title: Vital capacity versus maximal inspiratory pressure in patients with Guillain-Barré syndrome and myasthenia gravis.
abstract: BACKGROUND
  The objective is to determine whether maximal inspiratory pressure (P(imax)) measurement is more sensitive than vital capacity (VC) measurement to detect acute respiratory muscle failure considering a theoretical curvilinear relationship between volume and pressure.
  
  
  METHODS
  Review of VC and P(imax) of all patients hospitalized in ICU for Guillain-Barré syndrome (GBS) and myasthenia gravis (MG) exacerbation.
  
  
  RESULTS
  84 consecutive caucasian patients between 19- and 70-years-old hospitalized in intensive care unit from April 2008 to December 2010, for MG exacerbation (44 patients) and GBS (40 patients). The regression curve between VC and P(imax) was linear rather than exponential (r = 0.599, P > 0.0001). The contingency table demonstrated agreement between VC and P(imax) (χ(2)= 26.7, P = 0.0001), with similar number of patients having abnormal P(imax) associated to normal VC and normal P(imax) associated to abnormal VC (9 (10.7%) vs. 8 (9.5%) respectively). Six of the patients developed an important decrease of VC from normal value to less than 60% of the predicted value and did not present evident curvilinear relationship between VC and P(imax) during this follow-up.
  
  
  CONCLUSIONS
  Because the regression between VC and P(imax) was linear rather than curvilinear, P(imax) was not more sensitive than VC for early detection of respiratory muscle failure in patients hospitalized in ICU for GBS and MG exacerbation. Therefore, VC remains well suited to assess acute respiratory muscle failure and P(imax) gives poor additional information.
authors: Physiologie-Explorations Fonctionnelles, Service de Réanimation Médicale, et Centre d'Innovations Technologiques UMR 805, Hôpital Raymond Poincaré, AP-HP, 92380 Garches, France.
authors: Hélène
authors: H
authors: Prigent
authors: David
authors: D
authors: Orlikowski
authors: Nadège
authors: N
authors: Letilly
authors: Line
authors: L
authors: Falaize
authors: Djilali
authors: D
authors: Annane
authors: Tarek
authors: T
authors: Sharshar
authors: Frédéric
authors: F
authors: Lofaso
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D020275:Guillain-Barre Syndrome / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D011312:Pressure; D012044:Regression Analysis; D012129:Respiratory Function Tests; D012131:Respiratory Insufficiency / Q000175:diagnosis* / Q000209:etiology; D012132:Respiratory Muscles / Q000503:physiopathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014797:Vital Capacity