The present review deals with the physiological effects of delivering a certain tidal volume to the lungs of patients with ARDS, and suggests an approach to tidal volume selection.Įxperimental evidence has accumulated in the last 30 years showing that mechanical ventilation provided with elevated volumes and/or pressures can directly injure the lung ( 5). As a consequence, the so-called “protective ventilation” is an approach which aims to an individual tailoring of ventilatory support, according to the best compromise among respiratory mechanics, recruitability, gas exchange and hemodynamics. Indeed, mechanical ventilation itself can bring to a further damage of the lung, through the activation of an inflammatory response and it has been demonstrated that, even in the absence of a pre-existing lung injury, mechanical ventilation may lead to the development of ventilator-induced lung injury (VILI). Unfortunately, a completely “safe” lung ventilation does not exist, and the main side-effects related to mechanical ventilation are the hemodynamic instability secondary to the increased intrathoracic pressures and the mechanical trauma to the lung structure. On the other hand, it is the ventilation delivered by the mechanical ventilation, which is allows for carbon dioxide (CO 2) elimination. Then, the effect on oxygenation provided by mechanical ventilation is dual: it allows for an accurate titration of the fraction of oxygen in the inspired gas, and it provides an inspiratory pressure which is enough to open some of the collapsed lung units, thus making it possible for the blood passing through these regions to be oxygenated during the inspiratory phase. Indeed, the respiratory muscles of patients with ARDS are unable, for several reasons, to drive lung ventilation to a level which is enough to meet patients’ need. In ARDS, minute ventilation is increased to a level that is much greater than in healthy subjects, due to an abnormally increased respiratory drive ( 3) and the elevated amount of pulmonary dead space ( 4). This effect is achieved by taking over the function of patients’ respiratory muscles ( 2). In fact, mechanical ventilation per se is not a cure for ARDS it works by simply buying time by maintaining a sufficient gas exchange for patient survival. Despite extensive research over nearly half a century, no specific therapy exists for ARDS, and mechanical ventilation remains the key form of supportive care ( 1). The wide majority of critically ill patients are subject to invasive mechanical ventilation during their stay in the intensive care unit, and patients with acute respiratory distress syndrome (ARDS) are almost invariably managed by invasive mechanical ventilation. Keywords: Acute respiratory distress syndrome (ARDS) mechanical ventilation tidal volume ventilator-induced lung injury (VILI) Eventually, the role of other ventilator-related parameters in the generation of VILI will be considered (namely, plateau pressure, airway driving pressure, respiratory rate (RR), inspiratory flow), and the promising unifying framework of mechanical power will be presented. An ultra-low tidal volume strategy with the use of extracorporeal carbon dioxide removal (ECCO 2R) will be presented and discussed. The still actual suggestion of a lung-protective ventilatory strategy based on the use of low tidal volumes scaled to the predicted body weight (PBW) will be presented, together with newer strategies such as the use of airway driving pressure as a surrogate for the amount of ventilatable lung tissue or the concept of strain, i.e., the ratio between the tidal volume delivered relative to the resting condition, that is the functional residual capacity (FRC). The relationship between tidal volume and the development of VILI, the so called volotrauma, will be reviewed. The present paper illustrates the physiological effects of delivering a tidal volume to the lungs of patients with ARDS, and suggests an approach to tidal volume selection. Experimental evidence accumulated over the last 30 years highlighted the factors associated with an injurious form of mechanical ventilation. Moreover, it can further damage the lung, leading to the development of a particular form of lung injury named ventilator-induced lung injury (VILI). However, this form of support does not constitute a cure for acute respiratory distress syndrome (ARDS), as it mainly works by buying time for the lungs to heal while contributing to the maintenance of vital gas exchange. Policy of Dealing with Allegations of Research MisconductĪbstract: Mechanical ventilation is the type of organ support most widely provided in the intensive care unit.Policy of Screening for Plagiarism Process.
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