| Summary: | Thesis (MSc (Physiology))--University of Stellenbosch, 2000. === 251 leaves single sided printed, preliminary pages and numbered pages 1-151. Includes bibliography, list of appendixes, abbreviations, variables, figures and tables. Digitized at 300 dpi (OCR), using a Bizhub 250 scanner. === ENGLISH ABSTRACT: The Whistle Watch™, an innovative and commercialised peak flow monitor, inspired
this study, with its abnormal and complex measuring behaviour. The Whistle
Watch™ latter is an audible peak flow monitor with a threshold-activated whistle as
the essential component. The whistle is calibrated for a certain flow, and then encased
in a body with a variable exhaust valve to atmosphere. Using the Whistle Watch™,
with the exhaust valve pre-set, executing a forced expiratory effort, the audible
notification of the whistle would indicate a stable asthmatic condition at that setting.
No audible notification would result in the use of medication as a preventative
measure. Due to the absence of existing theories and literature on the mechanics of
whistles, the Whistle Watch™ was empirically developed.
This study therefore, focuses on the characterisation and consequent improved
understanding ofthe mechanics ofa whistle, with the objective to monitor pulmonary
function in a novel way.
During this study, a novel technique was developed to determine the reed activation
point, or onset of oscillation, in terms of pressure. This technique was then
implemented throughout the study.
The initial observation and experimentation underlined the whistle's activation
sensitivity towards any irregularities of the reed surface. A statistical spread of reed
activation pressures defined the reed's inherent non-linear properties. A high
dependence of reed activation towards upstream geometry was noted, and a
clarification hypothesis was formulated. The effect of reed dimensions on activation
pressure was exposed as a complex unexplored field. Existing mathematical reed
theories only accommodate steady state oscillations, whereas the completed study
indicated a high sensitivity of the reed activation pressure towards different input
envelopes. This sensitivity was encapsulated in a mathematical model, with initial
support and proofprovided by a previous independent study.
All the observed effects and phenomena had far reaching practical application
towards the production and quality control ofthe Whistle Watch™. === AFRIKAANSE OPSOMMING: Whistle Watch™, 'n inoverende, kommersieel piekvloeimonitor, was die
inspirasie vir die studie, deur sy abnorrnale en ingewikkelde meet-gedragskenrnerke.
Laasgenoemde is 'n piekvloeimonitor met 'n fluit wat geaktiveer word by 'n vooraf
vasgestelde drempel. Die fluit word gekalibreer vir 'n bepaalde vloei, waarna dit
geenkapsuleer word in 'n hoofdeel met 'n veranderlike uitlaat na die atmosfeer. By
die gebruik van die Whislte Watch™, met die uitlaatklep gestel op 'n voorafbepaalde
vloeitempo, word 'n bepaalde ekspirasievlak verkry. Hierdie vlak het 'n hoorbare
kennisgewing tot gevolg, wat 'n stabiele asmatiese toestand aandui. In die
afwesigheid van 'n hoorbare respons, word medikasie as voorkornende rnaatreel
vereis. Die Whislte Watch™ is empiries ontwikkel in die afwesigheid van bestaande
teoriee en literatuur ten opsigte van die werking van fluite.
Die fokus van hierdie studie word dus geplaas op die karakterisering van die werking
van fluite, wat 'n beter begrip tot gevolg het. 'n Nuwe benadering tot die monitering
van die pulrnonere funksie is dus haalbaar.
Tydens die studie is 'n unieke tegniek ontwikkel om die aktiveringspunt van die riet,
of die aanvang van ossilasie in terrne van druk, te bepaal. Hierdie tegniek is toe
dwarsdeur die studie geiinplimenteer.
Die fluit se aktiveringssensitiwiteit, in terrne van die oppervlak-onreelmatighede, van
die riet was duidelik waarneembaar. Die inherente nie-liniere eienskappe van die riet
is duidelik waarneembaar in rietaktiveringsdrukke. 'n Verklarende hipotese is as
gevolg van 'n afhanklikheid van die rietaktiveringsdrukke relatief tot stroom-op
geometrie, gestel. Die effek wat rietafinetings op aktiveringsdrukke het, was
blootgel~ as 'n komplekse onontwikkelde gebied. Bestaande wiskundige rietteoriee
maak slegs voosiening vir nie-fluktuerende ossilasies. Na voltooiing van hierdie
studie is dit duidelik dat daar wei 'n hoe sensitiwiteit van die rietaktiveringsdrukke
bestaan, met verwysing na verskillende ekspiratoriese profiele. Hierdie sensitiwiteit
word vervat in 'n wiskundige model met toepaslilke ondersteuning en bewyse uit 'n
vorige, onathanklike studie.
Aile waarneembare phenomena het resulterende praktiese impakte ten opsigte van die
produksie en gehalteversekering van die Whistle Watch™.
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