title: Relation between peak and integral of the diaphragm electromyographic activity at different levels of support during weaning from mechanical ventilation: a physiologic study.
abstract: OBJECTIVE
  To investigate the relationship between peak (EAdipeak) and area under the curve (EAdiAUC) of diaphragm electrical activity, and to evaluate the validity of their ratio (P/I index) as a measure of the imbalance between drive and sustainability of effort demand at different support levels.
  
  
  METHODS
  Prospective physiological study on 18 ready-to-wean patients ventilated with neurally adjusted ventilatory assist (NAVA) undergoing 2 levels of NAVA (NAVA100% and NAVA50%) followed by a weaning trial with continuous positive airway pressure, according to which patients were classified as success or failure. Tidal volume (VT), respiratory rate, EAdipeak, EAdiAUC, rapid shallow breathing index (respiratory rate/VT), neuroventilatory index (VT/EAdipeak), and P/I index were obtained at the end of each step.
  
  
  RESULTS
  The slopes of regression line between EAdipeak and EAdiAUC (a mathematical equivalent of P/I index) and P/I index were significantly higher in failures. At variance with other variables, P/I index did not vary with level of support. P/I index was inversely correlated with inspiratory time at all support levels.
  
  
  CONCLUSIONS
  The relationship between EAdipeak and EAdiAUC and the P/I index may give important information on the balance between respiratory drive and inspiratory demand sustainability.
authors.affiliation: UOS Rianimazione, Department of Emergency Medicine and Intensive Care, "Ospedale Civile" Vimercate, Vimercate, MB, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Muttini
authors.affiliation: Department of Emergency Medicine and Intensive Care, "Ospedale Maggiore" Crema, Crema, CR, Italy.
authors.forename: Pier Giorgio
authors.initials: PG
authors.lastname: Villani
authors.affiliation: UOS Rianimazione, Department of Emergency Medicine and Intensive Care, "Ospedale Civile" Vimercate, Vimercate, MB, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Trimarco
authors.affiliation: Department of Health Science, University of Milan-Bicocca, Monza, MB, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Bellani
authors.affiliation: Department of Emergency Medicine and Intensive Care, San Gerardo Hospital, Monza, MB, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Grasselli
authors.affiliation: Department of Health Science, University of Milan-Bicocca, Monza, MB, Italy. Electronic address: nicolo.patroniti@unimib.it.
authors.forename: Nicolò
authors.initials: N
authors.lastname: Patroniti
mesh_terms: D000368:Aged; D019540:Area Under Curve; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D012131:Respiratory Insufficiency / Q000503:physiopathology* / Q000628:therapy; D056152:Respiratory Rate / Q000502:physiology; D013990:Tidal Volume / Q000502:physiology; D015300:Ventilator Weaning
keywords: Diaphragmatic electrical activity; Neutrally adjusted ventilator assist; Ventilator weaning