title: Dyspnea and surface inspiratory electromyograms in mechanically ventilated patients.
abstract: BACKGROUND
  Pressure support ventilation (PSV) must be tailored to the load capacity balance of the respiratory system. While "over assistance" generated hyperinflation and ineffective efforts, "under assistance" increased respiratory drive and causes dyspnea. Surface electromyograms (sEMGs) of extradiaphragmatic inspiratory muscles were responsive to respiratory loading/unloading.
  
  
  OBJECTIVE
  To determine if sEMGs of extradiaphragmatic inspiratory muscles vary with PSV settings and relate to the degree of discomfort and the intensity of dyspnea in acutely ill patients.
  
  
  METHODS
  Pathophysiological study, prospective inclusions of 12 intubated adult patients.
  
  
  METHODS
  Two PSV levels (high and low) and two expiratory trigger (ET) levels (high and low).
  
  
  METHODS
  Surface electromyograms of the scalene, parasternal, and Alae Nasi muscles (peak, EMGmax; area under the curve, EMGAUC); dyspnea visual analogue scale (VAS); prevalence of ineffective triggering efforts.
  
  
  RESULTS
  For the three recorded muscles, EMGmax and EMGAUC were significantly greater with low PS than high PS. The influence of ET was less important. A strong correlation was found between dyspnea and EMGmax. A significant inverse correlation was found between the prevalence of ineffective efforts and both dyspnea-VAS and EMGmin.
  
  
  CONCLUSIONS
  Surface electromyograms of extradiaphragmatic inspiratory muscles provides a simple, reliable and non-invasive indicator of respiratory muscle loading/unloading in mechanically ventilated patients. Because this EMG activity is strongly correlated to the intensity of dyspnea, it could be used as a surrogate of respiratory sensations in mechanically ventilated patients, and might, therefore, provide a monitoring tool in patients in whom detection and quantification of dyspnea is complex if not impossible.
authors.affiliation: Université Paris 6, Pierre Et Marie Curie, ER10, Paris, France. matthieuschmidt@yahoo.fr
authors.forename: Matthieu
authors.initials: M
authors.lastname: Schmidt
authors.forename: Félix
authors.initials: F
authors.lastname: Kindler
authors.forename: Stewart B
authors.initials: SB
authors.lastname: Gottfried
authors.forename: Mathieu
authors.initials: M
authors.lastname: Raux
authors.forename: Francois
authors.initials: F
authors.lastname: Hug
authors.forename: Thomas
authors.initials: T
authors.lastname: Similowski
authors.forename: Alexandre
authors.initials: A
authors.lastname: Demoule
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004417:Dyspnea / Q000503:physiopathology*; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*