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Biomedical subjects

L W Organ

Publications and source records attributed to L W Organ.

At least 19 recordsLinked to original sources
PubMed1994

Segmental bioelectrical impedance analysis: theory and application of a new technique.

Bioelectrical impedance analysis (BIA) for body composition has been based on the volume conductor model that results in the mathematical relationship Ht2/R approximately FFM, where Ht is body height, R is whole body resistance or impedance, and FFM is fat-free mass. Although this relationship exists in the human subject, its strength and usefulness have been subject to conflicting reports. This study reassessed the theory and methodology of BIA and describes a new technique for measuring segmental impedance that may resolve some major limitations associated with the current whole body impedance methodology. By use of data from 200 adult subjects, a new theory and methodology for BIA were developed in four steps: 1) a rationale was presented for replacing the Ht2/R model by one based on electrical resistivity, 2) a practical six-electrode technique for segmental BIA that uses only peripheral electrode sites was described, 3) prediction equations for fat weight based on the new segmental BIA technique were developed, and 4) prediction equations for fat distribution, a potential new use of impedance methodology, were developed using a new measure of fat distribution, the impedance index.

Adult↗
PubMed1994

An automated real time underwater weighing system.

Hydrodensitometry generally involves up to 10 trials as the subject becomes familiarized with the underwater weighing and breathing apparatus. The final result is usually an average obtained from trials with the highest underwater weights. This study describes a new underwater weighing system based on automated data acquisition and real time display of data during underwater weighing and in-tank residual volume measurement. Results are immediately available after each trial, making possible the use of percent body fat as the criterion for selecting trials for averaging. It is proposed that percent fat is a more logical choice than maximum underwater weight, because for the use of the latter to be valid, true residual volume must be accurately determined. Accuracy of percent body fat requires only that corresponding values of underwater weight and lung volume be known, without the necessity for the weight to be maximum or the volume truly residual. This also reduces the number of trials, which in this study averaged 4.3 +/- 1.0, because each trial was potentially useful regardless of the magnitude of the underwater weight.

Adipose Tissue↗
PubMed1983

What happened to VIM thalamotomy for Parkinson's disease?

A prospective review of 75 of 190 parkinsonian patients undergoing unilateral thalamotomy was displayed with a computer graphics technique examining three equal consecutive groups from the pre-, early, and late L-dopa eras. Histograms for average function and scattergrams of individual patient's performance preoperatively and up to 2 years postoperatively were prepared. No ipsilateral effects or consistent iatrogenic deterioration of any function were identified. 2 years after surgery, 82% had no tremor in the contralateral fingers or hand and 7% had almost no tremor; contralateral tremor elsewhere was infrequent. Rigidity and manual dexterity improved less strikingly, the latter only reflecting abolition of tremor; locomotion, speech, facial movement and handwriting did not improve. There was no mortality, but 8% had persistent significant complications. VIM thalamotomy remains the treatment of choice for severe drug-resistant parkinsonian tremor.

Adult↗
PubMed1980

A new computer technique for continuous measurement of the pre-ejection period in the human fetus: physiologic significance of pre-ejection period patterns.

A new interactive computer graphics system was developed for continuous online or offline measurement of the pre-ejection period (PEP) in the human fetus during both the antepartum and the intrapartum period. A significant feature is the system's ability to accurately measure PEP from the onset of QRS complex to the beginning of aortic opening with a resolution of less than 2 milliseconds. Normal patterns of PEP prolongation were observed with fetal movement and occlusion of the umbilical cord, whereas progressive shortening of PEP was noticed with late decelerations associated with acute hypoxia. A pathologic pattern of PEP prolongation associated with late decelarations and poor heart rate variability was observed with chronic hypoxia and acidosis. These patterns suggest that continuous monitoring of PEP may be a useful adjunct to current monitoring methods when attempting to assess fetal cardiac performance and well-being.

Computers↗
PubMed1980

The pre-ejection period as an antepartum indicator of fetal well-being.

A preliminary study was made of the potential usefulness of the pre-ejection period (PEP) as an antepartum indicator of fetal well-being. PEP was evaluated in 108 subjects over a 2-year period. It is essential to correct for the effects of heart rate and gestational age on PEP before attempting to relate it ot fetal status. From the control group of 95 fetuses within our study, an equation to correct PEP to a standard heart rate of 140 beats per minute and gestational age of 40 weeks was derived: PEP140,40 = PEP + 0.36(FHR-140) + 1.4(40-GA). PEP140,40 for our control group was 72.9 +/- 2.8 msec. Of the 13 fetuses classified as abnormal in the study, four had a normal PEP140,40 eight showed significant shortening, and one had significant prolongation. These changes in PEP were related to underlying fetal status, and, when used together with other parameters of antenatal assessment, appear to be useful in predicting the ability of the fetus to withstand stress compatible with survival. Continuing evaluation on larger populations will be required to confirm the results of this study. The use of PEP140,40 is suggested as a valid method for comparing reports from different investigators.

Acidosis↗
PubMed1980

Visual phenomena evoked by electrical stimulation of the human brain stem.

19 visual effects have been elicited out of 9,383 sites during stimulation mapping for physiological localization during stereotactic surgery. It is proposed that three visual pathways can be recognized during subcortical electrical stimulation in man. The optic tract and geniculocalcarine pathway, projecting to area 17, are recognizable by the production of contralateral coloured phosphenes. The tectopulvinar pathway projecting to areas 18 and 19 is recognizable by the eliciting of contralateral or bilateral colourless phosphenes or 'negative' visual effects, the latter presumably reflecting inhibitory collicular influences. Finally, deep responses, consisting of apparent movement of the visual fields, intermingled with 'negative' visual and oculomotor effects, suggest activation of a visual-oculomotor coordinating system.

Brain Mapping↗
PubMed1980

Deafferentation and causalgia.

The concept of deafferentation pain has been developed as an entity distinct from somatic pain which can arise in the course of both cancerous and nonmalignant disease. Its distinctive clinical features and responses to diagnostic and therapeutic manipulations have been reviewed. Evidence is marshalled to show that it results from gradually developing alterations in the central nervous system, which, once established, persist despite removal of the original stimulus. Evidence is presented that the mesencephalic tegmentum may be part of a reticulothalamocortical system undergoing denervation hypersensitivity following deafferentation, whose stimulation by electric impulses, and, presumably, naturally occurring neural inputs, can result in a painful conscious experience reproducing the patient's pain in a manner similar to that whereby stimulation of temporal-parietal association cortex elicits recall of past events.

Anesthetics, Local↗
PubMed1978

Quantitative indices of short- and long-term heart rate variability.

Two quantitative indices of heart rate variability are proposed. Instantaneous variability is defined as the average of the absolute value of instantaneous rate differences over a 30 second interval. It is sensitive to short-term variability changes. Bandwidth variability is defined as twice the standard deviation of instantaneous heart rates over a 30 second interval, and it is a measure of long-term variability. The rationale for the choice of these indices is discussed, and they are compared with other published indices of variability. Samples of computer printout of instantaneous and bandwidth variability obtained from fetal heart rate records are given.

Electrocardiography↗
PubMed1978

Vestibulothalamic projections in man--a sixth primary sensory pathway.

1. Responses suggesting activation of the vestibular system, elicited by electrical stimulation of the human thalamus during 22 routine stereotaxic neurosurgical procedures, were examined in a retrospective study to determine the possible existence of vestibulothalamo-cortical projections in man. 2. Such responses were most frequently described as sensations of movement through space and were associated with two distinct vestibulothalamic projections: a) an anterior relay was situated ventral to the medial lemniscus, passing lateral to the red nucleus and dorsal to the subthalamic nucleus prior to terminating in the nucleus ventrointermedius (Vim) (comparable to VPLo in primates); b) a posterior relay associated with the auditory pathway (lateral lemniscus and brachium of the inferior colliculus) projected to the medial geniculate body. 3. The production of sensations of motion in conscious patients by stimulating areas that are similar to those reported constituting vestibulothalamic pathways in cats and primates implies a distinct primary sensory cortical projection for processing information from the vestibular receptors pertaining to the recognition of spatial movements.

Brain Mapping↗
PubMed1978

Computerized graphic display of physiological data collected during human stereotactic surgery.

An on-line computerized graphic display has been developed for use during stereotactic operations. This depicts in the form of figurine charts and alph-numeric symbols, appropriately oriented on saggital brain diagrams, the results of serial threshold stimulation of the brain. The display facilitates choice of target sites and the data can be stored in a tape library from which search-and-plot programs can be activated for any type or combination of types of response.

Brain↗
PubMed1977

Percutaneous radiofrequency lumbar rhizolysis (rhizotomy).

Low back pain may arise from degenerative changes in the posterior joints of the lumbar spine. These joints are innervated by a branch of the posterior primary ramus, which follows an anatomically constant course. Pain impulses from these joints can be interrupted by coagulating this nerve with a radiofrequency wave, the probe having been placed in the area of the nerve percutaneously. Percutaneous lumbar rhizolysis was carried out under local anesthesia on an outpatient basis in 82 patients, most of whom had multiple level rhizolysis. Rhizolysis was successful in 67% of patients with mechanical low back pain without evidence of disc herniation and nerve-root compression or psychogenic pain, who had not previously undergone an operation for relief of the pain.

Back Pain↗
PubMed1977

Computerized graphic display of results of subcortical stimulation during stereotactic surgery.

An on-line computer programme is described and illustrated which is capable of displaying graphically in the form of Woolsey-type figurine charts stimulation-induced responses obtained during stereotactic surgery. Not only can these data then be optimally utilized for lesion localization but also the programme includes facilities for a variety of types of analysis of the tape-stored data pooled from all patients studied.

Computers↗
PubMed1976

Measurement of the pre-ejection period during labor with the use of arterial pulse time.

A new fetal parameter, the arterial pulse time, is described. It is the time from the onset of the fetal electrocardiographic recording to the arrival of the arterial pulse wave recorded at the fetal head. Since arterial pulse time differs from the pre-ejection period by only an apparently constant value, it is proposed as a potential method for obtaining the pre-ejection period during labor.

Arteries↗