References:

1. Predicting Extubation Outcomes—A Model Incorporating Heart Rate Characteristics Index.  Nitin Goel, Mallinath Chakraborty, William John Watkins, Sujoy Banerjee.  J Pediatr 2018.
2. Predicting extubation outcomes using Heart Rate Characteristics Index in Preterm Infants – A Cohort Study.  Mallinath Chakraborty, William John Watkins, Katherine Tansey, William E. King, Sujoy Banerjee.  European Respiratory Journal 2020.