title: Effort of breathing in children receiving high-flow nasal cannula.
abstract: OBJECTIVE
  High-flow humidified nasal cannula is often used to provide noninvasive respiratory support in children. The effect of high-flow humidified nasal cannula on effort of breathing in children has not been objectively studied, and the mechanism by which respiratory support is provided remains unclear. This study uses an objective measure of effort of breathing (Pressure. Rate Product) to evaluate high-flow humidified nasal cannula in critically ill children.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Quaternary care free-standing academic children's hospital.
  
  
  METHODS
  ICU patients younger than 18 years receiving high-flow humidified nasal cannula or whom the medical team planned to extubate to high-flow humidified nasal cannula within 72 hours of enrollment.
  
  
  METHODS
  An esophageal pressure monitoring catheter was placed to measure pleural pressures via a Bicore CP-100 pulmonary mechanics monitor. Change in pleural pressure (ΔPes) and respiratory rate were measured on high-flow humidified nasal cannula at 2, 5, and 8 L/min. ΔPes and respiratory rate were multiplied to generate the Pressure.Rate Product, a well-established objective measure of effort of breathing. Baseline Pes, defined as pleural pressure at end exhalation during tidal breathing, reflected the positive pressure generated on each level of respiratory support.
  
  
  RESULTS
  Twenty-five patients had measurements on high-flow humidified nasal cannula. Median age was 6.5 months (interquartile range, 1.3-15.5 mo). Median Pressure,Rate Product was lower on high-flow humidified nasal cannula 8 L/min (median, 329 cm H2O·min; interquartile range, 195-402) compared with high-flow humidified nasal cannula 5 L/min (median, 341; interquartile range, 232-475; p = 0.007) or high-flow humidified nasal cannula 2 L/min (median, 421; interquartile range, 233-621; p < 0.0001) and was lower on high-flow humidified nasal cannula 5 L/min compared with high-flow humidified nasal cannula 2 L/min (p = 0.01). Baseline Pes was higher on high-flow humidified nasal cannula 8 L/min than on high-flow humidified nasal cannula 2 L/min (p = 0.03).
  
  
  CONCLUSIONS
  Increasing flow rates of high-flow humidified nasal cannula decreased effort of breathing in children, with the most significant impact seen from high-flow humidified nasal cannula 2 to 8 L/min. There are likely multiple mechanisms for this clinical effect, including generation of positive pressure and washout of airway dead space.
authors.affiliation: 1Departments of Pediatrics and Anesthesiology Critical Care Medicine, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA. 2Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Rubin
authors.forename: Anoopindar
authors.initials: A
authors.lastname: Ghuman
authors.forename: Timothy
authors.initials: T
authors.lastname: Deakers
authors.forename: Robinder
authors.initials: R
authors.lastname: Khemani
authors.forename: Patrick
authors.initials: P
authors.lastname: Ross
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Newth
mesh_terms: D057785:Catheters; D045422:Continuous Positive Airway Pressure / Q000295:instrumentation; D005260:Female; D006801:Humans; D006813:Humidity; D007223:Infant; D008297:Male; D009666:Nose; D010994:Pleura / Q000502:physiology*; D011312:Pressure; D011446:Prospective Studies; D056152:Respiratory Rate; D014939:Work of Breathing