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Biomedical subjects

C J Martin

Publications and source records attributed to C J Martin.

At least 73 records · Page 4Linked to original sources
PubMed1996

Job sharing at a children's hospital: evaluation by medical staff.

OBJECTIVE: To evaluate job sharing for registrars at Princess Margaret Hospital for Children, Perth, by seeking responses from members of the relevant medical teams. DESIGN: A questionnaire was sent to all 126 medical staff within the hospital (and three managers in medical administration) asking their views on job sharing for registrars. OUTCOME MEASURES: Whether job sharing should continue, who should do it, at what stage of training, and the effects on patient care. RESULTS: Among the 77 respondents (60%) there was broad support for the continuation of job sharing at the hospital: only 5 of 37 consultants and 2 of 19 non-job sharing registrars rejected the idea (with a further 4 consultants uncertain). 43% Of the consultants who had worked with job sharing registrars thought continuity of care was adversely affected. CONCLUSION: The committee for physician training of the Royal Australasian College of Physicians emphasises that advanced training should be flexible, with a wide range of opportunities for individuals to plan an appropriate training programme in line with their personal goals. This study has shown that job sharing for registrars at Princess Margaret Hospital for Children allows this choice. Action on concerns over any adverse effects on patient care should resolve any persisting disquiet.

Attitude of Health Personnel↗
PubMed1996

Thoracoscopic cardiomyotomy for achalasia.

Twelve patients with achalasia treated by cardiomyotomy via a thoracoscopic approach have been studied prospectively. Seven patient had previously undergone balloon dilatation with an unsatisfactory result. The procedure was completed successfully in all patients without recourse to thoracotomy. Morbidity was minimal and postoperative stay averaged 4 days. The functional result was good/excellent in 11 patients and fair in one.

Adult↗
PubMed1996

Dose-area product measurements in paediatric radiography.

The dose-area product (DAP) could provide a useful quantity for monitoring doses for paediatric radiography, because it is a sensitive parameter, which is simple to record. A study of DAP measurements has been carried out for single radiographic projections for paediatric patients and comparisons made with measurements of entrance dose. The technique has been used to investigate doses for examinations performed with and without a grid. There is a linear relationship between DAP and entrance dose, with a variation of +/- 20% for pelvis, abdomen, spine and skull radiographs, but data for chests are more scattered. Logarithm of the DAP is linearly related to an equivalent patient diameter and reference levels could be set in terms of DAP either by patient age range or size. Effective doses determined from DAPs were 0.1-0.3 mSv for abdomen, pelvis and spine anteroposterior radiographs for 5-15 year olds, and less than 0.03 mSv for 0 and 1 year olds. Doses for examinations performed without a grid were only 20% of those for which a grid was used in the X-ray room studied. Significant reductions in doses for paediatric radiology can be achieved, where the use of grids can be avoided.

Adolescent↗
PubMed1996

Effective doses for coronary angiography.

A detailed study of dose data has been made for 100 coronary angiography examinations performed on a digital X-ray unit. Dose-area product (DAP) data have been analysed in terms of fluoroscopy and radiography for different projections. Projections patterns were similar for all cardiologists studied and the contribution to DAP from fluoroscopy was 32%. Data for 10 patients, selected because the percentage contributions to DAP from fluoroscopy and radiography were similar to the mean for the group, were used to derive conversion factors from DAP to effective dose. The mean DAP was 14 Gy cm2 and the effective dose 3.1 mSv. Conversion factors, based on the same protocol, were derived for a range of tube potentials and filtrations for use in estimation of effective doses with other units.

Coronary Angiography↗
PubMed1995

Reaction of the coordinate complexes of inositol hexaphosphate with first row transition series cations and Cd(II) with calf intestinal alkaline phosphatase.

The reaction of alkaline phosphatase (APase) with the complexes of myo-inositol hexakisphosphate (IHP) and various cations at pH 7.2 results in a decrease in activity. Singly, neither IHP nor metal ions induce such changes. IHP-Mn(II) complexes were the least effective. Using the ions of nickel or cadmium, activity was reduced by > 95%. A similar large decrease (> 99%) was seen previously in the reaction of APase with IHP-Cu(II) complexes. With Co(II) and IHP as reactants, the activity was reduced to 10-12% of that of the native enzyme. When the apoprotein, prepared by reaction of the enzyme with either EDTA or 1,10-phenanthroline, was titrated with Co(II), the activity was equal to that resulting from the reaction of the enzyme with IHP-Co(II) complexes. Titration with zinc restored 95% of the original activity. The products are metal-substituted derivatives in which the resident catalytic (A-site) zinc ions, at least, are replaced by the cation of the IHP complex that was used. The rates of such reactions were fastest with the complexes of Cu(II) and Cd(II) (0.12 min-1), less so with Co(II) as the ion (0.056 min-1), and slowest with complexes of nickel and manganese (0.01 min-1). In every case, the rate of reaction, but not its extent of change, was inhibited by zinc ions that reduced rate constants to 0.0014-0.0054 min-1. Magnesium ions had no effect. Likewise, Mn(II), with but one exception, did not affect the reactions. When present along with IHP-Ni(II) complexes, the rate was increased and the enzyme activity further decreased. If Zn(II) was also present, this enhancement was eliminated. All changes in enzyme activity were reversible by treatment with EDTA followed by reconstitution with zinc. Approximately 95% conversion to the original activity could be attained. Reactivation of modified APase preparation also could be attained, in some cases, by pre-incubation with Zn(II) at pH 8. For example, conversion of the Cd(II)-substituted APase to the zinc enzyme was rapid and complete in 15 min. With the Cu(II)-substituted derivative, reactivation was much slower. Incubation with zinc ions had little or no effect on other Me(II)-substituted APase preparations. Co-APase and Cu-APase, prepared from the apoprotein, behaved similarly to their respective "counterpart product" of the appropriate metal ion-exchange reaction. In contrast, Co-APase, but not Cu-APase, could be converted to the zinc enzyme by incubation with IHP-Zn(II) complexes at pH 7.2. The reaction rate of the various metal-substituted APase preparations with EDTA varied with the IHP-Me(II) used in its formation.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkaline Phosphatase↗
PubMed1995

Clinical and echocardiographic disease in patients starting end-stage renal disease therapy.

End-stage renal disease (ESRD) patients have a high cardiovascular mortality rate. Precise estimates of the prevalence, risk factors and prognosis of different manifestations of cardiac disease are unavailable. In this study a prospective cohort of 433 ESRD patients was followed from the start of ESRD therapy for a mean of 41 months. Baseline clinical assessment and echocardiography were performed on all patients. The major outcome measure was death while on dialysis therapy. Clinical manifestations of cardiovascular disease were highly prevalent at the start of ESRD therapy: 14% had coronary artery disease, 19% angina pectoris, 31% cardiac failure, 7% dysrhythmia and 8% peripheral vascular disease. On echocardiography 15% had systolic dysfunction, 32% left ventricular dilatation and 74% left ventricular hypertrophy. The overall median survival time was 50 months. Age, diabetes mellitus, cardiac failure, peripheral vascular disease and systolic dysfunction independently predicted death in all time frames. Coronary artery disease was associated with a worse prognosis in patients with cardiac failure at baseline. High left ventricular cavity volume and mass index were independently associated with death after two years. The independent associations of the different echocardiographic abnormalities were: systolic dysfunction-older age and coronary artery disease; left ventricular dilatation-male gender, anemia, hypocalcemia and hyperphosphatemia; left ventricular hypertrophy-older age, female gender, wide arterial pulse pressure, low blood urea and hypoalbuminemia. We conclude that clinical and echocardiographic cardiovascular disease are already present in a very high proportion of patients starting ESRD therapy and are independent mortality factors.

Cohort Studies↗
PubMed1995

Measurement of field distributions in ultrasonic cleaning baths: implications for cleaning efficiency.

The information available on ultrasound field distributions in cleaning baths is limited. Two techniques capable of providing this information have been investigated. The first employs a thermistor probe coated with ultrasound absorbing material and uses the rate of temperature rise when the ultrasound is switched on as a measure of local energy density. A motorized scanning frame has been used to map field distributions in three dimensions using the technique. The second technique, the Sarvazyan (dye/paper) method, uses Astralux paper placed in a bath containing an aqueous solution of methylene blue dye. More dye is transferred to the paper in areas where the ultrasound field is most intense. Pockets of gas are trapped in pores in the paper which provide additional nuclei for initiation of cavitation events and these produce small areas of intense staining about 1 mm in diameter, which are related to cavitational activity. The techniques reveal non-uniformities both in the field distribution and in the pattern of cavitational activity in ultrasound cleaning baths. Methods for assessing ultrasound field distributions are required in order to ensure that energy densities are sufficient to initiate cleaning action throughout ultrasonic cleaning baths.

Biophysical Phenomena↗
PubMed1995

Measurement of patient entrance surface dose rates for fluoroscopic x-ray units.

Measurements of patient entrance surface dose rate provide valuable data for interpreting results from dose-area product studies on fluoroscopic x-ray equipment. Methods for measurement of entrance surface dose rate with backscatter and incident dose rate without backscatter have been investigated. Entrance surface dose rate is measured with an ionization chamber in contact with a tissue-equivalent phantom. Backscattered radiation contributes 27-45% to the measurement and is affected by field size and chamber position. Incident dose rate measured using a copper phantom provides an alternative approach. Consistent relationships between thicknesses of Perspex and copper giving similar incident dose rates under automatic gain control have been established for different tube potentials with and without a grid. This allows measurements of incident dose rate made using copper to be linked to corresponding thicknesses of tissue-equivalent material. Since only a few millimetres of copper are required, contributions from backscatter can be minimized and transport of phantoms is simplified. Incident dose can be related to dose-area product and entrance surface dose derived using backscatter factors. Such measurements play a valuable role in interpreting patient dose data and recommending options to reduce patient dose.

Biophysical Phenomena↗
PubMed1995

Analysis of patient doses for myelogram and discogram examinations and their reduction through changes in equipment set-up.

Patient doses for myelogram and discogram examinations performed on two C-arm X-ray units have been measured using dose-area product meters. Contributions to the dose from fluoroscopy and radiography have been obtained from analysis of results for a selection of examinations. Information was recorded about the individual beam projections used, in order to allow estimates of effective dose. Effective doses for lumbar myelograms were 3-4 mSv and for cervical myelograms and discograms were 1 mSv. The doses on the two units were similar, but contributions from the various parts of the examinations were different. Quality assurance (QA) measurements of dose variables were used to determine reasons for these differences in performance. Fluoroscopic doses are influenced by image intensifier dose rate and by the way in which exposure factor selection has been set up for the automatic exposure control (AEC) system. Doses from digital fluorography on units for specialized applications may be greater than those with standard film/screen systems. Recommendations have been made concerning ways in which doses on each unit might be reduced. Detailed assessments of doses resulting from AEC set-up options, made during QA tests, can help to ensure that the optimum balance between patient dose and image quality is achieved.

Fluoroscopy↗
PubMed1995

An investigation into techniques for reducing doses from neo-natal radiographic examinations.

A survey of radiation doses received by infants having radiography in a neo-natal unit was undertaken at Aberdeen Maternity Hospital. Options for dose reduction recommended by the CEC Lake Starnberg Group were investigated. Techniques were implemented for clinical evaluation after assessments of image quality with test objects and phantoms. Clinical image quality of radiographs was evaluated by paediatric radiologists using CEC criteria. Results revealed a clear relationship between entrance dose and patient weight, indicating that reference doses for infants could be linked to weight. At the start of the study the mean entrance dose for chest anteroposterior (AP) radiographs was 65 microGy and the dose-area product 12.3 mGy cm2 for a system with 2.5 mm aluminum filtration using 50 kVp X-rays with a 200 speed class film/screen system. A 400 speed class film/screen combination was investigated but not evaluated clinically, because the image quality was not considered acceptable. Addition of 0.1 mm copper to the filtration of the X-ray tube reduced entrance doses by 50%, but the technique was not adopted, because of a poorer image quality with only 72% of features in clinical images being reproduced to an acceptable standard, compared with 87% with the original system. Use of faster processing chemicals, an increase in filtration to 3.5 mm aluminium and a tube potential of 60 kVp resulted in a 40% reduction in mean entrance dose to 37 microGy with satisfactory clinical image quality.

Body Weight↗
PubMed1994

An evaluation of safe practices to restrict exposure to electric and magnetic fields from therapeutic and surgical diathermy equipment.

Stray electric and magnetic fields have been measured near to therapeutic and surgical diathermy equipment for many different treatments. The highest field strengths are associated with continuous wave (cw) 27 MHz therapeutic diathermy equipment for which fields above national reference levels extend for 1 m from the electrodes and cables. The extent of the fields does not vary substantially with the type of treatment being performed. Recommendations that operators remain 1.0 m from cw therapeutic diathermy equipment, 0.5-0.8 m from pulsed treatments with capacitive electrodes and 0.2 m from pulsed inductive applicators can be applied to restrict exposure for any treatment with each type of unit. In a proposed European Community (EC) directive, action levels similar in magnitude to the reference levels are used to trigger requirements for assessments of hazard, measures to reduce exposure and personnel training. Assessments and appropriate recommendations of measures to reduce exposure can be linked to the type of equipment. Fields associated with electrosurgical units operating at frequencies of 0.3-0.5 MHz only approached reference levels within 20-30 cm of the cables, and because of the relatively short durations of the emissions, precautions were considered unnecessary with the units tested.

Diathermy↗
PubMed1994

The mathematical modelling of thermal responses of normal subjects and burned patients.

A model of the human thermoregulatory system has been developed for normal subjects and burned patients treated in the intensive care room at Aberdeen Royal Infirmary. The human body is split into eleven segments, each having core, muscle, fat and skin layers. Heat transport through blood flow and conduction are simulated, and surface heat loss is separated into radiative, convective and evaporative components. Measurement of skin temperature and evaporation of moisture have been made from all sections of the body for 22 normal subjects over a range of environmental temperatures from 20 degrees C to 40 degrees C. The model has been refined to fit the data through manipulation of heat flow commands and temperature set points controlling sweating and shivering. The model has been adapted to describe the responses of burn patients by the introduction of skin layer destruction, increased body metabolism and fluid loss from wounds. Predictions have been compared with measurements made on six patients. The model shows that the ambient temperature at which sweating occurs increases with the area of burn injury, which is confirmed by clinical observations. It has been used to predict optimum environmental temperatures for treatment of patients with burn wounds of varying extent.

Adult↗
PubMed1994

A study of the relationship between patient dose and size in paediatric radiology.

Entrance doses and dose-area products have been measured for paediatric X-ray examinations in a dedicated paediatric department. Dose-area products for barium meal and micturating cystourethrogram examinations involving fluoroscopy were substantially less than results from other studies. A number of factors contribute to this, including a high gain image intensifier used without a grid, shorter screening times, smaller numbers of films, exclusive use of a 100 mm camera and careful collimation of the X-ray field. Entrance air kerma has been measured for pelvis, abdomen, chest and skull radiographs. The relationship between dosimetric quantities and an equivalent patient diameter derived from data on patient height and weight has been studied. The results show a linear relationship between the logarithm of entrance air kerma and equivalent patient diameter for radiographic examinations performed on a single X-ray unit. Application of exponential correction factors could allow entrance doses for radiographs of children of different ages to be compared with appropriate reference doses.

Adolescent↗
PubMed1994

Reduction of patient doses from barium meal and barium enema examinations through changes in equipment factors.

A study of patient doses for barium meal and barium enema examinations has been made for X-ray departments throughout Grampian Region. Dose-area products are substantially less than UK reference levels. Contributions from fluoroscopy and radiography varied significantly between different units, with fluoroscopy making up 35-92% of the mean doses for barium meals and 24-57% for barium enemas. Equipment related factors had a greater influence on patient doses than radiologists' techniques. The gain of the image intensifier and the exposure factors selected by the automatic exposure control (AEC) were the most important factors determining doses for fluoroscopy. Changes in kV/mA factors selected by the AEC have allowed reductions of 20-50% to be made in effective dose from fluoroscopy with some units. The method used for recording images was the major influence on radiographic doses. Digital spot images or fluorographic films taken from the intensifier gave only 10-20% of the dose with a film/screen system and are recommended where the image quality is satisfactory for the application. Changes in film/screen systems have given worthwhile reductions in radiographic doses. If all factors are optimized, mean doses for barium examinations could be reduced to 20% of current reference levels.

Barium Sulfate↗
PubMed1993

Together again: business, government, and the quest for cost control.

Corporate America leads the pack in the collective anxiety attack over health care costs. But will the business community add its considerable political power to the movement for national health reform? Conventional wisdom suggests not: businessmen seldom rally for collective concerns, have traditionally been biased against government action, and have diverse interests. This article guardedly offers grounds for greater optimism about corporate participation, arguing that the proper institutional context can help businessmen to see their preferences as consistent with health reform. Business groups have already proven critical to the issue development stage, where a dedicated group of corporate health reformists were key to getting reform on the national agenda. Business may also respond to strong leadership from President Clinton and assist in the legislation of national health reform. Yet the price of this corporate support is a decidedly conservative slant to the proposed legislation.

Commerce↗