Mechanical Power

Raw thresholds (ARDS). < 12 J/min lower risk; 12–17 J/min caution; ≥ 17 J/min associated with increased mortality (Serpa Neto et al., Intensive Care Med 2018).

Normalized thresholds. < 0.17 J/min/kg lower risk; 0.17–0.24 caution; ≥ 0.24 elevated. These are scaled from the raw cutoffs assuming a reference 70 kg PBW. The normalized value tells you whether a given energy dose is large relative to the patient's size — 17 J/min on a 50 kg patient delivers far more energy per unit of aerated lung than the same 17 J/min on a 90 kg patient. Use the normalized version when the patient is at body-size extremes (very short or very tall), or when comparing energy doses across different patients. Use the raw value for trending within a single patient over time.

Driving pressure. Target < 15 cmH₂O (Amato et al., NEJM 2015) — an independent signal worth tracking separately from MP.

Caveats. Power scales with the square of V_T and linearly with RR — V_T reductions have outsized effects. Thresholds derive from ARDS cohorts and may not generalize to non-ARDS, obese, or pediatric patients. PCV formula assumes near-complete equilibration of lung pressure during inspiration; short T_i or high resistance reduces accuracy. Normalized cutoffs are less mature in the literature than the absolute J/min thresholds.