The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

EFFECT OF SPONTANEOUS PEAK FLOW AND HIGH NASAL GAS FLOW ON UPPER AIRWAY PRESSURE.

Jonathan B.Waugh, PhD and Wesley M. Granger, PhD. University of Alabama at
Birmingham, Birmingham, AL.

INTRODUCTION: The purpose of this bench study was to determine the
variation in airway pressure differences [peak-to-valley (P-V)] and consistency at
different flows delivered by a high flow nasal cannula.

METHODS: A Vapotherm 2000i high flow nasal cannula was used at settings of 6, 20, and 40
L/min. Spontaneous breathing through a Laerdal Airway Management Modelwas simulated using a Michigan Instruments TTL lung simulator configured similar to the system described by Op’t Holt, et al (Respir Care 1982;27:1200-1209). The test system was set to achieve peak inspiratory and expiratory flow rates of 60 L/min. The P-V pressure differences from 50 breaths were measured
at each nasal cannula flow level. RESULTS: The coefficient of variation (CV) values were: 3.16 (6 L/min group), 4.96 (20 L/min group), and 6.60 (40 L/min group). The average P-V pressure difference was calculated for each flow level group and the absolute P-V difference for each breath was subtracted from the group mean and compared by ANOVA. The variations for each group indicated by this method were statistically different (p<0.001). See graph for data



distributions.

CONCLUSIONS: These results from simulated spontaneous
breathing flow rates double that of typical resting ventilation yielded CV values
close to the traditional 5% standard. The pressure variations around the mean
difference were significant and increased as the cannula flow rate increased. This
flow-controlled device gave relatively consistent P-V pressure differences across
its operating range. Comparison to human data at similar flows would be helpful.

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