Oscillatory velocity profiles and the pressure-flow relationship were measured in a 3:1 scale rigid model of the human central airways. A reciprocating pump provided flows with frequencies of 0.25, 1, 2 and 4 Hz and tidal volumes of 300, 500 and 1500 mL giving tracheal Womersley numbers up to 31 and peak tracheal Reynolds numbers up to 17000. A hot wire anemometer was used to measure velocities along two perpendicular diameters (one in the plane of the model and the other in the plane perpendicular to the model) at 10 stations distributed through the model. Velocities were also measured with and without a model larynx and with tracheal intubation in steady inspiratory flows. The flow distribution to the five lobar bronchi was identical in all experiments. / Oscillatory velocity profiles were compared with the steady velocity profiles at nearly identical Reynolds numbers. The flow in a branch was quasi-steady below a critical Strouhal number in agreement with an order of magnitude analysis. For quasi-steady oscillatory flows the velocity profile developed from an initially flat shape to the profiles characteristic of steady flow in branching tubes. Flows that were not quasi-steady exhibited relatively flat profiles over the entire respiratory cycle. The effects of tidal volume, frequency and the geometry of the airways on the velocity profiles were determined. / While the larynx produced a significant jet within the trachea it had no effect on the velocity profiles beyond the carina. The presence of a concentric endotracheal tube located halfway between the glottis and the carina had little effect on the velocity profiles in the main stem and the lobar bronchi. Inserting the tube further into the trachea altered the velocity profiles in the right upper lobar bronchus. / In oscillating flow the pressure was essentially uniform around the periphery of a branch in strong contrast to the results for steady flow. The pressure drop in oscillating flow was much larger than the pressure drop in steady flow at an equivalent flow rate. The functional form of the relationship between the pressure drop across the different branches of the model and the tracheal Reynolds number was similar to that suggested by earlier researchers, however the coefficients were very sensitive to the geometry of the model.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.72009 |
| Date | January 1985 |
| Creators | Menon, Anilkumar S. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Chemical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000218901, proquestno: AAINL20873, Theses scanned by UMI/ProQuest. |
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