Date of Award

5-10-2021

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Respiratory Therapy

First Advisor

Douglas S. Gardenhire, EdD, RRT, RRT-NPS, FAARC

Second Advisor

Robert B. Murray, MS, RRT

Third Advisor

Kyle J. Brandenberger, PhD

Abstract

Introduction: High flow nasal cannulas (HFNC) are an oxygen supply device that has become increasingly popular. This high flow therapy was initially utilized in the neonatal populations for treatment of conditions such as bronchiolitis and respiratory distress. The mechanism of treatment behind HFNC in these conditions relies upon the large amount of flow which produces continuous positive airway pressure (CPAP) against the airways. This pressure maintains the structural patency of the airway, allowing for continuous flow during inspiration and expiration. The small amount of CPAP generated by the HFNC assists in oxygenation and gas exchange by expanding the size of alveoli at end expiration and generating a greater surface area for diffusion across the alveolar capillary membrane. The purpose of this study was to determine if greater flows generated from the HFNC to a pediatric in vitro model would affect the mean airway pressure (MAP). Method: A pediatric in vitro model was utilized to simulate two spontaneous breathing patterns with the use of a Dual Adult Test and Training Lung (TTL) connected to a Hamilton-G5 ventilator. Positive pressure ventilation delivered to one side A of the Dual Adult TTL simulated a spontaneously breathing negative pressure model on the other side B of the Dual Adult TTL. The two sides of the Dual Adult TTL were connected via a wooden board and clamped to cause simultaneous movement of both lungs. HFNC delivered flow to side B through a fabricated airway. A pressure sensor placed between the MIL TTL and the fabricated airway and connected to an auxiliary pressure monitoring port on the Hamilton-G5 ventilator. Three different HFNC were used and tested at two various flows (10, 15, and 20 liters per minute (L/min)) and two different respiratory patterns (labored and unlabored). No other parameters were changed. Data Analysis: two-way analysis of variance (ANOVA), descriptive statistics, and post hoc Bonferroni were used for this study. SPSS 26.0 for Windows was used for all data analysis in this study Results: The average MAP produced by all three HFNC were increased at all flow rates. Greater flow rates up to 20 L/min created a greater amount of MAP, an average of 2.34 cm H2O and 2.49 for unlabored and labored breathing pattern respectively at 20 L/min. The Hudson HFNC generated the greatest MAP of all three HFNC (3.81 cm H2O at 20 L/min, labored breathing pattern). Based on ANOVA analysis, increased flows through all devices were statistically significant based on a p value of 0.05. Conclusions: A significant difference in MAP was found between flow rates for all devices and simulated breathing patterns, devices for all flow rates and simulated breathing patterns, and both simulated breathing patterns for all devices and flow rates.

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