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W J Goedhard

Publications and source records attributed to W J Goedhard.

At least 37 records · Page 2Linked to original sources
PubMed1985

The pressure dependent dynamic elasticity of 35 thoracic and 16 abdominal human aortas in vitro described by a five component model.

Segments of 35 thoracic and 16 abdominal human aortas, including nine pairs, aged 30-78 yr at autopsy, were perfused with 37 degrees C Tyrode's solution at in situ length. Diameter changes due to 20 mmHg pressure steps between 20 and 180 mmHg were measured to 1 micron accuracy at an equivalent noise level of 0.1 micron RMS, using balanced transducers. Aortic creep curves at each pressure level were described individually by a constant plus bi-exponential creep model characterized by two creep fractions (alpha 1 and alpha 2) and two time constants (tau 1 and tau 2). Creep fractions and time constants increased substantially with the pressure level, indicating a significant effect of pressure or distension on aortic viscoelasticity. At 110 mmHg the mean +/- 1 S.D. parameter values were: thoracic aorta: alpha 1 = 0.076 +/- 0.017, alpha 2 = 0.102 +/- 0.028, tau 1 = 0.73 +/- 0.29 s, tau 2 = 14.0 +/- 4.1 s; abdominal aorta: alpha 1 = 0.078 +/- 0.017, alpha 2 = 0.101 +/- 0.025, tau 1 = 0.61 +/- 0.12 s, tau 2 = 12.1 +/- 3.4 s. Nine paired comparisons at each pressure level showed that creep fractions and time constants of thoracic and abdominal segments were not significantly different (p = 0.05).

Adult↗
PubMed1985

[The effect of aging and sclerosis on the viscoelastic properties of the human thoracic aorta].

This paper describes some results of our research on the viscoelastic properties of the human aorta. Pressure-diameter relations of 45 thoracic aortas, aged 30 to 88 years, were measured. The complex static measurement results were described by a model (formula) with three parameters. The dynamic (viscous) measurement results needed four parameters in a different model. De model parameters were next related to the age and the degree of sclerosis of the aortic segments. The results can be summarized as follows: the static properties change strongly with age; aortic compliance decreases substantially with aging; the dynamic (viscous) properties of the aorta do not change with age; although the degree of sclerosis of the aorta increased with age, we could not demonstrate a significant difference in the viscoelastic properties of 'normal' and sclerotic aortas. An explanation for the latter phenomenon was found in the dilation of the aorta which accompanies the increase of the degree of sclerosis and which serves as a hemodynamic compensation.

Adult↗
PubMed1984

The static elastic properties of 45 human thoracic and 20 abdominal aortas in vitro and the parameters of a new model.

Segments of 45 human thoracic and 20 abdominal aortas, including 13 pairs, aged 30-88 yr at autopsy, were perfused with 37 degrees C Tyrode's solution at in-situ length. Diameter changes due to 20 mmHg pressure steps, between 20 and 180 mmHg, were measured to 1 micron accuracy with balanced transducers. Absolute diameter at 100 mmHg was measured to 50 micron accuracy. At 100 mmHg, cross-sectional area ranged from 2.6 to 7.6 for thoracic and from 1.0 to 3.2 cm2 for abdominal segments. Compliances ranged from 1.9 to 17 for thoracic and from 0.6 to 4.4 mm3/mmHg.cm for abdominal segments. An arctangent model with three free parameters A(p) = Am(1/2 + tan-1 [p-p0)/p1)/pi) explained over 99% of the variance in area with pressure for each aorta. Changes in compliance, characteristic impedance and propagation velocity are equally well described. Abdominal fits on the average appeared down scaled by a factor of 2 and shifted 20 mmHg towards lower pressures from paired thoracic (significant at p = 0.001).

Adult↗
PubMed1981

[Advice on scientific research on the aged person].

A few years ago, the Ministry of Culture, Recreation and Social Welfare inaugurated a Planning group to establish a scientific program for research on ageing. This contribution gives comment on this advice just published. In general the program will only be used to a certain extent. The planning group advises to inaugurate another steering committee, that should control the research itself and its evaluation. The commentators hope that this steering committee will be enabled to apply the program in a fairly independent way. Why: because the advice lacks a strong structure. It is clear that the gerontological field is such a vast area, that it is impossible to do research on all topics. Therefore, we need some more clear alternatives to choose between. The commentators stress three different alternatives: 1. the fundamental research in bio-medical as well as in behavioural sciences; 2. the major practical problems of ageing people and their support; 3. accent on development of methods and measures. The comment emphasizes also the conditions for research-education at university level and the stimulation of grants for developing new research projects. In addition, some remarks are made about the composition of the planning group. Unfortunately, in that group the medical practitioner and the psychologist were missing.

Aged↗
PubMed1979

[We all will age].

In 1977/78 the American Research-plan toward understanding aging 'Our future selves' was published. In this article the report of the panel on biomedical research is reviewed. The report appears to be very comprehensive and to give a carefully detailed research plan. It will certainly take many years to realise all the plans. Part of the research could very well be done in the Netherlands although only to a limited extent. The governmental planning-group, which is developing a research plan for gerontology in the Netherlands, should make a sensible selection out of the many items mentioned in the American plan. After all, it is of vital importance to all of us, our future selves.

Aged↗
PubMed1979

Ballistocardiography: past, present and future.

In this paper, an analysis is given of the present state of ballistocardiography. It is concluded that several aspects of the method have to be improved before successful application in medicine can follow. These aspects are, for example, (a) physiological backgrounds of the method, and (b) signal analysis of the ballistocardiogram. Recent developments on these items are discussed and some preliminary results are given. Research on ballistocardiography is worthwhile to be continuing, since the method offers good perspectives for application in preventive medicine (early detection of coronary heart disease) and in clinical medicine.

Adult↗