Neurally Adjusted Ventilatory AssistversusPressure Support Ventilation in Difficult Weaning

Abstract

Background Difficult weaning frequently develops in ventilated patients and is associated with poor outcome. In neurally adjusted ventilatory assist, the ventilator is controlled by diaphragm electrical activity, which has been shown to improve patient–ventilator interaction. The objective of this study was to compare neurally adjusted ventilatory assist and pressure support ventilation in patients difficult to wean from mechanical ventilation. Methods In this nonblinded randomized clinical trial, difficult-to-wean patients (n = 99) were randomly assigned to neurally adjusted ventilatory assist or pressure support ventilation mode. The primary outcome was the duration of weaning. Secondary outcomes included the proportion of successful weaning, patient–ventilator asynchrony, ventilator-free days, and mortality. Weaning duration was calculated as 28 days for patients under mechanical ventilation at day 28 or deceased before day 28 without successful weaning. Results Weaning duration in all patients was statistically significant shorter in the neurally adjusted ventilatory assist group (n = 47) compared with the pressure support ventilation group (n = 52; 3.0 [1.2 to 8.0] days vs. 7.4 [2.0 to 28.0], mean difference: −5.5 [95% CI, −9.2 to −1.4], P = 0.039). Post hoc sensitivity analysis also showed that the neurally adjusted ventilatory assist group had shorter weaning duration (hazard ratio, 0.58; 95% CI, 0.34 to 0.98). The proportion of patients with successful weaning from invasive mechanical ventilation was higher in neurally adjusted ventilatory assist (33 of 47 patients, 70%) compared with pressure support ventilation (25 of 52 patients, 48%; respiratory rate for neurally adjusted ventilatory assist: 1.46 [95% CI, 1.04 to 2.05], P = 0.026). The number of ventilator-free days at days 14 and 28 was statistically significantly higher in neurally adjusted ventilatory assist compared with pressure support ventilation. Neurally adjusted ventilatory assist improved patient ventilator interaction. Mortality and length of stay in the intensive care unit and in the hospital were similar among groups. Conclusions In patients difficult to wean, neurally adjusted ventilatory assist decreased the duration of weaning and increased ventilator-free days. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

Neurally adjusted ventilatory assist in acute respiratory failure: a randomized controlled trial

“…Since all that is set during NAVA is the proportion of effort provided by the ventilator to supplement the patient's ventilatory drive, for a given NAVA level, the airway pressure varies breath-by-breath in proportion to Edi. Three randomized controlled trials on NAVA have been previously published [9,11,12]. Demoule et al [9] randomized 128 patients ready for partial ventilatory support to NAVA or pressure support.…”

“…Although they also reported fewer hospital deaths in the NAVA group, no significant differences were observed in ICU, 28-day, or 90-day mortality. Most recently, Liu et al [12] randomized the use of NAVA and pressure support in 99 difficult-to-wean patients. They observed that NAVA reduced the time of weaning and increased VFDs, with no effects on ICU, 28-day, or hospital mortality.…”

Clinical strategies for implementing lung and diaphragm-protective ventilation: avoiding insufficient and excessive effort

“…Also, diaphragm inactivity due to over-assistance is unlikely in NAVA, as low diaphragm activity will immediately reduce inspiratory assist. Future studies should confirm the role of NAVA in lung and diaphragm-protective ventilation, but recent randomized trials suggest clinical benefit of NAVA (reduced time on the ventilator) compared to pressure support mode [ 40 , 41 ].…”

Proportional modes of ventilation: technology to assist physiology

“…A recent study confirmed acceptable adherence to the assigned mode beyond 48 h when comparing NAVA with PSV [21]. Furthermore, Liu et al recently showed shorter weaning duration with NAVA compared to PSV in selected difficult-to-wean patients [20].…”

“…Moreover, safe targets for respiratory effort may vary among patients, depending on the severity of lung injury and diaphragm function [15][16][17]. The uncertainty regarding titration of inspiratory support with NAVA and PAV+ might be one of the reasons why there is still limited data showing improved clinical outcomes when using proportional modes as compared to conventional modes [18,19], but clinical benefits of NAVA compared to PSV were recently demonstrated in difficult-to-wean patients [20,21]. At the same time, despite having very complex physiological consequences, PSV maintains an appearance of simplicity and is the most frequently used partially supported mode of ventilation [22].…”