Higher Work of Breathing at the End of Successful Spontaneous Breathing Trial Does Not Predict Extubation Failure

Abstract

PURPOSE: Spontaneous breathing trial (SBT) is the gold standard process to assess readiness for extubation in mechanically ventilated patients. Approximately 15% of extubated patients require reintubation within 48 hours. We hypothesized that patients having higher work of breathing (WOB) at the end of successful SBT would have higher likelihood re-intubation. METHODS: We performed a prospective observational study to calculate the WOB at the end of first successful SBT using proportional assist ventilation (PAV) mode of ventilation in intubated medical intensive care unit patients. The ventilator used was Purtian Bennet 840 equipped with PAV+ software capable of showing WOB scale of 0.0 to 2.0 J/L in proportional assist ventilation (PAV) mode. WOB was further divided as: low WOB (0.0 to 0.3 J/L), normal WOB (0.3-0.7 J/L),high WOB (0.7-1.0 J/L) and very high WOB (1.2 to 2.0 J/L). At the end of successful SBT patient were switched over to PAV mode with 5 % of total WOB support provided by ventilator for 5 minutes and the data was collected. This data was not used for clinical management and patients were extubated based on judgement of the treating physician. Extubated patients were followed for 48 hours. Extubation failure was defined as the need for reintubation or the use of non-invasive positive pressure ventilation (NIPPV) for respiratory distress within 48 hours of extubation. RESULTS: Data from the first successful SBTs in 111 patients was analyzed. Only 67.5% (75/111) of patients were extubated on the same day of the first successful SBT. Overall rate of extubation failure was 11.7% (13/111, 8 patients needed re-intubation, 4 patients needed NIPPV and 1 patient needed NIPPV and was subsequently intubated). Three (23%) patients had high WOB and 0 (0%) patient had very high WOB in the failure group and 10 (16.4%) patients had high WOB and 3 (4.9%) patients had very high WOB in success group (p¼0.86).