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S R Kaye

Publications and source records attributed to S R Kaye.

9 recordsLinked to original sources
PubMed1997

On the asymmetry of bifurcations in the bronchial tree.

The branching pattern of the conducting airways is significantly asymmetrical in the human, and even more so in other species. Although this asymmetry is believed to have an important effect on air flow and other transport processes in the bronchial tree, both experimental and theoretical studies have predominantly employed symmetrical model bifurcations. In this paper, published morphometric data for four species (human, dog, rat and hamster) is used to calculate the frequencies with which different degrees of asymmetry occur, and to examine the relationships between four of its manifestations, asymmetry of the cross-sectional areas, the lengths, the branching angles and the flow rates of the daughter branches. The observed characteristics are compared with some of the theoretical 'branching laws' which have been proposed. Quantification of the correlations between the different manifestations of asymmetry allows the geometrical characteristics to be specified for a range of realistic asymmetrical bifurcations, for use in either theoretical or experimental studies of transport in the bronchial tree.

Animals↗
PubMed1995

Diameter-based analysis of the branching geometry of four mammalian bronchial trees.

A diameter-based classification technique, which we have previously used to analyse human bronchial geometry (Phillips et al., Respir. Physiol. 98: 193-217, 1994) is applied also to the partial measurements of the dimensions of dog, rat and hamster conducting airways, made by Raabe et al. (Tracheobronchial Geometry: Human, Dog, Rat, Hamster, 1976). The local branching patterns are characterised by means of three parameters, which reflect the asymmetry and the degree of expansion at each bifurcation, and the ratio of the length of each branch to its diameter. The mean values of these parameters as functions of diameter, calculated from the raw morphometric data, are shown for the four species. A statistical reconstruction technique is then used to estimate from the incomplete measurements of Raabe and coworkers some geometrical properties of the whole system of conducting airways, which are likely to influence transport processes in the lung. These include the distribution of the total airway volume between branches of different diameters, the mean and variance of the total lengths of different pathways through the bronchial tree, and a simple model for the variation of flow velocity with airway diameter. Our results show significant differences between the branching structures of all four species. In particular, the human differs from the others in branching much more symmetrically, and in that branches of a given diameter are typically much longer than in the other species; together, these observations imply that the human bronchial tree is geometrically very different from those of the other species.

Animals↗
PubMed1994

A diameter-based reconstruction of the branching pattern of the human bronchial tree. Part I. Description and application.

We propose an analysis of the branching pattern of the conducting airways of the human bronchial tree, based on classifying airways by diameter rather than by some essentially topological measure of their position in the whole lung. A diameter-based statistical reconstruction technique is applied to the partial measurements of airway dimensions made by Raabe et al. (1976), to quantify some aspects of bronchial geometry likely to influence transport processes in the lung. We give predictions for the total number of airways with each diameter, and for the partitioning of the total bronchial wall area and airway volume between airways of different diameters. We also consider the variability of the lengths of different pathways through the bronchial tree, and using a simple model for the distribution of air flow in the lung, we predict how the average flow velocity depends on airway diameter. Comparison of these results with equivalent predictions derived from Weibel's symmetrical lung model shows qualitative differences, which probably result from Weibel's use of extrapolation techniques to compensate for the lack of data on smaller conducting airways. Comparison with the predictions of Horsfield and Cumming's asymmetrical lung model shows generally good agreement, although there are significant differences relating to the asymmetry of bifurcations and to the diameter-dependence of the flow velocity in the smallest conducting airways.

Airway Resistance↗
PubMed1994

A diameter-based reconstruction of the branching pattern of the human bronchial tree. Part II. Mathematical formulation.

In this paper we present the mathematical details of the diameter-based reconstruction technique used in the companion paper (Phillips et al., 1994 - referred to below as Part I) to analyse the morphometric data of Raabe et al. (1976) on the human bronchial tree. In the first section we outline the technique as applied to the incomplete set of measurements in order to estimate properties of the bronchial tree as a whole; in the second section we consider what form these properties would take if the bronchial tree were geometrically self-similar, as has often been assumed to be approximately the case.

Airway Resistance↗
PubMed1993

Dispersion and uptake in a coiled tube.

We have investigated the dispersion characteristics of a highly soluble tracer gas in a coiled tube lined with wet gelatine. Our experiments indicate that absorption and desorption of the gas at the wall dominates tracer dispersion along the tube. The results confirm previous experiments in a branching geometry indicating that the influence of secondary flows on dispersion is reduced if the tracer is very soluble in the wall.

Absorption↗
PubMed1993

An experimental model of gas dispersion and uptake at the bronchial wall.

Dispersion and uptake of gas boli of a range of solubilities was examined in lung airway models; first a straight tube, then a four generation network. Airway liquid lining was simulated with gelatin. The bolus dispersion was determined from the first three moments of the concentration profile measured at two positions down-stream. The disruption of the flow by the bifurcations significantly reduces the dispersion of an insoluble gas, compared to that predicted in an equivalent network of parallel straight tubes. Retention of gas in the wall increases with solubility causing increased bolus dispersion and decreased average speed. For highly soluble gases this process dominates and the effect of bifurcations becomes less significant.

Absorption↗