Respiratory failure following extubation causes significant morbidity and increases mortality in teh surgical intensive care unit (SICU). However the causes of respiratory failure following extubation remain poorly understood. The investigators hypothesize that extubation failure can be predicted based on preoperative risk factors as well as ICU acquired morbidities including muscle weakness and renal failure.

Both extubation delay and extubation failure are related to adverse outcomes. A spontaneous breathing trial is therefore recommended to predict extubation readiness. However, depending on the disease entity and local culture, a range of 10-20 per cent incidence of extubation failure has been described from tertiary care hospitals. The aim of this trial is to identify additional variables in surgical patients that can be used to support a clinician's decision on whether or not to extubate a patient's trachea.

Te investigators have recently developed and validated the SPORC (Brueckmann, 2013), a score that predicts the risk of extubation failure following surgery based on patients comorbidities and the acuity of the disease leading to surgery, and the investigators hypothesize that the SPORC will also predict extubation failure in the surgical ICU.

In addition, it is likely that ICU acquired morbidity also predicts extubation failure. In fact, the investigators have recently shown that muscle weakness is a predictor of aspiration (Mirzakhani, 2013), and the investigators speculated that muscle weakness may also respiratory failure after extubation.

Finally, it has been suggested that the increased mortality seen in patients with acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) versus end stage renal disease (ESRD) patients requiring CRRT can be attributed to an increased need for mechanical ventilation. (Walcher, 2011). Therefore, the investigators also hypothesize that acute kidney injury increases the vulnerability of patients to postextubation respiratory failure.

Inclusion Criteria:

• Adults (18 years of age or greater)
• Patients who have been extubated following mechanical ventilation in the surgical ICU

Exclusion Criteria:

• Preexisting end-stage renal disease
• Neurological disorder associated with severe muscle weakness
• Goals of care focused on comfort

The population of patients used for this study will be those admitted to the Surgical Intensive Care Unit