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Biomedical subjects

V C Roberts

Publications and source records attributed to V C Roberts.

At least 19 recordsLinked to original sources
PubMed1992

Triaxial force transducer for investigating stresses at the stump/socket interface.

Although normal pressures at the stump socket interface of the lower-limb amputee have been investigated, little is known about the shear stresses that also occur. Studies suggest that the combination of both shear and normal stresses significantly exacerbates discomfort and vascular and tissue damage. A means of simultaneously measuring normal and shear stresses will aid in the investigation and improvement of prosthetic fit. A miniature triaxial force transducer (4.9 x 16 mm diameter) has been developed which can be recessed into the socket wall. The principle of operation, construction, performance and limitations of the device are described. Preliminary measurements of the interface stress variations over the gait cycle in a supra-condylar PTB socket are presented. These show clear differences in the stress patterns present when two different prosthetic feet are used.

Amputation Stumps↗
PubMed1991

Accuracy of colour Doppler ultrasound velocity measurements in small vessels.

Colour Doppler ultrasound offers the possibility of imaging small vessels not visible by B-mode alone. The colour Doppler image of velocities allows the course of small vessels to be imaged in the X-Y plane of the scan provided the Doppler frequency shift is of sufficient magnitude. This permits alignments of the Doppler cursor, allowing angle correction to provide true velocity measurements from the Doppler shift obtained. Before attempting to make velocity measurements, however, it is essential to be aware of the possible error in the Z plane caused by the thickness of the Doppler sample volume. To quantify this source of error, hydrophone and flow-rig measurements were performed on an Acuson 128 colour Doppler scanner with both 5 MHz linear-array and 3.5 MHz phased-array transducers. Measurements of the transmitted pulses using a point hydrophone showed that both probes employ approximately 3.5 MHz Doppler pulses (in both colour and pulsed Doppler modes). The two transducers have the same axial resolution. In colour Doppler mode the axial length of the sample volume increases automatically with depth by up to 0.5 mm. Measurements of colour and pulsed Doppler signal strength were obtained in a controlled flow rig. Both transducers produced accurate colour flow images of the phantom at their optimum depths; flow velocity errors due to Z-plane thickness are less than 5%. There was, however, substantial error outside these optimum conditions (up to 20%).

Arteries↗
PubMed1991

Digital artery calibre measurement--a new technique of assessing Raynaud's phenomenon.

This study evaluated the use of a high frequency A-mode ultrasound scanner (CUTECH DM70) for monitoring the digital artery vasospasm of Raynaud's Phenomenon (RP). The technique was evaluated on 12 RP patients and 12 age and sex matched controls. The diameter of a single digital artery was measured in these subjects over a range of finger temperatures between 14-35 degrees C. The reproducibility of the measurements was assessed by repeating the procedure in two subjects (a control and an RP patient) on 5 separate days. The results confirmed that the technique is reproducible and monitored vasospasm occurring in all 12 RP patients. In the temperature range tested, none of the controls developed digital artery vasospasm. At finger temperatures greater than 25 degrees C the response to thermal stimuli of the digital arteries in RP patients and controls was similar. However, at temperatures less than 25 degrees C a marked vasoconstriction leading to complete digital artery closure was seen in the RP patients and not in the controls. This technique may prove useful in monitoring RP patients.

Adult↗
PubMed1990

Ultrasound imaging of digital arteries.

This study assessed the use of high frequency ultrasound (CUTECH DM70) in the measurement of digital artery diameters. The accuracy of the technique was assessed using a model. Four silicone tubes of different diameters were embedded in opaque agar. Three independent observers measured the diameter of the tubes using the CUTECH DM70 and the measurements obtained were compared with those obtained using a travelling light microscope. The technique was then evaluated on digital arteries. Ten recordings of digital artery diameter were made at a fixed point on the index finger in two subjects at 20 degrees C and at 30 degrees C. There was no statistical difference between the mean diameters obtained by the three observers using the CUTECH DM70 on the model. No statistical difference was noted when the mean diameters measured using the travelling microscope were compared with those obtained by the three observers. The diameter differences between the tubes were all highly significant (P less than 0.001 Mann Witney). The variability in the recordings of digital artery diameter in the two subjects was very low (maximum coefficient of variance less than 4%). A significant difference in the mean measured vessel diameter at the two different temperatures was obtained (P less than 0.001 Mann Witney). We conclude that digital artery diameter can be measured using the CUTECH DM70.

Arteries↗
PubMed1989

Detection of breast cancer by measuring areolar blood flow--a pilot study.

Regional blood flow in the areola was measured by using the non-invasive transient thermal clearance method in normal breasts and in breasts involved with cancer. Areolar blood flow (ABF) in normal breasts was almost constant for women in the age range 20-60y, but decreased at higher ages. ABF in breasts involved with cancer was higher than that in the contralateral breast, and higher than the average normal ABF in the corresponding age group. The effect was more prominent in the left breast. The transient thermal clearance method provides a potential non-invasive means for detection of breast cancer.

Adult↗
PubMed1989

The effect of footwear mass on the gait patterns of unilateral below-knee amputees.

This study reports an investigation into the effect of shoe mass on the gait patterns of below-knee (BK) amputees. Ten established unilateral BK, patellar-tendon-bearing prosthesis wearers were assessed using a VICON system of gait analysis. Incremental masses of 50g (up to 200g) were added to the subjects' shoes and data captured as they walked along a 15m measurement field. Coefficients of symmetry of various parameters of the swing phase (knee frequency symmetry, swing time symmetry) were measured and their correlation was tested with the patient's preferred shoe mass and also their own shoe mass, all expressed as a proportion of body mass. The subjects' 'preferred' shoe mass (139-318g) showed the greatest symmetry in all the parameters examined (correlations 0.78-0.81 p less than 0.01 and less than 0.005), whereas there was no correlation between the subjects' own shoe mass (121-325g) and the symmetry coefficients measured.

Amputation, Surgical↗
PubMed1989

Wound hematoma: prophylaxis with topical thrombin.

We studied 123 patients having elective exploratory laparotomy through a midline vertical incision for gynecologic disease; patients were randomized to receive wound irrigation with either saline or topical thrombin before closure of the incision. Seven patients were not evaluable. No patient received low-dose heparin therapy perioperatively. No patient in either group had a clinically significant wound hematoma or disruption. Minor wound hematomas were more common in the saline group, a finding that approached statistical significance. Blood coagulation profiles were not different in the two groups either preoperatively or postoperatively. Topical thrombin is probably not clinically useful in preventing wound hematomas in patients who do not receive perioperative treatment with low-dose heparin; however, it seems to be safe for application to open wounds.

Administration, Topical↗
PubMed1988

Evaluation of a computerised test for the assessment of peripheral vascular disease.

This paper reports a study carried out in 200 patients to assess the effectiveness of a clinical vascular laboratory in the routine assessment of peripheral vascular disease (PVD) of the lower limb. Laboratory assessments involved a computer based hierarchical testing system incorporating pedal pressure indices, maximum walking distances and principal component analysis of the common femoral artery blood velocity waveform. The study fell into two parts. In the first, the laboratory assessments of 100 patients referred six years ago were compared retrospectively with their eventual clinical outcome. In this comparison, the laboratory provided a "diagnosis" which was 79% correct. In the second, a double blind prospective study was carried out in 100 patients to compare the vascular laboratory "diagnosis" with the diagnosis and prognosis of a skilled clinician, the outcome being compared one year after the initial assessment. In this study the laboratory proved to be correct in 78% of cases, the clinician in 70%. With a slightly modified computer protocol for the non vascular diagnosis, the computer would have been correct in 85% of cases. This test provides a quantitative and objective assessment of PVD which can assist in the patient's clinical diagnosis and management.

Diabetic Angiopathies↗
PubMed1988

An epidemiological survey of Raynaud's phenomenon.

A questionnaire was sent to 1000 patients with Raynaud's phenomenon (RP) and an equal number of controls in order to accumulate one of the largest patient data banks currently available. Five-hundred and seventy-one correctly completed paired returns were processed so as to investigate the association between Raynaud's phenomenon and other factors suspected of influencing the condition. The involvement of female sex hormones in RP was indicated by the predominance of women (93%), a 6% (P less than 0.02) higher incidence of infertility and the influence of menstruation (15%), the menopause (73%) and pregnancy (53%) on symptoms. Patients with scleroderma had a 5% higher incidence of stillbirths. A familial predisposition for RP was noted dependent on age at onset of symptoms (age less than 30, 14% greater than 30, 4.9%). The Raynaud's group overall had a significantly higher percentage who had been treated for migraine (7% higher P less than 0.01), angina (3% higher P less than 0.05) and duodenal ulcer (3% higher P less than 0.001). Of the respondents who had undergone sympathectomy (n = 140, 24.5% of the total), 18.6% claimed lasting benefit and 66.4% claimed no benefit after one year. The mean age at sympathectomy was 38.6 years (S.D. +/- 13 range 14-78) with a mean age of start of symptoms of 29.2 years (S.D. +/- 14.7, range 0-70). There was no significant difference between the effects of sympathectomy on those patients with and those without associated conditions.

Adolescent↗
PubMed1988

The transient thermal clearance method for regional blood flow measurement--the influence of tissue heat conduction.

When heat is supplied to or retrieved from living tissue, the heat in or out is either conducted by means of the tissue or convected by blood. In order quantitatively to assess blood flow by thermal clearance the contributions of conduction and convection have to be separated, and various methods have been developed for this purpose. The various methods are reviewed and it is shown that the adequacy of each depends on the specific thermal clearance method used. The review concentrates on aspects of the role of thermal conduction in the non-invasive transient thermal clearance method. It is shown that by applying correct methodology, for regional blood flow of around 0.0025 ml blood per ml tissue per second the predominant contribution to the heat transfer is by convection. However, if the regional blood flow is much lower, the effect of heat conduction cannot be ignored.

Adult↗
PubMed1988

Assessment of regional blood flow and specific microvascular resistance in the foot by means of the transient thermal clearance method.

Measurements of skin blood flow have been made in a group of 34 patients presenting with symptoms of peripheral vascular disease. Of the patients, 18 were non-diabetic and the remainder diabetic. Measurements of blood flow were made using the transient thermal clearance method, and of systolic blood pressure in the dorsalis pedis artery using a CW ultrasonic Doppler blood velocimeter and an occluding cuff. There was no difference in pressure index between the two groups. Neither a linear pressure/flow relationship nor the presence of autoregulation was demonstrated. The derivation of specific vascular resistance (SVR) for the two groups shows that in the diabetic it was 7.07 +/- 2.2, while in the non-diabetic it was 11.12 +/- 3.9. The difference is significant (P less than 0.005) and suggests that measurement of SVR may be useful in the differential diagnosis of vascular disease.

Blood Pressure↗
PubMed1987

Limb perfusion in the lower limb amputee--a comparative study using a laser Doppler flowmeter and a transcutaneous oxygen electrode.

Accurate and objective assessment of amputation level in the lower limb plays an important role in patient management. Laser Doppler flowmetry (LDF) is a new and noninvasive technique for skin blood flow measurement and has been used pre-operatively in 25 patients undergoing amputation for vascular disease and in five normal controls. Baseline flux measurements were made at room temperature on the medial aspect of legs and then again after local heating of the skin for five minutes. Transcutaneous oxygen measurements were made at the same site for comparison and amputation level in patients selected on this basis. Significant differences (p less than 0.001) in TcPO2 values were found between controls (10.9 +/- 0.5 kPa), below-knee (BK) amputees (6.0 +/- 1.5 kPa) and above-knee (AK) amputees (1.5 +/- 0.6 kPa). Baseline LDF flux did not differ significantly between any group. Heated flux values did however show a significant difference (p less than 0.005) between controls (52.4 +/- 23.5) and both BK (20.6 +/- 9.2) and AK groups (8.1 +/- 7.7) and also between the amputee groups. The relative increase in flux (heated flux/baseline flux) differed significantly between the BK (3.3 +/- 1.5) and AK (1.2 +/- 0.3) groups (p less than 0.001) and between these two and the controls (11.2 +/- 5.4) (p less than 0.001). The correlation between relative increase in flux and TcPO2 was 0.7 (p less than 0.001). It is concluded that laser Doppler flowmetry used in conjunction with thermal stressing could provide a quick, simple and non-invasive method for objectively determining amputation level in the lower limb.

Amputees↗
PubMed1987

The effect of adjuvant oxygen therapy on transcutaneous pO2 and healing in the below-knee amputee.

The effects on tissue oxygenation of postoperative adjuvant oxygen have been studied in a group of 20 patients undergoing below-knee (BK) amputation for vascular disease. Ten patients received no therapy, the remainder receiving 28% oxygen for 48 hours following surgery. The results showed that the transcutaneous pO2 in the amputation flaps fell significantly by some 20 mmHg (p less than 0.01) following surgery and that this fall was prevented by the use of adjuvant oxygen. The fall was not observed in the non-amputated limbs. TcpO2 took almost two weeks to reach its pre-operative levels in the amputated limbs. The effect on stump healing of adjuvant oxygen therapy was investigated in a randomized controlled trial in a series of 39 patients undergoing BK amputation. There were 22 patients in the control (untreated) group and 17 in the treated group (adjuvant oxygen for 48 hours). In the treated group 14 patients healed primarily and three amputations failed. In the untreated group 14 limbs healed primarily, one secondarily and there were 7 failures. The pre-operative transcutaneous values in the stumps which failed (26 mmHg +/- 14) was significantly lower (p less than 0.005) than in those which healed (40 mmHg +/- 9). The mean pre-operative TcpO2 in the patients in whom healing occurred in the treated group (35 mmHg +/- 10) was significantly lower (p less than 0.001) than the mean pressure observed in the untreated group (44 mmHg +/- 9).

Aged↗
PubMed1987

Evaluation of introducing the team approach to the care of the amputee: the Dulwich study.

The effects of introducing the Team Approach to the management of the lower limb amputee has been assessed in a consecutive series of 233 patients over a five year period. During the first year, baseline data was collected and during the subsequent yearly phases the effects of introducing a physiotherapist co-ordinator, visiting prosthetist and medical officer from the local Artificial Limb and Appliance Centre (ALAC), and finally trained surgeons were studied. During the final phases of the study, the effects of changing team staff were monitored. The results have shown that only when the full Team Approach is adopted are the best results achieved, but that, once this approach is established, staff changes can be made without serious reductions in effectiveness. The study has shown that the team can reduce in-patient stay by 20 days; reduce the need for post-discharge physiotherapy by 94%; increase the proportion of patients discharged with a prosthesis more than fivefold and increase the effectiveness of long term rehabilitation threefold.

Amputation, Surgical↗