title: Inspiratory pressure/maximal inspiratory pressure ratio: a predictive index of weaning outcome.
abstract: OBJECTIVE
  To compare the accuracy of PI/PImax ratio and other commonly used indices in predicting weaning outcome.
  
  
  METHODS
  A prospective study.
  
  
  METHODS
  Intensive care unit.
  
  
  METHODS
  31 stable intubated patients ready to undergo weaning trial.
  
  
  METHODS
  A simple method was developed to measure the PI and PImax in intubated patients. The accuracy of PI/PImax ratio and other commonly used indices in predicting outcome were compared. All indices were measured prior to weaning trial using standardized methods.
  
  
  RESULTS
  Minute ventilation of the successful patients (13.00 +/- 0.67 (SE) l/min) was not significantly different from the failure patients (10.64 +/- 1.26 l/min, p = 0.10). The PI and PImax for the successful patients (11.48 +/- 1.25 cmH2O and 47.77 +/- 4.48 cmH2O, respectively) and the unsuccessful patients (14.32 +/- 2.31 cmH2O and 40.16 +/- 4.55 cmH2O, respectively) were also not significantly different (p = 0.28 and 0.24, respectively). The PI/PImax ratio was lower for the weaning successes (0.26 +/- 0.03) than for the weaning failures (0.36 +/- 0.04, p < 0.05). The threshold value of 0.3 for PI/PImax provided the best separation between weaning success and failure patients. The combined usage of rapid shallow breathing index and PI/PImax ratio provided the highest accuracy with sensitivity of 0.81 and specificity of 0.93.
  
  
  CONCLUSIONS
  The PI/PImax ratio provided a good separation between the patients who were successfully weaned and those who failed. It provides additional discriminative power to f/VT.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of Texas Health Science Center, Houston.
authors.forename: K L
authors.initials: KL
authors.lastname: Yang
mesh_terms: D000368:Aged; D000402:Airway Obstruction / Q000503:physiopathology; D005260:Female; D006333:Heart Failure / Q000503:physiopathology; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D007320:Inspiratory Capacity / Q000502:physiology; D007362:Intensive Care Units; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D009468:Neuromuscular Diseases / Q000503:physiopathology; D011014:Pneumonia / Q000503:physiopathology; D011379:Prognosis; D012123:Pulmonary Ventilation / Q000502:physiology; D012128:Respiratory Distress Syndrome / Q000503:physiopathology; D015300:Ventilator Weaning