LAUSR

Weaning from mechanical ventilation is defined as a separation of the patient from the ventilator. Because prolonged mechanical ventilation is associated with a risk of multiple complications (i.e., hospital-acquired infections, intensive care unit–acquired neuromuscular disorders, ventilator-induced lung injury, diaphragm dysfunction, etc.), shortening the weaning phase clearly constitutes a major clinical challenge, especially in the case of difficult-to-wean patients, who are particularly exposed to the devastating consequences of prolonged mechanical ventilation. Over recent decades, manufacturers and researchers have worked together and developed various tools to hasten weaning. Proportional assist modes of mechanical ventilation seem promising techniques with which a level of assistance is proportional to the need of the patients. Neurally adjusted ventilatory assist is one of these proportional assist modes. Neurally adjusted ventilatory assist delivers a level of assistance that is proportional to the electromyographic activity of the crural diaphragm (monitored by a nasogastric feeding tube equipped with electrodes), a close surrogate for the respiratory drive. In this issue of Anesthesiology, Liu et al. report a randomized clinical trial that evaluates the impact of neurally adjusted ventilatory assist in difficult-to-wean patients. Difficult weaning was defined as one failure of the spontaneous breathing trial or one reintubation within 48 h after extubation. Over a 6-yr period, 99 patients were randomly assigned to neurally adjusted ventilatory assist or pressure support ventilation. The primary outcome was the duration of weaning, defined as the time from study enrollment to successful ventilator liberation. Clinically relevant secondary outcomes were the proportion of patients with successful weaning, ventilator-free days, and mortality. The two groups were correctly balanced on inclusion. Patients were mechanically ventilated for 5 days. The predefined ventilator strategy from randomization to extubation was clearly described for both groups. The main and major result of the study was the shorter duration of weaning in the neurally adjusted ventilatory assist group compared to the pressure support ventilation group (3 vs. 7 days). In addition, the proportion of patients with successful weaning from invasive mechanical ventilation was higher in the neurally adjusted ventilatory assist group (33 of 47, 70%) than in the pressure support ventilation group (25 of 52, 48%). Finally, the number of ventilator-free days at day 14 and day 28 was higher in the neurally adjusted ventilatory assist group than in the pressure support ventilation group. However, mortality was not significantly different between the two groups (48% vs. 34% in the pressure support ventilation group and neurally adjusted ventilatory assist group, respectively). Neurally adjusted ventilatory assist has been available for clinicians for more than 10 yr. Physiologic studies have demonstrated that neurally adjusted ventilatory assist improves load/capacity balance and patient–ventilator interaction, prevents lung overdistension, and improves patient–ventilator asynchrony. However, to date, few studies had evaluated the benefit of neurally adjusted ventilatory assist in terms of clinical outcomes. In a study comparing neurally adjusted ventilatory assist and pressure support ventilation, neurally adjusted ventilatory assist did not improve the weaning process and did not reduce the duration of mechanical ventilation in an unselected population of critically ill patients. While neurally adjusted ventilatory assist is “...neurally adjusted ventilatory assist may become the preferred mode of mechanical ventilation in difficult-to-wean patients.”