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Pediatr Pulmonol. 2016 Jan;51(1):60-9. doi: 10.1002/ppul.23197. Epub 2015 Apr 7.

Factors influencing delivered mean airway pressure during nasal CPAP with the RAM cannula.

Gerdes JS1,2,3, Sivieri EM1,2, Abbasi S1,2,3.

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Section on Newborn Pediatrics, Pennsylvania Hospital, Philadelphia, Pennsylvania.
Department of Pediatrics, Division of Neonatology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.



To measure mean airway pressure (MAP) delivered through the RAM Cannula® when used with a ventilator in CPAP mode as a function of percent nares occlusion in a simulated nasal interface/test lung model and to compare the results to MAPs using a nasal continuous positive airway pressure (NCPAP) interface with nares fully occluded.


An artificial airway model was connected to a spontaneous breathing lung model in which MAP was measured at set NCPAP levels between 4 and 8 cmH2 O provided by a Dräger Evita XL® ventilator and delivered through three sizes of RAM cannulae. Measurements were performed with varying leakage at the nasal interface by decreasing occlusion from 100% to 29%, half-way prong insertion, and simulated mouth leakage. Comparison measurements were made using the Dräger BabyFlow® NCPAP interface with a full nasal seal.


With simulated mouth closed, the Dräger interface delivered MAPs within 0.5 cmH2 O of set CPAP levels. For the RAM cannula, with 60-80% nares occlusion, overall delivered MAPs were 60 ± 17% less than set CPAP levels (P < 0.001). Further, MAP decreased progressively with decreasing percent nares occlusion. The simulated open mouth condition resulted in significantly lower MAPs to <1.7 cmH2 O. The one-half prong insertion depth condition, with closed mouth, yielded MAPs approximately 35 ± 9% less than full insertion pressures (P < 0.001).


In our bench tests, the RAM interface connected to a ventilator in NCPAP mode failed to deliver set CPAP levels when applied using the manufacturer recommended 60-80% nares occlusion, even with closed mouth and full nasal prong insertion conditions.


NCPAP; mean airway pressure; nasal cannula; nasal prongs; premature infant; upper airway model

[Indexed for MEDLINE]

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