Computed Tomography (CT) images may provide a better indicator of lung edema. New insights were provided by the CT-scan over the last two decades, demonstrating that ARDS does not homogeneously affect the lung parenchyma. The lung injury severity is widely distributed in ARDS population (5 to 70% of the total lung weight) and it is strictly associated with the severity of injury: greater is the amount of gasless tissue at 5 cmH2O PEEP, greater is the amount of gasless tissue regaining aeration at 45 cmH2O airway pressure. The lung CT findings may provide a firm rationale for tailoring tidal volume (VT) and PEEP during mechanical ventilation. VT should be set according to the lung open to ventilation rather than to the body weight. PEEP should be evaluated on the basis of lung recruitability: higher PEEP should be applied in patients with higher recruitability, lower PEEP in patients with lower recruitability. Concepts as Ventilator Induced Lung Injury (VILI), lung stress and strain as triggers of VILI, transpulmonary pressure as the real distending force of the lung renewed the interest on esophageal pressure measurement as surrogate of pleural pressure. This measure, however, is quite controversial in the critically ill patients. The elastance and the position of the balloon, the tone of the esophageal wall, the weight of the heart and of the lung and the position of the patients may influence the relationship between esophageal and pleural pressure. It has been shown that pleural pressure varies along the vertical axis of the lung. In an experimental study on dogs pleural pressure has been measured by surface wafers and it was lower than esophageal pressure in the upper part on the lung, nearly equal in the central part and higher in the lower part. Recently some authors proposed and arbitrary correction of the absolute value of the esophageal pressure by 5 cmH2O to obtain positive transpulmonary pressure values. However, pleural pressure variations are similar to esophageal pressure variations at every lung level so we can say that it will be better to evaluate pressure variations rather than absolute values
Ventilatory monitoring in ARDS : role of CT scan, impedance monitoring and intra-esophagic pressure / L. Gattinoni. ((Intervento presentato al 7. convegno Intensive Care University Course tenutosi a Santiago nel 2012.
Ventilatory monitoring in ARDS : role of CT scan, impedance monitoring and intra-esophagic pressure
L. GattinoniPrimo
2012
Abstract
Computed Tomography (CT) images may provide a better indicator of lung edema. New insights were provided by the CT-scan over the last two decades, demonstrating that ARDS does not homogeneously affect the lung parenchyma. The lung injury severity is widely distributed in ARDS population (5 to 70% of the total lung weight) and it is strictly associated with the severity of injury: greater is the amount of gasless tissue at 5 cmH2O PEEP, greater is the amount of gasless tissue regaining aeration at 45 cmH2O airway pressure. The lung CT findings may provide a firm rationale for tailoring tidal volume (VT) and PEEP during mechanical ventilation. VT should be set according to the lung open to ventilation rather than to the body weight. PEEP should be evaluated on the basis of lung recruitability: higher PEEP should be applied in patients with higher recruitability, lower PEEP in patients with lower recruitability. Concepts as Ventilator Induced Lung Injury (VILI), lung stress and strain as triggers of VILI, transpulmonary pressure as the real distending force of the lung renewed the interest on esophageal pressure measurement as surrogate of pleural pressure. This measure, however, is quite controversial in the critically ill patients. The elastance and the position of the balloon, the tone of the esophageal wall, the weight of the heart and of the lung and the position of the patients may influence the relationship between esophageal and pleural pressure. It has been shown that pleural pressure varies along the vertical axis of the lung. In an experimental study on dogs pleural pressure has been measured by surface wafers and it was lower than esophageal pressure in the upper part on the lung, nearly equal in the central part and higher in the lower part. Recently some authors proposed and arbitrary correction of the absolute value of the esophageal pressure by 5 cmH2O to obtain positive transpulmonary pressure values. However, pleural pressure variations are similar to esophageal pressure variations at every lung level so we can say that it will be better to evaluate pressure variations rather than absolute valuesPubblicazioni consigliate
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