title: Clinical assessment of auto-positive end-expiratory pressure by diaphragmatic electrical activity during pressure support and neurally adjusted ventilatory assist.
abstract: BACKGROUND
  Auto-positive end-expiratory pressure (auto-PEEP) may substantially increase the inspiratory effort during assisted mechanical ventilation. Purpose of this study was to assess whether the electrical activity of the diaphragm (EAdi) signal can be reliably used to estimate auto-PEEP in patients undergoing pressure support ventilation and neurally adjusted ventilatory assist (NAVA) and whether NAVA was beneficial in comparison with pressure support ventilation in patients affected by auto-PEEP.
  
  
  METHODS
  In 10 patients with a clinical suspicion of auto-PEEP, the authors simultaneously recorded EAdi, airway, esophageal pressure, and flow during pressure support and NAVA, whereas external PEEP was increased from 2 to 14 cm H2O. Tracings were analyzed to measure apparent "dynamic" auto-PEEP (decrease in esophageal pressure to generate inspiratory flow), auto-EAdi (EAdi value at the onset of inspiratory flow), and IDEAdi (inspiratory delay between the onset of EAdi and the inspiratory flow).
  
  
  RESULTS
  The pressure necessary to overcome auto-PEEP, auto-EAdi, and IDEAdi was significantly lower in NAVA as compared with pressure support ventilation, decreased with increase in external PEEP, although the effect of external PEEP was less pronounced in NAVA. Both auto-EAdi and IDEAdi were tightly correlated with auto-PEEP (r = 0.94 and r = 0.75, respectively). In the presence of auto-PEEP at lower external PEEP levels, NAVA was characterized by a characteristic shape of the airway pressure.
  
  
  CONCLUSIONS
  In patients with auto-PEEP, NAVA, compared with pressure support ventilation, led to a decrease in the pressure necessary to overcome auto-PEEP, which could be reliably monitored by the electrical activity of the diaphragm before inspiratory flow onset (auto-EAdi).
authors: From the Department of Health Science, University of Milan-Bicocca, Monza, Italy, and Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy (G.B., N.P., A.P.); Department of Health Science, University of Milan-Bicocca, Monza, Italy (A.C., M.T., S.A.M., T.M.); and Department of Emergency and Intensive Care, San Gerardo Hospital, Monza, Italy (G.G.).
authors: Giacomo
authors: G
authors: Bellani
authors: Andrea
authors: A
authors: Coppadoro
authors: Nicolò
authors: N
authors: Patroniti
authors: Marta
authors: M
authors: Turella
authors: Stefano
authors: S
authors: Arrigoni Marocco
authors: Giacomo
authors: G
authors: Grasselli
authors: Tommaso
authors: T
authors: Mauri
authors: Antonio
authors: A
authors: Pesenti
mesh_terms: D000368:Aged; D003964:Diaphragm / Q000502:physiology*; D055724:Electrophysiological Phenomena; D005260:Female; D006801:Humans; D059725:Interactive Ventilatory Support / Q000379:methods*; D008297:Male; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies