Biomedical subjects

A Rendas

Publications and source records attributed to A Rendas.

6 recordsLinked to original sources

PubMed1999

A computer simulation designed for problem-based learning.

OBJECTIVES: As problem-based learning is increasingly used in medical education, there is a growing need to capture the diversity of the events occurring during problem-based learning sessions in order to understand the way in which students learn. The computer simulation described attempts to analyse a posteriori how students reason and learn during such sessions. DESIGN: A computer simulation was designed to perform a detailed analysis of the following features: pattern of information searched, formulation of working hypothesis and identification of learning issues. The program, which has been running successfully for 2 years, was developed using local resources and accepts any clinical problem, provided it is written in a suitable text file format. The program has been applied in the discipline of pathophysiology. SETTING: Faculty of Medical Sciences of Lisbon, Portugal. SUBJECTS: Medical students. RESULTS: An example is presented of how prints were analysed in order to evaluate the 'progression profile' of the students, and a comparison is made with other similar instruments. CONCLUSIONS: The program improved understanding of the relationships between the inquiry strategy and hypothesis formulation and also of how self-learning (triggered by learning issues) influenced further analysis of the cases.

Computer Simulation↗

PubMed1983

Pulmonary vasculature of piglets after correction of aorta-pulmonary shunts.

In a previous article we described the functional and structural changes produced in the pulmonary arterial circulation of the growing pig by an aorta-pulmonary shunt. The present work describes the hemodynamic and morphologic adaptation that follows correction of the shunt. In four piglets, aged 5 weeks, an anastomosis was made between the thoracic descending aorta and the pulmonary trunk and left patent for 5 weeks. At the end of that time the mean pulmonary artery pressure (PAP) was 20 +/- 3.8 mm Hg (mean +/- SD), compared with 9 +/- 2.1 mm Hg in a group of four age-matched sham-operated control piglets. The shunt was then surgically closed. After 10 weeks' recovery, the PAP was similar and normal in the two groups. We have already shown that pulmonary hypertension of similar degree and duration to that at the end of the patent shunt period produces the following structural changes, assessed by quantitative techniques: (1) preacinar arteries of normal external diameter but with a thicker medial coat than normal and (2) intra-acinar arteries in normal concentration, of smaller external diameter than normal, but with a medial coat appropriate to the external diameter: Smooth muscle is found in more peripheral arteries than is normal. In the present study, at the end of the recovery period, the shunt animals were compared with the sham-operated animals and had thicker medial coats in preacinar and intra-acinar arteries, muscle in more peripheral arteries than is normal, and an increased arterial and alveolar concentration for unit lung area. These results indicate that, in the growing porcine lung, "recovery" from an aorta-pulmonary shunt that was associated with moderate pulmonary hypertension restores external arterial diameter to normal but leaves a thicker medial coat at the preacinar and intra-acinar levels and muscle more peripheral in the arterial bed. In addition, after shunt correction, multiplication of alveoli and arteries proceeds at a faster rate than normal, at least during the first 10 weeks of recovery.

Animals↗

PubMed1982

Response of the pulmonary circulation to acute hypoxia in the growing pig.

In a previous article we have analyzed the structure of the growing pig lung and correlated the findings with cardiorespiratory function studies on the same animals (J. Appl. Physiol: Respirat. Environ. Exercise Physiol. 45: 806-817, 1978). The present study analyzes the pulmonary and systemic vascular responses to acute hypoxia in some of those animals at three ages, 2-4, 5-8, and 9-12 wk, the lung of the 12-wk-old pig being structurally similar to that of the adult. In all anesthetized animals, acute hypoxia (5 min 10% fractional inspired oxygen concentration) increased mean pulmonary arterial pressure (Ppa) and total pulmonary resistance (TPR). The increase over base line of Ppa was 41.3% in animals aged 2-4 wk; 83.0% in those aged 5-8 wk, and 136.9% in those aged 9-12 wk; for TPR the increase in the three age groups was 66.4, 92.4, and 138.9%, respectively. This difference in vasoactivity with age is associated with the progressive extension of smooth muscle into the intra-acinar arterial tree, which we have previously shown is an important feature of the structural remodeling that occurs during postnatal lung development in both man and swine.

Acute Disease↗

PubMed1980

Prematurity, hypoplasia of the pulmonary vascular bed, and hypertension: fatal outcome in a ten-month-old infant.

The present report describes an infant weighing 610 g who did not develop respiratory distress at birth, but who failed to thrive, and died at 10 months of age with suprasystemic pulmonary hypertension of unknown cause. Morphometric analysis of the lung, including the pulmonary artery circulation and serial reconstruction of several arterial pathways, revealed hypoplastic arteries both for age and lung size, and also arterial dilatation lesions and interpulmonary artery anastomoses. Pulmonary hypertension of this degree, which is noncardiac in origin, has not been reported before in a premature infant within the first year of life.

Arteries↗

PubMed1979

Aorta-pulmonary shunts in growing pigs. Functional and structural assessment of the changes in the pulmonary circulation.

Aorta-pulmonary shunts were produced in growing pigs, 4 to 12 weeks of age, by anastomosing the thoracic descending aorta to the pulmonary trunk, and the animals were followed for periods of 1 to 3 months. Correlation between the hemodynamic findings and the lung structure, analyzed by quantitative methods, showed that the young group (operated upon at 4 weeks of age) developed more severe pulmonary hypertension with increased muscularization of arteries of all sizes and reduction in the size of those running with respiratory bronchioli and beyond. Since this response is similar to that seen in cases of left-to-right shunt associated with congenital heart defects and pulmonary hypertension early in life, it seems that the present experiments reproduce the early response of the growing lung to such hemodynamic disturbance.

Animals↗

PubMed1978

Growth of pulmonary circulation in normal pig--structural analysis and cardiopulmonary function.

Morphometric analysis of the postnatal development of the pig lung, with emphasis on alveoli and vessels, shows features of growth similar to man, but occurring at a much faster rate in the pig, which telescopes in the first 3 mo the changes seen in human childhood and adolescence. During the first weeks, arteries (birth to 2 wk) and alveoli (1--12 wk) increase in number, whereas increase in size continues until adulthood. Wall thickness decreases soon after birth in arteries 15--200 micrometer, and by 8 wk in those 200-1,000 micrometer. At this age the adult left ventricular predominance in weight is already present. Throughout growth the venous wall thickness does not change. Cardiopulmonary function studies in pigs, from 2 to 16 wk, show that, during the period of rapid postnatal lung growth, there is no change in tidal volume, dynamic compliance, and thoracic gas volume as related to body weight; right ventricular and pulmonary arterial pressures also remain unchanged, whereas pulmonary vascular resistance decreases during the 1st mo.

Animals↗