title: Ultrasound evaluation of diaphragm function in mechanically ventilated patients: comparison to phrenic stimulation and prognostic implications.
abstract: In intensive care unit (ICU) patients, diaphragm dysfunction is associated with adverse clinical outcomes. Ultrasound measurements of diaphragm thickness, excursion (EXdi) and thickening fraction (TFdi) are putative estimators of diaphragm function, but have never been compared with phrenic nerve stimulation. Our aim was to describe the relationship between these variables and diaphragm function evaluated using the change in endotracheal pressure after phrenic nerve stimulation (Ptr,stim), and to compare their prognostic value.
  
  
  
  Between November 2014 and June 2015, Ptr,stim and ultrasound variables were measured in mechanically ventilated patients <24 hours after intubation ('initiation of mechanical ventilation (MV)', under assist-control ventilation, ACV) and at the time of switch to pressure support ventilation ('switch to PSV'), and compared using Spearman's correlation and receiver operating characteristic curve analysis. Diaphragm dysfunction was defined as Ptr,stim <11 cm H2O.
  
  
  
  112 patients were included. At initiation of MV, Ptr,stim was not correlated to diaphragm thickness (p=0.28), EXdi (p=0.66) or TFdi (p=0.80). At switch to PSV, TFdi and EXdi were respectively very strongly and moderately correlated to Ptr,stim, (r=0.87, p<0.001 and 0.45, p=0.001), but diaphragm thickness was not (p=0.45). A TFdi <29% could reliably identify diaphragm dysfunction (sensitivity and specificity of 85% and 88%), but diaphragm thickness and EXdi could not. This value was associated with increased duration of ICU stay and MV, and mortality.
  
  
  
  Under ACV, diaphragm thickness, EXdi and TFdi were uncorrelated to Ptr,stim. Under PSV, TFdi was strongly correlated to diaphragm strength and both were predictors of remaining length of MV and ICU and hospital death.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS1158 Neurophysiologie respiratoire expérimentale et clinique, Paris, France.|Département de médecine, service de pneumologie, Hôpital Hôtel-Dieu du Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, Québec, Canada.
authors.forename: Bruno-Pierre
authors.initials: BP
authors.lastname: Dubé
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS1158 Neurophysiologie respiratoire expérimentale et clinique, Paris, France.|AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département "R3S"), F-75013, Paris, France.
authors.forename: Martin
authors.initials: M
authors.lastname: Dres
authors.affiliation: AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département "R3S"), F-75013, Paris, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Mayaux
authors.affiliation: AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département "R3S"), F-75013, Paris, France.
authors.forename: Suela
authors.initials: S
authors.lastname: Demiri
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS1158 Neurophysiologie respiratoire expérimentale et clinique, Paris, France.|AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département "R3S"), F-75013, Paris, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Similowski
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, INSERM, UMRS1158 Neurophysiologie respiratoire expérimentale et clinique, Paris, France.|AP-HP, Groupe Hospitalier Pitié-Salpêtrière Charles Foix, Service de Pneumologie et Réanimation Médicale (Département "R3S"), F-75013, Paris, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Demoule
mesh_terms: D000368:Aged; D003422:Critical Care / Q000379:methods; D003964:Diaphragm / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay / Q000706:statistics & numerical data; D060526:Magnetic Fields; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology; D011379:Prognosis; D012372:ROC Curve; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000379:methods; D012680:Sensitivity and Specificity; D018805:Sepsis / Q000503:physiopathology / Q000628:therapy; D014463:Ultrasonography
keywords: Assisted Ventilation; Imaging/CT MRI etc; Respiratory Muscles