title: Neuroventilatory efficiency and extubation readiness in critically ill patients.
abstract: BACKGROUND
  Based on the hypothesis that failure of weaning from mechanical ventilation is caused by respiratory demand exceeding the capacity of the respiratory muscles, we evaluated whether extubation failure could be characterized by increased respiratory drive and impaired efficiency to generate inspiratory pressure and ventilation.
  
  
  METHODS
  Airway pressure, flow, volume, breathing frequency, and diaphragm electrical activity were measured in a heterogeneous group of patients deemed ready for a spontaneous breathing trial. Efficiency to convert neuromuscular activity into inspiratory pressure was calculated as the ratio of negative airway pressure and diaphragm electrical activity during an inspiratory occlusion. Efficiency to convert neuromuscular activity into volume was calculated as the ratio of the tidal volume to diaphragm electrical activity. All variables were obtained during a 30-minute spontaneous breathing trial on continuous positive airway pressure (CPAP) of 5 cm H₂O and compared between patients for whom extubation succeeded with those for whom either the spontaneous breathing trial failed or for those who passed, but then the extubation failed.
  
  
  RESULTS
  Of 52 patients enrolled in the study, 35 (67.3%) were successfully extubated, and 17 (32.7%) were not. Patients for whom it failed had higher diaphragm electrical activity (48%; P < 0.001) and a lower efficiency to convert neuromuscular activity into inspiratory pressure and tidal volume (40% (P < 0.001) and 53% (P < 0.001)), respectively. Neuroventilatory efficiency demonstrated the greatest predictability for weaning success.
  
  
  CONCLUSIONS
  This study shows that a mixed group of critically ill patients for whom weaning fails have increased neural respiratory drive and impaired ability to convert neuromuscular activity into tidal ventilation, in part because of diaphragm weakness.
  
  
  BACKGROUND
  Clinicaltrials.gov identifier NCT01065428.
authors: Ling
authors: L
authors: Liu
authors: Huogen
authors: H
authors: Liu
authors: Yi
authors: Y
authors: Yang
authors: Yingzi
authors: Y
authors: Huang
authors: Songqiao
authors: S
authors: Liu
authors: Jennifer
authors: J
authors: Beck
authors: Arthur S
authors: AS
authors: Slutsky
authors: Christer
authors: C
authors: Sinderby
authors: Haibo
authors: H
authors: Qiu
mesh_terms: D060666:Airway Extubation; D001784:Blood Gas Analysis; D016638:Critical Illness; D003964:Diaphragm / Q000294:innervation; D005260:Female; D006801:Humans; D008297:Male; D012121:Respiration, Artificial; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D017211:Treatment Failure; D015300:Ventilator Weaning