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 Decades of research in the neonatal intensive care unit have focused on making every breath easier for infants' fragile lungs.
One effective method, first described in 1971, uses nasal continuous positive airway pressure to provide noninvasive respiratory support for premature infants, both early in their course and upon extubation from mechanical ventilation.
However, use of nasal CPAP can be clinically challenging, and humidified high-flow nasal cannula (HHFNC) therapy is gaining popularity as an alternative noninvasive respiratory support modality. It is increasingly used in patient populations previously treated with nasal CPAP, though definitive demonstration of safety and efficacy is lacking.
Neither modality will ever completely supplant mechanical ventilation, but both hold promise as therapies to decrease long-term pulmonary morbidity among NICU survivors.
Inner workings
Nasal CPAP is used to provide noninvasive respiratory support for infants with a wide range of pulmonary diseases, as well as premature infants with central apnea. It can be used as primary support, as an alternative to intubation and mechanical ventilation, and as transitional support at the time of endotracheal extubation.
Numerous devices and methods of providing this therapy now are commercially available.1 It works by improving alveolar recruitment, stabilizing functional residual capacity, and increasing intrathoracic gas volume. By increasing alveolar gas exchange surface area, nasal CPAP decreases ventilation/perfusion mismatch. It can be delivered by continuous flow (e.g., bubble CPAP or via a ventilator) or variable flow (e.g., infant flow driver).
Variable-flow CPAP enables patient exhalation to induce variation, or "flip," in the flow delivered at the nosepiece, and exhalation is directed through an expiratory channel. These flow characteristics help decrease airway resistance and expiratory work of breathing. By also allowing air entrainment through the expiratory channel, an infant potentially may add to inspiratory flow during a large or vigorous spontaneous breath. Evidence has shown variable-flow CPAP achieves lower work of breathing and greater lung recruitment than continuous-flow CPAP.2,3 All dedicated nasal CPAP systems use a combination of harness or cap and prongs or nasal mask to deliver positive pressure to the airway. Consistency in the intrathoracic pressure delivered by nasal CPAP depends upon a closed system with a good seal of the prongs in the nares, patency of the prongs and upper airway, and the absence of an open mouth.4 Acute changes in mouth closure and prong flow can alter airway pressure and potentially contribute to air leak.
Some units routinely use chin straps to keep an infant's mouth closed while on nasal CPAP, while others do not. In practice, simply keeping a pacifier in the mouth appears to be an effective way to sustain oropharyngeal pressure.
Avoiding complications
Excessive localized pressure on any skin interface can lead to pressure necrosis. A common complication of nasal CPAP is pressure necrosis of the tip of the nose, nasal septum, nares, or philtrum.
Common causes of this potentially disfiguring complication include improperly fitted nasal prongs, harness, or cap, and asymmetric or excessive tension of the securing straps. Prongs that are too large exert undue pressure on the mucosal surfaces. Prongs that are too small result in leak, which can prompt the unwary therapist or nurse to tighten the straps, resulting in excessive pressure. Improvements in the material and design of CPAP prongs have alleviated some of the risks, but in the smallest infants, particularly those less than 1,000 grams, maintaining proper fit and pressure distribution can be nearly impossible.
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