Forty-six percent of patients admitted to the intensive care unit (ICU) require mechanical ventilation (MV) to support and maintain life; however, MV is associated with significant rates of morbidity and mortality, both directly proportional to MV duration and failure to successfully terminate MV (weaning). Despite the large number of studies on weaning, there continues to be a high frequency of failure when weaning off of MV, on average 30%, among critically ill patients in the ICU. Considering the high rates of morbidity and mortality related to MV this study was designed with the following objectives: 1 – To assess each stage of weaning in critically ill patients, as established in the medical literature 2 – Based on the empirical data collected and analyzed as well as compared to the medical literature, seek to improve the weaning process 3 – Test the hypothesis that the respiratory frequency (RF), an important variable associated with respiration, can be an effective predictor, by comparing it to the rapid shallow breathing index (RSBI), which is an important predictor of weaning 4 – Finally, to develop a weaning protocol consistent with the results of this study