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At least 271 records · Page 15Linked to original sources
PubMed1990

A proposed new mechanism of traumatic aortic rupture: the osseous pinch.

The currently accepted mechanism to explain traumatic aortic rupture from rapid deceleration involves a combination of traction, torsion, and hydrostatic forces. The authors hypothesize that aortic isthmus lacerations result from a pinch of the aorta between the spine and the anterior bony thorax (manubrium, clavicle, and first ribs) during chest compression caused by abrupt deceleration. Compression of an articulated, normally moving thoracic skeleton containing a synthetic aorta consistently caused transection of the aorta at the isthmus between the spine and anterior bony structures. Analysis of rotation of the first rib in 10 consecutive patients undergoing computed tomography of the chest demonstrated interposition of the distal aortic arch and isthmus between the vertebrae and anterior bony thorax in each instance. Aortas excised from laboratory dogs were pinched between structures simulating bones to reproduce intimal and medial lesions indistinguishable from lesions associated with naturally occurring traumatic disruptions. Although further studies in cadaveric specimens are necessary to confirm this mechanism of injury, the authors believe that their results support the osseous-pinch mechanism of aortic rupture.

Animals↗
PubMed1981

Chest wall shape during forced expiratory maneuvers.

Abdominothoracic shape during the forced vital capacity was studied in 10 normal subjects using magnetometers to monitor anteroposterior diameters at the level of the manubrium, xiphoid, and epigastrium, lateral rib cage diameter at the xiphoid level, and vertical motion of the rib cage. Thoracic cross-sectional area change at the xiphoid level was found to lag lung volume change, due to an early paradoxical increase (or lack of change), of lower anteroposterior rib cage diameter. To the extent that the resulting rib cage deformation can influence the pleural pressure gradient, the observed shape changes provide a potential mechanism for early preferential emptying of the upper lobes and later more homogeneous emptying in forced, compared to slow, vital capacity maneuvers. Comparisons of shape changes during Valsalva and abdominal expiratory ("expulsive") maneuvers suggest that lower rib cage deformation may not simply be due to the action of rib cage muscles affecting predominantly the lateral rib cage but rather the results of diaphragmatic activity and the influence of abdominal shape on the lower rib cage.

Adult↗
PubMed1991

Adaptive modeling of the human rib cage in median sternotomy.

This paper describes a limited computer-analyzed kinematic model of the rib cage that can be adapted to individual subjects. Also described is its validation and use in assessing the changes in chest wall shape after coronary artery bypass graft (CABG) surgery in 12 patients. The positions of a small number of anatomic locations on the thoracic spine, ribs, manubrium, and sternum are measured from lateral and posterior-anterior chest radiographs. The computer program puts these two views together removing the magnification and reconstructs any missing points to give a three-dimensional picture of the rib cage to which mathematical models of the bones are scaled. The patients had chest radiographs taken at total lung capacity (TLC) and residual volume (RV) to investigate the source of the restrictive ventilatory defect that follows CABG. The predictions from the model were tested by comparing full-sized computer plots with the actual chest radiographs. The estimates of the bony structures were accurate to +/- 3 degrees for orientations and +/- 6 mm for positions. We found reduced rib motion both "pump-handle" (theta) and "bucket handle" (psi) going from theta, psi left, psi right = 9 degrees, 10 degrees, 14 degrees to 4 degrees, 10 degrees, 9 degrees, respectively, after surgery with P less than 0.025, 0.42, 0.07. The angles were measured from the horizontal and increased caudally. There was also reduction in the range of angles subtended by the arc of the thoracic vertebrae between TLC and RV, which went from 12 degrees to -1 degrees (P less than 0.015). These data explain the fall in lung volumes that follow CABG and provide insight into the contribution made by the ribs and spine in full inspiration and full expiration.

Coronary Artery Bypass↗
PubMedDate not supplied

Central neural circuitry in the jellyfish Aglantha: a model 'simple nervous system'.

Like other hydrozoan medusae, Aglantha lacks a brain, but the two marginal nerve rings function together as a central nervous system. Twelve neuronal and two excitable epithelial conduction systems are described and their interactions summarized. Aglantha differs from most medusae in having giant axons. It can swim and contract its tentacles in two distinct ways (escape and slow). Escape responses are mediated primarily by giant axons but conventional interneurons are also involved in transmission of information within the nerve rings during one form of escape behavior. Surprisingly, giant axons provide the motor pathway to the swim muscles in both escape and slow swimming. This is possible because these axons can conduct calcium spikes as well as sodium spikes and do so on an either/or basis without overlap. The synaptic and ionic bases for these responses are reviewed. During feeding, the manubrium performs highly accurate flexions to points at the margin. At the same time, the oral lips flare open. The directional flexions are conducted by FMRFamide immunoreactive nerves, the lip flaring by an excitable epithelium lining the radial canals. Inhibition of swimming during feeding is due to impulses propagated centrifugally in the same epithelium. Aglantha probably evolved from an ancestor possessing a relatively simple wiring plan, as seen in other hydromedusae. Acquisition of giant axons resulted in considerable modification of this basic plan, and required novel solutions to the problems of integrating escape with non-escape circuitry.

Action Potentials↗
PubMed2006

Key features of the human middle ear.

The human middle ear was investigated using a generalised circuit model which can simulate the spatial vibrations of the ossicular chain. The behaviour was observed for acoustic excitation via the normal air conduction path and for mechanic excitation due to shaking the complete temporal bone. More insight into the functionality of the middle ear was obtained by also considering abnormal conditions such as stiffenings. It turned out that the mammalian middle ear is superior to a columella ear due to its particular design. The placement of comparably heavy bones (malleus head and incus body) outside the main transmission path between the manubrium and the stapes footplate in combination with a very flexible ossicular chain creates several favourable properties.

Acoustic Stimulation↗
PubMed1986

Detection of lung abnormalities by auscultatory percussion: a comparative study with conventional percussion.

Auscultatory percussion is a new method of physical examination developed by Guarino [Lancet i: 1332-1334, 1980]. It consists in tapping lightly the manubrium sterni with the distal phalanx of the middle finger while listening over the chest wall posteriorly with a stethoscope; a decrease in sound intensity is usually attributed to lung abnormalities. The aim of our study was to assess the validity of the method as compared to classical percussion, a point not entirely clear in the original study. Two observers independently examined 281 unselected patients (170 men; 111 women) referred for chest X-ray studies. Roentgenographic analysis, carried out by a third observer, revealed 12 categories of abnormalities in 96 patients. The validity of auscultatory and conventional percussion was calculated by taking the product of sensitivity and specificity of each method. For both observers and both methods, the values of this index were always found to be below 0.25, indicating that the results can be explained entirely by chance. When the roentgenographic category was taken into account, both methods of percussion were valid only to detect large pleural effusions. Auscultatory percussion failed completely to detect many other abnormalities including solitary nodules less than 6 cm in diameter. There is no single hypothesis to explain these results. Various possibilities are discussed.

Adult↗
PubMed1982

A critical review of experimental observations on ear-drum structure and function.

This paper presents a review of the experimental data available concerning ear-drum structure, properties and behaviour, in order to provide a basis for quantitative modelling and to identify areas where further information is required. The review of anatomy and structure indicates a lack of quantitative data about thickness, fibre distribution, three-dimensional curvature, and post-natal development. The mechanical properties of the ear-drum and attached structures are very poorly known, particularly with respect to isotropy, uniformity and damping. A historical review of observations of ear-drum vibration patterns shows general agreement that at low frequencies the displacements of the manubrium are smaller than those of the surrounding drum. Possible reasons are suggested for the apparent incompatibility of Békésy's capacitive-probe measurements with this picture.

Animals↗
PubMed1992

Diagnosis of the ossicular chain in the middle ear by high-resolution CT.

This study was conducted to assess the usefulness and limitations of high-resolution CT for diagnosing the ossicular chain in the middle ear. The CT images in this study were obtained in as much detail as possible and 2 direction images. Preoperative CT findings of the ossicular chain were compared with operative findings in 26 patients with ossicular defects. Preoperative detection of the complete defect of the malleus head and the body and long process of the incus by high-resolution CT was possible in all cases, while detection of the defect of the manubrium of the malleus and superstructure of the stapes could be made in 33.3 and 60%, respectively. The defect of the incudostapedial joint (1 case) and partial defect of the stapes crus (2 cases) could not be diagnosed correctly by preoperative estimation.

Cholesteatoma↗
PubMedDate not supplied

Etretinate-induced malformation of the first two branchial arches: differential staining and microdissection study of embryonic cartilage.

Malformations of the cranial base, temporal bone and middle ear were induced in the offspring of Sprague-Dawley rats by a single intraperitoneal injection of 10-30 mg/kg etretinate (Tigasone) at days 8.5-10.5 of gestation. By differential staining of the embryonic craniofacial cartilage and bone, and microdissection of the otomandibular complex, the induced malformations were studied specifically. Defective formations of Meckel's cartilage and the cartilaginous skull base were found to be prominent features of the malformation. The malformation included defective middle-ear ossicles; especially the malleus and incus were fused with a shorter than normal long process and manubrium. In conjunction with the distal part of Meckel's cartilage, mandibular micrognathia was observed. All of the malformed tissues are derivatives of the first and second branchial arches. The teratogenically induced defects in the rat embryos show some similarities to the clinical syndromes of the first and second branchial arches in man.

Abnormalities, Multiple↗
PubMed1999

Effect of lung volume reduction surgery on diaphragm length in severe chronic obstructive pulmonary disease.

Lung volume reduction surgery (LVRS) has been suggested as improving respiratory mechanics in patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that LVRS might lengthen the diaphragm, increase its area of apposition with the chest wall, and thereby improve its mechanical function. To determine the effect of bilateral LVRS on diaphragm length, we measured diaphragm length at TLC, using plain chest roentgenograms (CXRs), in 25 patients (11 males and 14 females) before LVRS and 3 to 6 mo after LVRS. A subgroup of seven patients (reference data) also had diaphragm length measurements made with CXRs, using films made within a year before their presurgical evaluation. Right hemidiaphragm silhouette length (PADL) and the length of the most vertically oriented portion of the right hemidiaphragm muscle (VDML) were measured. Diaphragm dome height was determined from the: (1) distance between the dome and transverse diameter at the manubrium; and (2) highest point of the dome referenced horizontally to the vertebral column. Patients also underwent spirometry, measurements of lung volumes and diffusion capacity, an incremental symptom-limited maximum exercise test, and measurements of 6 min walk distance (6MWD) and transdiaphragmatic pressures during maximum static inspiratory efforts (Pdimax sniff) and bilateral supramaximal electrophrenic twitch stimulation (Pditwitch) both before and 3 mo after LVRS. Patients were 58 +/- 8 yr of age, with severe COPD and hyperinflation (FEV1 = 0.68 +/- 0.23 L, FVC = 2.56 +/- 7.3 L, and TLC = 143 +/- 22% predicted). Following LVRS, PADL increased by 4% (from 13.9 +/- 1.9 cm to 14.5 +/- 1.7 cm; p = 0.02), VDML increased by 44% (from 2.08 +/- 1.5 cm to 3.00 +/- 1.6 cm, p = 0.01), and diaphragm dome height increased by more than 10%. In contrast, diaphragm lengths were similar in subjects with CXRs made before LVRS and within 1 yr before evaluation. The increase in diaphragm length correlated directly with postoperative reductions in TLC and RV, and also with increases in transdiaphragmatic pressure with maximal sniff (Pdimax sniff), maximal oxygen consumption (V O2max), maximal minute ventilation (V Emax), and maximum voluntary ventilation following LVRS. We conclude that LVRS leads to a significant increase in diaphragm length, especially in the area of apposition of the diaphragm with the rib cage. Diaphragm lengthening after LVRS is most likely the result of a reduction in lung volume. Increases in diaphragm length after LVRS correlate with postoperative improvements in diaphragm strength, exercise capacity, and maximum voluntary ventilation.

Diaphragm↗
PubMed1993

Characteristics of the snoring noise in patients with and without occlusive sleep apnea.

We analyzed snoring noise from 10 nonapneic heavy snorers and nine patients with obstructive sleep apnea (OSA). Sound was recorded simultaneously through two microphones, one attached to the manubrium sterni and one suspended in the air 15 cm from the patient's head. Signals were stored on magnetic tape, digitized, and displayed in the time and frequency domains. Most of the power of snoring noise was below 2,000 Hz, and the peak power was usually below 500 Hz. When snores were generated during nose-only breathing (nasal snores), the sound spectrum was made up of a series of discrete, sharp peaks, with a fundamental note and harmonics similar to the spectrum of voiced sounds. When snores were generated during breathing through nose and mouth (oronasal snores), the spectra showed a mixture of sharp peaks and broad-band white noise. Patients with apnea showed a sequence of snores with spectral characteristics that varied markedly through an apnea-respiration cycle. The first postapneic snore consisted mainly of broad-band white noise with relatively more power at higher frequencies, so that the ratio of power above 800 Hz to power below 800 Hz could be used to separate snorers from patients with OSA. Other breaths in the cycle resembled oronasal or nasal snores in nonapneic subjects. Characteristics of the noise give information about the possible mechanism of sound generation and thus about the behavior of the pharynx during snoring. Quality of snoring sound may help to separate patients with obstructive apnea from those with simple snoring.

Adolescent↗
PubMed2001

Long-term monitoring of respiration with a mediastinal pressure sensor in dogs.

The ability of an implanted mediastinal pressure sensor to produce a stable respiratory signal that could be used to trigger stimulation of upper airway muscles was examined. In 6 dogs, a pressure sensor was secured to the manubrium (4 by wires and 2 by transmanubrial placement). In 6 other dogs, the pressure sensor was placed in the upper anterior mediastinum. The animals were monitored for a minimum of 8 weeks (2 transmanubrial sensors for 12 months). Sensors that were able to maintain a midline position, high in the mediastinum, had the best signals. A caudal sensor position or abutment against an intrathoracic structure caused signal inversion (unusable signals). Transmanubrial placement resulted in a stable signal for 1 year. We conclude that long-term monitoring of respiration with a mediastinal pressure sensor can be successfully performed in dogs, providing an adequate signal for nerve-muscle stimulation. Separation from cardiovascular structures improves signal quality.

Animals↗
PubMed2003

Fixation of the anterior mallear ligament: diagnosis and consequences for hearing results in stapes surgery.

In the search for possible causes of unfavorable results after stapes surgery, the study reported here focused on the anterior mallear ligament, since it has been previously reported that partial mallear fixation (PMF) leads to functional failure in 38% of cases of stapes revision surgery. The aims of the study were to identify effective methods for the diagnosis of PMF and experimentally assess the conductive hearing loss that results from PMF. The study included vibration amplitude measurements of the ossicles by laser Doppler interferometry (LDI) in 19 patients and 5 fresh human temporal bone (TB) specimens. Analysis of their dynamic behavior was performed by finite element modeling (FEM). Similar, significant changes of manubrium vibration patterns for PMF were found by FEM calculations, in TB experiments, and in patients. We could identify PMF either before operation, using LDI, or during operation, by manual palpation. In the TB experiments and FEM calculations, the attenuation of the stapes displacement due to an isolated PMF was approximately 10 dB and frequency-dependent. Untreated anterior mallear ligament fixation produced a persistent air-bone gap of approximately 10 dB after stapedioplasty.

Acoustic Impedance Tests↗
PubMed2004

Malleus removal and total cartilage reinforcement in intact canal wall tympanoplasty for cholesteatoma.

This study analyzes the morphological and hearing results obtained from intact canal wall cholesteatoma surgery by removing the malleus, reinforcing the whole tympanic membrane with cartilage, and performing an ossiculoplasty with a hydroxyapatite prosthesis. The results were compared to those obtained in intact canal wall cholesteatoma surgery by preserving the malleus manubrium, partially reinforcing the tympanic membrane with cartilage, and predominantly using an ossicle to perform the ossiculoplasty. One- or two-stage intact canal wall procedures were performed in 390 adult patients (416 ears) who had a nonoperated middle ear cholesteatoma. Recurrent and residual cholesteatoma rates were evaluated. Hearing results were analyzed according to the Committee on Hearing and Equilibrium Guidelines of the American Academy of Otolaryngology-Head and Neck Surgery. There was a statistically significant decrease in the recurrence rate in patients who had total cartilage reinforcement of the tympanic membrane versus patients who had partial tympanic membrane cartilage reinforcement. This technique using a hydroxyapatite prosthesis for ossiculoplasty gave good hearing results.

Adolescent↗
PubMedDate not supplied

Human tympanic membrane--malleus attachment. Preliminary study.

The relationship between the malleus handle and the tympanic membrane in humans has been studied with primary attention being directed to the fibrous layer of the tympanic membrane and its method of attachment to the malleus. This attachment is most intimate at the level of the umbo and becomes progressively more tenuous as the short process is approached. The long process of the malleus, comprised of a bony core, has a definite sleeve of cartilage surrounding its entire length. This cartilage is surrounded by a perichondrial layer which has previously been termed a periosteum. In the lower third, the fibrous lamina propria appears to split equally and the fibers then blend imperceptively with those of the perichondrial layer surrounding the manubrium. At high levels, the attachment is less intimate, most of the fibers appearing to pass lateral to the malleus handle. The embryologic development of the tympanic membrane-malleus junction has been considered and the anatomical features of this area have been considered in relation to functional requirements.

Ear Ossicles↗
PubMedDate not supplied

Thymopharyngeal duct cyst: a form of cervical thymus.

The various types of cervical thymus may present as a neck mass, usually laterally, from the angle of the mandible to the manubrium. Since it is rare to diagnose the entity preoperatively, the differential diagnosis includes the more common branchial cleft cyst, thyroglossal duct cyst, cystic hygroma, cystic dermoid, and lesions of the salivary gland, thyroid, parathyroid, and cervical lymph nodes. Because cervical thymic tissue in various forms has been reported so frequently, we feel the entity should be considered in the clinical differential diagnosis of lateral neck mass, especially in the younger age group.

Branchioma↗
PubMed1988

Age-related epithelial migration on the tympanic membrane of the Mongolian gerbil.

Epithelial migration on the tympanic membrane of young and aged gerbils was studied; Sudan black B was used as a marker dye. The epithelial migration center was found at the region of umbo, manubrium, and the short process of the malleus. The epithelial migration rates of the gerbils aged 3 to 6 months, 9 to 12 months, and 24 to 30 months were approximately 116, 113, and 86 micron per day, respectively. These findings suggest that the low epithelial migration rate on the tympanic membrane and external ear canal might play an important role on the high occurrence rate of external ear keratosis that results from accumulation of keratin debris in the aged gerbil ears.

Aging↗
PubMed2006

Percutaneous subclavian artery stent-graft placement following failed ultrasound guided subclavian venous access.

BACKGROUND: Ultrasound guidance for central and peripheral venous access has been proven to improve success rates and reduce complications of venous cannulation. Appropriately trained and experienced operators add significantly to diminished patient morbidity related to venous access procedures. We discuss a patient who required an arterial stent-graft to prevent arterial hemorrhage following inadvertent cannulation of the proximal, ventral, right subclavian artery related to unsuccessful ultrasound guided access of the subclavian vein. CASE PRESENTATION: During pre-operative preparation for aortic valve replacement and aorto-coronary bypass surgery an anesthetist attempted ultrasound guided venous access. The ultrasound guided attempt to access the right jugular vein failed and the ultrasound guided attempt at accessing the subclavian vein resulted in inappropriate placement of an 8.5 F sheath in the arterial system. Following angiographic imaging and specialist consultations, an arterial stent-graft was deployed in the right subclavian artery rather than perform an extensive anterior chest wall resection and dissection to extract the arterial sheath. The patient tolerated the procedure, without complication, despite occlusion of the right internal mammary artery and the right vertebral artery. There were no neurologic sequelae. There was no evidence of hemorrhage after subclavian artery sheath extraction and stent-graft implantation. CONCLUSION: The attempted ultrasound guided puncture of the subclavian vein resulted in placement of an 8.5 F subclavian artery catheter. Entry of the catheter into the proximal subclavian artery beneath the medial clavicle, the medial first rib and the manubrium suggests that the operator, most likely, did not directly visualize the puncture needle enter the vessel with the ultrasound. The bones of the anterior chest impede the ultrasound beam and the vessels in this area would not be visible to ultrasound imaging. Appropriate training and supervised experience in ultrasound guided venous access coupled with quality ultrasound equipment would most likely have significantly diminished the likelihood of this complication. The potential for significant patient morbidity, and possible mortality, was prevented by implantation of an arterial stent-graft.

Journal Article↗