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Contains fulltext : 206223.pdf (publisher's version ) (Closed access)

Contains fulltext : 206223.pdf (publisher's version ) (Closed access)

Contains fulltext : 206223.pdf (publisher's version ) (Closed access)

Background: Endogenous pulmonary reflexes may protect the lungs during mechanical ventilation. We aimed to assess integration of continuous neurally adjusted ventilatory assist (cNAVA), delivering assist in proportion to diaphragm's electrical activity during inspiration and expiration, and Hering-Breuer inflation and deflation reflexes on lung recruitment, distension, and aeration before and after acute lung injury (ALI). Methods: In 7 anesthetised rabbits with bilateral pneumothoraces, we identified adequate cNAVA level (cNAVA(AL)) at the plateau in peak ventilator pressure during titration procedures before (healthy lungs with endotracheal tube, [HLETT]) and after ALI (endotracheal tube [ALI(ETT)] and during non-invasive ventilation [ALI(NIV)]). Following titration, cNAVA(AL) was maintained for 5 min. In 2 rabbits, procedures were repeated after vagotomy (ALI(ETT+VAG)). In 3 rabbits delivery of assist was temporarily modulated to provide assist on inspiration only. Computed tomography was performed before intubation, before ALI, during cNAVA titration, and after maintenance at cNAVA(AL). Results: During ALI(ETT) and ALI(NIV), normally aerated lung-regions doubled and poorly aerated lung-regions decreased to less than a third (p < 0.05) compared to HLETT; no over-distension was observed. Tidal volumes were <5 ml/kg throughout. Removing assist during expiration resulted in lung de-recruitment during ALI(ETT) but not during ALI(NIV). During ALI(ETT+VAG) the expiratory portion of EAdi disappeared, resulting in cyclic lung collapse and recruitment. Conclusions: When using cNAVA in ALI, vagally mediated reflexes regulated lung recruitment preventing both lung over-distension and atelectasis. During non-invasive cNAVA the upper airway muscles play a role in preventing atelectasis. Future studies should be performed to compare these findings with conventional lung-protective approaches.

Purpose: Diaphragmatic electrical activity (EAdi), reflecting respiratory drive, and its feedback control might be impaired in critical illness-associated polyneuromyopathy (CIPM). We aimed to evaluate whether titration and prolonged application of neurally adjusted ventilatory assist (NAVA), which delivers pressure (P aw) in proportion to EAdi, is feasible in CIPM patients. Methods: Peripheral and phrenic nerve electrophysiology studies were performed in 15 patients with clinically suspected CIPM and in 14 healthy volunteers. In patients, an adequate NAVA level (NAVAal) was titrated daily and was implemented for a maximum of 72h. Changes in tidal volume (V t) generation per unit of EAdi (V t/EAdi) were assessed daily during standardized tests of neuro-ventilatory efficiency (NVET). Results: In patients (median [range], 66 [44-80]years), peripheral electrophysiology studies confirmed CIPM. Phrenic nerve latency (PNL) was prolonged and diaphragm compound muscle action potential (CMAP) was reduced compared with healthy volunteers (p<0.05 for both). NAVAal could be titrated in all but two patients. During implementation of NAVAal for 61 (37-64)h, the EAdi amplitude was 9.0 (4.4-15.2)μV, and the V t was 6.5 (3.7-14.3)ml/kg predicted body weight. V t, respiratory rate, EAdi, PaCO2, and hemodynamic parameters remained unchanged, while PaO2/FiO2 increased from 238 (121-337) to 282 (150-440)mmHg (p=0.007) during NAVAal. V t/EAdi changed by −10 (−46; +31)% during the first NVET and by −0.1 (−26; +77)% during the last NVET (p=0.048). Conclusion: In most patients with CIPM, EAdi and its feedback control are sufficiently preserved to titrate and implement NAVA for up to 3days. Whether monitoring neuro-ventilatory efficiency helps inform the weaning process warrants further evaluation