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PubMed1992

Detection of mass lesions in the collapsed lung by ultrasonography.

Ultrasonography is useful in the detection of mass lesions in the collapsed lung, using the collapsed lungs as a "sonic window". Twenty-four patients suspected of having a tumor causing lung collapse, as shown on their chest radiographs, were examined by ultrasonography. Eighteen out of 24 patients were found to have mass lesions in their collapsed lungs. Thoracic computed tomography (CT) was also performed in 12 of these 18 patients; of those, 11 showed compatibility with sonographic findings in the detection of mass lesions in their collapsed lungs. The remaining six of these 24 patients with no mass lesions detected by ultrasonography were proven to have collapsed lung due to sputum impaction (n = 2) and lung cancer (n = 4). The fact that four patients had lung cancer that was not detectable by ultrasonography, might have been due to relatively small mass lesions at deep locations (main or intermediate bronchus) and narrowing of the "sonic window" (partial lung collapse). Though it has some limitations, ultrasonography is helpful in detecting mass lesions in collapsed lungs. Sono-guided fine needle aspiration biopsy (SGFNAB) can also be performed simultaneously, smoothly and without any major complications. In our series, SGFNAB was performed in eight out of 18 patients to make a cytopathologic diagnosis. We recommend this safe, convenient, and noninvasive method to screen for lesions in the collapsed lung, especially when bronchoscopic examination is impossible.

Aged↗
PubMedDate not supplied

Inspiratory and fixed nasal valve collapse: clinical and rhinometric assessment.

BACKGROUND: Acoustic rhinometry (AR) has been used to assess nasal valve obstruction. Standard AR measurement of the cross-sectional area (CSA) of the nasal valve is done in the apneic phase, whereas collapse often occurs on inspiration. We used the ratio of the CSA obtained during active inspiration and during apnea to compute a more meaningful method of diagnosing nasal valve collapse. METHODS: AR was performed in 40 patients without nasal valve obstruction and 47 patients diagnosed with nasal valve obstruction. Patients with septal deflection or anterior inferior turbinate hypertrophy were excluded. The internal and external nasal valve area was observed during apnea and on active inspiration. AR measurement of the CSA of both nasal valves was performed during the apneic phase and during active inspiration and the CSA (inspiratory)/CSA (apneic) ratio was calculated. RESULTS: The CSA (inspiratory)/CSA (apneic) ratio was > or = 1 in normal patients and in patients with fixed nasal valve collapse. The ratio was <1 in patients with inspiratory collapse. Data from history, physical examination, and dual-mode AR testing successfully differentiated patients into (1) normal valves, (2) fixed valve collapse, and (3) inspiratory valve collapse. A large number of patients with collapse had both internal and external valve obstruction and a large number also had a combination of inspiratory and fixed collapse. CONCLUSION: Dual-mode AR testing is an effective tool in more precisely identifying nasal valve obstruction and is the first objective test shown to be highly diagnostic of inspiratory nasal valve collapse.

Apnea↗
PubMed2005

[Calculation of articular surface area of osteonecrosis and its application in predicting collapse of the femoral head].

OBJECTIVE: To explore the program for calculating the necrotic articular surface area (NASA) and the ratio of NASA to whole articular surface area (WASA) of osteonecrosis of the femoral head (ONFH), to verify the accuracy of this calculation and to predict the collapse of the femoral head clinically using this program. METHODS: From June 2001 to June 2003, The specimens of the necrotic femoral head from eight patients (13 hips) were obtained by total hip arthroplasty. The magnetic resonance imaging (MRI) was taken in all patients before operation. According to a series of T1-weight pictures, the NASA and the ratio of NASA to WASA were calculated by designing program. The specimens of the necrotic femoral head were sawed into lays similar to MRI pictures using the coordinate paper stick on the auricular surface, the data processing were done by analytic instrument for pictures. The data of both were analyzed statistically by software SPSS 10.0 edition. The NASA and the ratio of NASA to WASA were calculated on MRI in ARCO Stage I, II 16 patients (25 hips) with non-operation. Follow-up was done to the patients with collapse of the femoral head and to the patients with no collapse for at least 24 months. The data were compared in collapse group and non-collapse group. RESULTS: There were no significant differences between MRI pictures calculation and specimens measurement (NASA: 0. 412, ratio of NASA to WASA: 0.812, P>0.05). Of the 25 hips followed up, collapse occurred in 17 hips. NASA was 31.06+/-8.10 cm2, (95% CI. 26.58 to 35.55), the ratio of NASA to WASA was 58.91%+/-15.11%, (95% CI: 51.14 to 66. 68). No collapse appeared in 8 hips. NASA was 14.16+/-9.32 cm2 (95% CI: 6.04 to 21. 95), the ratio of NASA to WASA was 29.48%+/-19.76% (95% CI: 12.97 to 45.99). The ratio in the patients with collapse was beyond 33%. CONCLUSION: The NASA and the ratio of NASA to WASA in patients with ONFH can be accurately calculated with the MRI pictures. The possibility of collapse can be predicted by this method. As it is complicated in operation, improvement should be made in order to put it into clinical use.

Adult↗
PubMed1991

Intracellular calcium levels do not change during contact-mediated collapse of chick DRG growth cone structure.

When the growth cone of a chick dorsal root ganglion (DRG) neurite contacts the neurite of a chick retinal ganglion cell in vitro, the growth cone typically responds by withdrawing its lamellipodia and filopodia and collapsing. We have used the fluorescent calcium indicator dye fura-2 and digital imaging microscopy to measure calcium levels within DRG growth cones and to determine whether changes in calcium levels are responsible for the collapse of growth cone morphology when a DRG growth cone contacts a retinal ganglion cell neurite. Calcium levels within DRG growth cones were stable during neurite outgrowth. Calcium was typically distributed homogeneously throughout the growth cone, though occasionally gradients of free calcium were present. When calcium gradients were observed, calcium levels appeared higher in the active veil regions than in the central core region. Calcium levels in DRG growth cones appeared to remain stable during the period of contact-mediated growth cone collapse. Low concentrations of the calcium ionophore ionomycin increased calcium levels two- to threefold without having any observable morphological effects on DRG growth cones. Likewise, depolarization with 15 mM KCl caused a transient two- to threefold increase in calcium levels without having any observable morphological effect. These results suggest that changes in calcium levels are not responsible for contact-mediated collapse of growth cone structure. A growth cone collapsing activity has been solubilized from embryonic chick brain (Raper and Kapfhammer, 1990). Application of this material to cultures of DRG neurons caused growth cones to collapse but had no effect on calcium levels within the growth cones. The crude growth cone collapsing activity was not blocked by the presence of cobalt, nickel, lanthanum, nifedipine, or reduced-calcium medium, suggesting that transmembrane calcium fluxes were not required for growth cone collapse. These results suggest that the morphological changes associated with the collapse of growth cone structure can be independent of changes in growth cone calcium levels, and that second messengers other than calcium are likely to be involved in the regulation of many growth cone behaviors.

Animals↗
PubMed1997

Collapsed ultraendurance athlete: proposed mechanisms and an approach to management.

OBJECTIVE: To review the common conditions causing collapse in ultraendurance athletes, to propose appropriate treatment protocols for the more common medical conditions that are encountered, and to provide practical guidelines for the management of the medical facilities at these endurance events. DATA SOURCES: Books published on the subject, abstracts of the American College of Sports Medicine Annual Congress dealing with the subject over the last 5 years, and electronic search of the Medline and Current Contents databases (last searched May 1995). German articles were included in the search criteria. STUDY SELECTION: Articles dealing generally with the management of medical facilities at endurance events were chosen. Articles dealing more specifically with the common medical conditions encountered at these events were then sourced and included in this review. DATA EXTRACTION: Multiple reader extraction of relevant data. DATA SYNTHESIS: A practical guideline to the management of the medical facility at an endurance event is detailed, expanding specifically on the nature of the conditions causing collapse during or after endurance exercise with a proposed classification of causes of collapse for optimizing immediate management and management protocols for specific conditions such as heatstroke, hyponatremia, hypoglycemia, exercise-associated collapse, and muscle cramps. CONCLUSION: The most commonly encountered medical condition at endurance athletic events is collapse after the event. The popular view that all persons who collapse have dehydration-induced hyperthermia has been challenged. Here we extend that argument and provide diagnostic and management protocols and propose a triage system that considers the most common causes of collapse in ultraendurance athletes. These protocols can optimize the efficient and safe management of large numbers of collapsed ultraendurance athletes. It is proposed that these protocols can optimize the efficient and safe management of large numbers of collapsed ultra endurance athletes.

Adult↗
PubMed1998

cAMP-mediated regulation of neurotrophin-induced collapse of nerve growth cones.

Neurotrophins are known to promote the survival, differentiation, and neurite outgrowth of developing neurons. Here we report that acutely applied brain-derived neurotrophic factor (BDNF) induces rapid growth cone collapse and neurite retraction of embryonic Xenopus spinal neurons in culture. The collapsing effect of BDNF depends on the activation of Trk receptor tyrosine kinase, requires an influx of extracellular Ca2+, and is regulated by cAMP-dependent activity. Elevation of intracellular cAMP levels ([cAMP]i) by forskolin or (Sp)-cAMP completely blocked the collapsing effect, whereas inhibition of protein kinase A (PKA) by (Rp)-cAMP potentiated the collapsing action. BDNF-induced growth cone collapse was only observed in 6 hr cultures but not in 24 hr cultures. However, inhibition of PKA by (Rp)-cAMP restored the collapsing response of these "old" neurons in 24 hr cultures, suggesting that embryonic Xenopus spinal neurons may upregulate their endogenous cAMP-dependent activity during development in culture, leading to the blockade of their collapsing response to BDNF. Taken together, our results suggest the presence of cross-talk between Ca2+- and cAMP-signaling pathways involved in the collapsing action of neurotrophins, in which the cAMP-pathway regulates the Ca2+-mediated signal transduction required for BDNF-induced collapse. By modulating the cAMP-dependent activity through the intrinsic programming or interaction with other factors present in the environment, a neuron thus could respond to the same extracellular factors with different morphological and cellular changes at different stages during development.

Actins↗
PubMed1989

Collapse and reexpansion of lungs increase microvascular permeability in sheep.

The pathogenesis of reexpansion pulmonary edema has not been well studied. We tested the hypothesis that both long term collapse and subsequent reexpansion of the lungs cause reexpansion pulmonary edema by increasing pulmonary microvascular permeability. We investigated lymph dynamics in 15 experiments on collapsed lung and 10 experiments after lung reexpansion in 14 unanesthetized sheep with chronic lymph fistulas. We found that 24-hr left lung collapse increased lymph flow through the caudal mediastinal lymph node from the baseline of 1.71 +/- 0.97 (mean +/- S.D.) g/15 min to 2.01 +/- 0.99 g/15 min, although 2-hr collapse did not affect lymph flow. The L/P ratio did not fall below baseline in either experiment. Pulmonary arterial pressure increased by only about 6 cmH2O both in 2-hr and 24-hr collapse. Reexpansion after 24-hr lung collapse also increased lymph flow from the baseline of 1.64 +/- 0.52 g/15 min to 3.20 +/- 0.79 g/15 min during the first 2 hr after reexpansion. The lymph-to-plasma protein concentration ratio did not fall below the baseline. Reexpansion after 2-hr collapse did not affect these variables. We conclude that both long term lung collapse and subsequent reexpansion lead to reexpansion pulmonary edema by increasing pulmonary microvascular permeability.

Animals↗
PubMed2000

Two-state expansion and collapse of a polypeptide.

The initial phase of folding for many proteins is presumed to be the collapse of the polypeptide chain from expanded to compact, but still denatured, conformations. Theory and simulations suggest that this collapse may be a two-state transition, characterized by barrier-crossing kinetics, while the collapse of homopolymers and random heteropolymers is continuous and multi-phasic. A new rapid-mixing flow technique has been used to resolve the late stages of polypeptide collapse, at time scales >/=45 microseconds. We have used a laser temperature-jump with fluorescence spectroscopy to resolve the complete time-course of the collapse of denatured cytochrome c with nanosecond time resolution. We find the process to be exponential in time and thermally activated, with an apparent activation energy approximately 9 k(B)T (after correction for solvent viscosity). These results indicate that polypeptide collapse is kinetically a two-state transition. Because of the observed free energy barrier, the time scale of polypeptide collapse is dramatically slower than is predicted by Langevin models for homopolymer collapse.

Animals↗
PubMed1996

Optimizing the lyophilization cycle and the consequences of collapse on the pharmaceutical acceptability of Erwinia L-asparaginase.

The antileukemia enzyme, Erwinia L-asparaginase, occurs as a tetramer which can be dissociated by the stresses of lyophilization into four subunits (subunit M(r) 34 000 Da). Dissociation can be reduced by adding protectants to the formulation to stabilize the biopolymer, while the product should dry to form a pharmaceutically elegant, shelf-stable cake which is readily soluble. Using analytical ultracentrifugation, HPLC, and circular dichroism we have related structural dissociation of the enzyme during lyophilization to biological activity. Additives such as mannitol prevent ablation loss of vial contents and dry to form cosmetically elegant cakes but provide little biological protection, since during freezing they crystallize and are removed from the preparation. Excipients persisting throughout the cycle in the amorphous state provide improved biological protection, although high molecular weight compounds such as Dextran (M(r) 70000 Da) are most effective only during product freezing or storage. Low molecular weight sugars are protective throughout the cycle although formulations containing monosaccharides often exhibit low collapse temperatures (Tc) measured using a freeze-drying microscope or glass transition temperatures (Tg') measured by thermal analysis, but these formulations distort as drying progresses to form a collapsed, cosmetically unacceptable cake, with reduced activity, poor stability, a high moisture content, and reduced solubility. Collapse can be avoided by formulating with disaccharides, which display higher Tc temperatures than monosaccharides, or drying below Tc. Dried samples which persist in the amorphous state can also collapse when stored above their solid-state collapse temperatures when they decay at a faster rate than predicted by Arrhenius kinetics. The solid-state collapse temperature can be significantly decreased by the diffusion of moisture from the stopper into the dry product resulting in an increase in sample water content. Lyophilization cycle times can be reduced by analyzing collapse characteristics so that the relationship between product temperature and chamber pressure can be controlled so that drying rates can be optimized while ensuring that the product does not melt or collapse during sublimation.

Antineoplastic Agents↗
PubMed2006

Collapse and shedding transitions in binary lipid monolayers coating microbubbles.

We report on a fluorescence microscopy study of the monolayer collapse and shedding behavior due to shell compression during the dissolution of air-filled, lipid-coated microbubbles in degassed media. The monolayer shell was comprised of saturated diacyl phosphatidylcholine (C12:0 to C22:0) and an emulsifier, poly(ethylene glycol)-40 stearate. The morphologies of monolayer collapse structures and shed particles were monitored as a function of phospholipid acyl chain length (n) and temperature. The two components formed a single miscible phase when the phospholipid was near or above its main phase transition temperature, and collapse occurred via suboptical particles to vesicles (both were shed) and tubes as chain length increased. Conversely, two-phase coexistence was observed when the lipid was below its main phase transition temperature. For these bubbles, a transition from primary collapse to secondary collapse was observed. Primary collapse was observed as a loss of expanded phase due to vesiculation. Secondary collapse involved the rapid propagation of monolayer folds and simultaneous deformation. For very rigid monolayers, we observed substantial surface buckling with simultaneous nucleation and growth of folds. The folds merged at a single point or region, providing a conduit for the entire excess lipid to shed in a single event, and the bubble smoothed and became more spherical. These results are discussed in the context of general binary phospholipid collapse behavior, microbubble dissolution behavior, medical applications, and the dissolution behavior of natural microbubbles.

Hot Temperature↗
PubMed2001

Mechanisms by which AC leakage currents cause complete hemodynamic collapse without inducing fibrillation.

INTRODUCTION: The first study of weak alternating current (AC) stimulation in closed chest humans showed that complete hemodynamic collapse can occur below the threshold for inducing ventricular fibrillation (VF), a heretofore unknown danger to patients. This article, and the accompanying simulation article, explore the mechanisms responsible for the collapse. METHODS AND RESULTS: A quadripolar pacing catheter was placed in the right ventricle (RV) of six dogs. The tip of the catheter (17 mm2) carried 5 seconds of AC stimulation ranging from 10 to 160 Hz and 10 to 1,000 microA. The lead II body surface ECG, femoral artery pressure, and a bipole from the proximal pair of electrodes on the RV catheter were recorded 2 seconds before, during, and 2 seconds after stimulation. Based on the blood pressure, every episode was categorized as VF, COLLAPSE without VF, extrasystolic without COLLAPSE (EFFECT), or having caused no effect (NSR). The electrical activation interval (interspike interval [ISI]) from the RV bipole was compared with the mechanical activation interval, determined from M-mode ultrasound. COLLAPSE is associated with a short ISI (NSR = 408+/-110 msec; EFFECT = 305+/-113 msec; COLLAPSE = 179+/-25 msec; P < 0.001) with a high degree of regularity (P < 0.001): coefficient of variation of ISI for COLLAPSE (0.038+/-0.069) versus VF (0.389+/-0.222), EFFECT (0.420+/-0.241), and NSR (0.016+/-0.048). Electrical activation and mechanical activation rates occurred at integer multiples of the AC stimulation period. CONCLUSION: COLLAPSE (86+/-37 microA; minimum 50 microA in two animals) occurs below the VF threshold (108+/-28 microA) by causing rapid, regular excitation.

Action Potentials↗
PubMed2003

How fast is protein hydrophobic collapse?

One of the most recurring questions in protein folding refers to the interplay between formation of secondary structure and hydrophobic collapse. In contrast with secondary structure, it is hard to isolate hydrophobic collapse from other folding events. We have directly measured the dynamics of protein hydrophobic collapse in the absence of competing processes. Collapse was triggered with laser-induced temperature jumps in the acid-denatured form of a simple protein and monitored by fluorescence resonance energy transfer between probes placed at the protein ends. The relaxation time for hydrophobic collapse is only approximately equal to 60 ns at 305 K, even faster than secondary structure formation. At higher temperatures, as the protein becomes increasingly compact by a stronger hydrophobic force, we observe a slowdown of the dynamics of collapse. This dynamic hydrophobic effect is a high-temperature analogue of the dynamic glass transition predicted by theory. Our results indicate that in physiological conditions many proteins will initiate folding by collapsing to an unstructured globule. Local motions will presumably drive the following search for native structure in the collapsed globule.

Biophysical Phenomena↗
PubMed2000

Upper airway collapsibility in habitual snorers and sleep apneics: evaluation with drug-induced sleep endoscopy.

Increased upper airway collapsibility has been suspected of being involved in the pathogenesis of sleep-related diseases. It is assumed that patients with severe obstructive sleep apnea syndrome (OSAS) show a stronger collapse of the upper airway compared with habitual snorers. It was the objective of this study to analyze the patterns of upper airway collapse in habitual snorers and patients with OSAS and to correlate these results with data from polysomnography. Endoscopy was carried out during drug-induced sleep (with propofol) and collapsibility was analyzed at two major levels (palatal and tongue base). A total of 207 habitual snorers and 117 patients with OSAS underwent endoscopy after overnight polysomnography in our sleep laboratory. In 95% of cases we were able to induce snoring during drug-induced sleep. The collapsibility in the area of the base of the tongue correlated with higher values of the respiratory disturbance index (RDI) as recorded by standard polysomnography. Patients with OSAS showed significantly stronger collapsibility compared with snorers. The difference was more evident at the tongue-base level. We found no significant correlation between the applied CPAP pressure and collapsibility in patients with OSAS. These results show that collapsibility at the tongue-base level is a factor relevant in sleep-related breathing disorders.

Adolescent↗
PubMed2000

The incidence of right upper-lobe collapse when comparing a right-sided double-lumen tube versus a modified left double-lumen tube for left-sided thoracic surgery.

UNLABELLED: Lung deflation for left-sided thoracic surgery can be accomplished by using either a left- or right-sided double-lumen endotracheal tube (L-DLT or R-DLT). Anatomic variability of the right mainstem bronchus and the possibility of right upper-lobe obstruction have discouraged the routine use of R-DLT. There are, however, situations in which it is preferable to avoid manipulation/intubation of the left main bronchus, requiring placement of a R-DLT. We compared the modified L-DLT with the R-DLT to determine whether R-DLTs can be used during left-sided thoracic surgery without an increased risk of right upper-lobe collapse. Forty patients requiring left lung deflation were randomly assigned to one of two groups. Twenty patients received a modified L-DLT BronchoCath((R)) (Mallinckrodt Medical Inc., St. Louis, MO), and 20 received a R-DLT BronchoCath((R)). The following variables were studied: 1) time required to position each tube until satisfactory placement was achieved; 2) number of times fiberoptic bronchoscopy was required to readjust tube position; 3) number of malpositions after initial tube placement; 4) time required for left lung collapse; 5) incidence of right upper-lobe collapse from an intraoperative chest radiograph obtained in a lateral decubitus position; 6) overall surgical exposure; and 7) tube acquisition cost. Median time required for initial tube placement was greater in the R-DLT group (3.4 min) versus the L-DLT (2.1 min); P = 0.04. Overall tube cost was also larger for the R-DLT group (US $1819.40) versus the L-DLT group (US $1107.75). The incidence of malpositions, (five versus two), need for fiberoptic bronchoscopy, time for adequacy of left lung collapse, and incidence of intraoperative right upper-lobe collapse (0) did not significantly differ between R-DLT and L-DLT groups. We conclude that R-DLTs can be used for left-sided thoracic surgery without an increased risk of right upper-lobe collapse. Our data suggest that R-DLTs may be more prone to intraoperative dislodgment/malposition than L-DLTs; however, in all cases, correction of malposition was easily achieved. IMPLICATIONS: In this study, right-sided double-lumen tubes (R-DLTs) were compared with modified left-sided double-lumen tubes in patients requiring one-lung ventilation for left-sided thoracic surgery. The incidence of right upper-lobe collapse was assessed intraoperatively by a chest radiograph which showed no collapse of the right upper lobe in all patients who received R-DLTs or left-sided double-lumen tubes. Therefore, we conclude that R-DLTs present no increased risk of complications for left-sided thoracic surgery and should not be abandoned.

Adult↗
PubMed1983

Computed tomography of lobar collapse: 1. Endobronchial obstruction.

The computed tomographic (CT) appearance of lobar collapse has yet to be defined. In an attempt to determine the characteristic appearance of collapse 95 cases were reviewed retrospectively in a wide variety of clinical settings over a 3 year period ending January 1983. In this report 38 cases of lobar collapse secondary to endobronchial occlusion are analyzed; the appearance of collapse without endobronchial obstruction forms the basis of a subsequent report. Computed tomography was accurate in determining the site of bronchial occlusion in all cases. In 36 of 38 cases collapse was caused by endobronchial tumors, including bronchogenic carcinoma, bronchial carcinoids, endobronchial metastases, and lymphoma. Differentiation between these tumors was not feasible with CT. Most cases of collapse were caused by central tumor. In those cases in which a bolus of contrast material was used differentiation between tumor mass and collapsed pulmonary parenchyma was possible. Two of 38 cases were found to have benign bronchial occlusion. In one case a mucous plug obstructing the left lower lobe bronchus was accurately defined. In another case a bronchial stricture occluded the right lower lobe bronchus. This represented the only false positive case in this series. It is concluded that CT is an accurate means for establishing the diagnosis of endobronchial obstruction. In most cases the diagnosis of neoplasia was possible, provided a bolus of contrast material was used to define tumor mass. The potential role of CT in evaluating patients with lobar collapse is discussed.

Adenocarcinoma↗
PubMed1997

Effects of frictional losses and pulsatile flow on the collapse of stenotic arteries.

High-grade stenosis can produce conditions in which the artery may collapse. A one-dimensional numerical model of a compliant stenosis was developed from the collapsible tube theory of Shapiro. The model extends an earlier model by including the effects of frictional losses and unsteadiness. The model was used to investigate the relative importance of several physical parameters present in the in vivo environment. The results indicated that collapse can occur within the stenosis. Frictional loss was influential in reducing the magnitude of collapse. Large separation losses could prevent collapse outright even with low downstream resistances. However, the degree of stenosis was still the primary parameter governing the onset of collapse. Pulsatile solutions demonstrated conditions that produce cyclic collapse within the stenosis. This study predicts certain physiologic conditions in which collapse of arteries may occur for high-grade stenoses.

Arterial Occlusive Diseases↗
PubMed1994

Intervertebral disk vacuum phenomenon secondary to vertebral collapse: prevalence and significance.

PURPOSE: To evaluate the prevalence of the intervertebral vacuum phenomenon in disks adjacent to vertebral collapses of various causes. MATERIALS AND METHODS: The authors retrospectively studied 310 consecutive patients who had at least one vertebral collapse. The vacuum phenomena were divided into collapse-related (ie, adjacent to a collapse) and degenerative (ie, not associated with a vertebral fracture) ones. Plain radiography was performed in all patients, and, in addition, conventional tomography, computed tomography, and/or magnetic resonance imaging was performed in 175 patients. RESULTS: Collapse-related vacuum phenomena were seen in 15% of patients with plain radiography and in 21% when all of the imaging modalities were considered. They occurred in association with all of the causes of collapse (ie, osteoporosis, multiple myeloma, metastasis, acute trauma, and vertebral osteomyelitis), although the prevalence was lower in association with metastasis or trauma (P = .008). The occurrence of collapse-related vacuum phenomenon was correlated with age (P = .001) and with the coexistence of degenerative disk-related vacuum phenomenon in the same patient (P = .0002). CONCLUSION: Occurrence of a vacuum cleft in disks adjacent to a vertebral collapse is common and appears as the second cause of vacuum phenomenon after degenerative disk disease.

Adult↗
PubMed2000

True-lumen collapse in aortic dissection: part I. Evaluation of causative factors in phantoms with pulsatile flow.

PURPOSE: To investigate the causative factors in true-lumen collapse in a model of aortic dissection. MATERIALS AND METHODS: Phantoms with an aortic arch, true and false lumina with abdominal branch vessels, and a distal bifurcation were used to model a Stanford type B aortic dissection. The effects of anatomic factors (entry-tear size, branch-vessel flow distribution, fenestrations, distal reentry communication) and physiologic factors (peripheral resistance in the branch vessels, pump output and rate, vascular compliance) on true-lumen collapse were investigated. The morphology of the true lumen was observed. Branch pressures and flow rates were measured. RESULTS: True-lumen collapse was induced and was exacerbated by an increase in the size of the entry tear, a decrease in the false-lumen outflow caused by occluding the false-lumen branch vessels, and an increase in the true-lumen outflow caused by lowering the peripheral resistance in true-lumen branch vessels. Two kinds of true-lumen collapse depended on pump output. With low pump output and low outflow resistance from the true lumen, the true lumen collapsed. With high pump output and low inflow resistance in the false lumen, the true lumen was compressed. Distal reentry communication between the true and false limbs was more effective than aortic fenestrations in preventing true-lumen collapse. CONCLUSION: True-lumen collapse in this dissection model strongly depends on the difference in the ratios of inflow capacity to outflow capacity in the true and false lumina. Both anatomic and physiologic factors can affect true-lumen collapse.

Aortic Dissection↗