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Smaller Vessels (smaller + vessel)
Selected AbstractsNoise exposures aboard catcher/processor fishing vesselsAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 8 2006Richard L. Neitzel MS Abstract Background Commercial fishing workers have extended work shifts and potential for 24 hr exposures to high noise. However, exposures in this industry have not been adequately characterized. Methods Noise exposures aboard two catcher/processors (C/P) were assessed using dosimetry, sound-level mapping, and self-reported activities and hearing protection device (HPD) use. These data were combined to estimate work shift, non-work, and 24 hr overall exposure levels using several metrics. The length of time during which HPDs were worn was also used to calculate the effective protection received by crew members. Results Nearly all workers had work shift and 24 hr noise levels that exceeded the relevant limits. After HPD use was accounted for, half of the 24 hr exposures remained above relevant limits. Non-work-shift noise contributed nothing to 24 hr exposure levels. HPDs reduced the average exposure by about 10 dBA, but not all workers wore them consistently. Conclusions The primary risk of hearing loss aboard the monitored vessels comes from work shift noise. Smaller vessels or vessels with different layouts may present more risk of hearing damage from non-work periods. Additional efforts are needed to increase use of HPDs or implement noise controls. Am. J. Ind. Med. 2006. © 2006 Wiley-Liss, Inc. [source] Disparity in regional and systemic circulatory capacities: do they affect the regulation of the circulation?ACTA PHYSIOLOGICA, Issue 4 2010J. A. L. Calbet Abstract In this review we integrate ideas about regional and systemic circulatory capacities and the balance between skeletal muscle blood flow and cardiac output during heavy exercise in humans. In the first part of the review we discuss issues related to the pumping capacity of the heart and the vasodilator capacity of skeletal muscle. The issue is that skeletal muscle has a vast capacity to vasodilate during exercise [,300 mL (100 g),1 min,1], but the pumping capacity of the human heart is limited to 20,25 L min,1 in untrained subjects and ,35 L min,1 in elite endurance athletes. This means that when more than 7,10 kg of muscle is active during heavy exercise, perfusion of the contracting muscles must be limited or mean arterial pressure will fall. In the second part of the review we emphasize that there is an interplay between sympathetic vasoconstriction and metabolic vasodilation that limits blood flow to contracting muscles to maintain mean arterial pressure. Vasoconstriction in larger vessels continues while constriction in smaller vessels is blunted permitting total muscle blood flow to be limited but distributed more optimally. This interplay between sympathetic constriction and metabolic dilation during heavy whole-body exercise is likely responsible for the very high levels of oxygen extraction seen in contracting skeletal muscle. It also explains why infusing vasodilators in the contracting muscles does not increase oxygen uptake in the muscle. Finally, when ,80% of cardiac output is directed towards contracting skeletal muscle modest vasoconstriction in the active muscles can evoke marked changes in arterial pressure. [source] Variable-Pulse Nd:YAG Laser in the Treatment of Facial TelangiectasiasDERMATOLOGIC SURGERY, Issue 1 2006AVERY A. BEVIN MD BACKGROUND Variable-pulse 1,064 nm wavelength lasers have been used with good effectiveness on leg telangiectasias and reticular veins and have shown promising results on facial telangiectasias as well. OBJECTIVE To investigate the effectiveness of a variable-pulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using a small spot size in the treatment of facial telangi-ectasias. METHODS Eight male patients (mean age 75 years) underwent a single treatment session using a variable-pulse 1.5 mm spot size Nd:YAG laser with epidermal cooling. Telangiectasia diameters were 0.3 to 2.0 mm. Test sites were performed using three pulse widths (3, 20, and 60 ms), with fluences varying depending on vessel size and response. Full treatments were per-formed using test parameters giving the best response. Thirteen weeks later, the patients returned for final evaluation and satisfaction rating. RESULTS Fluences ranged from 226 to 425 J/cm2, with smaller vessels requiring larger energies. Pulse duration was equally divided between the 20 and 60 ms settings. The shortest pulse width (3 ms) was inferior in all patients. Longer pulse durations achieved superior vessel elimination with minimal immediate purpura and no postinammatory hyperpigmentation. The average mean vessel clearance was 26 to 50% in half of the patients and 51 to 75% in the other half as evaluated by three unbiased dermatologists with extensive laser experience. CONCLUSION A small,spot size Nd:YAG laser using a pulse width of 20 ms or higher appears to be effective in clearing a significant percentage of facial telangectasias with a single pass. The side effects were minimal. [source] Endogenous functional CBV contrast revealed by diffusion weightingNMR IN BIOMEDICINE, Issue 8 2006Todd B. Harshbarger Abstract Functional MRI (fMRI) based on the blood oxygenation level dependent (BOLD) contrast often suffers from a lack of specificity because of the vascular spread of oxygenation changes. It is suggested from the optical imaging and animal fMRI literature that cerebral blood volume (CBV) changes are more closely tied to the smaller vessels. As such, fMRI contrast based on CBV changes will have improved spatial specificity to the neuronal activities as they are immediately adjacent to the smaller vessels. In this paper, an endogenous contrast mechanism based on a diffusion weighting strategy that could detect functional CBV changes is presented. Initially, a theoretical framework is presented to model the functional signal changes as a function of CBV under diffusion weighting, which predicts peak CBV sensitivity at various vessel,tissue mixtures. It was found that a b factor over 1500,s/mm2 would be necessary to achieve dominant CBV contrast. Further, two sets of experimental results are also presented. In the first experiment, diffusion weighting at a set of b factors ranging from 300 to 600,s/mm2 was used. The results indicated that while the positive activation (predominantly BOLD signal) continued to reduce in magnitude and spatial extent, the negative activation (predominantly CBV signal) remained virtually constant with increasing b factors. The second experiment used a b factor of 1600,s/mm2 and showed extensive negative activation in the visual cortex and greatly reduced positive activations compared with images with no diffusion weighting. The time course of negative activation showed a faster time to peak and return to baseline than the positive BOLD activity, consistent with the small vessel origin of the signal changes. These results suggest that appropriate diffusion weighting could be used to measure activation related CBV changes. Copyright © 2006 John Wiley & Sons, Ltd. [source] Improved spatial localization based on flow-moment-nulled and intra-voxel incoherent motion-weighted fMRINMR IN BIOMEDICINE, Issue 3 2003Allen W. Song Abstract Functional MRI signal based on the blood oxygenation level-dependent contrast can reveal brain vascular activities secondary to neuronal activation. It could, however, arise from vascular compartments of all sizes, and in particular, be largely influenced by contributions of large vein origins that are distant from the neuronal activities. Alternative contrasts can be generated based on the cerebral blood flow or volume changes that would provide complementary information to help achieve more accurate localization to the small vessel origins. Recent reports also indicated that apparent diffusion coefficient-based contrast using intravoxel incoherent motion (IVIM) weighting could be used to efficiently detect synchronized signal changes with the functional activities. It was found that this contrast has significant arterial contribution where flow changes are more dominant. In this study, a refined approach was proposed that incorporated the flow-moment-nulling (FMN) strategy to study signal changes from the brain activation. The results were then compared with those from conventional IVIM- and BOLD-weighted acquisitions. It was shown that the activated region using the new acquisition strategy had smaller spatial extent, which was contained within the activated areas from the other two methods. Based on the known characteristics of the conventional IVIM and BOLD contrasts, it was inferred that the FMN,IVIM acquisition had improved selective sensitivity towards smaller vessels where volume changes were prevalent. Therefore, such an acquisition method may provide more specific spatial localization closely coupled to the true neuronal activities. Copyright © 2003 John Wiley & Sons, Ltd. [source] Outcomes with drug-eluting stents versus bare metal stents in acute ST-elevation myocardial infarction: Results from the Strategic Transcatheter Evaluation of New Therapies (STENT) Group,CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 7 2008Bruce R. Brodie MD Abstract Objectives: This study compares outcomes with drug-eluting stents (DES) versus bare metal stents (BMS) in patients with ST-elevation myocardial infarction (STEMI). Background: DESs have been effective in elective percutaneous coronary intervention (PCI), but their safety and efficacy in patients with STEMI have not been well studied. Methods: The STENT Registry is a multicenter United States registry evaluating outcomes of DES. Our study population includes patients with STEMI treated with either a DES or BMS who completed 9-month or 2-year follow-up. Outcomes were adjusted using propensity score analysis. Results: DES patients were younger, had less prior infarction and prior bypass surgery, but had smaller vessels and longer lesions. After adjusting for differences in baseline variables, there were no significant differences between DES and BMS in death, reinfarction, or major adverse cardiac events (MACE). DES had lower rates of stent thrombosis at 9 months (1.0% vs. 2.7%, HR 0.40 [0.17,0.95]) and lower rates of target vessel revascularization (TVR) at 9 months (4.0% vs. 7.5%, HR 0.55 [0.34,0.88]) and 2 years (8.0% vs. 11.3%, HR 0.57 [0.35,0.92]). There was a nonsignificant increase in stent thrombosis with DES versus BMS from 1 to 2 years (1.1% vs. 0.3%, P = 0.28). Conclusions: Our data suggest that DES used with primary PCI for STEMI are more effective than BMS in reducing TVR and are safe for up to 2 years. Whether DES are safe beyond 2 years and whether the reduction in TVR is enough to justify their use in STEMI will have to wait for the results of large randomized trials. 2008 Wiley-Liss, Inc. [source] Effect of stents in reducing restenosis in small coronary arteries: A meta-analysisCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 4 2004FSCAI, Paul T. Vaitkus MD Abstract The ability of stents to reduce restenosis was established in larger coronary arteries. Clinical trials of stenting in smaller vessels have yielded conflicting results due in part to their sample sizes. The aim of this meta-analysis was to increase the statistical power by pooling data from these clinical trials. Trials were identified from Medline search, review of recent cardiology meetings' abstracts, and manual review of bibliographies. Studies were included if they were prospective randomized controlled trials. Endpoints examined included a dichotomized definition of angiographic restenosis, target lesion revascularization (TLR), target vessel revascularization (TVR), or any repeat revascularization. Pooling of data was performed by calculating a Mantel-Haenszel odds ratio (OR). The analysis included 2,598 patients enrolled in eight clinical trials. Stenting significantly reduced restenosis (OR = 0.62; 95% CI = 0.61,0.63). Concordantly, stenting reduced TLR (OR = 0.49), TVR (OR = 0.90), and any revascularization (OR = 0.48). This meta-analysis supports the hypothesis that stenting reduces restenosis in small coronary arteries as well as in larger coronary arteries. The apparent discordant result of individual clinical trials was due in part to underpowering related to small sample sizes. Catheter Cardiovasc Interv 2004;62:425,429. © 2004 Wiley-Liss, Inc. [source] | ||||||||||