New Integrated Weaning Indexes
Condition: Mechanical Ventilation Weaning
Study type: Observational

Summary: 
      The purpose of this study is to determine whether introducing the new weaning indexes can
      predict better than traditional ones?
    

Detailed description: 
      The study was divided into two parts: First, the threshold values of the indexes that
      discriminated best between successful weaning and weaning failure were determined in training
      set (n = 208). Second, the accuracy of each index was scrutinized prospectively in an
      additional group of patients (prospective-validation data set, n = 967). One thousand one
      hundred and seventy-five patients who were on mechanical ventilation for more than 24 hours
      were evaluated.Informed consent was obtained from each patient, whenever possible, or from
      the patient's next of kin. The samples were selected using a simple random sampling method in
      which the entry number of eligible patients was considered to be the sampling ID number.
      Using Random Allocation Software (RAS), random numbers were generated to select the study
      participant.

      The ventilators used were Evita XL and Evita 4 edition (Draeger, Lubeck, Germany).

      According to a protocol that have introduced in two studies, the protocol established. All of
      the mechanically ventilated patients undergoing assessment for extubation undergo a daily SBT
      if predetermined eligibility criteria for weaning are met . According to this protocol,
      sedation would be discontinued before evaluation of weaning. Patients who meet these criteria
      are initially placed on SBT (continuous positive airway pressure of 5 mmHg, FiO2≤0.4) for 3
      minutes to obtain weaning parameters. If the Oxygen saturation is ≥ 92% on pulse oximetry
      with FiO2≤0.4 and RSBI <104 breaths/minute/L, patients are continued on the SBT for 30 to 120
      minutes. All clinical and ventilator parameters are monitored closely for signs of
      respiratory distress (respiratory rate > 30 breaths/minute, SaO2< 90%, heart rate > 140
      breaths/minute, or a sustained increase or decrease of heart rate of >20%, blood pressure>200
      mm Hg or <80 mm Hg, and agitation, diaphoresis, or anxiety). At the end of the SBT, the RSBI
      is measured again, ABG is obtained, and the predetermined values are calculated and measured.
      The decision to return to mechanical ventilation made by the two subspecialists in pulmonary
      and lung diseases, who were chief supervisor of both ICU in two cities (who were completely
      blind to the study and the results of the indexes evaluated), based on airway competence
      (cough, sputum production, neurologic status, level of consciousness, and maximal inspiratory
      pressure). Patients who remain extubated at 48 hours are classified as having had a
      successful extubation. Baseline demographics, initial diagnosis, and pre-extubation clinical,
      ventilator, laboratory, and radiographic data are collected for each patient.

      To assess the prognostic value of new indices, receiver operator characteristic (ROC) curves
      was drawn for each formula in addition for other conventional criteria used in this area. For
      each ROC curve analysis, sensitivity, Specificity, Positive Predictive Value, Negative
      Predictive Value, diagnostic accuracy, likelihood ratio of a positive test (LR+) and the
      likelihood ratio of a negative test (LR-), probability for weaning success when test is
      positive and probability for weaning success when test is negative of the indexes were used
      to predict the weaning outcome in the prospective-validation data set.

      Hanley and McNeil method was used to calculate the area under curve (AUC) for each formula
      and then the methods developed by the same authors were used to compare these AUCs. Bayes'
      theorem was used to compute the weaning outcome the probability for weaning success when test
      is positive and negative (post-test probability) in the prospective-validation data set to
      assess the perform
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        One thousand one hundred and seventy-five patients who were on mechanical ventilation for
        more than 24 hours were evaluated.
      
Keywords: new integrative weaning indexes; mechanical ventilation; ICU