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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
1
|
| pubmed:dateCreated |
1993-4-6
|
| pubmed:abstractText |
Measurement of input respiratory impedance is carried out by superimposing forced oscillations on spontaneous breathing. The latter thus acts as a quasi-steady unidirectional flow component, with effects on the measured impedance that are habitually neglected (linearity assumption). We examined the validity of that assumption in the case of a turbulent steady flow. We tested the validity of a fluid dynamics criterion previously proposed in water channel experiments for gas flow in a tube. This criterion states that oscillatory and continuous turbulent flow may or may not interact if the Stokes boundary layer (ls) is embedded within the viscous sublayer (lv), i.e., if lS+ = lS/lv < or = 10, implying Re7/8 < or = (100 alpha/square root of 2), for a fully developed hydraulically smooth turbulent flow in a tube (where alpha is Womersley parameter and Re is Reynolds number of the steady-flow component). Experiments were performed in long rigid circular and semicircular tubes by superimposing two independent well-defined flows: 1) laminar oscillatory flow obeying the linear transmission line model (frequency = 1.5-250 Hz, i.e., alpha = 6-80) and 2) fully developed turbulent flow characterized by Blasius resistance formula (Re = 3,000-16,000). Confirming the validity of the criterion above, we found that the real and the imaginary parts of the long-tube impedance did not differ from those measured in the absence of a steady-flow component, provided lS+ < or = 10. On the contrary, the real parts measured with and without the continuous component differed greatly as soon as lS+ > 10, both for circular and semicircular tubes and for outward as well as inward steady flows. We concluded that the proposed criterion is pertinent for predicting appropriate oscillation frequency for a given rate of spontaneous flow, such that oscillatory and turbulent flows do not interact. Application of the forced oscillation measurement technique during spontaneous breathing requires use of a range of oscillatory frequencies higher than the frequency range classically used during apnea.
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| pubmed:language |
eng
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| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:status |
MEDLINE
|
| pubmed:month |
Jan
|
| pubmed:issn |
8750-7587
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
74
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
116-25
|
| pubmed:dateRevised |
2008-11-21
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| pubmed:meshHeading |
pubmed-meshheading:8444681-Air Movements,
pubmed-meshheading:8444681-Air Pressure,
pubmed-meshheading:8444681-Airway Resistance,
pubmed-meshheading:8444681-Intubation, Intratracheal,
pubmed-meshheading:8444681-Models, Biological,
pubmed-meshheading:8444681-Respiratory Physiological Phenomena,
pubmed-meshheading:8444681-Viscosity
|
| pubmed:year |
1993
|
| pubmed:articleTitle |
Interaction of oscillatory and steady turbulent flows in airway tubes during impedance measurement.
|
| pubmed:affiliation |
Institut National de la Santé et de la Recherche Médicale Unité 296, Centre Hospitalo-Universitaire Henri Mondor, Créteil, France.
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| pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
|