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Biomedical subjects

S C Jacobsen

Publications and source records attributed to S C Jacobsen.

17 recordsLinked to original sources
PubMed1989

Quantitation of human shoulder anatomy for prosthetic arm control--II. Anatomy matrices.

Part I presented mathematically continuous surfaces and origin-to-insertion centroidal trajectory data for the muscles of the human shoulder. Part II presents linear trajectory data for the same muscles, in addition to kinematic descriptions of the joints. 'Anatomy' matrices for musculature, which convert muscle forces (as estimated by cutaneously monitored EMG signals) to moments, within a prosthetic arm controller, are developed for both the linear and non-linear (centroidal) data, and then compared. Graphical analyses of the muscle functions are also presented via computer-generated 'circle diagrams'.

Arm↗
PubMed1989

Quantitation of human shoulder anatomy for prosthetic arm control--I. Surface modelling.

Anatomical data and models for the human shoulder musculo-skeletal system are developed with the intent of quantifying physiological subcomponents of a model-based multi-axis prosthetic limb control scheme which has heretofore been implemented empirically. Part I presents the controller formulation, the surface descriptions of the muscles (and bones), and the centroidal trajectory data of the muscles. The data partially quantify the muscle modelling components of the controller, and set the stage for the analysis of the force-to-moment anatomical conversion factors of Part II.

Arm↗
PubMed1989

Extended physiologic taction: design and evaluation of a proportional force feedback system.

In both robot teleoperation and prosthetics, the feeding back of touch information to the human operator in a physiologically compatible manner is an important problem. Most research in feedback systems for prosthetic devices has concentrated on electrotactile or vibrotactile stimulation of the skin. While these techniques can transmit information to the user, the user does not have the same sensation as if he were grasping an object in his natural hand. The present research investigates a third method of stimulation using direct force. In the sense of Simpson's Extended Physiologic Proprioception (EPP), it is called: Extended Physiologic Taction (EPT). The EPT system produces a one-to-one correspondence of touch sensation to user stimulation. The EPT system applies a force on the surface of the skin of the operator proportional to the grip force applied at the terminal device, or applies a vibration to the operator proportional to the vibration at the terminal device. A method of quantifying grip controllability has also been developed. A prototype was built and tested using a myoelectrically-controlled prosthetic terminal device as the remote gripping device. Quantifiable comparisons can be made between different feedback and gripping systems as well as comparisons between artificial terminal devices and the natural hand. Results are reported of improved grip control and of improved ability to manipulate objects when using the EPT system.

Equipment Design↗
PubMed1988

Painless cauterization of spider veins with the use of iontophoretic local anesthesia.

Treatment of small vascular abnormalities of the skin is painful, and injections of local anesthetic agents distort the operating field. Iontophoresis of salt-free, 4% lidocaine, with and without epinephrine, delivered to the skin from a receptacle with a semipermeable membrane, and with the use of a current-controlled electrical system, resulted in effective anesthesia of the skin for cauterization of "spider" veins. Fourteen subjects received 32 treatments. Sixteen paired areas of spider veins were anesthetized with iontophoresis of lidocaine and with lidocaine plus epinephrine 1/50,000. The duration of anesthesia with lidocaine averaged 14 minutes; relief of pain was complete in 9/16 treatments, adequate in 6/16, and inadequate in 1/16. Lidocaine plus epinephrine supplied anesthesia for 56 minutes; relief of pain was total in 14/16 treatments and adequate in the remaining two. Thus iontophoresis with the use of selected local anesthetic and iontophoretic equipment provides adequate conditions for cauterization of spider veins, a procedure poorly served by conventional local anesthesia.

Anesthesia, Local↗
PubMed1984

Potential novel methods for insulin administration: I. Iontophoresis.

It is theoretically feasible to administer an ionized solute transcutaneously using an electric current. Attempts by our group to administer conventional, regular (soluble) insulin to human volunteers by iontophoretic methods failed, probably because such insulin is only weakly ionized and much of it is present in the polymeric form. Animal experiments with pigs defined patterns of portal and systemic insulin concentrations for native insulin secretion, intraperitoneal injection of insulin, and peripheral (intramuscular) injection of insulin. Using a more strongly ionized and predominantly monomeric form of insulin, transcutaneous administration of this hormone by iontophoresis was demonstrated in an experimental animal.

Animals↗
PubMed1984

Potential novel methods for insulin administration: II. Self-regulating internal drug delivery systems.

Several glycosylated insulins were synthesized and their binding constants to a lectin, Concanavalin A (Con A), as compared to that of glucose, were assessed. When Con A-glycosylated insulins were placed in fluids containing different concentrations of glucose, competitive displacement of glycosylated insulin occurred to a degree dependent upon the ambient concentration of glucose. As these glycosylated insulins possess a biological activity (80% of that of standard soluble insulin) such results demonstrate the beginnings of a "chemical" artificial beta cell.

Animals↗
PubMed1983

Intraperitoneal insulin regimens and diabetic nephropathy.

Five patients with severe diabetic nephropathy (SN) and six patients with moderate diabetic nephropathy (MN) have been treated with intraperitoneal (i.p.) insulin administered by multiple injections. The five SN patients progressed to end-stage kidney disease. The six MN patients (five of whom are described) show stabilisation (and in two cases possibly some improvement) of renal function over time intervals ranging from eight to 23 months.

Blood Glucose↗
PubMed1980

Rotating disk device for slit radiography of the chest.

A pair of rapidly rotating disks was assembled with multiple radial slits for obtaining chest radiographs in 1/60-1/20 sec., using automatic exposure timing, without visible images of individual slits. Substantial reduction of scattered radiation levels is achieved (one half to one fourth), especially in the retrocardiac and central mediastinal areas of the chest film. Full realization of the potential contrast improvement resulting from this degree of scatter reduction is impaired by the limited latitude of x-ray films used for radiography. These problems and potential solutions are discussed.

Radiography, Thoracic↗
PubMed1978

Combined technological-clinical approach to wearable dialysis.

To evaluate the constraints imposed upon the design of wearable dialysis systems, prototypes using currently available hardware were applied to three different dialysis formats: 1) the wearable artificial kidney (WAK) for hemodialysis (HD), 2) reciprocating peritoneal dialysis (RPD), and 3) alternating sorbent based dialysis/diafiltration(Ds/F) with a highflux membrane. 1) WAK dialysis has undergone extensive clinical trials with results comparable to standard HD. This system, including a self-contained power source, weighs 4.5 kg. The pulsatile blood flow can be disadvantageous, and cost of disposables is high. 2) RPD is shown to be an effective PD format, with the clearance of urea averaging 29.7 (23.9 to 41.5) ml/min in 14 patients, totalling 548 RPD dialyses. 3) After four conceptual trials, the Ds/F system was used for one treatment. Mass transfer results show removal of: urea nitrogen, 15.4 g; creatinine, 1.9 g; uric acid, 1.2 g; potassium, 89.2 mEq; and a positive bicarbonate balance of 94 mEq. The design constraints of these systems were elucidated, and prototype compact delivery systems have been constructed. It is concluded that a) non-mechanical PD wearability exists and b) true wearability of HD or Ds/F systems is not yet technologically feasible, but constraints are less rigid for Ds/F than for HD.

Biomedical Engineering↗
PubMed1976

Portable/wearable artificial kidney (WAK) - initial evaluation.

This report discusses the modus operandi and results achieved using this new mode of haemodialysis. An insulated 20 L dialysate bath acts as a carrying case for the system. When empty the case is large enough to hold the wearable module and complete supplies for one week's operation. The total weight is 17 kg. The wearable unit consists of a combined blood and dialysate pump (1.2 kg), rechargeable batteries, tubing, Dow dialyser and charcoal regeneration module with a total weight of 3.5kg. Ideally the patient dialyses using a single needle some 3 hours/day, 6 days/week. It is necessary for the wearable module to be connected to the 20 L dialysate bath for an average of 90 minutes to achieve adequate urea and 5+ removal. One patient was dialysed on 35 consecutive days and 4 others were dialysed intermittently. Routine laboratory tests and mass balance studies were performed on all patients. Ultrafiltration rates reached 700 ml/hour, routine serum chemistries remained stable and mass balance studies demonstrated a daily removal of urea 14-20 G, creatinine 1500-2000 mg, uric acid 500-900 mg and K+ 30-55 mEq. It is concluded that dialy dialysis with WAK is biochemically adequate and also permits the patient a much less restricted esistence.

Evaluation Studies as Topic↗