Description and validation of a novel score (Flow Index) as a clinical
indicator of the level of respiratory support to children on high flow
nasal cannula.
Abstract
Objective: Describe & validate flow index (FiO2×flow rate/weight) to
report the degree of respiratory support to children on high flow nasal
cannula (HFNC) Methods: Retrospective chart review. Children managed
with HFNC from 01/01/15 to 12/31/19. Variables included in the flow
index (weight, FiO2, flow rate) and outcomes (hospital and ICU length of
stay [LOS], escalation to the ICU) extracted from medical records.
Max flow index defined by the earliest timestamp when patients FiO2×Flow
rate was maximum. Step-wise regression used to determine the
relationship between outcome (length of stay and escalation to ICU) and
flow index Results: 1537 patients met the study criteria. Median 1st and
maximum flow index of the population 24.1 and 38.1, respectively. Both
1st and maximum flow indexes showed a significant correlation with the
LOS (r 0.25 and 0.31). 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 1st and max flow index derived using quartiles and
showed significant age and diagnosis independent association with LOS.
Patients with 1st flow index >20 and maximum flow index
>59.5 had increased odds ratio of escalation to ICU (OR
2.39 and 8.08). The 1st flow index had a negative association with rapid
response activation. Conclusions: Flow index is a valid measure for
assessing the degree of respiratory support for children on HFNC. High
flow index associated with longer hospital LOS and the risk of
escalation to ICU.