Post extubation support of neonatal respiratory insufficiency.
Review important mechanisms of action; identify detrimental approaches to high-flow nasal cannula (HFNC) therapy; recommendations for initiation, adjusting, and weaning HFNC.
High-flow nasal cannula (HFNC) support, more properly termed heated humidified high-flow nasal cannula (HHHFNC), has also been described as nasal high-flow therapy (nHFT). The shorter term, HFNC, will be used throughout this chapter, but the importance of proper heating and humidification must not be forgotten when using HFNC. First used in NICUs in the early 2000s, HFNC is now almost universally available in NICUs around the world, despite the fact the first randomized trial was not published until December 2012. In many clinical units, HFNC has nearly completely superseded the application of nasal CPAP. Important mechanisms of action for HFNC support of respiratory function include: 1) optimal heating and humidification of inspired gas to reduce metabolic work, improve airway mechanics, and maintain epithelial cell integrity; 2) increased gas flow rates equal to or greater than normal peak inspiratory flow to augment inspired tidal volume, offload diaphragmatic muscle activity, and enhance gas washout of respiratory dead space; 3) provision of minimal to moderate level of positive airway pressure that contributes to increased end expiratory lung volume.
When properly applied, randomized trials demonstrate that HFNC has similar efficacy to nasal CPAP in post-extubation support of preterm infants (Figure 22.1). To date there are limited data from randomized controlled trials defining safety and efficacy for preterm infants below 28 weeks’ gestation. Nonetheless, large retrospective and prospective observational studies have not found evidence for increased adverse events associated with HFNC in this population, while reporting effective noninvasive respiratory support.
Randomized controlled trials demonstrate that HFNC, as compared to nasal CPAP, is inferior as the initial respiratory support mode for the primary treatment of neonatal respiratory distress syndrome (RDS) (Figure 22.2).
Use only HFNC systems that allow proper heating (35–37°C) and humidification (100%) of gas; ensure that adequate gas egress is maintained from the nares by limiting nasal cannula (NC) diameter to approximately 50% and no more than 80% of the diameter of the nares; recognize that at flow rates equal to or greater than weight in kilogram, the blended FiO2 is equal to the FiO2 delivered to the infant.
Manage HFNC with an approach similar to other advanced modes for noninvasive respiratory support; specifically, wean FiO2 initially until <30%, then wean flow as tolerated to a level acceptable for transition to room air or standard NC support; escalation in flow rates should be considered for increasing FiO2 needs and for signs of increasing work of breathing or respiratory distress.
Simplified meta-analysis comparing the use of high-flow nasal cannula (HFNC) to nasal CPAP for post-extubation respiratory support in neonates. (Yoder B, University of Utah, January 2019.)