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Biomedical subjects

R T Schmidt

Publications and source records attributed to R T Schmidt.

At least 19 recordsLinked to original sources
PubMed1999

Reduce risk of inducing spatial disorientation using physiologically compatible ground lighting.

Spatial disorientation that occurs while landing aircraft during night operations may result in accidents and fatalities which are often classified as secondary to "pilot error." It has now been determined that the use of "expedient" lights, which include flares, flashlights, automobile headlights, etc., can induce spatial disorientation in pilots. The element that contributes to induction of spatial disorientation is the "point source of light" provided by these lights. Impingement on the retina of concentrated photon emissions, as supplied by incandescent (filament) lamps, flares, etc., produces an "after image," such as occurs when one briefly looks into the sun. The "after image" is caused by the time lag required for reconstitution of the neurohumoral transmitter substances in the retinal rods and cones. Pilots who develop "after images" during the final stage of landing a helicopter at night are predisposed to experiencing spatial disorientation, leading to aircraft mishaps. In contrast to flares or incandescent light sources, cold cathode lamps lack a "point source" of light emission, do not create an "after image," and are ideal to use in night landing operations. Cold cathode lights operating in the range of 512 nm (blue-green) are thought to be the most physiologically efficient color to use for night landing operations. Light sources in this nanometer range provide maximum visibility and safety for the pilot during landing operations under all environmental conditions.

Accidents, Aviation↗
PubMed1991

Breast cancer in women under 35 years of age.

A review was undertaken of 226 patients with primary breast carcinoma who were 35 years of age, or younger, from 1960 to 1987. Comparisons to other studies of young and older women were made for clinical, pathologic, and survival characteristics. Young patients with breast cancer share many of the same disease characteristics of tumor type, location, size, and nodal involvement as their older counterparts. Five- and 10-year survival rates were comparable for patients with stage I or stage II disease and negative axillary lymph nodes. However, patients with stage II disease and positive nodes appear to have a decreased survival compared with older patients.

Adult↗
PubMed1988

Potential for misleading associations between exposure and disease when reviewing multiple epidemiologic studies.

In reviewing evidence from multiple epidemiologic studies, a statistical artifact can leave an impression that a relationship exists between an exposure and a disease even if none exists. In this paper, two fundamental properties of probability were applied to hypothetical situations where results from independent studies were combined. It was evident that, even when a cause-effect relationship did not exist, several studies still appeared to confirm the relationship. This statistical artifact was related primarily to the total number of independent studies reviewed and to a lesser degree to the size of a given study. Thus, in examining evidence for a cause-effect relationship from multiple published articles, some studies are likely to show the association and some not, even if no association exists. If only the studies which show the association are considered, without regard to the total number of studies, the reviewer can be misled. This statistical effect is illustrated with an example from the rubber worker literature.

Environmental Exposure↗
PubMed1983

Pre-operative versus postoperative irradiation in stage I carcinoma of the endometrium.

A retrospective analysis of 180 cases with clinical stage I endometrial carcinoma was done in an attempt to determine the role of pre- versus postoperative irradiation (RT). One hundred and forty-eight patients were treated pre-operatively and 32 patients received postoperative irradiation. The incidence of middle and outer 1/3 myometrial invasion was 7% and 4% in the pre-operative RT versus 28% and 31% in the postoperative RT group, respectively. Three percent of the pre-operative RT group and 28% of the post-operative RT patients were found to have a higher pathological stage at the time of hysterectomy. The overall five year actuarial survival rate in the pre- and postoperative irradiation groups was 88% and 75% (p = 0.128) respectively. The 10 year survival in the pre-operative RT group was 84% versus 51% (p = 0.056) in the postoperative RT patients. There was a significant improvement (p = 0.006) in ten year actuarial survival of patients with hysterectomy specimen free of malignancy (97%) as compared to (70%) survival of patients with residual diseases. The overall failure rate was lower (9%) in the pre-operative RT as compared to 28% in the postoperative RT group (p = 0.02) with pelvic recurrences of 2% and 13%, respectively (p = 0.01). The major complication rate was 3% in the pre-operative RT versus none in the postoperative RT group. The rate of complications correlated with the dose and technique of irradiation. Our results suggest that pre-operative irradiation decreases the depth of myometrial invasion and the rate of pelvic recurrences, lowers the pathological stage and probably increases the survival compared with postoperative irradiation.

Carcinoma↗
PubMed1976

Safety and the problem employee.

Approximately 5 to 7% of workers in any large employee population can be described as having borderline acceptable work performance and fluctuating emotional stability. This subpopulation of employees can be characterized as suffering from attitudinal disturbances ranging from mild to severe. At times physical illness can be an important contributing factor, but more commonly the sole attribute these individuals possess is a negative attitude toward work. It is this sub-group of problem employees which contribute the largest percent of unsafe acts leading to the greatest numbers of industrial accidents in the work community. Identification of this sub-group in the work force and utilization of selective physician-management counseling are definite steps that can be taken to improve the overall performance of the work group. Above average frequency of industrial accidents as well as above average rates of short term absence are significant job performance characteristics which correlate highly with identification of the problem employee. The mutual interchange between supervisor and employee of the counseling session provides a significant contribution to the employees coping mechanism. In our experience 85% of employees improve their job performance following counseling without the need for additional disciplinary action. A follow-up review of job performance with the employee is held within three to six months to reinforce the corrective steps already begun. Cost savings resulting from this approach can be significant. In this study a cost savings of $185 per employee per year was generated in a small isolated work group between 1972 to 1975. The calculation of direct dollar savings foe improvement in lost time statistics probably represent minimal cost savings, as some studies assume the total cost for sickness absence are 2-1/2 times the direct cost.

Absenteeism↗
PubMed1976

Comparison of dantrolene sodium and diazepam in the treatment of spasticity.

The effects of dantrolene sodium and diazepam were compared in a double crossover study of 42 patients with spasticity due to stable multiple sclerosis. Both drugs reduced the findings of spasticity, clonus, and hyperreflexia, and the complaints of muscle stiffness and cramping. Each drug had different side effects which suggest indications and contraindications for its use in spastic patients.

Clinical Trials as Topic↗
PubMed1975

Cyclophosphamide in exacerbations of multiple sclerosis. Therapeutic trial and a strategy for pilot drug studies.

Cyclophosphamide (CY) has been shown to reverse the signs of experimental allergic encephalomyelitis (EAE) even after the onset of neurological deficits. Because of the analogy of EAE to exacerbations of multiple sclerosis (MS) a clinical trial of CY in acute MS exacerbations was undertaken. A 'sequential criterion' method was used to minimize the size of sample needed for this pilot study. CY failed to alter significantly the course of acute exacerbations of MS. Possible reasons for this failure, and the value of the sequential criterion method in pilot studies, are discussed.

Acute Disease↗
PubMed1975

A pharmacologic study of the stiff-man syndrome. Correlation of clinical symptoms with urinary 3-methoxy-4-hydroxy-phenyl glycol excretion.

We have investigated hypotheses that link the stiff-man syndrome to an imbalance of neurotransmitter systems. No evidence was found to support the concept of defective synaptic transmission at either cholinergic input to Renshaw inhibitory elements or at glycinergic inhibitory input to motoneurons from spinal interneurons, since neither physostigmine nor glycine altered symptomatology. Urinary excretion of the norepinephrine metabolite 3-methoxy-4-hydroxy-phenyl glycol showed a high correlation with clinical status. This suggests the involvement in the stiff-man syndrome of a central norepinephrine neuronal system that has net excitatory effects upon motoneurons, a system whose activity can be increased slightly by levodopa and decreased markedly by diazepam, with corresponding changes in stiffness.

Diazepam↗