title: Spontaneous breathing trial and post-extubation work of breathing in morbidly obese critically ill patients.
abstract: Predicting whether an obese critically ill patient can be successfully extubated may be specially challenging. Several weaning tests have been described but no physiological study has evaluated the weaning test that would best reflect the post-extubation inspiratory effort.
  
  
  
  This was a physiological randomized crossover study in a medical and surgical single-center Intensive Care Unit, in patients with body mass index (BMI) >35 kg/m2who were mechanically ventilated for more than 24 h and underwent a weaning test. After randomization, 17 patients were explored using five settings : pressure support ventilation (PSV) 7 and positive end-expiratory pressure (PEEP) 7 cmH2O; PSV 0 and PEEP 7cmH2O; PSV 7 and PEEP 0 cmH2O; PSV 0 and PEEP 0 cmH2O; and a T piece, and after extubation. To further minimize interaction between each setting, a period of baseline ventilation was performed between each step of the study. We hypothesized that the post-extubation work of breathing (WOB) would be similar to the T-tube WOB.
  
  
  
  Respiratory variables and esophageal and gastric pressure were recorded. Inspiratory muscle effort was calculated as the esophageal and trans-diaphragmatic pressure time products and WOB. Sixteen obese patients (BMI 44 kg/m2± 8) were included and successfully extubated. Post-extubation inspiratory effort, calculated by WOB, was 1.56 J/L ± 0.50, not statistically different from the T piece (1.57 J/L ± 0.56) or PSV 0 and PEEP 0 cmH2O (1.58 J/L ± 0.57), whatever the index of inspiratory effort. The three tests that maintained pressure support statistically underestimated post-extubation inspiratory effort (WOB 0.69 J/L ± 0.31, 1.15 J/L ± 0.39 and 1.09 J/L ± 0.49, respectively, p < 0.001). Respiratory mechanics and arterial blood gases did not differ between the five tests and the post-extubation condition.
  
  
  
  In obese patients, inspiratory effort measured during weaning tests with either a T-piece or a PSV 0 and PEEP 0 was not different to post-extubation inspiratory effort. In contrast, weaning tests with positive pressure overestimated post-extubation inspiratory effort.
  
  
  
  Clinical trial.gov (reference NCT01616901 ), 2012, June 4th.
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France.
authors: Martin
authors: M
authors: Mahul
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France.|Centre National de la Recherche Scientifique (CNRS 9214) - Institut National de la Santé et de la Recherche Médicale (INSERM U-1046), Montpellier University, Montpellier, France.
authors: Boris
authors: B
authors: Jung
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France.
authors: Fabrice
authors: F
authors: Galia
authors: Department of Statistics, University of Montpellier Lapeyronie Hospital, UMR 729 MISTEA, Montpellier, France.
authors: Nicolas
authors: N
authors: Molinari
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France.
authors: Audrey
authors: A
authors: de Jong
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France.|Centre National de la Recherche Scientifique (CNRS 9214) - Institut National de la Santé et de la Recherche Médicale (INSERM U-1046), Montpellier University, Montpellier, France.
authors: Yannaël
authors: Y
authors: Coisel
authors: Anaesthesia and Intensive Care Medicine, Maggiore della Carità Hospital, Novara, Italy.
authors: Rosanna
authors: R
authors: Vaschetto
authors: Centre National de la Recherche Scientifique (CNRS 9214) - Institut National de la Santé et de la Recherche Médicale (INSERM U-1046), Montpellier University, Montpellier, France.
authors: Stefan
authors: S
authors: Matecki
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France.|Centre National de la Recherche Scientifique (CNRS 9214) - Institut National de la Santé et de la Recherche Médicale (INSERM U-1046), Montpellier University, Montpellier, France.
authors: Gérald
authors: G
authors: Chanques
authors: Keenan Research Centre, St Michael's Hospital, Toronto, Canada.|Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.
authors: Laurent
authors: L
authors: Brochard
authors: Intensive Care Unit, Anaesthesia and Critical Care Department, Saint Eloi Teaching Hospital, Centre Hospitalier Universitaire Montpellier, 80 avenue Augustin Fliche, F-34295, Montpellier, Cedex 5, France. s-jaber@chu-montpellier.fr.|Centre National de la Recherche Scientifique (CNRS 9214) - Institut National de la Santé et de la Recherche Médicale (INSERM U-1046), Montpellier University, Montpellier, France. s-jaber@chu-montpellier.fr.
authors: Samir
authors: S
authors: Jaber
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D060666:Airway Extubation / Q000379:methods* / Q000639:trends; D016638:Critical Illness / Q000628:therapy*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy*; D011175:Positive-Pressure Respiration / Q000379:methods* / Q000639:trends; D011446:Prospective Studies; D014939:Work of Breathing / Q000502:physiology*
keywords: Acute respiratory failure; Mechanical ventilation; Obese; Weaning; Work of breathing