Showing papers in "Journal of Medical Engineering & Technology in 1983"

Clinical gait assessment: A personal view

Abstract: Some problems of the establishment and management of a clinical gait assessment laboratory are explored. It is suggested that the term ‘gait analysis’ should be restricted to data gathering and that the term ‘gait assessment’ be used for the integration of this information with that from other sources for the purpose of clinical decision-making. Particular problems derive from the fact that gait analysis measures the effects of combined causes and compensatory activities of the body. The identification of causes requires, therefore, an initial theory which has to be tested by some interference with the system and this repeated as this proves necessary. This may be facilitated by a computer-aided decision program. The overall implications are that the whole body needs to be studied by a wide range of devices in a situation where the contribution of the clinician in regard to time more nearly matches that of the bioengineer than is customary.

Using body surface movements to study breathing.

Abstract: The chest wall comprising both rib cage and abdomen moves during breathing, and when suitably calibrated this motion can be used to monitor pulmonary ventilation without the need for face-masks or mouthpieces. Such non-invasive methods of studying breathing are likely to become more widely used in the future, especially in the investigation of respiratory control and sleep-disordered breathing. This review describes the physiological basis of these measurements and examines the practical and theoretical limitations of calibration techniques based on the two degrees-of-freedom model of chest-wall motion.

A temperature-sensitive cardiac pacemaker

Abstract: An artificial cardiac pacemaker which is sensitive to the temperature of blood in the right atrium has been fabricated. For a temperature change of 20°C the circuit achieves 90% of its final response within a period of 18s. In the authors’ opinion this is satisfactory since changes in blood temperature are generally small. Cardiac output in dogs rose from 2.37 ± 0.65 to 4.54 ± 1.15 l/min when the rate was increased from 202-6 beats/min (b.pm.)at 37.6° C to 231.6 b. p.m. at 41°C. Cardiac output was found, from statistical observation, to be improved at temperatures over 39.6°C.

Defibrillator design and development–a review

Abstract: This article discusses what is currently known about ventricular fibrillation (VF) and follows the historical development of efforts to deal with it. The modern damped sinusoidal defibrillator is examined in detail and associated hazards and safety standards are considered. Advice is given concerning the choice of defibrillators.

The monitoring of critically ill neonates.

Abstract: Present-day neonatal intensive-care demands minute-by-minute knowledge of many different physiological parameters in order to anticipate, and hopefully avoid, crises which may adversely affect the individual's potential. Machines monitoring temperature, respiration and apnoea, heart-rate and rhythm, inspired oxygen, arterial oxygen and transcutaneous oxygen, blood-pressure and transcutaneous carbon dioxide are physically and electronically complex and yet they will have to be understood by clinicians and nurses without more than minimal training in their use. This paper assesses the clinical needs of the neonatal unit and discusses the available monitors from the clinician's point of view. The role of trend monitors, and monitoring of sick infants during transport from hospital to hospital are also discussed. If these monitors can be used correctly by medical and nursing staff, valuable time can be gained for the nursing of the baby. Failure of correct application may make life more dangerous for the sick or preterm infant.

A system for monitoring the position and time of feet contact during walking.

Abstract: An analogue time/distance measurement for use in walking studies and based on foot contact is presented. The system utilizes a d.c. current source, feeding resistance wires bonded longitudinally to a walkway, and shorted by conducting strips on the shoe. An example of an application of the system is included: a comparison of the walking performance of an amputee with two different knee systems.

Tourniquets for surgery: safety aspects.

Abstract: There are a variety of different types of pneumatic tourniquets in constant use within the UK Health Service. These range from simple manually operated units to more complex gas-powered devices. Fatalities have occurred following the failure of pneumatic tourniquets during surgery when the local anaesthetic agent administered to the patient entered the circulation. Investigation has revealed that certain tourniquet systems have design defects, for example deterioration of rubber tubing, inadequate securing of pressure tubing, excessive wear in a pressure regulator. With any tourniquet system, routine maintenance coupled with regular user checks are essential to ensure reliability.

A microcomputer system for the identification of drug interactions.

Abstract: The condition of critically ill patients may change rapidly. The consequent alterations in drug therapy may result from the advice of a number of specialists, some of whom may not be skilled in the problems of adverse drug interactions. As a result, screening for drug contra-indications by someone with the necessary experience often occurs after the patient has already received the drug. By providing information on drug interactions on an inexpensive microcomputer, the necessary screening for adverse interactions can take place before the administration of the drug. A software package, written in FORTRAN, which can handle the storage and retrieval of this type of information, is described. The system can assess up to 18 drugs simultaneously, from a data-base comprising the 102 stock drugs held by the Intensive Therapy Unit at Rotherham District General Hospital, together with 25 other drugs, which could interact with the stock drugs to produce serious or possibly fatal consequences. It also differentiates between therapeutic interactions and chemical or physical incompatibilities.

New techniques for the treatment and disruption of renal calculi.

Abstract: Kidney stones are a major cause of morbidity and affect 3 to 4% of Western Europeans. Two new techniques have been developed in the last five years which reduce the morbidity, hospital stay and convalescent period of patients compared with those undergoing conventional renal surgery. These methods, percutaneous nephrolithotomy and extracorporeal stone disintegration, are examined with particular reference to the equipment necessary for stone disintegration. There is little doubt that these techniques will supersede conventional surgical procedures in the near future.

The UK Department of Health and Social Security's Scientific and Technical Services Branch.

Abstract: The DHSS's Scientific and Technical Services Branch is an organization believed to the United Kingdom. About half the staff work in Artificial Limb and Appliance Centres providing support services for disabled people. The other half are in DHSS headquarters working in a range of activities aimed at helping the National Health Service in its procurement of medical equipment and supplies as well as the support of the British medical product industry.

A microcomputer-based multithermocouple system for use in microwave fields.

Abstract: A PET-controiled multithermocouple system employing Analog Devices 4 channel amplifiers has been constructed. The intended application of the equipment is the measurement of the temperature distribution in patients receiving microwave hyperthermia as part of cancer therapy. The equipment has been shown to be sufficiently accurate and, in addition, is not susceptible to r.f. interference at the power levels in use in this hospital for microwave hyperthermia.

Corrosive effect of carbon-fibre reinforced plastic on stainless-steel screws during implantation into man

Abstract: The corrosion of stainless-steel screws used to fix carbon-fibre reinforced plastic (CFRP) plates to human fractures was compared with the corrosion on similar screws used to fix stainless-steel AO plates. Corrosive changes were noted in both sets of screws with similar frequency and severity; however, the stainless-steel plates were ‘in situ’ almost twice as long as the CFRP ones, showing that the corrosive changes occurred more rapidly on screws in contact with CFRP. Nevertheless, over the implantation time necessary for bone healing, corrosion was very mild and there is no clinical contra-indication to the use of stainless-steel and CFRP together in this particular application.

An Air-Enti Ainment Device for Preparing Precision Gas Mixtures

Abstract: Three low-cost venturi's built from readily available materials are described and evaluated to determine whether they can be used to prepare precision gas mixtures for the calibration of gas analysers. Using pure oxygen (02) and nitrogen as the priming gases the venturi's generated mixtures with an 02 concentration within the range 12-53% 02. Over a two-week period, the variability was found to be less than 0-25% 02. The mixtures produced were found to vary according to the density of the priming gas, but were virtually independent of the priming flow rate. We conclude that the venturi may offer a simple and inexpensive method of preparing precision gas mixtures suitable for the calibration of gas analysers.

Health activities of the U.S. Office of Technology Assessment.

Abstract: The Office of Technology, Assessment (OTA) was formed us part of the US Congress in 1972. The ‘Health Program was established in 1975. The purpose of the OTA is to advise Congress on the positive and negative implications of technological change. Since its beginning, the Health Program has spent most of its effort in describing technology assessment in health care and federal policies toward such assessment. A number of specific medical technologies have also been evaluated. Reports on health-care topics by the OTA have had some specific effects in Congress, but the more important impact is probably on the broader climate of opinion concerning medical technology and its bene fits, risks, and costs. Technology assessment has become an established part of the Congressional decision-making process and is being used increasingly in countries other than the United States.Summary and conclusionsThe Office of Technology Assessment was established less than a decade ago because of general concerns about the place...

A microcomputer system for real-time analysis of cardiac action potentials.

Abstract: A system for performing real-time analysis of cardiac action potentials has been developed using a microcomputer based on the Motorola 6800 central processor. Transmembrane potentials obtained using standard microelectrodes were digitized to 8 bits at 80 ms intervals, stored in cyclic memory buffer from which they could be selected for analysis, converted back to analogue form and displayed on an oscilloscope in real time. For each action potential, amplitude, the maximum rate of change of potential and the action potential duration at 50% repolarization and 100% repolarization were measured. In addition, conduction time (taken as the interval between the stimulus artefact and the action potential) was measured. All data were stored in memory and later printed, together with the time at which the recording was made. The system was designed for analysis of action potentials recorded using floating microelectrodes. The computer was controlled by three remote switches and a potentiometer, positioned close to...

A suction electrode net for precordial ECG mapping

Abstract: Precordial ECG mapping has been the subject of much study, yet a multi-electrode system that can easily and repeatedly be applied to a patient in bed, remains undescribed. A matrix of ECG electrodes has been developed, which uses a vacuum pump to suck onto the patient's chest. This will facilitate repeated bedside examination of certain types of patient.

The BBC Model B microcomputer in clinical instrumentation

Abstract: Using a microcomputer as the core of a monitoring or other clinical instrument is an attractive idea in principle. With the operating characteristics principally defined in software which can be altered or replicated easily and cheaply, the major part of the capital investment is in hardware that can be reused in many different applications.Costing around ±400-00 the BBC Model B microcomputer provides a combination of hardware and software facilities that with marketing and product support of comparable quality could make the idea a practicable and cost-effective one for a range of clinical instrumentation tasks.

Assessment of the design and performance of the Sage syringe pump model 341A, with particular reference to its accuracy and stability.

Abstract: Consideration of the timing circuitry employed in the Sage pump model 341 A indicates that the pump's performance will be strongly affected by component tolerances, and our measurements have confirmed this impression. Thus, delivered, flow rates may deviate considerably from those indicated on the calibration chart; our instrument was about 10% slow at all settings. For many’ applications it will be necessary to carry out a full calibration procedure, which should be repeated following any repairs to the electronic circuitry. The pump also suffered from drift at certain settings because un inappropriate component had been used in the timing circuitry. These findings will also apply’ to the Sage pump models 240 A and 242 A, which employ, similar timing circuitry to the 341 A. When precautions are taken to overcome these problems, the pump's performance is satisfactory. for both clinical use and some laboratory applications.

Long-term flow measurement: an assessment of the Siemens Servo 900B expiratory flowmeter.

Abstract: The accuracy and linearity of three Siemens Servo 900B expiratory flowmeters have been assessed by comparison with a dry gas meter. Their performance was reassessed after 792,966 and 950 h respectively. The effects of changes in respiratory rate, relative humidity and oxygen concentration on the meters were studied. It was found that the meters were accurate and linear and that reliable measurements could still be made after long periods of continuous use. The meters were found to be less accurate at low respiratory rates. Relative humidity had little effect on flow measurement. Changes in oxygen concentration, and hence viscosity, led to errors of up to 16% in flow measurement.

Electrocardiographic recording in high-intensity electric fields: an application of radio-telemetry.

Abstract: The use of radio-telemetry to monitor physiological variables is now an accepted part of routine hospital practice. There are other areas of health care, particularly in the field of industrial medicine, where telemetry may be used to advantage. The use of such a system for ECG monitoring in the presence of high-intensity electric fields is described.

Non-invasive microwave monitoring of respiratory pattern

Abstract: A non-invasive system for monitoring chest and abdominal motion is described. The system is based on the use of two microwave interferometers. A linear relationship with tidal volume can be obtained using an isovolume technique for calibration. Although the system is not an improvement on existing equipment, it is simpler and cheaper and well suited to rehabilitation work.

Medical equipment inventory and service scheduling by computer: Experience with a working scheme

Abstract: In Liverpool Health Authority a computer inventory of over 6000 items of medical equipment is used as an aid to servicing and management. Extracts from the inventory are used to guide work in several different servicing units and the cross-referencing facility is employed to provide lists of equipment by category (for example, manufacturer, hospital, department, cost band, age etc.).After four years' experience of this scheme we conclude that the costs are justified by the benefits to the equipment servicing programmes and to the management of equipment. However, the information made available for other purposes within the health authority (administration, supplies, finance etc) has not been made use of to the extent that the whole cost could be justified as a management service. We have also found that the quality of inventory records and usage are improved where technicians can use the computer directly, and we find that medical physics technicians quickly come to understand such systems thereby minimiz...

Correlation between walking energy expenditure and tachographic gait parameters

Abstract: A group of 53 adult men, normal subjects as well as victims of different types of lower-extremity handicaps, took part in tachographic gait studies and measurements of physiological energy expenditure whilst walking at a self-selected pace. The observations were analysed to explore the relationships between walking energy expenditure and various gait parameters. This analysis allowed the authors to identify some biomechanical indices which can be used for objective evaluations of human performance in locomotion. The investigation reported in this paper is a follow-up to the authors’ pilot study which was published in an earlier issue of'JMET.

The assessment of the post-thrombotic limb by foot volumetry and pedal venous pressure.

Abstract: Various tests, such as foot volumetry, static and ambulatory venous pressure measurements, Doppler flow recordings and calf plethysmography, have recently been developed to aid and to attempt to quantify venous insufficiency. This paper describes a simple device for measuring foot volume changes during the prescribed exercise. The foot is placed in a water-bath and the change in foot volume is recorded by a strain-gauge pressure transducer. The transducer responds to the head of water change. which, in turn, is directly proportional to the volume change. Also described is a simple device for the measurement of pedal venous pressure using a standard, commercially available transducer. The methodology of the tests is discussed, together with sample results.

A speech-prompted communication aid for the severely handicapped.

Abstract: The construction of a microprocessor-based communication aid for a severely handicapped teenager is described, and certain aspects of microprocessor systems development are discussed.