title: Factors influencing delivered mean airway pressure during nasal CPAP with the RAM cannula.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors: 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.
authors: Jeffrey S
authors: JS
authors: Gerdes
authors: Section on Newborn Pediatrics, Pennsylvania Hospital, Philadelphia, Pennsylvania.|Department of Pediatrics, Division of Neonatology, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors: Emidio M
authors: EM
authors: Sivieri
authors: 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.
authors: Soraya
authors: S
authors: Abbasi
mesh_terms: D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008168:Lung / Q000503:physiopathology*; D008954:Models, Biological; D009296:Nasal Cavity / Q000503:physiopathology; D011312:Pressure; D012122:Ventilators, Mechanical
keywords: NCPAP; mean airway pressure; nasal cannula; nasal prongs; premature infant; upper airway model