Estudio comparativo de dos métodos de programación de la presión positiva al final de la espiración en pacientes con síndrome de distrés respiratorio agudo.

Abstract

BACKGROUND: Nowadays the treatment of the ARDS is based on the respiratory support while treating the underlying cause. However the respiratory support could also be a cause of ARDS itself. Among the respiratory support, only the mechanical ventilation with lower tidal volume (6 ml/kg body weight) has reduced the mortality due to ARDS, as compared to traditional tidal volume (12 ml/kg body weight) described in the ARDS Network trial44. The use of PEEP on mechanical ventilation allows not only to keep open the alveolus by improving the oxygenation, but also to avoid ventilation-induced lung injury. Even though there are different methods to determine its level, none of them has demostrated a reduction on mortality. We think the the PEEP level should be individualized for each patient according to their lung mechanics on each moment, which should be valued depending on the respiratory pressure volume curve. OBJECTIVE: The main objective of this study is to demostrate that the PEEP level in patients with ARDS should be determined based on the pressure-volume curve of the respiratory system. Thos method not only reduces the mortality at day 28 when compared to an empirical determination of PEEP level based on the fraction of inspired oxygen requirements, but also identifies the factors influencing mortality. The secondary objectives are to measure it´s effect on oxygenation, hemodynamics, length of mechanical ventilation, length of stay in the ICU and hospital, inflammatory mediators, level of sedation and use of sedatives and neuromuscular blockers, and organ dysfunction. DESIGN: Randomized, controlled clinical trial. SETTING: Intensive Care Unit of the “Príncipe de Asturias” Universitary´s Hospital. PATIENTS AND INTERVENTIONS: 70 patients with ARDS admitted into ICU and on mechanical ventilation, with lower tidal volumes (6 ml/kg body weigth) and limitation on airway pressure at 35 cm of water. They were divided at random in two PEEP level groups, one based on the pressure-volume curve of each patient (“PEEP medida” group) and the other based on the method used on the ARDS Network44 clinical trial (“PEEP tabla” group). MEASUREMENTS AND MAIN RESULTS: Mortality at day 28 was 38,9% on “PEEP tabla” group vs 20,6% on “PEEP medida” group (p = 0,12). At day 28, the patients included on “PEEP medida” group had more organ dysfunction free-days (20,5 days (0 - 26) vs 6 days (0 – 23,75), p = 0,02); as though a tendency to a better oxygenation, lower airway pressures and a better lung compliance. The global mortality at day 28 was 30% and hospital mortality was 42,85%. The multivariate analysis of mortality at day 28 showed that the variables associated independently with a increase in mortality were the following: female sex, “PEEP tabla” group, SOFA364> 9, APACHE II363 > 19 and a pH < 7,34. CONCLUSIONS: A mechanical ventilation on patients with ARDS based on low tidal volume, limitation on airway pressure at 35 cm of water and a level of PEEP level set above the lower inflection point of the pressure volume curve of the respiratory system is associated with more organ dysfunction free-days at day 28, and a tendency to a lower mortality at day 28.