title: Estimation of patient's inspiratory effort from the electrical activity of the diaphragm.
abstract: OBJECTIVE
  To calculate an index (termed Pmusc/Eadi index) relating the pressure generated by the respiratory muscles (Pmusc) to the electrical activity of the diaphragm (Eadi), during assisted mechanical ventilation and to assess if the Pmusc/Eadi index is affected by the type and level of ventilator assistance. The Pmusc/Eadi index was also used to measure the patient's inspiratory effort from Eadi without esophageal pressure.
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  One general ICU.
  
  
  METHODS
  Ten patients undergoing assisted ventilation.
  
  
  METHODS
  Pressure support and neurally adjusted ventilator assist delivered, each, at three levels of ventilatory assistance.
  
  
  RESULTS
  Airways flow and pressure, esophageal pressure, and Eadi were continuously recorded. Sixty tidal volumes for each ventilator settings were analyzed off-line, at three time points during inspiration. For each time point, Pmusc/Eadi index was calculated. Pmusc/Eadi index was also calculated from airway pressure drop during end-expiratory occlusions. Pmusc/Eadi index was very variable among patients, but within one patient it was not affected by type and level of ventilator assistance. Pmusc/Eadi index decreased during the inspiration. Pmusc/Eadi index obtained during an occlusion from airway pressure swing was tightly correlated with that derived from esophageal pressure during tidal ventilation and allowed to estimate pressure time product.
  
  
  CONCLUSIONS
  Pmusc is tightly related to Eadi, by a proportionality coefficient that we termed Pmusc/Eadi index, stable within each patient under different conditions of ventilator assistance. The derivation of the Pmusc/Eadi index from Eadi and airway pressure during an expiratory occlusion enables a continuous estimate of patient's inspiratory effort.
authors.affiliation: Department of Experimental Medicine, University of Milan-Bicocca, Monza, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Bellani
authors.forename: Tommaso
authors.initials: T
authors.lastname: Mauri
authors.forename: Andrea
authors.initials: A
authors.lastname: Coppadoro
authors.forename: Giacomo
authors.initials: G
authors.lastname: Grasselli
authors.forename: Nicolò
authors.initials: N
authors.lastname: Patroniti
authors.forename: Savino
authors.initials: S
authors.lastname: Spadaro
authors.forename: Vittoria
authors.initials: V
authors.lastname: Sala
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Foti
authors.forename: Antonio
authors.initials: A
authors.lastname: Pesenti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D003964:Diaphragm / Q000502:physiology*; D004576:Electromyography; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012121:Respiration, Artificial / Q000379:methods*