BACKGROUND: Heated and humidified high-flow nasal cannula (HFNC) is a widely used form of respiratory support; however, data regarding optimal flows for a given patient size or disease state are lacking. A comprehensive study of the physiologic effects of HFNC is needed to better understand the mechanisms of action. The objective of the current study was to quantify the effect of HFNC settings in age-specific, anatomically correct nasal airways and spontaneously breathing lung models. We hypothesized that there is an effect of flow on pressure and ventilation. METHODS: Three-dimensionally printed upper airway models of a preterm neonate, term neonate, toddler, small child, and adult were affixed to the ASL 5000 test lung to simulate spontaneous breathing with age-appropriate normal ventilation parameters. CO ₂ was introduced to simulate profound hypercapneic respiratory failure with an end-tidal partial pressure of carbon dioxide (P ETCO ₂ ) of 90 ± 1 mm Hg. Two commercially available HFNC systems were applied to the airway models, and PEEP, inspired CO ₂ , and exhaled CO ₂ (P ETCO ₂ ) were recorded for 6 min across a range of flow. RESULTS: Increasing HFNC flow provided a non-linear increase in PEEP in closed-mouth models, with maximum tested flows generating 6 cm H ₂ O in the preterm neonate to 20 cm H ₂ O in the small child. Importantly, PEEP decreased by approximately 50% in open-mouth models. Increasing HFNC flow improved expiratory CO ₂ elimination to a certain point, above which continued increases in flow had minimal additional effect. This change point ranged from 4 L/min in the preterm neonate to 10 L/min in the small child. CONCLUSIONS: These findings may help clinicians understand the effects of HFNC at different settings and may inform management guidelines for patients with respiratory failure.

Pediatric patients are different from adult patients with respect to airway anatomy and breathing patterns. They are also incapable of following commands and often reject breathing treatments. For these reasons, aerosol drug delivery is one of the most technically challenging aspects for clinicians providing respiratory care to young children. Improvements in nebulizer technology have provided better delivery options for pediatric patients. This review highlights research related to pediatric nebulizer and interface devices and how they can be used to provide the safest and most efficient treatments with the array of treatment delivery options. Also addressed are clinical controversies and debates in pediatric aerosol science, including drug delivery in crying versus resting infants, pressurized metered-dose inhalers and small-volume nebulizers for bronchodilator administration, continuous nebulization, noninvasive drug delivery options, and optimization of nebulizer performance during infant and large pediatric conventional and high-frequency ventilation.

The current trend for supporting neonates with respiratory distress syndrome is nasal continuous positive airway pressure (CPAP). Nearly half of all neonates who are supported with CPAP will still develop respiratory failure that requires potentially injurious endotracheal intubation and invasive ventilation. Thus, the role of any neonatal clinician is to minimize invasive ventilation whenever possible, to avoid the multitude of complications that can arise when using this form of therapy. Noninvasive ventilation (NIV) is a form of respiratory assistance that provides greater respiratory support than does CPAP and may prevent intubation in a larger fraction of neonates who would otherwise fail CPAP. With the inception of nasal airway interfaces, clinicians have ushered in many different forms of NIV in neonates, often with very little experimental data to guide management. This review will explore in detail all of the different forms of neonatal NIV that are currently focused within an area of intense clinical investigation.

Nasal continuous positive airway pressure (CPAP) is a noninvasive form of respiratory assistance that has been used to support spontaneously breathing infants with lung disease for nearly 40 years. Following reports that mechanical ventilation contributes to pulmonary growth arrest and the development of chronic lung disease, there is a renewed interest in using CPAP as the prevailing method for supporting newborn infants. Animal and human research has shown that CPAP is less injurious to the lungs than is mechanical ventilation. The major concepts that embrace lung protection during CPAP are the application of spontaneous breathing at a constant distending pressure and avoidance of intubation and positive-pressure inflations. A major topic for current research focuses on whether premature infants should be supported initially with CPAP following delivery, or after the infant has been extubated following prophylactic surfactant administration. Clinical trials have shown that CPAP reduces the need for intubation/mechanical ventilation and surfactant administration, but it is still unclear whether CPAP reduces chronic lung disease and mortality, compared to modern lung-protective ventilation techniques. Despite the successes, little is known about how best to manage patients using CPAP. It is also unclear whether different strategies or devices used to maintain CPAP play a role in improving outcomes in infants. Nasal CPAP technology has evolved over the last 10 years, and bench and clinical research has evaluated differences in physiologic effects related to these new devices. Ultimately, clinicians' abilities to perceive changes in the pathophysiologic conditions of infants receiving CPAP and the quality of airway care provided are likely to be the most influential factors in determining patient outcomes.

Inhaled nitric oxide (INO) is a colorless, odorless gas that is also a potent pulmonary vasodilator. When given via the inhaled route it is a selective pulmonary vasodilator. INO is approved by the...