J Pediatr Intensive Care 2023; 12(03): 173-179
DOI: 10.1055/s-0041-1731021
Original Article

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

1   Department of Pediatrics, OSF HealthCare Children's Hospital of Illinois, Illinois, United States
2   Healthcare Analytics, OSF Healthcare Children's Hospital of Illinois, Peoria, Illinois, United States
Nadia Shaikh
1   Department of Pediatrics, OSF HealthCare Children's Hospital of Illinois, Illinois, United States
2   Healthcare Analytics, OSF Healthcare Children's Hospital of Illinois, Peoria, Illinois, United States
› Author Affiliations


This study's objective was to describe and validate flow index (flow rate × FiO2/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 [FiO2], 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 FiO2 × 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.


This study has been accepted for oral presentation as “STAR research” for the 50th National Congress of the Society of Critical Care Medicine (SCCM), February 2 to 13, 2021. Abstract from this study has been accepted for presentation at the Virtual Pediatric Academic Society (PAS) meeting 2021.

Authors' Contributions

S.T. conceptualized and designed the study, assisted in data extraction, supervised analysis and interpretation, and wrote the final manuscript. J.M. conducted the statistical analysis and interpretation and assisted in drafting the methodology and results. N.S. assisted in the design, literature search, and proposal development. L.M. extracted all the data from electronic medical records and its validation. All authors reviewed and approved the final manuscript as written.

Supplementary Material

Publication History

Received: 11 March 2021

Accepted: 16 April 2021

Article published online:
26 June 2021

© 2021. Thieme. All rights reserved.

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

  • References

  • 1 Coletti KD, Bagdure DN, Walker LK, Remy KE, Custer JW. High-flow nasal cannula utilization in pediatric critical care. Respir Care 2017; 62 (08) 1023-1029
  • 2 Ricard JD. High flow nasal oxygen in acute respiratory failure. Minerva Anestesiol 2012; 78 (07) 836-841
  • 3 Rochwerg B, Granton D, Wang DX. et al. High flow nasal cannula compared with conventional oxygen therapy for acute hypoxemic respiratory failure: a systematic review and meta-analysis. Intensive Care Med 2019; 45 (05) 563-572
  • 4 Lin J, Zhang Y, Xiong L, Liu S, Gong C, Dai J. High-flow nasal cannula therapy for children with bronchiolitis: a systematic review and meta-analysis. Arch Dis Child 2019; 104 (06) 564-576
  • 5 Trachsel D, McCrindle BW, Nakagawa S, Bohn D. Oxygenation index predicts outcome in children with acute hypoxemic respiratory failure. Am J Respir Crit Care Med 2005; 172 (02) 206-211
  • 6 Mayordomo-Colunga J, Pons M, López Y. et al. Predicting non-invasive ventilation failure in children from the SpO2/FiO2 (SF) ratio. Intensive Care Med 2013; 39 (06) 1095-1103
  • 7 Roca O, Caralt B, Messika J. et al. An index combining respiratory rate and oxygenation to predict outcome of nasal high-flow therapy. Am J Respir Crit Care Med 2019; 199 (11) 1368-1376
  • 8 Roca O, Messika J, Caralt B. et al. Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: the utility of the ROX index. J Crit Care 2016; 35: 200-205
  • 9 Parke RL, McGuinness SP. Pressures delivered by nasal high flow oxygen during all phases of the respiratory cycle. Respir Care 2013; 58 (10) 1621-1624
  • 10 Duncan H, Hutchison J, Parshuram CS. The Pediatric Early Warning System score: a severity of illness score to predict urgent medical need in hospitalized children. J Crit Care 2006; 21 (03) 271-278
  • 11 Wing R, James C, Maranda LS, Armsby CC. Use of high-flow nasal cannula support in the emergency department reduces the need for intubation in pediatric acute respiratory insufficiency. Pediatr Emerg Care 2012; 28 (11) 1117-1123
  • 12 Cheifetz IM. Pediatric ARDS. Respir Care 2017; 62 (06) 718-731
  • 13 Ferguson ND, Fan E, Camporota L. et al. The Berlin definition of ARDS: an expanded rationale, justification, and supplementary material. Intensive Care Med 2012; 38 (10) 1573-1582
  • 14 Kamit Can F, Anil AB, Anil M. et al. Predictive factors for the outcome of high flow nasal cannula therapy in a pediatric intensive care unit: is the SpO2/FiO2 ratio useful?. J Crit Care 2018; 44: 436-444
  • 15 Brasel KJ, Lim HJ, Nirula R, Weigelt JA. Length of stay: an appropriate quality measure?. Arch Surg 2007; 142 (05) 461-465
  • 16 Pollack MM, Holubkov R, Funai T. et al; Eunice Kennedy Shriver National Institute of Child Health and Human Development Collaborative Pediatric Critical Care Research Network. Pediatric intensive care outcomes: development of new morbidities during pediatric critical care. Pediatr Crit Care Med 2014; 15 (09) 821-827
  • 17 Van Voorhis KT, Willis TS. Implementing a pediatric rapid response system to improve quality and patient safety. Pediatr Clin North Am 2009; 56 (04) 919-933
  • 18 Chen J, Bellomo R, Hillman K, Flabouris A, Finfer S. MERIT Study Investigators for the Simpson Centre and the ANZICS Clinical Trials Group. Triggers for emergency team activation: a multicenter assessment. J Crit Care 2010; 25 (02) 359.e1-359.e7