Effect of Ultraprotective Ventilation on the Lung Inflammatory Response in Patients With Acute Pulmonary Edema Treated With Venoarterial Extracorporeal Oxygenation
Effect of Ultraprotective Ventilation on the Lung Inflammatory Response in Patients With Acute Pulmonary Edema Treated With Venoarterial Extracorporeal Oxygenation
Mechanical ventilation, in spite of being a life-saving technique, can also induce lung injury (VILI) mediated by an inflammatory response, thus having a profound impact in the course of critically ill patients. Ventilatory strategies aimed to minimize this VILI have reduced mortality rates. Patients suffering cardiogenic pulmonary edema may need venoarterial extracorporeal oxygenation, at the same time they are being mechanically ventilated. The objective of this study is to analyze changes induced by the use of utraprotective ventilatory strategies in the inflammatory lung response of these patients and their impact on outcomes.
Mechanical ventilation is the cornerstone of the critically-ill patients support, providing better gas exchange conditions while respiratory muscles rest. Providing this life-support technique may be harmful on the lung tissue, last decades research efforts were focused on minimizing the ventilator-induced lung injury (VILI). Knowledge regarding the mechanisms of this injury has led to changes in the clinical practice, consisting on the application of positive end-expiratory pressure (PEEP) and the use of low tidal volumes, giving rise to the strategy known as "protective ventilation". Moreover, the use of extracorporeal membrane oxygenation (ECMO) techniques contributes to maintaining an adequate gas exchange until lung damage resolution. A tidal volume in the range of 6 ml/Kg of ideal body weight, with a reasonable level of PEEP is the standard of care for patients with the ARDS. However, optimal levels of tidal volume and PEEP have not been completely established. On the other side, decreasing tidal volume below 6 ml/Kg faces its own problems. The role of the so-called "ultraprotective" approaches, in which extracorporeal support is required to reduce tidal volumes up to 3 ml/kg or less, although feasible, is currently under research. During venoarterial ECMO, blood is removed from the vessels and pumped through a circuit where is oxygenated and CO2 is removed; finally, the blood is returned to the arterial circulation. The development of new circuits and devices made this therapy become safer and more useful, improving outcomes so that its application has been widespread to many centers all over the world. One of the ECMO advantages is carbon dioxide removal, which allows reducing tidal volume below 6 ml/kg. Ultraprotective strategies with 3 ml/kg have demonstrated to be feasible, but the additional benefit of this strategy is to be demonstrated. Therefore, in this study, patients suffering cardiogenic pulmonary edema requiring ECMO and mechanical ventilation are submitted to an ultraprotective ventilator strategy. Lung inflammatory response is measured before and after the intervention, in order to evaluate its impact in this subset of patients.
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