Lung-protective ventilation strategy in acute respiratory distress syndrome: a critical reappraisal of current practice.

Abstract

Recognition of ventilator-induced lung injury has led to the development of lung-protective ventilation strategies, significantly influencing the management of acute respiratory distress syndrome (ARDS). By the end of the 20th century, five randomized controlled trials had compared the survival benefits of low tidal volume (VT) ventilation with those of traditional high VT ventilation. Two studies demonstrated favourable outcomes, most notably the landmark ARDS Network trial, which established the widely recommended VT of 6 mL/kg predicted body weight. However, the universal application of a fixed VT has been controversial, with poor adherence in clinical practice. The two trials used a greater contrast in VTs (6 vs. 12 mL/kg) than did the others (7-11 mL/kg) and incorporated methodological extremes, including toleration of elevated airway pressures or encouragement of unnecessary increases. In addition, disparities in underlying aetiologies and ventilatory parameters, such as unbalanced positive end-expiratory pressure and respiratory rates, may have influenced the results. There is no conclusive evidence to support the superiority of 6 mL/kg over intermediate VTs (7-10 mL/kg). Many subsequent studies have suggested that VT requirements should be individualized on the basis of lung mechanics and physiological status. The benefits of the current recommendations may be limited by factors such as the severity of hypoxemia, lung compliance, dead-space fraction, and inaccuracies in formula-based lung volume estimation. The goal of mechanical ventilation in ARDS patients is supportive rather than curative; therefore, a moderate approach is recommended in clinical practice. Further studies are needed to establish an individualized, patient-centred approach that allows more flexible and moderate settings.