Effect of Tidal Volume on Pulmonary Outcomes After Surgery

To the Editor The inherent physiological rationale for lowering tidal volume during mechanical ventilation is to decrease strain on the lung tissue to avoid ventilator-induced lung injury. In the study by Dr Karalapillai and colleagues, there was a considerable difference in tidal volumes between the groups (mean, 396.6 [SD, 83.5] mL vs 611.1 [SD, 111.9] mL). However, ventilator-induced lung injury is not only a function of static parameters such as strain from tidal volume or stress from inspiratory pressures, but also from the complex interplay between static and dynamic variables, including the rate of lung deformation (strain rate) and the cycling frequency, or respiratory rate. A measure that aims to integrate static and dynamic parameters of ventilation is mechanical power, which estimates the energy per minute that is applied to the respiratory system. Although controversies still exist regarding its computation, high mechanical power has been associated with increased lung injury and mortality.
Source: JAMA - Category: General Medicine Source Type: research