Resistance to Gas Flow across 14 CPAP Devices for Newborns

Abstract

We evaluated the resistance to gas flow in vitro in regular and trimmed endotracheal tubes of different size and in several commercially available nasal CPAP devices of different size. The highest resistance—141 cm H₂O/L/s at 6 L/min flowrate and 92 cm H₂O/L/s at 3 L/min—was present in the longest nasal device (6.0 cm) with the smallest diameter (ID, 1.7 mm; OD, 2.5 mm). Of the shorter nasal devices (0.5-1.0 cm), the one with the largest diameter (ID, 3.0 mm; OD, 5.5 mm) had the lowest resistance—11 cm H₂O/L/s at 6 L/min flowrate and 8 cm H₂O/L/s at 3 L/min. The resistance present in most devices was similar to the natural resistance in the upper airway and, therefore, should have minimal impact on the work of breathing.