![]() ![]() In vivo and in vitro hot wire anemometry measurements at the exterior nares indicated low velocity and turbulence intensity flows at peak inspiration and a high velocity jet with high turbulence during peak expiration. ![]() Introduction of NHF therapy produced significant increases in all mean and peak airway pressures within the upper airway with a flow rate of 30 LPM fulfilling the inspiratory work requirements presented by the upper airway resistance. In vitro measurements of static pressure during natural breathing found similar flow resistances across the nasal passage for inspiratory and expiratory flow directions however, across the entire upper airway greater resistance was seen for inspiration. In vivo measurement of a natural breathing flow pattern was scaled to an average population tidal volume and respiratory rate for in vitro use. The human respiratory system was faithfully replicated for CO2 washout experiments with physiological CO2 diffusion into the lung replicated by a constant flow of CO2 into the lung pump. Two proposed mechanisms of action, the CO2 washout of anatomic dead space and the production of positive airway pressure, are investigated in this thesis for the use of the Fisher & Paykel Healthcare Ltd (FPH) Optiflow™ adult nasal cannula through a range of experiments.įive anatomically correct upper airway models produced from computed tomography (CT) scan data via 3D printing were employed during in vitro experiments and two live subjects participated in in vivo measurements. A number of in vivo studies have proven its effectiveness at improving blood oxygenation however, its mechanisms of action remain widely unproven. Nasal high flow (NHF) therapy is a recent form of non-invasive respiratory support for patients suffering from respiratory distress that supplies high flows of heated and humidified air, oxygen or a mix via a nasal cannula. ![]()
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