatory adjustments

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Abstract
Background Mechanical power (MP) integrates multiple ventilatory variables into a single measure of the energy delivered to the respiratory system and has been associated with ventilator-induced lung injury and adverse outcomes. However, it remains unclear whether ventilatory observations meeting conventional protective criteria also exhibit low MP and whether small ventilatory adjustments can meaningfully reduce MP in severely burned patients undergoing pressure-controlled ventilation (PCV). Methods This interventional repeated-measures study with randomized sequence of ventilatory adjustment protocols included adult burn patients receiving PCV in an intensive care unit. A total of 123 paired ventilatory observations were screened. Three reductive ventilatory strategies were assessed: reduction of inspiratory pressure variation by 2 cmH2O (ΔPinsp), reduction of respiratory rate by 2 breaths/min (RR), and combined reductions of 1 cmH2O and 1 breath/min (RR–ΔPinsp). Thirty-nine ventilatory observations meeting predefined protective tidal-volume and pressure criteria constituted the analytical sample. MP was calculated using the simplified Becher equation. Clinical, arterial blood gases, and ventilatory effects were evaluated at baseline and one hour after the interventions, as well as migration between MP categories (<1 8 and ≥ 18 J/min). Results Oxygenation remained stable, with no significant changes in PaO2, SpO2, or PaO2/FiO2. PaCO2 increased modestly and arterial pH decreased slightly, but both remained within physiological limits. No desaturation, clinically relevant acidosis, hemodynamic instability, or ventilatory asynchrony was observed. Among the 39 ventilatory observations, 17 (43.6%) had MP ≥ 18 J/min at baseline. MP decreased significantly from 17.39 to 15.02 J/min overall (P < 0.001). The greatest reduction was observed in the ΔPinsp group (3.00 J/min), followed by RR–ΔPinsp (2.34 J/min) and RR (1.78 J/min), with significant differences among strategies. Ventilatory observations with MP <18 J/min increased from 22/39 (56.4%) to 34/39 (87.2%), whereas those with MP ≥ 18 J/min decreased from 17/39 (43.6%) to 5/39 (12.8%) (P < 0.001). Conclusions A substantial proportion of ventilatory observations meeting conventional protective criteria still exhibited elevated MP. Small ventilatory adjustments during protective PCV were associated with significant reductions in calculated MP and migration toward values below 18 J/min without compromising short-term arterial blood gases or clinical stability. Reduction in inspiratory pressure variation produced the greatest effect on MP. Keywords: Mechanical Power, Burns; Mechanical Ventilation; Pressure-Controlled Ventilation; Ventilator-Induced Lung Injury.

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