title: Feasibility of neurally adjusted positive end-expiratory pressure in rabbits with early experimental lung injury.
abstract: BACKGROUND
  During conventional Neurally Adjusted Ventilatory Assist (NAVA), the electrical activity of the diaphragm (EAdi) is used for triggering and cycling-off inspiratory assist, with a fixed PEEP (so called "Triggered Neurally Adjusted Ventilatory Assist" or "tNAVA"). However, significant post-inspiratory activity of the diaphragm can occur, believed to play a role in maintaining end-expiratory lung volume. Adjusting pressure continuously, in proportion to both inspiratory and expiratory EAdi (Continuous NAVA, or cNAVA), would not only offer inspiratory assist for tidal breathing, but also may aid in delivering a "neurally adjusted PEEP", and more specific breath-by-breath unloading.
  
  
  METHODS
  Nine adult New Zealand white rabbits were ventilated during independent conditions of: resistive loading (RES(1) or RES(2)), CO2 load (CO2) and acute lung injury (ALI), either via tracheotomy (INV) or non-invasively (NIV). There were a total of six conditions, applied in a non-randomized fashion: INV-RES(1), INV-CO2, NIV-CO2, NIV-RES(2), NIV-ALI, INV-ALI. For each condition, tNAVA was applied first (3 min), followed by 3 min of cNAVA. This comparison was repeated 3 times (repeated cross-over design). The NAVA level was always the same for both modes, but was newly titrated for each condition. PEEP was manually set to zero during tNAVA. During cNAVA, the assist during expiration was proportional to the EAdi. During all runs and conditions, ventilator-delivered pressure (Pvent), esophageal pressure (Pes), and diaphragm electrical activity (EAdi) were measured continuously. The tracings were analyzed breath-by-breath to obtain peak inspiratory and mean expiratory values.
  
  
  RESULTS
  For the same peak Pvent, the distribution of inspiratory and expiratory pressure differed between tNAVA and cNAVA. For each condition, the mean expiratory Pvent was always higher (for all conditions 4.0 ± 1.1 vs. 1.1 ± 0.5 cmH2O, P < 0.01) in cNAVA than in tNAVA. Relative to tNAVA, mean inspiratory EAdi was reduced on average (for all conditions) by 19 % (range 14 %-25 %), p < 0.05. Mean expiratory EAdi was also lower during cNAVA (during INV-RES(1), INV-CO2, INV-ALI, NIV-CO2 and NIV-ALI respectively, P < 0.05). The inspiratory Pes was reduced during cNAVA all 6 conditions (p < 0.05). Unlike tNAVA, during cNAVA the expiratory pressure was comparable with that predicted mathematically (mean difference of 0.2 ± 0.8 cmH2O).
  
  
  CONCLUSIONS
  Continuous NAVA was able to apply neurally adjusted PEEP, which led to a reduction in inspiratory effort compared to triggered NAVA.
authors.affiliation: Department of Critical Care Medicine, Nanjing Zhong-Da Hospital, Southeast University School of Medicine, 87 Dingjiaqiao Street, Nanjing, 210009, China. liulingdoctor@126.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Liu
authors.affiliation: Division of Pediatrics, Fukuda Hospital, 2-2-6, Shinmachi, Chuou-ku, Kumamoto city, 860-0004, Japan. hidaiji@gmail.com.
authors.forename: Daijiro
authors.initials: D
authors.lastname: Takahashi
authors.affiliation: Department of Critical Care Medicine, Nanjing Zhong-Da Hospital, Southeast University School of Medicine, 87 Dingjiaqiao Street, Nanjing, 210009, China. haiboq2000@163.com.
authors.forename: Haibo
authors.initials: H
authors.lastname: Qui
authors.affiliation: Keenan Research Centre for Biomedical Science of St. Michael's Hospital; Department of Critical Care, St. Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B1W8. slutskya@smh.ca.|Department of Medicine and Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada. slutskya@smh.ca.
authors.forename: Arthur S
authors.initials: AS
authors.lastname: Slutsky
authors.affiliation: Keenan Research Centre for Biomedical Science of St. Michael's Hospital; Department of Critical Care, St. Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B1W8. sinderby@rogers.com.|Department of Medicine and Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada. sinderby@rogers.com.|Institute for Biomedical Engineering and Science Technology (iBEST) at Ryerson University and St-Michael's Hospital, Toronto, Canada. sinderby@rogers.com.
authors.forename: Christer
authors.initials: C
authors.lastname: Sinderby
authors.affiliation: Keenan Research Centre for Biomedical Science of St. Michael's Hospital; Department of Critical Care, St. Michael's Hospital, 30 Bond Street, Toronto, ON, Canada, M5B1W8. jennifer.beck@rogers.com.|Department of Pediatrics, University of Toronto, Toronto, Canada. jennifer.beck@rogers.com.|Institute for Biomedical Engineering and Science Technology (iBEST) at Ryerson University and St-Michael's Hospital, Toronto, Canada. jennifer.beck@rogers.com.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Beck
mesh_terms: D055371:Acute Lung Injury / Q000503:physiopathology / Q000628:therapy*; D000818:Animals; D045853:Exhalation / Q000502:physiology; D005240:Feasibility Studies; D001239:Inhalation / Q000502:physiology; D059725:Interactive Ventilatory Support / Q000379:methods*; D008297:Male; D011175:Positive-Pressure Respiration / Q000379:methods*; D011817:Rabbits; D013990:Tidal Volume / Q000502:physiology