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Abstract

Introduction: Though multiple methods to predict successful extubation exist, minute ventilation has traditionally been disregarded in favor of rapid shallow breathing index (RSBI). This study was undertaken to determine if, amongst patients in a surgical intensive care unit, minute ventilation prior to extubation is higher in patients who required early reintubation. Hypothesis: We hypothesized that, amongst patients meeting standard criteria for extubation, high minute ventilation (MV) prior to extubation would be associated with increased risk for early failure. Methods: This retrospective cohort study assessed all patients admitted to the surgical intensive care unit at LAC/USC hospital who required mechanical ventilation and had at least one attempt at extubation over a 1-year period. Patients who died without attempted extubation, those with tracheostomies, and patients who self-extubated were excluded. Demographics, APACHE-II score, respiratory rate, and tidal volume were collected. MV was calculated from values recorded immediately prior to extubation. Failed extubation attempts were considered for this study if re-intubation occurred within 12 hours. Logistic regression, adjusted for age and APACHE II score was used to assess for the independent contribution of MV to failed extubation. Results: Over the study period, 161 patients met our inclusion criteria. The mean age of patients was 37 years (SD 17.3) and the mean APACHE score was 12 (SD 5). There were a total of 27 (17%) failed extuabtions. Patients who failed extubation had a significantly higher pre-extubation MV than those who were successful extubated (6643ml vs 5903ml, p=0.02). After adjusting for age and APACHE-II score, higher MV remained a significant predictor of failed extubation (p=0.01). Conclusions: Though RSBI is a useful indicator of successful extubation, it fails to consider the potential for fatigue that occurs with high minute ventilation requirements. For patients at the high end of adequate RSBI, high MV may identify patients who will tire, requiring early reintubation. This is the first study to assess high MV as predictor of failed extubation, and further prospective studies are warranted.