Mechanical Power in Pediatric Mechanical Ventilation

Overview

Mechanical power is the amount of energy transferred to the respiratory system of patients during each breath period. After overcoming the resistances required for respiration, the remaining energy may end up by damaging the lung parenchyma. Promising studies are showing that this amount of energy, which can be calculated mathematically, can be used as a single indicator instead of the limits used for barotrauma, volu-trauma, or atelecto-trauma in adult patients. However, the MP limit that should not be exceeded in pediatric patients is not yet clear. In this study, we present our MP calculations in pediatric anesthesia

Mechanical ventilation is applied to millions of healthy and sick lungs every year in perioperative conditions and intensive care units. Meanwhile, the energy applied to the lungs by the ventilator during mechanical ventilation is usually used to overcome resistance in the chest wall and airways. Leftover energy is consumed by temperature, inflammation, and potentially lung tissue damage (1). The risk of ventilation-related damage increases in lungs with impaired homogeneity and ventilation-perfusion imbalance (1). As demonstrated by experimental and clinical studies, mechanical ventilation-induced lung injury (VILI) is associated with tidal volume, peak pressure, respiratory rate, and airflow. The physical force applied during ventilation TV increases exponentially with driving pressures (ΔPaw), flow (exponent = 2), and respiration rate (RR) (exponent = 1.4), and linearly with positive end-expiratory pressure (PEEP) (2). When the effects of these parameters are formulated, the energy applied to the lungs is revealed. This energy has been formulated as Joule/minute and has now taken its place as mechanical power (MP) in the literature. (2). A benefit of the MP calculation is that it is a single, easily calculated indicator parameter that can be used for the risks of barotrauma, volutrauma, or atelectotrauma associated with VILI. As shown in different publications, high MP values were associated with negative outcomes such as increased 30-day mortality in intensive care patients, increased length of stay in hospital and intensive care unit, and decreased number of ventilator-free days(3)(4). Cressoni et al. showed in their experimental study that MP values above 12 J/min in healthy pigs are associated with MV-related complications and this value can also be used as an alarm limit in humans(5). In addition, Costa et al found that 0.32 ± 0.14 J / min/ kg indexed MP(MP/Kg) was associated with increased mortality in ARDS patients(6). Some recent studies also support the conclusion that Mp calculation is beneficial(7)(8). For this reason, Gattinoni et al. suggests that MP limits and formula should be added to the mechanical ventilator software(2). However, studies on MP have often focused on ARDS and have been performed on intensive care patients or experimental animal models(9). Although MP is a promising safety limit with its easy computability, there are still questions about the formula and its usefulness. The success of the MP formula in perioperative situations and especially in pediatric patients has not been adequately tested. As far as we know, our study is one of the first publications to question the MP threshold in healthy pediatric cases. In this study, our primary aim is to calculate the MP applied in pediatric cases who will undergo inguinal hernia surgery under general anesthesia. Our other aims are the calculation of the mechanical power applied per kilogram and the other transferred energies, their comparison with the literature, and questioning the possible contribution of a mechanical power formula to safe mechanical ventilation in pediatric cases.