The energy load is the integral of PdV along the PV curve. If an "excess" of energy is loaded to the system we may expect that the unrecovered energy is sufficient to break molecular bonds of the polymers of the extracellular matrix, to detach endothelial and epithelial cells from the basement membrane, and to fracture the capillary walls. Of note the alteration of the extracellular matrix with the appearance of polymers with lower molecular weight, associated with capillary micro-fractures, may activate the inflammatory reaction and micro-hemorrhage leading to extracellular edema typical of VILI. The tidal change in lung volume is associated with a cyclic energy load to the lung parenchyma. In contrast, PEEP, once applied, does not cause any cyclic energy load as the volume due to PEEP application is constant (dV=0). Therefore, considering both the lung volume distortion and the energy load to the lung parenchyma, we aimed to answer the following question: is there any threshold of volume distortion/energy load producing VILI? Is the application of PEEP protective per se or is it just an indirect effect, due to the concomitant reduction in tidal volume when PEEP is applied? The threshold for VILI development is the lower limit of inspiratory capacity. Below this threshold VILI does not occur. Within its borders severe/lethal VILI occurs depending on the dynamic component. Above inspiratory capacity stress at rupture may occur. PEEP is protective only if associated to a decreased tidal volume, otherwise it is indifferent/harmful.
|Titolo:||The energy load|
GATTINONI, LUCIANO (Primo)
|Data di pubblicazione:||18-mar-2015|
|Settore Scientifico Disciplinare:||Settore MED/41 - Anestesiologia|
|Citazione:||The energy load / L. Gattinoni. ((Intervento presentato al 35. convegno International Symposium on Intensive Care and Emergency Medicine tenutosi a Brussels nel 2015.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|