Introduction: For patients on prolonged mechanical ventilation (PMV; > 21 days), successful weaning has been attributed to various factors. The aim of this study is to determine the usefulness of the rapid shallow breathing index(RSBI) and other potential predictors of successful weaning in patients unable to wean and requiring extreme PMV at a hospital-based long-term ventilator facility in Israel. Material and ethods: Retrospective analysis of prospectively collected data over 5 years.
Results: A total of 150 subjects on PMV, ready to undergo a weaning process, were included in the study. Of them, 60 (40.0%) were males. The mean age of the whole study population was 76.5 years (SD = 13.6; range 22.0-96.0 years). The subjects were on MV for a mean period of 170.1 days (SD = 237.6; range 25.0-1624.0 days). Sixty patients (40%) were successfully weaned. The mean RSBI in the successfully weaned population was 41.9 breaths/min/L (SD = 12.3; range 13.0-80.4 breaths/min/L), in the population where weaning failed, it was 114.8 breaths/min/L (SD = 69.2; range 47.5-450.0 breaths/min/L). By univariate logistic regression analysis, younger age (p < 0.007), female gender (p < 0.001), decreased duration of MV (p < 0.023), re-spiratory rate (p < 0.001) and RSBI (p < 0.001), increased tidal volume/ideal body weight (p < 0.001) and minute ventilation (p < 0.01) were found to be factors that significantly predict successful weaning. By multivariate analysis, increased tidal volume/ /ideal body weight (p < 0.007) and decreased RSBI (p < 0.046) were found to be independent predictors of successful weaning (p < 0.001; R2 Nagelkerke = 0.90).
Conclusions: Factors independently predicting successful weaning in patients requiring extreme PMV included increased tidal volume/ideal body weight and decreased RSBI.
Keywords: mechanical ventilation; mechanical ventilator weaning; respiratory mechanics; respiratory rate; tidal volume.