The Science Journal of the American Association for Respiratory Care

2012 OPEN FORUM Abstracts


Dave N. Crotwell, Donna Dupras, Robert DiBlasi; Respiratory Care, Seattle ChildrenÂ’s Hospital, Seattle, WA

INTRODUCTION-Heated/humidified high flow nasal cannula (HHHNC) and continuous positive airway pressure (CPAP) are two forms of non-invasive respiratory support strategy that are widely used in spontaneously breathing infants with RSV Bronchiolitis. We designed a series of descriptive studies to compare differences in lung model pressure and carbon dioxide elimination between these two forms of support. METHODS: An anatomically accurate infant nasal airway model, fabricated using a 3D printer and dimensions obtained from a CT-scan of an infant, was attached to a spontaneously breathing test lung (ASL 5000, Ingmar Medical; settings: Inspiratory muscle pressure=-13 cmH2O, R=300 ml/cmH2O, and C=2 mL/cmH2O, RR=30br/min, and Tidal Volume=26 mL, and active expiratory pressure=5 cmH2O. Prior to testing, a fixed amount of carbon dioxide was bled into the lung model to obtain a baseline ETCO2 measurement~100 mmHg during unsupported spontaneous breathing. The nasal airway model was then affixed with each of the following devices and their respective proprietary nasal airway interfaces: 1) Vapotherm Precision FLow HHHFNC, 2) Fisher-Paykel HHHFNC, 3) Carefusion Infant Flow CPAP and 4) Fisher-Paykel Bubble CPAP. Lung model pressures and ETCO2 changes were measured at baseline (no support) and after adjusting flows at 2, 4, 6, 8 L/min. RESULTS: We observed differences in the pressure delivered in the test lung between different non invasive respiratory support devices. See figure. CONCLUSION/DISCUSSION: These data suggest that both the Vapotherm and the Fisher Paykel HHHNC devices provided distending pressure to the lung model, although the Fisher Paykel system showed no increase in distending pressure after 3.5 cmH2O. We feel that the lower distending pressure from the Fisher Paykel HHHNC was attributed to its circuit pressure pop off which vents gas once circuit pressure reaches 35-45 cmH2O. Both NCPAP devices provided the set 5 cmH2O CPAP when common flows for clinical use were used. All systems tested exhibited comparable CO2 flushing capabilities, although the Infant flow NCPAP systems CO2 flushing was slightly lower than the continuous flow systems. We feel that its variable flow design impacted its ability to flush CO2, although we do not know whether this would be clinically relevant. Sponsored Research - None