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At least 55 records · Page 3Linked to original sources

PubMed1987

Localisation of cardiac related impedance changes in the thorax.

The existence of variations of normal human thoracic impedance, during the cardiac cycle to high frequency electrical current is well known. Since the impedance variations within the thorax are synchronous with the electrocardiogram (ECG), they are attributed to cardiac activity. They can arise from the change of either the rate of blood flow or the blood volume in the heart chambers, the great blood vessels and the lungs. However, their relative contribution is not known. Many investigators have worked on the non-invasive determination of some cardiac parameters using surface electrode impedance measurements on the thorax. Since the relationships between the measurement results and the pulsatile circulation of blood in various organs inside the chest are not well known, the information determined by surface impedance measurements is not as accurate as the results of invasive techniques. Recent advances in the clinical use of applied potential tomography (APT), or electrical impedance imaging, showed that the APT system gives a good soft-tissue contrast and has good sensitivity to resistivity changes. It is therefore concluded that the origin of thoracic impedance changes related to cardiac activity can be deduced from APT images. Our initial studies of ECG gated dynamic APT images of the thorax show that cardiac related thoracic impedance variations originating from different organs can be separated. Sequential APT images of the thorax during the cardiac cycle are presented. The movement of blood from the ventricles to the lungs and vascular system and back to the ventricles is observable in these images.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1976

Heat exchange in relation to blood flow between thorax and abdomen in bumblebees.

1. The narrow passage within the petiole between thorax and abdomen is anatomically constructed so that counter-current exchange should retain heat in the thorax despite blood flow to and from the cool abdomen. 2. However, the counter-current heat exchanger can be physiologically circumvented. Exogenously heated bumblebees prevented overheating of the thorax by shunting heat into the abdomen. They also regurgitated fluid, which helped to reduce head temperature but had little effect on thoracic temperature. 3. Temperature increases in the ventrum of the abdomen occurred in steps exactly coinciding with the beats of the ventral diaphragm, and with the abdominal 'ventilatory' pumping movements when these were present. The ability to prevent overheating of the thorax by transport of heat to the abdomen was abolished when the heart was made inoprative. 4. At low thoracic temperatures the ventral diaphragm beat at a wide range or rates and with varying interbeat intervals, while the heart beat at a high frequency relative to the ventral diaphragm, but at a very low amplitude. However, when thoracic temperature exceeded 43 degrees C the amplitudes of both were high, and the interbeat intervals as well as the beating frequencies of the two pulsatile organs became identical in any one bee. Furthermore, heated bees engaged in vigorous abdominal pumping at the same frequency as that of their heart and ventral diaphragm pulsations. 5. The results indicate that the anatomical counter-current heat exchanger is reduced or eliminated during heat stress by 'chopping' the blood flow into pulses, and the blood pulses are shunted through the petiole alternately by way of a switch mechanism.

Abdomen↗

PubMed1981

Pulmonary, chest wall, and lung-thorax elastances in acute respiratory failure.

The usefulness of lung-thorax compliance (or elastance) as an index of pulmonary compliance (or elastance) was examined in 15 patients being ventilated for acute respiratory failure. Mean lung-thorax elastance (ELT) was 27.9 +/- 2.6 cm H2O/L, and the chest wall accounted for 34 +/- 2 percent of the mean total value. Changes in ELT caused by increments of positive end-expiratory pressure correlated only with changes in pulmonary elastance (r = 0.96; P less than 0.001) and not with chest wall elastance, although individual patients varied as to the contribution of the chest wall component. Lung-thorax elastance increased in direct proportion (1:1) to increases in pulmonary elastance, whereas the changes in lung-thorax compliance were only half those in pulmonary compliance. We conclude that elastance is a more useful clinical index than compliance.

Acute Disease↗

PubMed1979

[Architectonics of the thorax (author's transl)].

Blunt traumata cause injury to the thorax and intrathoracic organs by deforming the chest wall and the enclosed structures. Neither examination of the dead person and re-enactment of the accident nor experimental studies on the living or dead person can fully elucidate the course of events. A more satisfactory approach is to use biomechanic models to simulate the structure of the thorax and the type of deformation it undergoes when subjected to various traumata. Such an elasto-static analysis presupposes knowledge of (1) the global geometry of the thorax; (2) the cross sectional geometry of the individual components; (3) the mechanical properties of the material; (4) the force of the impact; (5) concomitant conditions. The results obtained with the models are reviewed. They make it possible to predict the deformation of the thorax in response to the force of the impact, the location and type of fracture of the ribs and the deformation of the intrathoracic organs.

Anthropometry↗

PubMed2000

Staging computed tomography of the thorax for nasopharyngeal carcinoma.

BACKGROUND: To assess the role of staging CT of the thorax in advanced nodal stage nasopharyngeal carcinoma and to examine the hypothesis that contiguous spread of nodal metastases from the supraclavicular region to the upper mediastinal region occurs in this cancer. METHODS: Forty-four patients with newly diagnosed nasopharyngeal carcinoma with neck node metastases to the supraclavicular region (ie, AJCC N3b stage) underwent contrast-enhanced CT (CECT) thorax for staging. CT findings and clinical outcome were analyzed. RESULTS: No patient was found to have intrathoracic metastasis, although 1 had hepatic metastases on CECT of the thorax, resulting in upstaging in 1 of 44 (2%) of patients. With a median follow-up time of 21 months, 3 patients had lung metastases and 2 had axillary nodal metastases develop without evidence of upper mediastinal nodal metastases. CONCLUSION: Staging CECT of the thorax has a very low yield in nasopharyngeal carcinoma, even in advanced nodal disease. The hypothesis that contiguous spread of nodal metastases from the supraclavicular region to the upper mediastinum is not substantiated, and no evidence suggests that radiation therapy for N3b-stage disease needs to encompass the upper mediastinum.

Adult↗

PubMed1978

[Traffic accidents and seat belts: thorax injuries (author's transl)].

The types of injuries to 313 automobile accident victims, especially thorax injuries, are compared. Independent of seat belt use (42%), there was in general a higher degree of injury. Those wearing seat belts had a markedly less severe AISm (median degree of injury of body region) and less severe thorax injury. Severe thorax injury was first found at speeds greater than 24 km/h above average. Severer thorax injury is to be expected with defective seat belts (AISm = 1.25) than with properly functioning belts (AISm = 0.32).

Accidents, Traffic↗

PubMed1996

[Calculated organ doses and effective dosage for computerized tomography examination of the thorax and abdomen: are these doses realistic?].

PURPOSE: To analyse how far dose calculations for the CT examination of the thorax and abdomen can lead to faulty estimations of organ doses and effective dose due to differences in the topographic anatomy between mathematical phantom and man. METHODS: For the CT examination of the thorax, upper abdomen, pancreas, pelvis and the entire abdomen, organ doses were calculated with conversion factors, first with regard to the topographic relation within the phantom, then with additional regard to the real anatomy of the man. RESULTS: In the phantom, the abdomen lies outside the scan volume in case of CT-examination of the thorax and the whole intestine outside the scan volume in case of CT-examination of the upper abdomen and the pancreas, whereas the entire intestine is directly exposed in case of CT-examination of the pelvis. Dependent on whether dose calculations take real anatomy into account, doses of special organs can differ by a factor greater than 15. The calculated effective doses differ by a factor less than 1.5. CONCLUSIONS: Calculations of organ doses for the CT examination of the thorax and abdomen can lead to considerable errors due to different topographic relations between phantom and man. In contrast the calculated effective dose is realistic. Hence, dose calculations with the help of mathematical phantom is an efficient method to estimate the total radiogenic risk.

Female↗

PubMed1995

[Normal ultrasound curves of the fetal osseous thorax and fetal lung].

Over and above the evaluation of fetal standard data, chest and lung measurements were performed in a prospective cross-sectional study with real-time ultrasound. The study group consisted of 610 patients between 12 and 41 weeks' gestation. Only uncomplicated pregnancies with carefully documented gestational age were included. Patients with multiple pregnancy, fetal anomalies, intrauterine growth retardation or macrosomia and patients with oligohydramnios were excluded. Transversal (BTTD) and sagittal (BTSD) diameter of the bony fetal thorax were measured as an outer-outer-measurement at the level of the atrioventricular valves; the thorax should be as circular as possible and at right angles to the fetal spine. Lung measurements (LD) were performed in the same plane in the direct extension of the long axis of the fetal heart. The circumference of the bony thorax (BTC) was calculated from the two thoracic diameters according to the formula BTC = (BTTD+BTSD)/2 x 3.142. For all parameters growth curves with 5., 50. and 95. percentiles were established. Growth of the bony thorax as well as the lung diameter was shown in a nonlinear function. Lung diameter and thoracic circumference were used to calculate the ratio of these two parameters with reference to the gestational age.

Anthropometry↗

PubMedDate not supplied

Electric field plethysmography signals of the human thorax as determined by a 2-D FE-model.

Electric field plethysmography (EFPG) signals of the human thorax consist of a baseline component, a respiratory component and a cardiac component. This paper investigates to what extent a two-dimensional finite-element model of the human thorax can serve as a tool for signal prediction allowing for both optimisation of electrode position and effective signal interpretation. In the model inspiration is taken into account by decreasing lung conductivity. Modelling of cardiac activity involves heart geometry changes and lung conductivity increase. Comparison with experiments shows that the model is more effective for strip than spot electrodes for current injection. Modelling results suggest that the thorax behaves approximately as a homogeneous structure with an inspiratory conductivity increase of about 5%. Two electrode pairs are preferable for monitoring respiration in general. As cardiac activity involves two counter-acting signal sources in the thorax, optimum electrode position is obtained using four separated electrodes. However, recommendable positions for two electrode pairs are on the left sternal and right parasternal line. The investigation shows that in providing a proper modelling of respiration and cardiac activity, a 2-D model provides a practical tool for modelling EFPG signals with the cost of a few structural and systematical restrictions.

Cardiography, Impedance↗

PubMed1993

The evolutionary history of Drosophila buzzatii. XXVII. Thorax length is positively correlated with longevity in a natural population from Argentina.

The correlation between body size and longevity was tested in an Argentinian natural population of Drosophila buzzatii. Mean thorax length of flies newly emerging from rotting cladodes of Opuntia vulgaris was significantly smaller than that of two samples of flies caught at baits. The present results which might be interpreted as directional selection for longevity favoring larger flies are in agreement with previous results achieved in a Spanish natural population of D. buzzatii. Flies emerging from different substrates showed significant differences in thorax length, suggesting that an important fraction of phenotypic variance can be attributed to environmental variability. However, laboratory and field work in different populations of D. buzzatii showed a significant genetic component for thorax length variation.

Animals↗

PubMed1987

Acute and chronic effects of xanthine oxidase on lung thorax-compliance in guinea pigs.

Xanthine oxidase was given intratracheally in a single dose to guinea pigs. Lung compliance was measured after 4 h and 14 days respectively. Lung-thorax compliance was significantly lower compared with saline-treated controls both 4 h and 14 days after application of fluid. At 14 days there was a dose-related response between lung-thorax compliance and xanthine oxidase administered in the range 0-1.0 U. Superoxide dismutase (SOD) had a protective effect on xanthine oxidase action at 4 h, but not after 14 days. We suggest that the decreased lung-thorax compliance was caused by superoxide radicals, produced by the hypoxanthine-xanthine oxidase system, damaging lung tissue. We speculate that free oxygen radicals produced by the hypoxanthine-xanthine oxidase system could be an important contributory pathogenetic factor in producing both acute and chronic lung damage in, for instance, premature babies or adults, with respiratory distress syndrome.

Animals↗

PubMed2004

Thorax vibrations of a stingless bee ( Melipona seminigra). I. No influence of visual flow.

An important question in stingless bee communication is whether the thorax vibrations produced by foragers of the genus Melipona upon their return to the nest contain spatial information about food sources or not. As previously shown M. seminigra is able to use visual flow to estimate flight distances. The present study investigated whether foraging bees encode the visually measured distance in their thorax vibrations. Bees were trained to collect food in flight tunnels lined with a black-and-white pattern on their side walls and floor, which substantially influenced the image motion they experienced. When the bees had collected inside the tunnels the temporal pattern of their vibrations differed significantly from the pattern after collecting in a natural environment. These changes, however, were not associated with the visual flow experienced inside the tunnel. Bees collecting in tunnels offering little visual flow (stripes parallel to flight direction) modified their vibrations similarly to bees collecting in tunnels with high image motion (cross stripes). A higher energy expenditure due to drastically reduced flight velocities inside the tunnel is suggested to be responsible for changes in the thorax vibrations. The bees' vibrations would thus reflect the overall energetic budget of a foraging trip.

Animal Communication↗

PubMed2004

Thorax vibrations of a stingless bee ( Melipona seminigra). II. Dependence on sugar concentration.

Using a laser vibrometer we studied the influence of the food's sugar concentration on different parameters of the thorax vibrations produced by foragers of Melipona seminigra during trophallaxis in the nest. The concentrations tested (20-70% sugar w/w) were within the biologically relevant range. They substantially influenced different parameters of the thorax vibrations. An increase of energy gains at the food source due to an increased sugar concentration was followed by an increase of both the pulse duration and the duty cycle and by a decrease of the pause duration between two subsequent pulses. These findings further support the hypothesis that the temporal pattern of the thorax vibrations reflects the energy budget of a foraging trip rather than food source distance. Likewise, the steep increase of pulse duration variability with sugar concentration is hard to reconcile with the assumption that pulse duration conveys reliable information about food source distance when bees collect at high-quality food sources.

Animal Communication↗

PubMed1975

Localization of hyperfunctioning parathyroid tissue. Radioimmunoassay of parathyroid hormone on samples from the large veins of the neck and thorax and selectively catheterized thyroid veins.

Radioimmunoassay of parathyroid hormone on samples obtained from the large veins of the neck and thorax was utilized for localization in twenty-one patients with hyperparathyroidism. In seventeen of these patients, as many of the thyroid and mediastinal veins as possible were also sampled. This study reveals that sampling of the large veins of the neck and thorax is an insensitive means of adenoma from hyperplasia. Anatomic variations in the drainage of the inferior thyroid veins and dilution of the parathyroid venous effluent by the large veins of the neck and thorax seem to explain this insensitivity and the occasionally misleading results of large vein sampling. Sampling of the small thyroid veins, however, is a sensitive and specific means of localization and permitted preoperative differentiation of adenoma from hyperplasia in fourteen of our seventeen patients. Communications between the inferior thyroid and thymic veins and the fact that mediastinal adenomas frequently bring their blood supply down from the cerevical area suggest that sampling of the small thyroid veins may be of only limited value in identifying a mediastinal adenoma.

Adenoma↗

PubMed1990

Three-dimensional osseo-ligamentous model of the thorax representing initiation of scoliosis by asymmetric growth.

A biomechanical model of the human thorax was constructed to investigate how asymmetric growth of the thorax might initiate spinal lateral curvature and axial rotation as seen in scoliosis deformities. Geometric data specifying nodal points of the model were taken from stereo-radiographs of an adolescent subject. An initially symmetrical geometry was created by 'mirroring' measurements of a hemi-thorax and spine. Published data provided cross-sectional measurements of the ribs, material properties of tissues and global flexibilities of the intervertebral motion segments. The ribs, sternum, intervertebral motion segments and intercostal ligaments were represented by elastic elements. Model deformations were calculated by the direct stiffness finite element method, with growth represented by an initial strain term in the constitutive law. Non-linear behavior was accommodated by running the model recursively, with updated node locations at each step. Both stress relaxation and stress modulation of growth in the component tissues were simulated. Thoracic growth of 20% with asymmetric growth of the ribs was simulated to give rib length asymmetries of 11%. similar to that observed in a previous study of patients with idiopathic scoliosis. This resulted in the model having a small thoracic scoliosis curvature convex toward the side of the longer ribs. Variations of the model which permitted free motion at the costo-vertebral joints or produced changes in the curvature of the posterior parts of the ribs resulted in axial rotation of the vertebrae similar to that observed clinically. The model supports the idea that growth asymmetry could initiate a small scoliosis during adolescence.

Adolescent↗

PubMed1985

Influence of thorax irradiation on the survival of mice with spontaneous or artificial lung metastases from a transplantable mammary adenocarcinoma.

The effect of thorax irradiation on lung metastases, either occurring spontaneously from a primary mammary adenocarcinoma (M8013X) transplanted on the leg or artificially induced by intravenous injection of tumor cells was studied. Increasing the interval between the moment at which lung metastases are supposed to originate and the thorax irradiation resulted in a rapid decrease of the effectiveness of this treatment in preventing the development of lung metastases. Early treatment of the mice not only resulted in a considerable number of animals that were cured, but also in a significant decrease in the number of tumor localizations in the lung of those animals still developing metastases. Thorax irradiation performed later was much less effective; at autopsy the lung showed a large number of small metastases. Increasing the radiation dose led to an increased number of cures; however, an increased number of mice dying of lethal lung damage was also observed. Irradiation of the lungs of mice with 5 or 10 Gy, 24 hours, 7 days or 14 days prior to i.v. injection with tumor cells, did not significantly increase the number of mice with lung metastases. Immunological resistance against the tumor played a role in our experiments with both spontaneous and artificial lung metastases.

Adenocarcinoma↗

PubMed2005

Stroke affects the coordination and stabilization of head, thorax and pelvis during voluntary horizontal head motions performed in walking.

OBJECTIVE: This study was conducted to investigate and compare the coordination and stabilization of axial segments during walking with and without horizontal voluntary head turns, in healthy (n=5) and hemiparetic (n=10) subjects. METHODS: Subjects were instructed to turn the head as fast and as soon as possible in the direction indicated by an illuminated arrow signal (right, left or none) that was triggered at initial contact of the right (healthy) or paretic (hemiparetic) foot. Head, thorax, and pelvis motions were obtained from a 9-segment model using retro-reflective markers and a Vicon-512 system with 6 high-resolution cameras. Coordination of axial segments in the horizontal plane was characterized using cyclographs and cross-correlation analyses. Stabilization of the segments was quantified using root mean square (RMS) values of the segment's normalized acceleration profile. RESULTS: The healthy subjects showed a direction-dependent modulation of axial segment coordination, with head turns toward and away from the stance limb favoring and hindering, respectively, the contra-rotational pattern of the thorax with respect to the pelvis during locomotion. Meanwhile, pelvis motions remained unaltered. This direction-specific modulation pattern was disrupted in the hemiparetic subjects, both in the spatial and temporal domains. Moreover, larger RMS values for head and thorax segments were observed in the hemiparetic groups, both with and without the superimposition of voluntary head motions. CONCLUSIONS: The findings suggest that: (1) head rotations during walking modify axial segment coordination in a direction-specific manner, (2) the pelvic rotations associated with locomotion remained unaffected by head rotations and (3) stroke alters this coordination behavior, which may contribute to balance dysfunctions during locomotion.

Aged↗

PubMed2004

The association between upper trapezius activity and thorax movement in classical singing.

This study aimed to examine in classical singing the phasing of the activity in upper trapezius (TR) to upper and lower thorax movement and to the phasing of activity in the intercostals (INT) and in the lateral abdominal (OBL) muscles. Electromyographic (EMG) activity was recorded from the TR, INT, and OBL muscles on the right side. Thorax movement (TX) was traced with two strain gauge sensors placed around the upper and lower thorax. Four professional opera singers (soprano, mezzo, tenor, and baritone) and four advanced student classical singers (three sopranos and one mezzo) participated. Three of the professional singers were 33 years, and one was 40 years. The students were between 23 and 30 years. Different arias, freely chosen by the singers from their professional repertoire, served as the singing task for the opera singers. All students sang "Summertime" from Porgy and Bess. All subjects performed their task three times with variation in vocal loudness (normal, forte, piano). Thereafter, for all subjects, a biofeedback (BF) procedure was performed on TR to lower TR activity and a repeat performance of the singing tasks was carried out. EMG activity from the three recording sites and upper and lower TX circumference were compared before and after BF. A phasing of upper TR activity to INT and OBL activity was discovered, all muscles supporting the expiration phase. During phonation, the upper TR contributes in the compression of upper TX, thus serving as an accessory muscle of expiration. Group results from both opera singers and student singers showed that EMG activity was significantly lowered after BF. The lowered TR activity resulted in an expanded upper TX circumference and less TX respiratory movement after BF.

Abdominal Muscles↗