title: The weaning index as predictor of weaning success.
abstract: BACKGROUND
  The quest to obtain an accurate way to predict success when weaning a patient from mechanical ventilation continues. The established parameters such as tidal volume (Vt), respiratory rate (f), negative inspiratory force (NIF), vital capacity (VC), and minute ventilation (V) have not predicted weaning accurately. The frequency-to-tidal volume ratio (f/Vt), or rapid shallow breathing index (RSBI) is a good predictor of weaning success if the value is low, but not when the value approximates 105. Because of the aforementioned, we decided to add 2 corrective factors to the RSBI. The first one was elastance index (EI = peak pressure/NIF) and the second one, the ventilatory demand index (VDI = minute ventilation/10). The result of the product of the RSBI × EI × VDI was called the weaning index (WI).
  
  
  METHODS
  In order to assess the discriminatory power of WI, we obtained weaning parameters and calculated WI for 59 patients in our intensive care unit and extubated them if RSBI was ≤105. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver-operating characteristics (ROC) curves were obtained. The results were compared with the previous studies involving the RSBI.
  
  
  RESULTS
  The WI sensitivity was 98%, specificity was 89%, PPV was 95%, NPV was 94%, and area under the ROC curve was 95.9.
  
  
  CONCLUSIONS
  The WI is a simple and reproducible parameter that integrates breathing pattern, compliance, inspiratory muscle strength, and ventilatory demand and is the most accurate predictor of weaning success.
authors.affiliation: Department of Medicine, White Memorial Medical Center and Loma Linda University School of Medicine, Los Angeles, CA, USA.
authors.forename: Armando J
authors.initials: AJ
authors.lastname: Huaringa
authors.forename: Allan
authors.initials: A
authors.lastname: Wang
authors.forename: Manuel H
authors.initials: MH
authors.lastname: Haro
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Leyva
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000150:complications / Q000175:diagnosis / Q000628:therapy; D002561:Cerebrovascular Disorders / Q000150:complications / Q000175:diagnosis / Q000628:therapy; D003422:Critical Care / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007902:Length of Stay; D015141:Los Angeles; D008171:Lung Diseases / Q000150:complications / Q000175:diagnosis / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012372:ROC Curve; D012121:Respiration, Artificial / Q000379:methods; D056152:Respiratory Rate / Q000502:physiology; D012680:Sensitivity and Specificity; D013990:Tidal Volume / Q000502:physiology; D016896:Treatment Outcome; D015300:Ventilator Weaning / Q000379:methods* / Q000706:statistics & numerical data
keywords: elastance index; mechanical ventilation; rapid shallow breathing index; ventilatory demand index; weaning