Bedside calculation of mechanical power during volume- and pressure-controlled mechanical ventilation

Abstract

Background: Mechanical power (MP) is the energy delivered to the respiratory system over time during mechanical ventilation. Our aim was to compare the currently available methods to calculate MP during volumeand pressure-controlled ventilation, comparing different equations with the geometric reference method, to understand whether the easier to use surrogate formulas were suitable for the everyday clinical practice. This would warrant a more widespread use of mechanical power to promote lung protection. Methods: Forty respiratory failure patients, sedated and paralyzed for clinical reasons, were ventilated in volumecontrolled ventilation, at two inspiratory flows (30 and 60 L/min), and pressure-controlled ventilation with a similar tidal volume. Mechanical power was computed both with the geometric method, as the area between the inspiratory limb of the airway pressure and the volume, and with two algebraic methods, a comprehensive and a surrogate formula. Results: The bias between the MP computed by the geometric method and by the comprehensive algebraic method during volume-controlled ventilation was respectively 0.053 (0.77, − 0.81) J/min and − 0.4 (0.70, − 1.50) J/ min at low and high flows (r 2 = 0.96 and 0.97, p < 0.01). The MP measured and computed by the two methods were highly correlated (r 2 = 0.95 and 0.94, p < 0.01) with a bias of − 0.0074 (0.91, − 0.93) and − 1.0 (0.45, − 2.52) J/ min at high-low flows. During pressure-controlled ventilation, the bias between the MP measured and the one calculated with the comprehensive and simplified methods was correlated (r 2 = 0.81, 0.94, p < 0.01) with mean differences of − 0.001 (2.05, − 2.05) and − 0.81 (2.11, − 0.48) J/min. Conclusions: Both for volume-controlled and pressure-controlled ventilation, the surrogate formulas approximate the reference method well enough to warrant their use in the everyday clinical practice. Given that these formulas require nothing more than the variables already displayed by the intensive care ventilator, a more widespread use of mechanical power should be encouraged to promote lung protection against ventilator-induced lung injury.

Individualized flow-controlled ventilation compared to best clinical practice pressure-controlled ventilation: a prospective randomized porcine study

“…MV was significantly lower in the FCV group (6.0 vs 12.7, MD − 6.8 (− 8.2 to − 5.4) l/min; p < 0.001, Fig. 2 ) than in the PCV group, as well as calculated mechanical power (5.8 vs 22.0, MD − 16.2 (− 21.1 to − 11.4) J/min; p < 0.001) [ 11 ]. FCV animals showed significantly improved oxygenation (paO 2 119.8 vs 96.6, MD 23.2 (9.0 to 37.5) Torr; 15.97 vs 12.87, MD 3.10 (1.19 to 5.00) kPa; p = 0.010, Fig.…”

Quantification of Volatile Aldehydes Deriving from In Vitro Lipid Peroxidation in the Breath of Ventilated Patients

“…Mechanical power was calculated with the following formula: mechanical power (J·min −1 ) = 0.098 × respiratory rate (breaths·min −1 ) × tidal volume (mL) × (positive end-expiratory pressure (cmH 2 O) + driving pressure (cmH 2 O)) [ 38 ].…”

On the Transition from Control Modes to Spontaneous Modes during ECMO

“…The elastic component of mechanical power has been previously suggested to be a reliable and accurate proxy for the energy applied to the lung during mechanical ventilation that is valid among both paralyzed and spontaneously breathing patients [ 12 ]. This is in contrast to the full mechanical power value, which is not valid in spontaneously breathing patients [ 13 ]. The elastic component of mechanical power was calculated as: ½ × lung elastance × ( V T[in liters] 2 ) × respiratory rate …”