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Biomedical subjects

G Pelle

Publications and source records attributed to G Pelle.

26 records · Page 2Linked to original sources
PubMed1987

Density and frequency dependence of resistance in early airway obstruction.

The forced oscillation technique is a noninvasive and effort-independent test used to characterize the mechanical impedance of the respiratory system. The aim of this study was to assess the sensitivity of this method in detecting early airway abnormalities caused by smoking or occupational hazards. Respiratory mechanical parameters by the forced oscillation technique and maximal expiratory flow volume (MEFV) curves were obtained in a group of 82 workers from a gas manufacturing plant. In addition, the variations in the frequency dependence of total respiratory resistance between air breathing and a mixture of helium-oxygen (He-O2) were measured. All parameters were normalized for age, height, and weight. In order to compare the 2 types of testing, multiple linear regressions were performed with smoking or exposure as independent variables on one hand and parameters of the 2 types of testing on the other hand. This statistical procedure showed that 2 parameters of the forced oscillation technique constantly reached higher levels of significance than those of the MEFV parameters in the regression equations describing smoking history and occupational exposure: these were the frequency dependence of resistance and the change in frequency dependence between air and He-O2 breathing. When nonsmokers, ex-smokers, and smokers were considered separately, the degree of frequency dependence of resistance and the change in frequency dependence between air and He-O2 breathing were the only parameters that were significantly different between these 3 groups (one-way analysis of variance).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Real-time detection of ventilatory maneuvers by a microcomputer.

The SYTER software system was built around an Apple II microcomputer to automatically process the data yielded by three ventilatory tests: analysis of lung elasticity during an expiratory maneuver, plethysmographic measurement of airway resistance during a panting maneuver, and similar measurements of lung volumes. A volume signal is displayed to the operator throughout each test to help control the maneuver. The various stages of the test are recognized in real time by routines written in assembling language, so that significant data are displayed and stored during the maneuver. This paper describes the algorithms used to perform waveform analysis, and presents illustrative displays obtained in the Lung Function Laboratory.

Airway Resistance↗
PubMed1985

On line determination of airway resistance by plethysmography and microcomputer.

On line determination of airway resistance is carried out by an Apple II connected to a flow body plethysmograph. Recognition of the panting maneuver is performed in real time. Linear drift of plethysmographic volume V is eliminated by taking the derivatives V and Vm of V and mouth flow Vm. Linear regression of V on Vm yields an estimate R of airway resistance, at a volume close to functional residual capacity FRC. The values of FRC is given by linear regression of V on Pm, the derivative of mouth pressure. No significant difference has been found between the estimates of the specific conductance sG calculated by linear regression and by spectral analysis of V and Vm. As variability of sG can be kept below 10%, the regression technique appears to be reliable for routine patient testing and pharmacological studies.

Airway Resistance↗
PubMed1985

[Normalization of the dimensions of the left ventricle as measured by echocardiography].

An M mode echocardiographic study was performed, of left ventricular dimensions and wall thickness in two series of normal (N1, N2) and pathological (P1, P2) subjects. In the more recent series (N2 = 40, P2 = 17) data acquisition was facilitated by tests deduced from the technique of ultrasound transit time. The parameters compared were based on: 1) the proportionality between fractional shortening and fractional thickening (N1: not significant; N2: p less than 0.001), 2) the relationship between systolic radius and wall thickness (linear correlation, r = 0.95, between N2 and P2). The slope seemed to be related to the initial condition of contraction, the ratio of end diastolic wall thickness/radius (N1: p less than 0.01). There are several ways of normalising myocardial surface of section in adults and children; the normal surface is related to body surface area (r = 0.87; p less than 0.001 between calculated and predicted values for a N2 mean of 9.3 +/- 0.06 cm2/m2). The end diastolic diameters and wall thicknesses correlated with body surface area but the coefficients were not as statistically significant due to physiological variations in chamber filling. The indexed myocardial surface was increased (p less than 0.001) in the pathological series. The introduction of these tests improves the reliability of echocardiographic data. The use of several measurements simultaneously allows normalisation of body surface area and increases the diagnostic efficacy.

Echocardiography↗
PubMed1984

Theoretical models in mechanics of the left ventricle.

Different rheological concepts and theoretical studies have been recently presented using models of myocardial mechanics. Complex analysis of the mechanical behavior of the left ventricular wall have been developed in order to estimate the local stresses and deformations that occur during the heart cycle as well as the ventricular stroke volume and pressure. Theoretical models have taken into account non-linear and viscoelastic passive properties of the myocardium tissue, when subjected to large deformations, through given strain energy functions or stress-strain relations. Different prolate spheroid geometries have been considered for such thick shell cardiac structure. During the active state of the contraction, the rheological behavior of the fibers has been described using different muscle models and relationships between fiber tension and strain, and activation degree. A forthcoming approach for bridging the gap between the knowledge of the muscle fiber microrheological properties and the study of the mechanical behavior of the entire ventricle, consists in including anisotropic and inhomogeneous effects through fiber direction field.

Animals↗