Neurally adjusted ventilatory assist improves patient-ventilator synchrony during prophylactic helmet ventilation following aortic surgery

• Published in: Annales françaises d'anesthésie et de réanimation 2013-12, Vol.32 (12), p.e177-e183
• Main Authors: Almayrac, A., Demoule, A., Kindler, F., Ibanez-Esteve, C., Langeron, O., Similowski, T., Raux, M.
• Format: Article
• Language: English
• Subjects: Asynchronies; Asynchrony; Non-invasive ventilation; Postoperative; Postopératoire; Ventilation non invasive
• ISSN: 0750-7658; 1769-6623
• DOI: 10.1016/j.annfar.2013.09.007

During postoperative non-invasive ventilation (NIV), following abdominal aortic surgery, leaks and diaphragmatic dysfunction jeopardize patient-ventilator interaction. We hypothesized that neurally adjusted ventilatory assist (NAVA) would be efficient to perform NIV with a helmet, and would reduce triggering and cycling-off delays as well as major patient-ventilator asynchronies compared to pressure support ventilation (PSV). Nine postoperative patients receiving NIV with a helmet following abdominal aortic surgery were included. After optimization of ventilator settings, 15-min recording were performed with PSV (H-PSV) and NAVA mode (H-NAVA) in a non-random order. Breathing pattern descriptors, diaphragm electrical activity, leak volume, inspiratory trigger delay and cycling-off delay and the five main asynchronies were quantified. Asynchrony index (AI) and asynchrony index influenced by leaks (AILEAKS) were computed. Data is displayed as a median [25–75 interquartiles]. Trigger delays were lower with H-NAVA than with H-PSV (respectively 143 [54; 244] and 804 [406; 906] ms, P=0.02), as were the cycling-off delays (respectively −702 [−780; −534] and 437 [176; 695] ms, P=0.004). Although it had no effect on AI, H-NAVA decreased AILEAKS (5 [2; 10] vs. 16 [8; 28] %, P=0.004), mostly due to a drastic reduction of the prevalence of ineffective triggering (0.6 [0.1; 1.15] vs. 1.7 [1.1; 4.5] min−1, P=0.009). Tidal volumes and ventilatory command remained unchanged, but peak pressure level was lower with the H-NAVA than with H-PSV (16 [15–19] vs. 22 [20; 23] cmH2O, P=0.004). NAVA mode is sensitive enough to ensure ventilation despite postoperative diaphragmatic dysfunction. In combination with a helmet, NAVA improves patient-ventilator interaction during prophylactic postoperative NIV. The impact on patient outcome remains yet to be determined. Durant la ventilation non invasive (VNI) postopératoire de chirurgie aortique abdominale, la dysfonction diaphragmatique et les fuites mettent en péril la synchronisation patient-ventilateur. Notre hypothèse est que le mode NAVA (H-NAVA) par rapport au mode VSAI (H-VSAI) permet de réduire les délais de déclenchement et de cyclage ainsi que la survenue d’asynchronies en VNI avec casque. Neuf patients avec indication de VNI postopératoire après chirurgie aortique abdominale ont été inclus. Après optimisation des paramètres ventilatoires 15min d’enregistrement ont été effectués en H-VSAI puis en H-NAVA. Les variables ventilato