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Biomedical subjects

G D Swanson

Publications and source records attributed to G D Swanson.

At least 55 records · Page 3Linked to original sources
PubMed1983

Osteoarthritis in the hand.

Patients who have disabling osteoarthritis of the hand are frequently given the wrong diagnosis, poor professional advice, and inadequate treatment programs. The exact cause of primary osteoarthritis remains unknown; however, an interplay of genetic factors, mechanical factors, and biomechanical alterations in cartilage seems to be important. The incidence of primary osteoarthritis in the general population is very high. These patients should receive the benefits of good professional advice and reconstructive surgery when necessary. They may respond very well to moderating their activities and simple physical and medical therapy methods. Patients with destructive joint disease in the digits can have excellent results with arthrodesis and implant arthroplasty for the distal and proximal interphalangeal joints and with implant arthroplasty for the basal thumb joints. Surgical reconstruction is an important method in the rehabilitation of this group of individuals. The term "osteoarthritis" is preferred over "osteoarthrosis."

Adolescent↗
PubMed1983

A model evaluation of estimates of breath-to-breath alveolar gas exchange.

A mathematical model has been implemented for evaluation of methods for estimating breath-to-breath alveolar gas exchange during exercise in humans. This model includes a homogeneous alveolar gas exchange compartment, a dead space compartment, and tissue spaces for CO2 (alveolar and dead space). The dead space compartment includes a mixing portion surrounded by tissue and an unmixed (slug flow) portion which is partitioned between anatomical and apparatus contributions. A random sinusoidal flow pattern generates a breath-to-breath variation in pulmonary stores. The Auchincloss algorithm for estimating alveolar gas exchange (Auchincloss et al., J. Appl. Physiol. 21: 810-818, 1966) was applied to the model, and the results were compared with the simulated gas exchange. This comparison indicates that a compensation for changes in pulmonary stores must include factors for alveolar gas concentration change as well as alveolar volume change and thus implies the use of end-tidal measurements. Although this algorithm yields reasonable estimates of breath-to-breath alveolar gas exchange, it does not yield a "true" indirect measurement because of inherent error in the estimation of a homogeneous alveolar gas concentration at the end of expiration.

Evaluation Studies as Topic↗
PubMed1982

Uptake of nitrous oxide by man.

Because of discrepancy in reports concerning the rate of uptake of nitrous oxide by man, it seemed desirable to measure this factor when automatic control of concentrations and rapid computer measurement of breath to breath uptake became available. Six subjects inhaled 25 per cent nitrous oxide for two hours. Total uptake and alveolar uptake were determined. The total inhaled uptake, adjusted for a 70 kg subject inhaling 75 per cent nitrous oxide, corresponded well with an absorption of about 1000 ml the first minute. After a wash-in period of less than four minutes, the alveolar uptake, which at that time and subsequently equaled the total uptake, decreased approximately according to the square root of time in minutes. Considerable variation appeared between individuals, but each course approximated the same type of decrease. Absorption continued to occur during the two hour period of observation.

Absorption↗
PubMed1982

A prediction-correction scheme for forcing alveolar gases along certain time courses.

A computerized prediction-correction scheme has been devised for the control of alveolar gases. First, a model is run off-line to predict the inspiratory gas tensions at each second that should yield the desired alveolar patterns. Second, during the experiment, there is feedback correction based on the deviation of the actual alveolar values from the desired alveolar values. The actual alveolar values are found by a second computer and passed to the controlling computer using interrupts. The controlling computer has four digital-toi-analog outputs for controlling CO2, O2, N2, and air flows so as to achieve the commanded inspiratory PCO2 and PO2 (CO2 and O2 partial pressures, respectively). The scheme is illustrated for the generation of sinusoidal alveolar PCO2 with alveolar PO2 held constant and for steps of alveolar PCO2 at constant alveolar PO2.

Carbon Dioxide↗
PubMed1982

A fast gas-mixing system for breath-to-breath respiratory control studies.

A computer-controlled gas-mixing system that manipulates inspired CO2 and O2 on a breath-to-breath basis has been developed. The system uses pairs of solenoid valves, one pair for each gas. These valves can either be fully shut when a low voltage is applied, or fully open when a high voltage is applied. The valves cycle open and shut every 1/12 s. A circuit converts signals from the computer, which dictates the flows of the gases, into a special form for driving the valve pairs. These signals determine the percentage of time within the 1/12-s cycle each valve spends in a open state and the percentage of time it spends shut, which, in effect, set the average flows of the various gases to the mixing chamber. The delay for response of the system to commanded CO2 or O2 changes is less than 200 ms. The system has application for the manipulation of inspired gas fractions so as to achieve desired end-tidal forcing functions.

Carbon Dioxide↗
PubMed1981

The arthritic great toe metatarsophalangeal joint: a review of flexible silicone implant arthroplasty from two medical centers.

A review of 159 feet with double-stem silicone implants in the hallux metatarsophalangeal (MTP) joint was conducted in two medical centers. The majority of patients had a diagnosis of rheumatoid arthritis. Follow-up evaluations ranging between 18 months and six years indicate that pain relief was present in all cases with most having complete relief of pain. Hallux valgus was corrected in most and a functional range of motion as well as good muscle strength was restored. The stability provided by the procedure has improved the postoperative alignment of the lateral MTP joints from which the metatarsal heads had been excised. Operative technique must be precise and tissues must be handled and prepared for the implant with care.

Arthritis↗
PubMed1980

The Krukenberg procedure in the juvenile amputee.

The Krukenberg procedure has been performed unilaterally on juvenile amputee patients with congenital bilateral absence of the hands and observed by long-term follow-up examinations. The opposite extremity was routinely fitted with a standard prosthetic prescription as an assistive hand. In all cases, the Krukenberg stump became the leading hand. In some of the cases, the prosthesis on the opposite hand has been discarded in favor of the sensibility available without. The prehension ability of the Krukenberg stump has provided the patient with all of his functional needs. The results have been remarkably rewarding to these patients. There has been virtually no concern evidenced by the patient or the parents about the appearance of the stump. The surgical procedure has been considered to be reasonably uncomplicated. Postoperative rehabilitation has been simple and rapid. The patients have continued to improve in their rehabilitation, and the Krukenberg forceps with its improved prehension and sensibility has improved the quality of life of these people. This procedure should be extended to more individuals who have the severe handicap of bilateral hand loss.

Amputation, Surgical↗
PubMed1979

Transient response of the Geman-Miller respiratory oscillator model.

Recent evidence suggests that there is a persistence of elevated respiratory center activity for many respiratory cycles after the cessation of a neural stimulus. To explore the theoretical possibility that this behavior may be a consequence of the neural oscillator that dictates respiratory rhythm, the transient response of a mathematical model of a medullary respiratory oscillator recently described by Geman and Miller was examined using computer simulation. This concept was motivated by the presence of a persistent transient response behavior inherent in oscillators from mathematical physics. The results indicate that a transient persistence effect is evident in the model behavior under some conditions, and this effect as well as the steady-state amplitude is markedly sensitive to the shape of the saturation function that interconnects the neuron populations. Furthermore, this behavior is initiated by either an abrupt decrease in a tonic input or an abrupt decrease in the synaptic weights connecting subpopulations of neurons.

Animals↗
PubMed1979

A closed lung system study of inert gas absorption.

The demonstration that the rate of rise of the alveolar fraction of nitrous oxide is enhanced when the inspired N2O concentration is high is termed the "concentration effect." A similar effect on a second gas has been termed the "second gas effect". These effects have been observed in open systems and attributed to differential changes between inspired and expired ventilation. The purpose of this investigation is to study these effects in a closed system. A breath-holding maneuver was utilized with a high and a low N2O concentration in argon and oxygen. The results indicate that breath holding with a high N2O concentration "concentrates" both the alveolar fraction of N2O and argon. These results are attributable to alveolar volume shrinkage as a consequence of the large absorption of N2O by the pulmonary blood. A mathematical model verifies this interpretation and suggests that volume shrinkage can be important in breath-holding maneuvers designed for noninvasive measurement of cardiac output and lung tissue volume.

Argon↗