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Biomedical subjects

V C Roberts

Publications and source records attributed to V C Roberts.

At least 55 records · Page 3Linked to original sources
PubMed1984

Thermal entrainment and human ovulation.

The changes in the peripheral vascular response to temperature have been studied for ten menstrual cycles by calculating thermal entertainment levels. The entrainment levels exhibited peaks at around the time of ovulation, a result which we believe is due to the fluctuating levels of the hormones oestrogen and progesterone in the blood. An attempt has been made to explain the influence of these hormones on the vasomotor control system and where interactions may occur.

Adolescent↗
PubMed1983

Raynaud's phenomenon and thermal entrainment: an objective test.

A new objective test for diagnosing Raynaud's phenomenon was assessed in practice. The test is based on entrainment of the thermal vasomotor control system and entails non-invasive measurement of blood-flow responses in one hand while alternating thermal stimuli are applied to the contralateral hand. A significant (p less than 0.001) abnormality of vasomotor control was found in patients with Raynaud's phenomenon compared with normal subjects. When applied clinically this test is diagnostic and indicates the severity of the disease and the effect of treatment.

Adult↗
PubMed1983

Axillofemoral and femorofemoral grafts: a 6-year experience with emphasis on the relationship of peroperative flow measurement to graft survival.

Over a 6-year period 64 axillofemoral bypass and femorofemoral crossover grafts have been performed in 58 patients, most of whom were considered unfit for intra-abdominal surgery. Indications were peripheral ischaemia in 78 per cent and disabling claudication in 22 per cent. The limb salvage rate at 3 years was 75 per cent. No claudicants lost limbs, but only one-third of patients presenting with forefoot gangrene or ulceration avoided amputation. Most patients presenting with ischaemic symptoms at rest had associated femoropopliteal and distal disease, confirmed by the ankle pressure index measurements, and this influenced graft patency. Although the cumulative patency at 3 years for all grafts combined was 57 per cent with similar patencies for both the axillofemoral and femorofemoral grafts, early occlusion was more common in axillofemoral grafts and this may be reduced in bifemoral grafts by the increased flow rate in the vertical limbs. Peroperative electromagnetic flowmeter measurements were made after reconstruction on 55 femoral arteries in 46 of the patients and graft flow velocities were derived from these measurements. Comparison between velocities from those grafts remaining patent and those subsequently occluding showed a high incidence of occlusion in grafts with a maximal velocity after distal vasodilatation of less than 8 cm/s. Graft occlusion after the first postoperative month was more commonly associated with other factors such as continued smoking, severity of distal disease and perigraft infection.

Aged↗
PubMed1983

On-line analysis of the femoral artery flow velocity waveform and its application in the diagnosis of arterial disease.

Analysis of the instantaneous peak velocity waveform obtained from the common femoral artery can be used to provide an objective assessment of arterial disease in the leg. The calculation of waveform indices pulsatility index and rise time together with principal component analysis has been found to be the ideal method by which to assess the flow data on-line.

Blood Flow Velocity↗
PubMed1983

Per-operative haemodynamic assessment of lower limb arterial surgery. Part 1: Hydraulic impedance measurement.

Hydraulic impedance measurements have been made during surgery on 32 patients undergoing reconstructive arterial surgery. The reconstructive procedures included aorto-iliac, femoro-popliteal and axillo-femoral bypass, and extended deep femoral angioplasty. It was found that in aorto-iliac reconstruction the phase curves provide the means of assessing success, but that in other cases the impedance measurements though showing a similar trend are unable unequivocally to differentiate between success or failure.

Arteries↗
PubMed1983

Per-operative haemodynamic assessment of lower limb arterial surgery. Part 2: Modelling of the arterial system.

A simple lumped parameter model has been constructed to characterize the arterial system of the lower limb in man. It is found that such a simple model can represent the system and provide an excellent match with experimental blood flow and pressure data obtained during reconstructive arterial surgery. Based on the values of the model parameters, the model is able to predict the success and failure of surgery with the help of a discriminant function. The physical quantities of length and Young's Modulus of the model tube, however, are found to be outside the physiological range.

Arteries↗
PubMed1982

Blood flow in the diabetic neuropathic foot.

The mechanisms which underlie the development of Charcot joints and foot ulceration are poorly understood. The present study using non-invasive Doppler techniques demonstrates that in the neuropathic leg, the arteries are rigid, peripheral blood flow is increased and associated with arteriovenous shunting. We studied 10 diabetics with severe neuropathy (including five with Charcot changes), 16 diabetics without neuropathy and 10 control subjects. Markedly abnormal blood velocity profiles (sonograms) were demonstrated only in those patients with severe neuropathy. They showed increased diastolic flow (indicated by a reduced Pulsatility Index of 2.88 +/- 0.8 (mean +/- SD) compared with 9.53 +/- 4.0 (p less than 0.001) in the diabetics without neuropathy and 10.8 +/- 3.7 (p less than 0.001) in the control subjects) suggesting arteriovenous shunting. Increased rigidity was indicated by decreased transit times -57 +/- 6.3 ms (mean +/- SD) in the diabetics with neuropathy compared with 66 +/- 7.6 ms (p less than 0.01) in the diabetics without neuropathy and 67 +/- 9.1 ms (p less than 0.05) in the control subjects. This was accompanied by raised ankle systolic pressures -199 +/- 22 mmHg (mean +/- SD) in the diabetics with neuropathy compared with 151 +/- 15 mmHg, (p less than 0.001) in the diabetics without neuropathy and 146 +/- 18 mmHg (p less than 0.001) in the control subjects. Medial wall calcification occurred almost exclusively in the neuropathic subjects. These alterations in blood flow which include arteriovenous shunting may be important in the pathogenesis of complications of the neuropathic leg.

Adult↗
PubMed1982

International registration of clinical engineers.

This paper outlines the moves being made by the International Federation for Medical and Biological Engineering to establish an International Clinical Engineering Board. The purpose of this board is to stimulate, through the establishment of National Examining Authorities, international agreement on the minimum requirements needed for the registration or certification of professional clinical engineers.

Biomedical Engineering↗