Respiratory severity score and extubation readiness in very low birth weight infants

Abstract

Background: The respiratory severity score (RSS) is a byproduct of mean airway pressure (MAP) and fraction of inspired oxygen (FiO₂). We sought to determine whether RSS could be used as a screening tool to predict extubation readiness in very low birth weight (VLBW) infants.

Methods: In a retrospective cohort study, medical records of all VLBW infants admitted to our unit (6/1/09-2/28/12) were reviewed for infants' demographics, prenatal characteristics, and medication use. Also, records were reviewed for unplanned vs. planned extubation, blood gas, ventilator parameters and signs of severe respiratory failure [RF, defined as partial pressure of carbon dioxide (pCO₂) > 65, pH < 7.20, FiO₂ > 50%, and MAP > 10 cm] on the day of extubation.

Results: During the study period 31% (45/147) failed extubation. Overall, infants who failed extubation had a lower birth weight (BW) and gestational age (GA), and on the day of extubation had a higher RSS and percentage of having one or more signs of severe RF. In a logistic regression model, adjusting for BW, GA, RSS and RF, RSS remained the only risk factor associated with extubation failure [adjusted OR 1.63 (95% CI: 1.10-2.40); p = 0.01]. RSS had a sensitivity of 0.86 (95% CI: 0.72-0.94) at a cutoff of 1.26 and a specificity of 0.88 (95% CI: 0.80-0.94) at a cutoff of 2.5. There was no difference in extubation failure between unplanned vs. planned extubation [41% (9/22) vs. 29% (36/125); p = 0.25].

Conclusion: An elevated RSS is associated with extubation failure. Successful unplanned extubation is common in VLBW infants.

Keywords: extubation; mechanical ventilation; respiratory severity score; very low birth weight.