The earliest description of what is now known as the acute respiratory distress syndrome (ARDS) was a highly lethal double pneumonia. Ashbaugh and colleagues correctly identified the disease as ARDS in a paper published in the Lancet in 1967. Their initial study, showing the positive impact of mechanical ventilation with positive end-expiratory pressure (PEEP) on ARDS mortality, was dampened when it was discovered that improperly used mechanical ventilation can cause a secondary ventilator induced lung injury (VILI), greatly exacerbating ARDS mortality. This Synthesis paper will review the pathophysiology of ARDS and VILI from a mechanical stress-strain perspective. Although inflammation is also an important component of VILI pathology, it is secondary to the mechanical damage caused by excessive strain. The mechanical breath will be deconstructed and the role of the parameters that comprise the breath - airway pressure, flows, volumes and the duration during each breath that they are applied - on lung injury and protection will be discussed. Specifically, the impact of mechanical breath parameters on the development of excessive fluid flux and pulmonary edema, which are a hallmark of ARDS pathology, will be reviewed. Using our knowledge of how parameters in the mechanical breath impact lung physiology, the optimal combination of pressures, volumes, flows and durations that should offer maximum lung protection, will be postulated.
- Acute Lung Injury
- Copyright © 2015, Journal of Applied Physiology