The indexes were measured by the respiratory physiotherapists before the SBTs. The decision to return to mechanical ventilation was made by the physician Dasatinib chemical structure in charge (who was completely blind to the study and the results of the indexes evaluated), based on the signs of poor tolerance incorporated in our daily routine.Weaning was considered successful if spontaneous breathing was sustained for more than 48 hours after extubation [2]. During the two-hour period of SBT, tolerance was continuously evaluated by the physician in charge. When the patient remained stable after the two-hour period of SBT, the endotracheal tube was removed. The trial was stopped when at least one of the following poor tolerance criteria was present: SaO2 less than 90% and PaO2 less than 60 mmHg with FiO2 less than 0.

5 or SaO2 less than 88% and PaO2 less than 55 mmHg with FiO2 less than 0.5 in patients with chronic obstructive pulmonary disease (COPD); partial pressure of arterial carbon dioxide (PaCO2) more than 50 mmHg (or increased by 8 mmHg or more in COPD patients); arterial pH of 7.33 or less or decreased by 0.07 or more; f more than 38 breaths per minute or increased by 50% for five minutes or longer; heart rate of more than 140 beats per minute or a sustained increase or decrease in more than 20%; systolic blood pressure of more than 180 mmHg or less than 90 mmHg; or in the presence of agitation, diaphoresis, disorientation or depressed mental status. A clearly audible cough and adequate mental status were requirements for patients to be considered ready for extubation [15].

Weaning failure was determined if one of the following criteria occurred: failed SBT; reintubation and/or resumption of ventilatory support within 48 hours following successful extubation; or death within 48 hours following extubation [2]. The distinction between weaning failure (inability to tolerate spontaneous breathing without ventilatory support) and extubation failure (inability to tolerate removal of translaryngeal tube) was taken into account [15], although for results and statistical analysis considerations, all extubation failure patients were also regarded as weaning failure.The integrative weaning indexThe IWI uses three essential parameters that lend themselves to easy measurement and are independent of the patient’s cooperation.

The IWI evaluates, in a single equation, the respiratory mechanics, the oxygenation, and the respiratory pattern, through Cst,rs, SaO2 and f/Vt ratio respectively.Several reasons concurred to the choice Anacetrapib of the parameters above: f/Vt is considered the best [4] or one of the best indexes [8,16] to evaluate the weaning outcome; Cst,rs is associated with a shorter time to weaning when more than 20 ml/cmH2O [12]; and SaO2 has proven to be useful to evaluate the readiness for weaning or to indicate the weaning failure in several studies and revisions [1-3,5].