Low Tidal Volumes for Everyone?

Since the first description of mechanical ventilation, our understanding of the positive and negative effects of this form of life support has continued to evolve. To maintain “normal” aeration of the lungs and “normal” blood gas measurements, patients often require much higher airway pressures and tidal volumes than would be expected in a healthy, spontaneously breathing adult. In the early days of mechanical ventilation, the goal was to normalize the blood gas levels, but over the last several decades, we have developed a much better appreciation for the deleterious effects of mechanical ventilation. We have found that lower tidal volumes, which may actually worsen oxygenation and reduce clearance of CO2, can decrease the level of harm caused by mechanical ventilation. This scenario is best described and agreed upon in the setting of ARDS, but a growing body of evidence suggests that the use of higher tidal volumes is harmful in patients with normal lungs undergoing general anesthesia or in patients with lung diseases other than ARDS requiring mechanical ventilation. Finally, the concept of self-induced lung injury has emerged as a mechanism through which patients generating large negative intrathoracic pressures to achieve larger tidal volumes can contribute to worsened lung injury. Given a growing supportive evidence base, we suggest that efforts be made to achieve low tidal volume ventilation in all patients with lung injury or undergoing mechanical ventilation for any reason.