All current-generation positive-pressure ventilators-including those in the operating room-provide some monitoring of pulmonary mechanics at the bedside.
This produces scalar tracings of pressure-time, flow-time, and volume-time graphics, as well as flow-volume ( V ˙-V) and pressure-volume (P-V) loops. Waveforms are derived when one of the parameters of respiratory mechanics is plotted as a function of time or as a function of one of the other parameters. These factors directly affect lung volumes and therefore functional residual capacity (FRC) and gas exchange. From these, a variety of derived indices can be determined, such as flow, pressure, volume, compliance, resistance, and work of breathing (WOB). Respiratory mechanics refer to the expression of lung function through measures of pressure and flow. This review provides a brief overview on the measurement of respiratory (also referred to as pulmonary) mechanics and current developments in the field to achieve this goal. To do so, tidal volume (VT) and inspiratory pressures should be kept low to minimize the risk of barotrauma and volutrauma. To prevent VILI, the amount of energy transferred from the mechanical ventilator to the patient should be limited to a bare minimum. The so-called lung-protective ventilation strategies aim to minimize the occurrence of the pathophysiological features of VILI. 1 All these mechanisms together may result in inflammation through local production and release of inflammatory mediators, which is known as biotrauma. These 5 mechanisms have their own specific pathophysiological features but share similarities in their pathways of injuring the lungs (ventilator-induced lung injury ). Mechanical ventilation can harm lung tissue through barotrauma, volutrauma, atelectrauma, oxytrauma, and biotrauma.
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