The chief scientist reports...pressures produced on hospital mattresses.
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Bedding and Linens↗
Biomedical subjects
J C Barbenel
Publications and source records attributed to J C Barbenel.
Major pressure of sores.
A survey of 999 patients within the Borders Health Board area showed that 9.4 per cent had at least one pressure sore. J.C. Barbenel, M.M. Jordan and S.M. Nicol of the bioengineering unit, University of Strathclyde, describe how they assessed the extent and distribution of the condition, estimated to cost the NHS pound 150m a year.
Adult↗
Increased blood viscosity in young women using oral contraceptives.
Blood viscosity and its major determinants (hematocrit, plasma fibrinogen, and plasma viscosity) were measured in 25 men, 25 women who were not using oral contraceptives, and 25 women who had been using oral contraceptives for at least 3 months. Mean blood viscosity and hematocrit were significantly higher in women using oral contraceptives than in women who were not (p < 0.001), and use of oral contraceptives abolished the normal sex difference in blood viscosity and hematocrit. After correction to a standard hematocrit of 45%, blood viscosity was still higher in users or oral contraceptives, as was plasma fibrinogen (p < 0.05). Plasma viscosity was not significantly increased in users of oral contraceptives.
Adolescent↗
Relation between extent of coronary artery disease and blood viscosity.
Blood viscosity (shear rate 100/s) and its major determinants (packed cell volume, plasma fibrinogen concentration, and plasma viscosity) were measured before coronary angiography in 50 men aged 30-55 and related to the extent of coronary artery disease. Twenty-six men had extensive disease (stenosis of two or three major coronary vessels), and 24 had either stenosis of one vessel or no stenosis. The 26 men with extensive disease had significantly higher mean blood viscosity than those with mild or no disease and 25 healthy controls (p less than 0.001). The increased viscosity was due partly to a higher packed cell volume and partly to a higher fibrinogen concentration; plasma viscosity was not significantly increased. These differences could not be explained by smoking history. These results suggest an association between increased blood viscosity and extensive coronary artery disease in men, which merits further investigation.
Adult↗
The variability of skin surface contours.
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Aging↗
Pressure sore prevention for the wheelchair-bound spinal injury patient.
The concept of a wheelchair cushion fitting clinic for the prevention of pressure sores is reviewed in the light of recent estimates of the cost of pressure sores in the U.K. A method for measuring the pressure beneath the ischial tuberosities is discussed and techniques for measuring a patient's habitual exercise frequency and seated posture are described. Results from the records of 600 spinal injury patients including Rancho Los Amigos Hospital are reported and used to demonstrate the importance of low pressure beneath the ischial tuberosities as an indicator of wheelchair cushion suitability.
Humans↗
An assessment of red cell deformability using a simple filtration method.
We assessed the simple method of measuring red cell deformability described by Reid et al. The technique was found to be reproducible. The validity of the method as a measure of red cell deformation was confirmed by (a) marked reduction of the deformability index after fixation of red cells with glutaraldehyde, and (b) an inverse correlation of deformability index with high-shear blood viscosity (r = 0.4; P < 0.001). There was no correlation of deformability index with low-shear blood viscosity, plasma viscosity, fibrinogen, or the white cell count. In normal subjects, deformability index was similar in males and females, and in smokers and non-smokers. Patients with acute myocardial infarction, or intermittent claudication, had reduced deformability compared to controls (P < 0.01).
Blood Viscosity↗
The effects of age and cigarette-smoking on blood and plasma viscosity in men.
We measured blood viscosity and its major determinants (haematocrit, plasma fibrinogen and plasma viscosity) in 90 apparently healthy men aged 16 to 80 years. Cigarette-smokers (n = 45) had higher levels of blood viscosity, haematocrit and fibrinogen (p less than 0.001) and plasma viscosity (p less than 0.025) than non-smokers (n = 45). Blood viscosity was still higher in smokers after correction to a standard haematocrit (p less than 0.02). Fibrinogen, corrected blood viscosity and plasma viscosity rose with age in both groups, but young smokers had prematurely elevated levels of these variables and less pronounced rises with age. These results show that age and cigarette-smoking must be considered in studies of blood and plasma viscosity, and provide further evidence for an association between viscosity and arterial disease.
Adolescent↗
Structure and mechanics of tendon.
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Animals↗
Backscattering of light by red cell suspensions.
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Diffusion↗
Subcutaneous ancrod therapy in peripheral arterial disease: improvement in blood viscosity and nutritional blood flow.
Nine patients with extensive peripheral arterial disease were treated with subcutaneous injections of ancrod (Arvin) for 10 to 21 days. Reduction in plasma fibrinogen was associated with a sustained reduction in plasma and blood viscosity, and a sustained increase in nutritional skin blood flow, measured by a Xenon-133 clearance technique (P less than 0.001). These findings may be relevant to the therapeutic effect of ancrod in ischemic rest pain.
Adult↗
A quantitative method for the assessment of the microtopography of human skin.
The skin relief influences the exterior aspect of the skin which is very sensitive to aging. It could also be related to the mechanical properties and structure of both dermis and stratum corneum. Consequently, quantitative measurement of the skin surface roughness would seem most useful, as it would permit a quantification of skin aging, an in vivo analysis of mechanical forces acting on the skin structure, and the detection of abnormalities otherwise not visible. The method described comprises three steps: (1) making a silicone rubber negative replica, (2) making an Araldite positive cast, (3) roughness measurement of the cast with a device commonly used in engineering, which provides quantitative parameters: Ra, Rp, Rt, Rmax and others. The reliability of each of these steps was checked, and also the absolute need to locate precisely the site of sampling and to know the angle of the scanning direction with the main axis of the limb or the body. The method seems useful for studying aging, either normal or affected by UV rays and other physiopathological events influencing the skin surface.
Aging↗
Subcutaneous ancrod after operation for fractured hip--a dose-ranging and feasibility study.
We have conducted a dose-ranging and feasibility study of daily subcutaneous injections of ancrod (Arvin) as a potential antithrombotic method in 28 patients following operation for fractured neck of femur. Sustained, predictable fibrinogen depletion during the first post-operative week was induced by four different regimes. A total dose of 10 units/kg weight, given in divided doses starting on the day of operation, is suggested as a possible antithrombotic regime. Ancrod treatment produced a rise in fibrinogen/fibrin degradation products, prolongation of the thrombin clotting time, and a fall in plasminogen, plasma fibrinogen and corrected blood viscosity were observed in 14 control patients. Plasma fibrinogen was correlated with plasma viscosity and corrected blood viscosity. No adverse effects of treatment occurred. Subcutaneous ancrod appears to be a simple, safe, and feasible potential antithrombotic method, and merits trials of efficacy in the prevention of post-operative thromboembolism.
Adult↗
Incidence of pressure-sores in the Greater Glasgow Health Board area.
A survey was made by questionnaire of the prevalence and severity of pressure-sores on a given date among all hospital inpatients and all patients visited by a district nurse within the Greater Glasgow Health Board area. 8.8% of patients had a pressure-sore. Those aged 70 and over accounted for 70% of the patients with sores. Chairfast patients consistently had a higher pressure-sore frequency than bedfast patients of a similar degree of helplessness.
Adolescent↗
The time-dependent mechanical properties of skin.
The mechanical properties of the skin were investigated by applying a torsional deformation to a circumscribed area. Results of the tests indicate that the skin is nonlinear and time dependent. The dynamic response shows that the phase angle is insensitive to frequency below 1 Hz; the peak torque amplitude increases slowly above 0.004 Hz. A self-consistent description is presented utilizing continuous relaxation spectra. The technique describes the stress relaxation data and predicts the form of the dynamic response.
Biomechanical Phenomena↗
Structural and mechanical properties of tendon related to function.
Tendon normally fulfills its primary role as a flexible force transmitting element very effectively and yet failure of this passive tissue leads to great disability. As a connective tissue its structure is relatively simple and the peculiar helical arrangement of collagen fibres confers highly non-linear as well as time-dependent mechanical properties. Functional significance cannot be attributed to any facet of mechanical response until the physiological pattern of loading is established. In particular the rate of deformation and the minimum force experienced by tendon in normal locomotion have yet to be elicited. Most published values of maximum forces transmitted by tendon fall short of the measured quasi-static rupture strength. The fact that some estimates exceed this ultimate force illustrates the errors incurred in indirect assessment. Direct measurement techniques, which have now been demonstrated to be practicable, should yield valuable information when applied to tendons susceptible to spontaneous rupture. Other proposed mechanical functions of tendon are clearly of secondary importance. Much has yet to be learned of the response of muscle to rapid loading and extension before these hypotheses can be tested fully. With our scant knowledge of normal tendon function it is indeed fortunate that the techniques of repair and treatment of damaged tendon are rapidly advancing.
Animals↗