Does Increasing Flow To A High Flow Nasal Cannula Affect Mean Airway Pressure In An In Vitro Model?

Abstract

DOES INCREASING FLOW TO A HIGH FLOW NASAL CANNULA AFFECT MEAN AIRWAY PRESSURE IN AN IN VITRO MODEL? Introduction: High-flow nasal cannulas (HFNC) have become popular with many institutions for administration of oxygen (O2). HFNCs are also being used in pediatric and neonatal populations for administration of continuous positive airway pressure (CPAP) as a treatment for respiratory distress. Adult patients are being treated with HFNCs in a effort to provide a high percentage of O2 and correct hypoxemia and other related conditions. The purpose of this study was to examine the effect of increasing flow via a HFNC to an in vitro model to examine the effect of flow on mean airway pressure (MPAW). Method: An in vitro model to simulate non-labored and labored spontaneous breathing was developed using a Michigan Instrument Laboratory Test and Training Lung (MIL TTL) driven by a Hamilton Galileo ventilator to produce a negatively based, inspired tidal volume. Flow was introduced to the MIL TTL via a 41 French double lumen endotracheal tube. Airway pressure measurements were observed via a pressure monitoring port placed between the MIL TTL and the endotracheal tube and connected to the auxiliary pressure monitoring port located on the front of the Galileo ventilator. A Vapotherm 2000i with adult transfer chamber and adult cannula, a Fisher Paykel Optiflow, and a generic HFNC consisting of a concha column and a Salter labs high-flow cannula were tested at 20, 30, and 40LPM flowrates. Data was recorded using two respiratory rates (12 and 24) and two peak flowrates (35 and 65LPM) to simulate nonlabored and labored breathing. All other parameters were unchanged and the I:E ratio was consistent. Data Analysis: SPSS 16.0 for Windows was used to analyze all data for this study. Descriptive statistics, one-way analysis of variance (ANOVA), and post hoc Bonferroni was used for this study. A p value less than 0.05 were considered significant. Results: Average MPAW for all devices were increased at all three flowrates. MPAW was highest at 40LPM flow producing 3.1cmH2O averaged for all HFNCs and both respiratory patterns. The difference in MPAW produced by the three HFNCs were also significant with at p=0.000 at all flow rates. Post hoc Bonferroni adjusted probabilities further showed all device comparisons significant except for VapothermVapotherm Labored at 30 and 40 LPM flow rates and Vapotherm-Generic Labored at 20 LPM at p 0.05 and were statistically equal. The generic HFNC produced the highest MPAW (3.5cmH2O). Conclusion: Increased flow via a HFNC does increase MPAW. The Vapotherm, Optiflow, and generic HFNC did not produce the same level of MPAW in this study. DOES INCREASING FLOW TO A HIGH FLOW NASAL CANNULA AFFECT MEAN AIRWAY PRESSURE IN AN IN VITRO ADULT MODEL?