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Biomedical subjects

D L Newman

Publications and source records attributed to D L Newman.

At least 37 records · Page 2Linked to original sources
PubMed1990

What is evaluation: nurse decision-makers' perceptions of program evaluation.

This study investigates alternate reasons for conducting program evaluation in community health care settings and their relationship with information needs. One hundred and thirty-six community health nurses representing New York state associations were the decision makers used in the survey. Results indicated that the most frequent reasons cited for conducting program evaluation were accreditation and standard control. These were followed by need for information for formative program changes and aiding decision makers. Participatory and scientific evaluation purposes were rated last. When examining information sources, respondents were unable to differentiate needs on an independent item-by-item basis; all items were considered important. When asked, however, to select the most critical items of these sources, a pattern of needs was established. Decision makers felt that program goals, identification of staff concerns, and presentations of client opinions were the most crucial types of information.

Community Health Nursing↗
PubMed1990

Improving the use of evaluation in health settings: do data support and order of recommendation make a difference?

This study examined two variables associated with nurse decision makers' perceptions of the usefulness of program evaluation. The first variable represented amount of data support for recommendations; the second represented the order of presentation of supporting and nonsupporting recommendations. The sample of New York state nurses reflected two levels of decision makers: Supervised (staff nurses) and supervising (head nurses, supervisors, and directors). Results indicated that experience with decision making and order of presentation affected perceptions of recommendations and sufficiency of information.

Administrative Personnel↗
PubMed1990

Arterial tortuosity.

Vessel curvature or tortuosity has usually been ignored in haemodynamic studies of the vasculature, vessels are commonly assumed to be straight and axisymmetric. This assumption is generally not valid and even for those vessels which are relatively straight in early life, such as the abdominal aorta, there is a tendency to develop tortuosity with increasing age. This paper proposes a quantitative evaluation of tortuosity based on the standard deviation of the incremental displacements of the midline of a vessel. The tortuosity coefficients for the abdominal aorta were determined from the aortograms of 92 patients. For the majority of patients aged less than 40 years of age, the tortuosity coefficients were close to those expected for a straight vessel, i.e. less than 0.20. Above that age there is a rising incidence of tortuosity with, in some cases coefficients several times greater than those expected for the straight vessel case. This tortuosity is likely to be due to an aging of the vessel wall leading to loss of longitudinal stiffness. The haemodynamic implications of tortuosity are that it is likely to create flow profile asymmetries leading to abnormal wall shear stress and predispose the vessel to atherosclerosis. As a consequence tortuosity may be considered as a geometrical risk factor in the development of the disease.

Adolescent↗
PubMed1986

High frequency characteristics of the arterial system.

Pressure, flow and diameter were measured in the abdominal aorta of five anesthetized dogs during normal heart beats and heart beats with a superimposed impulse (generated by rapidly injecting a small volume of saline into the system). From Fourier analysis it was found that the impulse enhanced the amplitudes of the higher harmonics so that frequencies up to 80 Hz could be studied. Both the input impedance and apparent phase velocity above 20 Hz were independent of frequency and their average values were designated as characteristic impedance and true phase velocity. Average characteristic impedance for all five animals was 2.0 +/- 0.1 X 10(8) Nsm-5 and average phase velocity was 8.3 +/- 0.6 ms-1. Phase velocities calculated from characteristic impedance (1.76-2.39 X 10(8) Nsm-5) and from the slope of the pressure-diameter relation (0.102-0.25 X 10(-8) Nm-3) were similar to the true phase velocity as defined above (6.79-9.85 ms-1). It may be concluded that the input impedance converges to characteristic impedance and apparent phase velocity converges to phase velocity for high frequencies.

Animals↗
PubMed1984

Actions of cysteinyl leukotrienes in coronary, femoral and carotid vessels of the pig.

Coronary, femoral and carotid vascular beds of anaesthetised pigs were perfused with heparinised arterial blood using an extracorporeal perfusion system. Blood flow was measured in each vascular bed. Leukotriene (LT) D4 caused a dose-related reduction in flow in the left anterior descending (LAD) artery. LTs C4 and D4, angiotensin and noradrenaline caused dose-related reductions in flow in femoral and carotid vascular beds. High doses of LTD4 caused total cessation of blood flow in the LAD and femoral beds. In the femoral and carotid beds LTC4 but not LTD4 caused an initial increase followed by a prolonged reduction in flow. Indomethacin (1.4 X 10(-5) mol kg-1, i.v.) did not affect the vasoconstrictor action of LTs.

Angiotensin II↗
PubMed1983

Effects of intra-coronary administration of leukotriene D4 in the anaesthetized dog.

The left anterior descending coronary artery in anaesthetized greyhounds was perfused at constant pressure with blood pumped from the carotid artery. Phasic and mean coronary flow, left ventricular pressure, dP/dt, cardiac output, ECG, heart rate and systemic pressure were measured. Leukotriene (LT) D4 was administered into the left anterior descending coronary artery as a bolus injection. LTD4 caused dose-related reductions in coronary flow. Other parameters showed little immediate change although a gradual decrease in left ventricular pressure, dP/dt, cardiac output and systemic pressure occurred after administration of LTD4. Following intracoronary administration of LTD4 small surface haemorrhages were observed over the area perfused. The reduction in coronary flow was not inhibited by indomethacin.

Animals↗
PubMed1982

Effect of smooth muscle activity on the static and dynamic elastic properties of the rabbit carotid artery.

The variation of radius with pressure was measured in vitro in the carotid artery of ten rabbits. Experiments were performed without prior conditioning of the vessel, over an inflation-deflation cycle at pressures in the range 0 to 24 kPa during treatment with, and in the absence of noradrenaline (referred to as active and passive conditions). The effect of a step change in pressure (2.7 kPa) on the radius of the vessel was investigated on a further three specimens. Under passive conditions, the variation of the static and the real part of the dynamic incremental elastic modulus with pressure and stress was similar during both inflation and deflation. Under active conditions a large degree of pressure-radius hysteresis was observed. At physiological pressures smooth muscle activity was associated with a decrease in elastic modulus when compared to passive values at the same pressure or stress. At a stress above 2 x 10(5) N.m-2 yield of the constricted vessels was observed and on further inflation and subsequent deflation the pressure radius curve was identical to that obtained under passive conditions. We suggest that conditioning a vessel, by means of repeated inflation to a high pressure and deflation to zero pressure, before measuring its elastic properties may give misleading results when applied to the vessels of living animals.

Animals↗
PubMed1981

Impulse propagation in normal and stenosed vessels.

The propagation of a transient pressure impulse in a viscoelastic medium was investigated by experiments using water-filled latex rubber tubing and the aorta of anaesthetised dogs. A 5 ms pressure impulse was produced by the impact of a solenoid driven hammer. The propagation characteristics of the impulse (attenuation and propagation velocity) along the vessel were determined by means of a catheter-tip pressure manometer placed at various distances distal to the impulse generator. The presence of stenoses of varying degrees of severity resulted in reflection of the impulse and the appearance of reflected pulses whose magnitude depended on the stenotic severity. The experiments suggest that for the technique to be used in the detection of local reflecting sites such as might result from vascular occlusive disease, the lesions should occlude at least 70% of the lumen and should be no more than 0.20 m distal to the impulse generator.

Animals↗
PubMed1980

Influence of static and oscillatory pressure/strain on 131I-albumin uptake by the wall of the isolated pig thoracic aorta.

The uptake of 131I-albumin by the wall of the isolated pig thoracic aorta was investigated in vitro to achieve good control of the experimental conditions. The lumena of the arteries were perfused with a balanced salt solution (Hanks') containing the radioactively labelled albumin. Albumin flux was studied at three static intralumenal pressures, viz 6.7, 13.3 and 20 kPa (50, 100 and 150 mmHg) and uptake (normalised per unit dry tissue weight) was found to be approximately doubled on increasing the pressure from 6.7 to 20 kPa (50 to 150 mmHg). With a mean pressure of 6.7 kPa (50 mmHg) the uptake was studied in the presence of sinusoidal pressure oscillations of amplitude in the range 1.3 to 6.0 kPa (10 to 45 mmHg) at frequencies 1, 5 and 11 Hz. At each frequency the uptake was found to be dependent on the pressure amplitude. The dependence at 5 Hz was significantly stronger than at 1 Hz (P < 0.05) and although not significant there was a suggestion that the uptake was higher at 5 than 11 Hz. There was no significance and no suggestion of a difference at 1 and 11 Hz. The possible influence on uptake of the associated oscillatory wall shear component has been considered. The relevance of these findings to macromolecular transport and to the characteristic localisation of atheroma within the arterial tree is discussed.

Animals↗
PubMed1979

An in vivo study of the total occlusion method for the analysis of forward and backward pressure waves.

The arterial pressure wave, Pm, is composed of a forward travelling wave, Pf, and a backward travelling wave, Pb, resulting from partial reflection of PI at the peripheral beds. The magnitude of Pb depends on the degree of vasoconstriction. Total occlusion of the vessel distal to the pressure measurement site results in a wave which is equal to 2Pf. Subtraction of the derived Pf wave from Pm gives Pb, provided there is no re-reflection of Pb by proximal discontinuities. To test the validity of this total occlusion method for the determination of the components of Pm, measurements were carried out in an anaesthetised dog and the results compared with the method of Westerhof et al., (1972). The measurements were made at three arterial sites: 1. in the aorta just proximal to the junction of the renal artery; 2. at the termination of the aorta; and 3. in the femoral artery. The magnitude of Pb was varied by the infusion of vasoactive drugs. There was good agreement between the two methods at site 1 but at the other two sites the agreement was less good. It is shown that this is the result of re-reflection of the backward travelling waves produced by the occlusion at the aortic termination and the renal artery junction.

Animals↗