Showing papers in "Medical & Biological Engineering & Computing in 1968"
TL;DR: Despite a large number of publications reporting the results of this research, certain basic questions still remain unanswered.
Abstract: When electrical current is passed through the body by means of electrodes applied to the skin, sensory nerves can be stimulated. This results in sensations that vary from barely perceivable to highly unpleasant. Such electrocutaneous stimulation of sensory nerves has been studied by engineers, neurologists, physiologists and psychologists, who have investigated the interrelationship between the physical parameters of the electrical stimulus and the psychological effect that it evokes, have used electrical stimulation to study the nervous system and its pathologies and have tried to use cutaneous stimulation as a communication medium. Despite a large number of publications reporting the results of this research, certain basic questions still remain unanswered.
73 citations
TL;DR: The system described here uses the field gradient to a large, movable electromagnet to propel and guide a small permanent magnet through channels such as blood vessels to provide access to parts of the body otherwise inaccessible except by major surgery.
Abstract: Channels such as blood vessels may provide a valuable means of access to parts of the body otherwise inaccessible except by major surgery The system described here uses the field gradient to a large, movable electromagnet to propel and guide a small permanent magnet through such channels The permanent magnet may incorporate or tow any of a number of minute diagnostic or therapeutic devices A flexible catheter may be attached to conduct fluids to or from the tip and to provide additional control
64 citations
TL;DR: Three electronic methods have been used by the authors to study the tremor motion of the eyes which occurs during normal fixation and the results show the angular velocity of the eye as a function of time.
Abstract: Three electronic methods have been used by the authors to study the tremor motion of the eyes which occurs during normal fixation The first method depends on the use of a capacitance gauge for recording the motion of the corneal protuberance in relation to a fixed probe which is placed near to the eye The second involves the use of a piezoelectric strain gauge which is placed in contact with the sclera The third involves the use of an accelerometer which is fixed to a contact lens The merits and demerits of the three techniques are compared A description is given of the methods which have been used to calibrate the transducers A typical tremor record is given; this shows the angular velocity of the eye as a function of time The velocity spectral density curve is also given Although the transducers have been used mainly for studying fixation tremor, they can be used to record other small eye movements Involuntary saccades, nystagmoid movements, and those eye movements which are caused by vibrations are easily examined
42 citations
TL;DR: It is shown that a simplified 3-point version of the matched filter provides almost as much improvement with the added advantage that prior knowledge of the fetal waveshape is not required.
Abstract: Statistical decision theory indicates that the best way to locate a signal of known waveshape is to use a matched filter. The degree of improvement actually achieved is investigated using actual signals of varying signal-to-noise ratio in which the maternal complex has been automatically eliminated by computer processing. It is shown that a simplified 3-point version of the matched filter provides almost as much improvement with the added advantage that prior knowledge of the fetal waveshape is not required. It is possible to improve the performance further by using a two-stage process that exploits the almost-periodic characteristic of the fetal ECG.
38 citations
TL;DR: A mathematical model for the linear properties of the polarization impedance of cardiac pacemaker electrodes is presented that reproduces frequency and time domain behavior of the electrodes in physiological saline with good agreement between theory and experiment.
Abstract: A mathematical model for the linear properties of the polarization impedance of cardiac pacemaker electrodes is presented. This model reproduces frequency and time domain behavior of the electrodes in physiological saline.
38 citations
TL;DR: The mean breaking load of the Femora of female subjects is less than that of male subjects, and it is concluded that this difference is due to the smaller dimensions of the female skeleton; mechanical deterioration of bone tissue is responsible for reduction in strength of the femur with increasing age.
Abstract: Variation in dimensions and mechanical properties of the femur was examined in relation to variation in age and sex of the subject. One hundred and forty-five fresh, adult femora were studied. Mean values are given of the breaking load of the femur and the tensile strength of the femoral compact bone for members of each sex. The mean breaking load of the femora of female subjects is less than that of male subjects, and it is concluded that this difference is due to the smaller dimensions of the female skeleton; mechanical deterioration of bone tissue is responsible for reduction in strength of the femur with increasing age of the subject. It is suggested that factors other than increase in porosity are responsible for reduction in tensile strength of compact bone.
35 citations
TL;DR: The drinking response of the water deprived pigeon is analysed by means of feedback theory, and results indicate that the drinking response is basically an exponential function of time, the time-constant being determined by the gain of an injestion mechanism, and independent of the absorption constant.
Abstract: The drinking response of the water deprived pigeon is analysed by means of feedback theory. The techniques utilized include limiting the rate of water injestion in an operant situation, interrupting the drinking response for a specified interval, and altering the salinity of the drinking water. The results indicate that the drinking response is basically an exponential function of time, the time-constant being determined by the gain of an injestion mechanism, and independent of the absorption constant. The amount of water injested is attenuated as a function of injestion rate, and a thirst-threshold is thought to be responsible for this. The drinking response can be simulated by a second-order feedback mechanism, in which the damping factor is determined by the salinity of the injested water.
32 citations
TL;DR: Making certain simplifying assumptions, relationships are derived between the size and time interval between negative and positive peaks of compound nerve action potentials detected in a volume conductor, and the position of the recording electrode with respect to the nerve.
Abstract: Making certain simplifying assumptions, relationships are derived between the size and time interval between negative and positive peaks of compound nerve action potentials detected in a volume conductor, and the position of the recording electrode with respect to the nerve. Theoretical calculations and experimental results are also given showing the expected waveform change with the size of the detecting electrode.
25 citations
TL;DR: A new method of ventricular defibrillation is described and diagrams of the defibrillator, delivering two square-shaped pulses, are presented.
Abstract: A new method of ventricular defibrillation is described Diagrams of the defibrillator, delivering two square-shaped pulses, are presented
25 citations
TL;DR: The purpose of the initial study is to establish a correlation between some aspect of mechanical impedance and ‘clinical mobility’ or ‘looseness’ of teeth and to develop a suitable clinical instrument for measuring tooth mobility objectively.
Abstract: The mechanical input impedance of teethin vivo has been measured over the frequency range of 60–5000 c/s. A generator was used which delivered a sinusoidal force of variable frequency and constant peak-to-peak amplitude of 4·4×104 dyn. Our data plus those of others indicate that the suspensory apparatus of the tooth consists of several equivalent springs and dampers. The purpose of the initial study is to establish a correlation between some aspect of mechanical impedance and ‘clinical mobility’ or ‘looseness’ of teeth. An increase in tooth mobility has long been regarded as a cardinal finding in periodontal disease and a key consideration in determining the feasibility and mode of restoring lost dental function. Finally, we hope to develop a suitable clinical instrument for measuring tooth mobility objectively.
22 citations
TL;DR: It has to be concluded that in designing an arthroplasty of the hip joint it would be prudent always to consider the resultant force on the hip Joint as acting in a vertical direction and not to be over-optimistic in assuming a resultant force inclined in the strongly positive direction which is favourable to the mechanics of an ar Throplasty.
Abstract: 1.
The direction of wear encountered in soft p.t.f.e. sockets used in a now obsolete type of arthroplasty was measured in 37 patients.
2.
The direction of wear in the majority of cases lay in a direction inclined 10° to 15° away from the vertical and towards the mid-line of the body.
3.
It is presumed that this indicates the direction of the average resultant force.
4.
A small but significant number of cases revealed wear in directions which deviated grossly from the average, both qualitatively and quantitatively. No explanation of the deviation could be found from the clinical study of these exceptions.
5.
It has to be concluded that in designing an arthroplasty of the hip joint it would be prudent always to consider the resultant force on the hip joint as acting in a vertical direction and not to be over-optimistic in assuming a resultant force inclined in the strongly positive direction which is favourable to the mechanics of an arthroplasty.
TL;DR: A torsion balance, which electrically records the radiation pressure of very low intensity ultrasonic beams, is described, using a capacitive transducer attached to the balance arm to impress a magnetic force on the arm in such a way that the arm is always held in the same position.
Abstract: A torsion balance, which electrically records the radiation pressure of very low intensity ultrasonic beams, is described. The movement of the balance is detected by a capacitive transducer attached to the balance arm. Using the output from this transducer, a servosystem impresses a magnetic force on the arm of the torsion balance in such a way that the arm is always held in the same position. Ultrasonic power as low as 0·03 mW can be detected. In the 10 mW range, the error of the balance is less than 5 per cent.
TL;DR: These data, together with the low power requirement of implantable electronic devices (pacemakers, telemeters, etc.), suggest the feasibility of using these types of electrodes as a long term power source.
Abstract: Approximately 50–75 μW (microwatts) of electrical power can be obtained from an implantable platinum-black aluminum electrochemical cell. The implantations have been conducted in twelve rabbits for periods up to 200 days. The intensity of the initial tissue reaction and accumulation of insoluble aluminum oxidation products appear to be the factors limiting useful power available.
TL;DR: The spectra recorded in vivo differed greatly for fat, cysts with clear fluid, and a group of tissues including muscle, liver, kidney, and white and grey cerebral matter, however a study of spectra of autopsy specimens revealed small characteristic differences between these tissues.
Abstract: Tissue identification during organ puncture can be effected by reflection spectrophotometry using fibre optics. Reflection spectra at nine wave lengths were displayed on an oscilloscope. The spectra recordedin vivo differed greatly for fat, cysts with clear fluid, and a group of tissues including muscle, liver, kidney, and white and grey cerebral matter. The spectra for the latter group were strongly dependent on the amount of blood present; however a study of spectra of autopsy specimens revealed small characteristic differences between these tissues.
TL;DR: A lightweight, portable instrument, consisting of a polythene bellows spirometer and transistorized timing unit which provides a dial reading of the forced expiratory volume and forced vital capacity, the instrument has been found to be robust and reliable under field conditions.
Abstract: The spirometer described has been designed chiefly for use in clinical and epidemiological work where water and electricity may not be readily available. It is a lightweight, portable instrument, consisting of a polythene bellows spirometer and transistorized timing unit which provides a dial reading of the forced expiratory volume and forced vital capacity. The time interval remains constant over a wide range of temperature and battery voltage and the instrument has been found to be robust and reliable under field conditions. Comparative studies have shown that it compares favourably with a spirometer having a water-filled canister and an identical recording system.
TL;DR: A correlation is demonstrated between the value of the series electrolyte resistance and the performance in detecting activity in the cerebral cortex.
Abstract: Electrical measurements have been made on varnish insulated tungsten microelectrodes in an attempt to obtain a guide to their suitability for recording from nerve cells in the central nervous system. The variability of the behaviour of the metal-electrolyte interface rules out most tests. The series resistance offered by the electrolyte can be reliably estimated and, since it depends only upon the apparent size and shape of the free tip and upon the electrolyte resistivity, may be taken as an overall assessment of tip geometry. A correlation is demonstrated between the value of the series electrolyte resistance and the performance in detecting activity in the cerebral cortex.
TL;DR: A new method is described for detecting the Korotkoff sounds which signal systolic and diastolic blood pressure by mounting a sound transducer wholly within the conventional arm-encircling cuff.
Abstract: A new method is described for detecting the Korotkoff sounds which signal systolic and diastolic blood pressure. By mounting a sound transducer wholly within the conventional arm-encircling cuff, high intensity sounds can be detected with the cuff placed in any location on the upper arm. The blood pressure values obtained with the cuff-microphone are essentially the same as those measured with a sound detector placed in the antecubital fossa.
TL;DR: It is shown that the catheter itself may be made incapable of causing resonance; this can be accomplished by a form of impedance matching at the input; this technique only differs from normal telecommunication practice in respect of the ability of the system to operate down to zero frequency and in the deliberate mismatching of the output.
Abstract: The blood pressure wave-form recorded by a transducer of finite compliance at the end of a liquid-filled tube, is often distorted by acoustic resonance. In most recent publications, e.g.Leraand (1962),Yanov (1963), the theoretical treatment of this problem is based on the dubious asumption that the catheter compliance and the compressibility of the liquid are negligible, and that the system behaves as a simple resonant circuit with one degree of freedom, in which the mass of the fluid, or more correctly its inertance, resonates with the compliance (springiness) of the transducer. In a few cases the published theory does not rest on this assumption. In one article, the catheter has been considered as the π-section of a low-pass filter, in which half the compliance appears across the transducer,Vierhout (1965). This is shown to be quantitatively incorrect, as the effective fraction is one-third and not one-half. In any case the implication that there is a definite cut-off frequency is misleading.A. T. Hansen (1949) has made a more rigorous analysis in which the result is expressed in terms of complex hyperbolic functions, from which it seems difficult to draw conclusions except by numerical evaluation. It has, however, been found possible to simplify Hansen's results. It is shown that the catheter itself may be made incapable of causing resonance. This can be accomplished by a form of impedance matching at the input; this technique only differs from normal telecommunication practice in respect of the ability of the system to operate down to zero frequency and in the deliberate mismatching of the output. In principle the catheter input includes a constriction whose acoustic resistance is capable of absorbing half the pressure of a steepfronted pressure wave at the moment of its application. This loss of signal strength is exactly compensated by the response of the transducer both to the incident and reflected waves at the output, the latter being absorbed on its return to the constriction. This plan not only removes any sharply defined upper limit to the frequency which can be recorded, but also considerably simplifies the equalization problem. Except for minor adjustments, the equalization is independent of catheter length.
TL;DR: It is shown that for situations where the ratio of inside diameter to outside diameter of an artery changes during a flowmeter test, the sensitivity of the flowmeter changes, and this is shown to be an important consideration in research studies where vasodilation and vaso-constructors are used.
Abstract: The performance of electromagnetic flowmeters is reviewed in the light of data concerning the tensor conductivity of arterial walls. The muscular structures and its effect on external contact flowmeters is discussed. The situations where the wall effects must be considered are outlined and experimentally demonstrated. Maxwell's equations for the external contact electromagnetic flowmeter are solved considering the difference in conductivity of the wall radially and angularly. The importance of the blood conductivity to the wall conductivity ratio is also demonstrated. It is shown that for situations where the ratio of inside diameter to outside diameter of an artery changes during a flowmeter test, the sensitivity of the flowmeter changes. This is shown to be an important consideration in research studies where vasodilation and vaso-constructors are used.
TL;DR: The flow was accurately predicted not only under steady-state conditions but also in the presence of marked fluctuations in arterial pressure pattern, mean level, and heart rate.
Abstract: Dynamic renal arterial flow pattern, arterial compliance, and pre-glomerular conductance were predicted from the measured canine renal arterial pressure pulse pattern using on-line analog computer simulation of renal arterial parameters. The flow was accurately predicted not only under steady-state conditions but also in the presence of marked fluctuations in arterial pressure pattern, mean level, and heart rate. The model has five parameters: largeartery resistance, inertance, and compliance; a pre-glomerular arteriolar conductance; and a non-pulsatile glomerular pressure. The first two were set manually while the last three were automatically adjusted by the method of steepest descents to minimize the absolute error expressed as the instantaneous difference between the measured flow in the artery and the flow predicted by the computer.
TL;DR: The analysis of blood circulation is greatly simplified if blood flow is considered as a continuous, not a pulsatile flow, and some parameters of the circulation cannot be analyzed.
Abstract: RECENTLY there have been several successful attempts to analyze the blood circulation quantitatively (GRODINS, 1959; WARNER, 1960; BENEKEN, 1965 ; DEFARES, OSSORN and HARA, 1965). It must be pointed out, however, that the reader who consults these papers must have a considerable knowledge of mathematics. Some students of biology and medicine would perhaps prefer a less elaborate type of analysis that simplifies details but still contains the basic features of blood circulation. The analysis of blood circulation is greatly simplified if blood flow is considered as a continuous, not a pulsatile flow. Such analyses have already been published, and they have greatly helped to improve the understanding of the circulation (GuYToN, LINOSEY and KAUFMANN, 1955; GUYTON, 1963a). It is clear that in this sort of analysis some parameters of the circulation cannot be analyzed (e.g. the frequency of heart contractions), whereas the values of some other parameters must be regarded as average (e.g. blood pressure). by a four pole active network (a special form of an amplifier), as shown in Fig. 1. If there is no input voltage, there will be no output voltage however large the amplification. In this circtfit any voltage referred to earth would roughly correspond to the pressure referred to the atmospheric pressure, and amplification would correspond to the strength of contraction. For sake of brevity the term 'amplifier' will be used instead of the term 'four pole active network'.
TL;DR: This study of microwatt power telemetry transmitters serves as an introduction to this area of medical electronics.
Abstract: In Bio-Medical Telemetry, the power consumption of the system is to be minimized to reduce the overall size and weight or to extend the system life time. This is especially critical in implant systems. This study of microwatt power telemetry transmitters serves as an introduction to this area of medical electronics.
TL;DR: The results of a comparative load and stress evaluation of several different types of below-knee drop-foot braces are presented and suggest that considerable mechanical improvements can and should be made to the standard designs of braces.
Abstract: The results of a comparative load and stress evaluation of several different types of below-knee drop-foot braces are presented. The data obtained from this investigation suggest that considerable mechanical improvements can and should be made to the standard designs of braces. It is recommended that this method of investigation be more widely used in the assessment of structural or design changes in orthopedic appliances.
TL;DR: An upper bound for the effectiveness of arterio-arterial pumping is found by the formula, whereQhu is the stroke output of the unaided heart and ΔQh is the increment caused by the pump with a strokeQb.
Abstract: : In the technique of arterio-arterial pumping, a volume of fluid is withdrawn from the aorta during systole and reinjected during diastole, thereby reducing the systolic pressure of the heart and adding energy to the systemic circulation. It is found that an upper bound for the effectiveness of such devices is given by the formula (delta Q sub h/Q sub hu) - (delta P sub 1/P sub 1u) = (Q sub b/Q sub hu) ((P sub 1u - P sub 2u)/P sub 1u) where Q sub hu is the stroke output of the unaided heart and delta Q sub h is the increment caused by the pump with a stroke Q sub b. P sub 1u and P sub 2u are the systolic and diastolic pressures (unaided). Delta P sub 1 is normally negative and represents the reduction in ventricular pressure. The division of effort of the pump between the reduction of pressure and the increase of flow depends on the physiological-mechanical impedance of the heart. The total effect is, however, independent of the impedance. (Author)
TL;DR: The design and construction procedure for a local thermal dilution flowmeter are presented and the instrument was developed to measure blood flow in the veins of the human lower limb is suitable for use in conscious subjects and in patients undergoing operation.
Abstract: The design and construction procedure for a local thermal dilution flowmeter are presented. The instrument was developed to measure blood flow in the veins of the human lower limb; it is suitable for use in conscious subjects and in patients undergoing operation. Experiments in a laboratory model have shown that flow rate can be measured with an accuracy of ±5per cent over the range 40 to 870 ml/min. Measurements of deep venous flow have been made in conscious and anaesthetised patients. The effects upon flow of breathing, posture and calf muscle exercise have been observed.
TL;DR: A computer language particularly adapted to the needs of the biologist is described, which may be learned quickly and usable after less than one hour's instruction.
Abstract: The paper describes a computer language particularly adapted to the needs of the biologist. Although powerful, the language may be learned quickly and is usable after less than one hour's instruction.
TL;DR: Comparisons made of the construction and electrical characteristics of a novel electrode for physiology using carbon and manganese dioxide as depolarizer show that a MnO2 electrode being relatively non-polarizable may have some advantages as an electrode for recording biological d.c. potentials and as a stimulating electrode.
Abstract: Details given of the construction and electrical characteristics of a novel electrode for physiology using carbon and manganese dioxide as depolarizer. Comparisons made of its performance with that of more commonly used electrodes, showing that a MnO2 electrode being relatively non-polarizable may have some advantages as an electrode for recording biological d.c. potentials and as a stimulating electrode.
TL;DR: A detailed description of how information was presented to the data logger and examples of the punch tape output are given and a comparison of regional blood flow calculated by automated and non-automated methods is shown.
Abstract: Measurements of blood flow and ventilation per unit lung volume have been made by scanning the lung with scintillation counters after the intravenous injection or inhalation of the radioactive gas, xenon-133. The count rate at any level in the lung after display on a conventional recorder is laborious to read off and the calculations of blood flow per unit lung volume at each level are tedious. A data logger has been specially designed for parallel collection of these count rates on punch tape in a form acceptable for analysis by an Elliott 4100 computer. A detailed description of how information was presented to the data logger and examples of the punch tape output are given. A comparison of regional blood flow calculated by automated and non-automated methods is shown.