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Description and Validation of a Novel Score (Flow Index) as a Clinical Indicator of the Level of Respiratory Support
Sandeep Tripathi1, Jeremy S Mcgarvey2, Nadia Shaikh1
1Department of Pediatrics, OSF HealthCare Children's Hospital of Illinois, Illinois, United States.
Insights
The novel flow index effectively measures respiratory support in children using high flow nasal cannula (HFNC). This validated tool correlates with length of stay and need for intensive care unit escalation.
Area of Science:
- Pediatrics
- Respiratory Medicine
- Medical Informatics
Background:
- High flow nasal cannula (HFNC) is widely used for pediatric respiratory support.
- Quantifying the precise level of respiratory support provided by HFNC is challenging.
- A validated metric is needed to standardize reporting and assess HFNC effectiveness.
Purpose of the Study:
- To describe and validate the flow index (flow rate × FiO2 / weight) as a measure of respiratory support in children receiving HFNC.
- To assess the correlation between the flow index and clinical outcomes such as length of stay and ICU escalation.
Main Methods:
- Retrospective chart review of 1537 children managed with HFNC from 2015-2019.
- Extraction of variables including weight, fraction of inspired oxygen (FiO2), and flow rate to calculate the flow index.
- Step-wise regression analysis to determine the relationship between flow index and outcomes (LOS, ICU escalation).
Main Results:
- The median first and maximum flow indexes were 24.1 and 38.1, respectively.
- Both first and maximum flow indexes significantly correlated with hospital and ICU length of stay (r=0.25 and 0.31, p<0.001).
- Higher flow index values were associated with increased odds of ICU escalation and negatively correlated with rapid response activation.
Conclusions:
- The flow index is a valid and reliable measure for quantifying the degree of respiratory support in pediatric HFNC therapy.
- This metric demonstrates a stronger correlation with clinical outcomes than its individual components.
- The flow index can aid in standardizing care and predicting patient trajectories during HFNC treatment.
Abstract:
This study's objective was to describe and validate flow index (flow rate × FiO 2 /weight) as a method to report the degree of respiratory support by high flow nasal cannula (HFNC) in children. We conducted a retrospective chart review of children managed with HFNC from January 1, 2015 to December 31, 2019. Variables included in the flow index (weight, fraction of inspired oxygen [FiO 2 ], flow rate) and outcomes (hospital and intensive care unit [ICU] length of stay [LOS], escalation to the ICU) were extracted from medical records. Max flow index was defined by the earliest timestamp when patients FiO 2 × flow rate was maximum. Step-wise regression was used to determine the relationship between outcome (LOS and escalation to ICU) and flow index. Fifteen hundred thirty-seven patients met the study criteria. The median first and maximum flow indexes of the population were 24.1 and 38.1. Both first and maximum flow indexes showed a significant correlation with the LOS ( r = 0.25 and 0.31, p < 0.001). Correlation for the index was stronger than that of the variables used to calculate them and remained significant after controlling for age, race, sex, and diagnoses. Mild, moderate, and severe categories of first and max flow index were derived using quartiles, and they showed significant age and diagnosis independent association with LOS. Patients with first flow index >20 and maximum flow index >59.5 had increased odds ratio of escalation to ICU (odds ratio: 2.39 and 8.08). The first flow index had a negative association with rapid response activation. Flow index is a valid measure for assessing the degree of respiratory support for children on HFNC.
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