The effects of CPAP differ with the ventilation phase. recently showed that HFNC reduced the electrical activity of the diaphragm and decreased esophageal pressure swings, confirming the effectiveness of this therapy to reduce the work of breathing. In infants with bronchiolitis, Pham et al. It reduces obstructive apnea and supports the inspiratory effort when patient flow is limited. The pressures generated by the device prevent pharyngeal collapse, which may be very pronounced in some diseases.
Recording of the pharyngeal pressure (PP) at 1 and 7 L/min in an infant. The sinusoidal shape persisted when we increased the flow, but the two pressure components (inspiratory and expiratory) became positive after 7 L/min, thereby generating real CPAP. The pharyngeal pressure at a rate of 1 L/min appeared like a sine wave around the air pressure, being negative during inspiration and positive during expiration (Figure 2). Unfortunately, despite the overall shape of the curve, we could not predict whether a higher flow would provide greater pressure. When we indexed the flow to patient weight, we observed that the average pressure with a flow of 2 L/kg/min was about 4 cm H 2O. In a physiological study of infants with acute viral bronchiolitis, we measured pharyngeal pressure over the course of a gradual increase in flow up to 7 L/min (Figure 1). The inter- and intra-individual variations are nevertheless quite wide.
The pressure is determined not only by the flow, but also by the ratio of the prong/nostril fit and whether or not the mouth is closed. The range of indications for HFNC is also likely to broaden in the future, and further studies are therefore needed to ensure that the guidelines for use are evidence-based.Ī high-flow mixture is likely to create a maximum positive pharyngeal pressure of about 6 cm H 2O during expiration. Since the critical review of HFNC use in ill infants, children, and adults, additional physiological and clinical data have been reported, particularly in infants with acute viral bronchiolitis. Initiating HFNC is relatively simple, but close monitoring is essential. Its mode of action is original and complex. The cannula was first employed in intensive care units (ICUs), then in emergency departments, and today is finding use during pre- or inter-hospital transport.Ĭlinicians are quite rightly raising questions about where it should be positioned among the systems of noninvasive respiratory support, such as high-concentration face masks and nasal CPAP. Its use in pediatrics departments is more recent and generally is restricted to children with moderate bronchiolitis. Over the last decade, high-flow nasal cannula (HFNC) has increasingly been used for oxygen delivery in neonatology departments, gradually replacing nasal continuous positive airway pressure (CPAP).
As for any form of respiratory support, HFNC initiation in patients requires close monitoring, whether it be for pre- or inter-hospital transport or in the emergency department or the pediatric intensive care unit. But, the experience with this device in neonatology and adult intensive care may broaden the pediatric indications to include weaning from invasive ventilation and acute asthma. Currently, most of the studies in the pediatric literature suggest the benefits of HFNC therapy only for moderately severe acute viral bronchiolitis. HFNC may also create positive pharyngeal pressure to reduce the work of breathing, which positions the device midway between classical oxygen delivery systems, like the high-concentration face mask and continuous positive airway pressure (CPAP) generators. The use of nasal cannula adapted to the infant’s nares size to deliver heated and humidified gas at high flow rates has been associated with improvements in washout of nasopharyngeal dead space, lung mucociliary clearance, and oxygen delivery compared with other oxygen delivery systems. In pediatrics, HFNC use continues to increase as the system is easily set up and is well tolerated by patients. High-flow nasal cannula (HFNC) is a relatively new device for respiratory support.
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