Spontaneous breathing activity in acute lung injury and acute respiratory distress syndrome

Purpose of review We aimed at providing the most recent and relevant evidence regarding spontaneous breathing activity during mechanical ventilation in acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Both clinical and experimental data are depicted. Recent findings The use of unsupported spontaneous breathing has been associated with the most beneficial effects reported to date, but recent data favors also pressure-supported breathing activity in experimental ALI. In patients with ALI/ARDS, unsupported spontaneous breathing in combination with mandatory cycles has been shown to improve lung function, reduce the need for sedation and cardiocirculatory drug therapy, and speed weaning, with no effect on mortality. On the other hand, strong clinical evidence shows that the use of neuromuscular blocking agents in the first 48 h of mechanical ventilation with the volume assist-control ventilation mode reduces morbidity and mortality in severe ARDS compared to placebo. Summary In our opinion, spontaneous breathing activity should be avoided in the first 48 h of mechanical ventilation in patients with severe ARDS (PaO2/FIO2 < 120 mmHg), but it may be useful in less severe ARDS and ALI. Clearly, further clinical and experimental investigations on the use of different ventilation modes of supported/unsupported spontaneous breathing in ALI/ARDS are needed.