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Biomedical subjects

A Owen

Publications and source records attributed to A Owen.

At least 19 recordsLinked to original sources
PubMed1996

The third heart sound is the result of a shock wave caused by the ventricular inflow velocity exceeding the wave velocity.

The genesis of the third heart sound (S3) has been debated for over a century. An hypothesis is presented which proposes that S3 is the result of a shock wave which is generated when the ventricular inflow velocity exceeds the local wave velocity. Echocardiographic data that support the hypothesis are presented from patients with and without an S3.

Blood Flow Velocity↗
PubMed1996

Loss of antimicrobial susceptibility in aerobic gram-negative bacilli repeatedly isolated from patients in intensive-care units.

OBJECTIVE: To study the loss of antimicrobial susceptibility in repeat (same patient, same bacterial species, and same site) aerobic gram-negative bacilli (AGNB) isolated from individual patients during their stay in the intensive-care unit (ICU). SETTING: A 792-bed, tertiary-care community hospital with a total of 107 adult, pediatric, and neonatal ICU beds. METHOD: An observational prospective study performed November 1992 through mid-July 1993. RESULTS: Of 594 consecutive AGNB from 287 ICU patients, 117 isolates (20%) from 55 patients (19%) were repeat isolates, with the majority obtained from respiratory secretions (83%). Pseudomonas aeruginosa and Enterobacter species accounted for 61% of the isolates. Forty-two (36%) of the repeat isolates from 24 patients (44%) had > or = 4-fold increase in minimum inhibitory concentration to at least one antibiotic and no longer were considered fully susceptible based on National Committee on Clinical Laboratory Standards criteria. Loss of antimicrobial susceptibility often developed within several (median 8) days and was associated only infrequently with simultaneous transition from colonization to infection in the individual patient. Use of certain beta-lactam antibiotics was associated with increasing resistance to several other antibiotics in the same class. Concurrent use of beta-lactams and aminoglycosides did not prevent loss of antimicrobial susceptibility to the former in repeat isolates. CONCLUSION: We conclude that loss of antimicrobial susceptibility in repeat AGNB isolated from ICU patients is common, usually is not associated with transition from colonization to infection, and often is associated with prior use of antibiotics. Minimizing antibiotic use in ICU patients should help reduce the risk of antimicrobial resistance in repeat AGNB isolates.

Anti-Bacterial Agents↗
PubMed1996

Patterns and costs of post-acute care: a longitudinal study of people aged 60 and over in Dubbo.

Declining length of stay of older people in hospital has caused concern about shifting of costs from acute to community care services. Because the two types of care are funded through different programs and from different jurisdictions, the coordination of acute and post-acute care has become the major issue. There is, however, little information available on patterns of use and costs of post-acute care either in Australia or elsewhere. In an existing longitudinal community study of older people in Dubbo, New South Wales, data on use of services by people aged 60 years and over for 12 months of hospitalisations was collected by linkage to the records of Home and Community Care providers. Only a quarter of older people received any type of Home and Community Care service in the 12 weeks after discharge and two-thirds of these received only one type of service. While less than 5 per cent received a service from an occupational therapist, physiotherapist or speech therapist, 78 per cent visited a general practitioner after discharge. The average cost of all Home and Community Care services received after hospital discharge was around $12.50 per week per person discharged. The predictors of higher costs of service use were: living alone, and the interactions of high levels of disability with owning a house. Results on service coordination, the identification of post-acute services, cost consequences of program funding, assessment and discharge planning are related to debates emerging from the Commonwealth Heads of Government.

Aftercare↗
PubMed1996

Empirical error-confidence curves for neural network and Gaussian classifiers.

"Error-Confidence" measures the probability that the proportion of errors made by a classifier will be within epsilon of EB, the optimal (Bayes) error. Probably Almost Bayes (PAB) theory attempts to quantify how this confidence increases with the number of training samples. We investigate the relationship empirically by comparing average error versus number of training patterns (m) for linear and neural network classifiers. On Gaussian problems, the resulting EC curves demonstrate that the PAB bounds are extremely conservative. Asymptotic statistics predicts a linear relationship between the logarithms of the average error and the number of training patterns. For low Bayes error rates we found excellent agreement between the prediction and the linear discriminant performance. At higher Bayes error rates we still found a linear relationship, but with a shallower slope than the predicted-1. When the underlying true model is a three-layer network, the EC curves show a greater dependence on classifier capacity, and the linear predictions no longer seem to hold.

Bayes Theorem↗
PubMed1995

Acetylcholine as a regulator of neurite outgrowth and motility in cultured embryonic mouse spinal cord.

Time-lapse photography was used to examine the effects of acetylcholine on the outgrowth and motility of neurites in cultures of mouse spinal cord. Addition of acetylcholine to the culture medium at concentrations of 100, 10 and 1 microM, caused inhibition of neurite outgrowth. Outgrowth rates were significantly different from those of controls at all concentrations tested. The motility of the growth cones was significantly reduced by treatment with 100 and 10 microM acetylcholine. Blockade of the muscarinic receptor by atropine did not significantly alter the effects of acetylcholine on outgrowth or motility. However when the nicotinic antagonist mecamylamine was added at the same time as acetylcholine the inhibitory effects of the acetylcholine were blocked and no changes in the rate of neurite outgrowth or in growth cone motility were detected. These results suggest that acetylcholine may have a role in the regulation of process outgrowth within the spinal cord with these effects mediated through the nicotinic receptor.

Acetylcholine↗
PubMed1994

Aprotinin does not decrease early graft patency after coronary artery bypass grafting despite reducing postoperative bleeding and use of donated blood.

Forty-five male patients with planned coronary artery bypass operation were randomized in a double blind fashion to receive either 6 million kallikrein inactivator units of aprotinin (high-dose group), 2 million kallikrein inactivator units of aprotinin (low-dose group), or placebo (control group). Postoperative bleeding was significantly decreased in both aprotinin groups in comparison to that in the control group (590 ml [290 to 1800 ml] high-dose group and 650 ml [280 to 1900 ml] low-dose group versus 920 ml (350 to 2700 ml) control group, p < 0.001). There was no difference between the two aprotinin groups. The need for postoperative blood transfusion was significantly lower in the aprotinin groups (1.46 [0 to 4] blood units high-dose group and 1.65 [0 to 5] blood units low-dose group versus 2.43 [0 to 7] blood units control group, p < 0.05). All patients underwent coronary angiography between the seventh and twelfth postoperative day. No difference was found among the three groups in patency of vein grafts-93.8% in the high-dose group, 94.5% in the low-dose groups, and 93.3% in the control group. Therefore, aprotinin significantly reduced postoperative bleeding and transfusion requirement after coronary artery bypass grafting without influencing early graft patency.

Aprotinin↗
PubMed1994

The medical, social, and functional profile of Parkinson's disease patients.

The study looked at the medical, social, and functional aspects of 34 patients with idiopathic Parkinson's Disease (PD). Eighty-five percent were above 55 years and 35% were over 70 years. Twenty-four (71%) were males. Most patients had Stage II disease. Overall functional state of the patient correlated closely with the stage of Parkinson's disease. Patients were likely to be dependent if their disease severity was stage III or more. Eighteen (53%) patients would require a carer to be present at least part of the day and 3 (9%) patients would require a carer most of the time. Domestic chores such as meal preparation, housework, and shopping were also affected in most of those who were previously active in these tasks. Ten patients had given up work due to their Parkinson's disease. The lack of knowledge of the disease was shown both in the carers and the patients. Twenty-nine of the patients had no knowledge of the disease, and only one carer had superficial knowledge of the disease. The major social problems associated with the disease were loss of social contact, behavioural problems, family members under strain and communication problems within the family. Since Parkinson's Disease is a chronic illness, with associated disabilities, it is important that the physician should aim for a multidisciplinary approach. Patient and carer education should be given emphasis, and the many everyday functional problems addressed. Advice on life-style management and aids to overcome disabilities may help improve quality of life of the patient and reduce carer's stress.

Activities of Daily Living↗
PubMed1993

A numerical model of early diastolic filling: importance of intraventricular pressure wave propagation.

OBJECTIVE: The aim was to clarify the mechanism of the following observations: (1) left ventricular pressure recordings during diastole have shown that the minimum pressure at the base is greater than that at the apex; (2) echocardiographic measurements of the short axis dimension of the left ventricle during early filling have shown that the maximum rate of increase at the base occurs before that at mid-cavity. These observations cannot be explained on the basis of simple pressure-volume relationships and suggest that diastolic haemodynamics are more complex. METHODS: A numerical (computer) model of early diastolic filling was developed. The model represents the atrium and ventricle as distensible cylinders connected by a valve. Parameters in the model such as ventricular stiffness and rate and duration of relaxation can be varied and the resulting haemodynamic changes observed. RESULTS: Despite the simplicity of the model and the omission of several physiological variables, intracavity pressure gradients and the phase relation of radial wall movements are generated that appear to be similar to those found in the human heart. CONCLUSIONS: The results suggest that these observations can be explained by inflow causing a pressure disturbance at the base which propagates to the apex, and which is reflected back to the base. The time between peak rate of change of short axis dimension at the base and mid-cavity may thus be a practical way of assessing diastolic function independently of loading conditions. These values can easily be measured by M mode echocardiography.

Atrial Function↗
PubMed1993

Assessment of psychosocial experiences in childhood: methodological issues and some illustrative findings.

The development of a new standardised investigator-based interview, PACE (Psychosocial Assessment of Childhood Experiences), for the assessment of acute life events and long-term psychosocial experiences is described. An application of PACE to a sample of 84 children referred to psychiatric clinics and 22 general population controls, is presented. Reliability was assessed using a separate clinic sample of 15 child-parent pairs. The findings showed that PACE has satisfactory reliability and discriminant validity.

Adaptation, Psychological↗
PubMed1992

Physiological features of pericardial constriction in the absence of pericardial disease.

To sustain a clinical diagnosis of constriction it is classically held that the fibrous pericardium must be thickened and adherent to the surface of the heart. A case is presented in which leukaemic infiltration of the fat overlying the myocardium resulted in the physiological features of constriction, although all layers of the pericardium itself were normal. Constriction is thus a physiological diagnosis; it may develop in the absence of the classical anatomical findings.

Aged↗