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Biomedical subjects

D Charlesworth

Publications and source records attributed to D Charlesworth.

At least 91 records · Page 5Linked to original sources
PubMed1988

Results of excision of a cervical rib in patients with the thoracic outlet syndrome.

Excision of a cervical rib in patients with the thoracic outlet syndrome has been the subject of debate. One surgeon's experience of 23 cervical rib excisions is presented. Ten operations produced a complete cure, eleven improvement, and two no change in the patient's condition. Of 15 cases with neurological symptoms alone, 9 were cured, 5 improved and 1 was not helped; in contrast, of 8 patients with vascular symptoms, 1 was cured, 6 were improved and 1 was not helped. We conclude that cervical rib resection is the correct treatment for patients whose symptoms are predominantly neurological. Rib resection alone may not be sufficient in patients with vascular symptoms. The management of a cervical rib with vascular involvement is discussed.

Adult↗
PubMed1988

Atherosclerosis and disturbances in flow.

From experiments on flow in a tapered tube it was found that a ring vortex could be produced in certain circumstances. The parameter which determines the vortex formation is the product of peak reversed flow, Reynolds number, and the taper angle of the tube. Using dimensional analysis, conditions in a model were adjusted to simulate those in the unbranched superficial femoral artery. A vortex was formed when there was sufficiently strong reversed flow, and it did so over a range of nondimensional frequencies similar to those which occur in the artery in humans. When the vortex passes up the tube, the surface stresses oscillate at a frequency an order of magnitude higher than the pulse frequency. It is possible that this oscillating stress could trigger atherosclerosis. The initiating ring vortex could be induced by a slight stenosis distal to the site of atherogenesis.

Arteriosclerosis↗
PubMed1988

Inflammatory abdominal aortic aneurysms: a report of thirty-seven cases.

Of a total of 780 patients with abdominal aortic aneurysms, 37 patients (4.7%) had inflammatory aneurysms. Presenting symptoms included back and abdominal pain (76%), leg edema, melena, uremia, claudication and pancreatitis. Mean erythrocyte sedimentation rate was 45 mm/hr. Weight loss and anorexia were common. Elevated urea and creatinine were seen on 11 patients, nine of whom had obstructive uropathy. Average aneurysm size was 9.3 cm. Thirty-six patients were treated surgically and one was observed. Involvement of the suprarenal (nine cases) or thoracic (three cases) aorta was common. Elective operations included resection and grafting in 21 patients and axillofemoral bypass in four patients. Patients with ureteral entrapment underwent simultaneous ureterolysis. Among the elective operations four deaths were noted (15%). Ten emergency operations were done for posterior rupture (four cases), aortoduodenal fistula (one case), inferior vena cava obstruction or fistula (two cases), hemorrhage into the aneurysmal wall (two cases), or presumed rupture (one case). There were seven deaths (70%) in this group. The operation of choice for inflammatory aneurysm is a bifurcation graft combined with ureterolysis.

Aged↗
PubMed1988

Design considerations for a small bore vascular prosthesis.

No synthetic prosthesis has yet been found which can satisfactorily be used as a substitute for saphenous veins in vascular surgery. One explanation for the lack of success is that their properties and behaviour do not mimic those of the arteries they replace. The essential features for a successful vascular prosthesis, over and above biocompatibility, are a low friction non-thrombogenic flow surface, mechanical (elastic) behaviour that matches natural artery and dimensions that approximate the host vessels. This will allow a high velocity of flow with low impedance. A prosthesis with this specification would avoid the problems of flow disturbances and reflection at the anastomoses, pulse wave damping and large pressure gradients, all of which reduce pulsatile energy. We have designed a vascular prosthesis based upon the above criteria. It has an internal diameter of 4 mm and a wall thickness of 1 mm. Its geometry makes it kink resistant and a good match for tibial and coronary arteries. The prosthesis is made from polyurethane and its mechanical properties, which approximate to those of peripheral arteries, are achieved via a mechanism of internal wall compression rather than external circumferential expansion. To assess the in-vivo potential of this prosthesis, 21 grafts were implanted in 11 sheep, replacing a section of carotid artery with a 6 cm long prosthesis. All 21 grafts were patent after 3 months. One graft was removed for histological examination. 16 of the remaining 20 grafts were patent after 7 months. Problems associated with thrombosis were not encountered and we conclude that this prosthesis shows good potential as a small bore vascular substitute.

Animals↗
PubMed1987

The evolution of plant reproductive characters; sexual versus natural selection.

The rôle of sexual selection in the evolution of plant reproductive characters has become a widely discussed topic among plant population biologists. For many reproductive characters, it is difficult to distinguish whether sexual selection or natural selection has been the more important force. We propose a definition of sexual selection for cosexual species and critically review the topic of sexual selection in plants. The emphasis of the chapter is on the evolution of plant reproductive characters, rather than on the issue of whether certain phenomena should be classified as sexual or natural selection. We do, however, argue that the category of sexual selection should not include the phenomena of inbreeding depression, genetically based self-incompatibility systems controlled by one or a few loci, or the effects of wide crossing and specific combining ability. We then discuss the available information on pollen competition and progeny quality, fruit and seed abortion, and the rôle of pollinator attraction in male and female fertility.

Biological Evolution↗
PubMed1987

Combined aortobifemoral and femoropopliteal bypass in the management of patients with extensive atherosclerosis.

Certain patients have atherosclerosis in both aortoiliac and femoropopliteal segments of the arterial tree and thus do not have a good result from reconstruction of the aortoiliac segment. No method has been developed to identify these patients and we do not know whether, by combining a femoropopliteal bypass with an aortobifemoral bypass, the results can be improved. We present a series of 153 patients with severe multilevel occlusive disease treated by simultaneous reconstruction and followed for up to 6.5 years. The cumulative patency of the femoropopliteal bypasses was 80% at four years. Functional and symptomatic improvement was excellent, and operative mortality was low when one considers the age and poor general condition of the patients.

Aged↗
PubMed1986

Detection of stenoses in the internal carotid artery by waveform analysis of continuous wave ultrasound signals (I).

In this prospective study, the reliability of the morphologic analysis of the continuous Doppler signal was evaluated. Three parameters were considered: the maximum systolic frequency (max A), a resistance parameter (RP) and the degree of spectral broadening (SB). The apparatus used allowed us to construct a color arterial image. Seventy-four subjects were included in this study: 17 volunteers investigated by ultrasound only, and 57 patients investigated by ultrasound and arteriography. Anatomic correlation was obtained in 31 operated cases. The threshold values, as determined in the volunteers, were as follows: 3.5 kHz for max A, 0.86 for RP and 58% for SB. Sensitivity was 94% when max A, SB and cartography were combined to detect tight stenoses. The sensitivity for each of the parameters alone was much weaker (61% for max A and 33% for RP). For all carotid lesions, the sensitivity of detection when all parameters were combined was 68%. Specificity was 77%. The study of the carotid bifurcation by the continuous Doppler effect allowed us to identify tight stenosis with reliability. On the other hand, it was impossible to distinguish between normal arteries and moderate stenosis, or between tight stenosis and complete occlusion.

Adult↗
PubMed1986

Detection of stenoses in the internal carotid artery by waveform analysis of continuous wave ultrasound signals (II).

Analysis of the morphological aspects of continuous-wave Doppler examination is a reliable means of detecting carotid stenosis involving 50% or more of the diameter of the arterial lumen. This study was undertaken to evaluate the indexes likely to increase the diagnostic accuracy of this noninvasive investigation method. The indexes studied were the variations of the maximal frequency and the systolic peak frequencies, measured proximal to and at the level of stenosis, and the ratio of the systolic peak frequency measured in the internal carotid artery and in the common carotid artery. After obtaining data on an experimental model, the study was conducted in healthy volunteers (n = 24) and in patients with carotid atherosclerotic disease (n = 23). The experimental study confirmed that stenosis greater than 50% leads to a reduction of blood flow and that there is a mathematical relationship between the frequency measured proximal to and at the level of the stenosis and the degree of stenosis. Clinical data showed that there was a significant decrease in the frequency of the systolic peak in elderly "healthy" subjects as compared with younger subjects. However there was no difference between patients with and without stenosis. The index was 0.8 in young subjects, 1.3 in healthy elderly subjects, and greater than 1.3 in subjects who had a stenosis. There was no statistically significant difference between these two last groups. At the threshold value of 2.3, the sensitivity of the FI index was 22% and the specificity was 94% in the detection of carotid artery stenosis. In the assessment of the tight stenosis, sensitivity was 44%.

Adult↗
PubMed1986

Early results of femoropopliteal bypass using a five millimeter "thin wall" polytetrafluoroethylene (Gore-Tex) prosthesis.

We report the early results of a series of 86 femoropopliteal bypass operations in which a 5 mm diameter thin wall polytetrafluoroethylene (Gore-Tex) prosthesis was used. Sixty-five bypasses were implanted in men and 21 in women. Thirty bypasses were done in conjunction with an aortic bifurcation graft and 18 patients had a bilateral procedure. The indication for operation was severe claudication in 74 cases and critical ischaemia in 12 cases. The angiographic run-off was good (three patent vessels) in 22 limbs and poor (one or two patent vessels) in 64 limbs. The cumulative patency rate for the whole group was 62% after 18 months. Angiographic run-off and the indication for operation were both found to influence cumulative patency rate significantly (p = 0.035 and p = 0.055, respectively). We also compared the results obtained when run-off was poor with equivalent data from our own previously published series in which a standard 6 mm diameter Gore-Tex prosthesis was used. This shows a difference in patency rate, for example 57% against 37% after 18 months, in favour of the smaller bore thin wall graft.

Blood Vessel Prosthesis↗
PubMed1986

Options in the management of claudication.

Patients who complain of intermittent claudication vary considerably in age, fitness, and in their expectations, and in the distribution of occluded arteries. A careful assessment of all the variables helps the surgeon to choose appropriate treatment from the various options open to him.

Aorta, Abdominal↗
PubMed1985

Atypical claudication.

In a prospective study the incidence, causes and management of atypical claudication have been investigated. All patients had a clinical assessment, Doppler ultrasound studies and X-rays of the lumbosacral spine, some had epidural injections, myelography with computerized axial tomography and arteriography. The incidence of atypical claudication was low, 13 per cent of all claudicants referred to our department, and although difficulties in diagnosis were encountered an approximately equal incidence of spinal and arterial causes was found. Only one patient had a definite central spinal stenosis. The need for invasive investigations was low (18 per cent) and even lower for surgery (7 per cent); the majority of patients' symptoms responded to conservative management.

Arterial Occlusive Diseases↗
PubMed1984

An investigation into how the geometry of an end-to-side arterial anastomosis affects its function.

The effects of altering the geometry of an end-to-side junction were investigated in a hydraulic model. The dimensions of the tubes, pressures and flow rate and the frequency of pulsation were calculated by dimensional analysis, to produce a model which simulated pulsatile flow in small arteries. The ratio between the impedance of the 'bypass' and the impedance downstream from the junction was greater than unity when the two tubes forming the junction were of unequal diameter. No increase in downstream impedance was measured when the angle of junction was increased from 45 degrees to 135 degrees. Cine photographs of streamlines at the junction showed that flow passed smoothly through the junction irrespective of angle and that perturbations occurred only during that part of the cycle when flow was reversed. The results indicate that the angle at which a junction is made affects flow. The effect is small and is only seen when the ratio of diameters of the tubes is unity. The ratio of the diameters of the two tubes which make up the junction has the greatest effect on flow through the junction.

Arteries↗
PubMed1984

A comparison between two types of waveform analysis in patients with multisegmental arterial disease.

The results of an experiment to compare two different methods of analysing ultrasound signals are presented. Normal volunteers, both young and old, and patients with arteriosclerosis were examined with Doppler shifted ultrasound and the results of two forms of waveform analysis retrospectively compared with angiograms. The angiograms were used to divide the patients into groups with similar patterns of disease. The ability of the two methods of analysis, 'pulsatility Index' (PI) and 'Laplace transform damping factor' (LTD), to identify patients with haemodynamically significant disease in the aorta or iliac arteries was tested statistically (Mann-Whitney U test) and compared in receiver operator curves. The results showed that both tests were equally good in the identification of aortoiliac disease, even when the superficial femoral artery was occluded, and that, contrary to theoretical arguments, LTD was influenced by distal impedance.

Adult↗
PubMed1984

The uses and abuses of life-table methods in vascular surgery.

This paper details the calculations involved in a life-table analysis and appraises the current use of this technique in vascular research. We suggest that the presentation of patency curves should be standardized and recommend that: curves are presented as step rather than continuous graphs; the number of patients remaining in a study are shown at intervals along patency curves; the length of time for which a curve is claimed to hold is more rigorously defined; an attempt is made to increase, where possible, the frequency of patient review, particularly in the immediate postoperative period; ways of increasing the total sample size (e.g. multicentre studies) are investigated. We also recommend that a set of definitive guidelines on the presentation of graft patency data acceptable to all the major vascular journals be sought.

Actuarial Analysis↗