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 non-labored 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 Vapotherm-Vapotherm Labored at 30 and 40 LPM flow rates and Vapotherm-Generic Labored at 20 LPM at p<0.05. These three comparisons were 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.

Background: HFNC system is a novel device used with aerosol therapy and seems to be rapidly accepted. Although there are some studies conducted on HFNC and vibrating mesh nebulizer, the effect of HFNC on aerosol delivery using jet nebulizer or pressurized metered-dose inhaler (pMDI) has not been reported. In an effort to examine the effect of HFNC on aerosol deposition, this study was conducted to quantify aerosol drug delivery with or without a HFNC using either pMDI or jet nebulizer. Methodology: The SAINT model, attached to an absolute filter (Respirgard II, Vital Signs Colorado Inc., Englewood, CO, USA) for aerosol collection, was connected to a pediatric breathing simulator (Harvard Apparatus, Model 613, South Natick, MA, USA). To keep the filter and the SAINT model in upright position to collect aerosolized drug, an elbow adapter was connected between the absolute filter and the breathing simulator. An infant HFNC (Optiflow, Fisher & Paykel Healthcare LTD., Auckland, New Zealand) ran at 3 l/min O2 was attached to the nares of the SAINT model. Breathing parameters used in this study were Vt of 100 mL, RR of 30 breaths/min, and I:E ratio of 1: 1.4. Aerosol drug was administered using: 1) Misty-neb jet nebulizer (Allegiance Healthcare, McGaw Park, Illinois, USA) powered by air at 8 l/min using pediatric aerosol facemask (B&F Medical, Allied Healthcare Products, Saint Louis, MO, USA) to deliver albuterol sulfate (2.5 mg/3 mL NS), and 2) Four actuations of Ventolin HFA pMDI (90 μg/puff) (GlaxoSmithKline, Research Triangle Park, NC, USA) combined with VHC (AeroChamber plus with Flow-Vu, Monaghan Medical, Plattsburgh, NY, USA). Aerosol was administered to the model with and without the HFNC and another without (n=3). Drug was collected on an absolute filter, eluted and measured using spectrophotometry. Independent t tests were performed for data analysis. Statistical significance was determined with a p value of <0.05. Results: The mean inhaled mass percent was greatest for pMDI with (p = 0.0001) or without HFNC (p = 0.003). Removing HFNC from the nares before aerosol treatment trended to increase drug delivery with the jet nebulizer (p = 0.024), and increased drug delivery by 6 fold with pMDI (p = 0.003). Conclusions: Aerosol drug may be administered in pediatrics receiving HFNC therapy using either jet nebulizer or pMDI. However, using pMDI, either with or without HFNC, is the best option. When delivering medical aerosol by mask, whether by jet nebulizer or pMDI, removing HFNC led to an increase in inhaled mass percent. However, the benefit of increased aerosol delivery must be weighed against the risk of lung derecruitment when nasal prongs are removed.