Majority Of Filters Research Articles

Method for analisis of the structure and properties of regenerated polimer fibrous filter for thin cleaning of airl

Stricter requirements for the quality and reliability of manufactured products, as well as the need to increase the service life of machines, mechanisms and various devices, the operation of which is associated with the use of liquid or gas-air media, is the reason for the emergence of new and improvement of traditional methods for obtaining filter materials with higher performance characteristics. A method for a comprehensive analysis of the properties of regenerated filter materials for fine air purification is proposed. The overwhelming majority of filters, after their service life is exhausted, cannot be regenerated, since this, as a rule, is associated with high energy costs. At the same time, the development of methods for such regeneration is quite relevant from the point of view of resource conservation. In this regard, the purpose of this work is to use a number of physical research methods for the purpose of a comprehensive analysis of polymeric fibrous filter materials for air purification that have undergone regeneration. Filtration materials obtained by the «melt-blowing» method from polymer granules by processing the granulate in an extruder, aerodynamic spraying of the melt and the formation of a fibrous-porous layer on a forming mandrel were selected for research. The main filtration characteristics of the original and regenerated filter materials (breakthrough coefficient, aerodynamic drag),as well as the electrophysical properties of the primary and secondary filter materials, the presence of a spontaneous electret charge have been investigated. The main stages of regeneration and evaluation of physicochemical, mechanical and operational properties of fibrous-porous materials that have undergone secondary thermo-aerodynamic processing in comparison with the original ones are described. It is shown that the studied materials retain their basic properties, while the structure of the fibers changes and the electret effect is enhanced.

Why Temporary Filters Are Not Removed: Clinical Predictors in 1,000 Consecutive Cases

Compared to permanent inferior vena cava (IVC) filters, higher complication rates occur with long-term use of temporary IVC filters. We aimed to identify patient clinical factors at the time of placement that could predict failure to remove a temporary IVC filter. A retrospective review was performed of both vascular surgery and interventional radiology prospective databases between December 2008 and December 2013. We analyzed a total number of 1,024 consecutive, temporary IVC filters stratified by whether retrieval was attempted or made permanent. Univariate, multivariate, and prediction modeling analyses with internal validation were performed on abstracted data, which included risk factors, treatment modalities, and indications for IVC filter placement. Of 1,024 temporary IVC filters, removal was attempted in 60% and no attempt at removal (kept permanent) in 40%. Of the 619 with attempted removal, the overall successful retrieval rate was 95%. The majority of filters were not attempted to be removed because of persistent filter indications (360 cases). Risk factors associated with IVC filter permanence included male sex, older age, history, or indication of venous thromboembolism (VTE) with inability to anticoagulate, malignancy, and neurologic condition. Risk factors most predictive of permanence in the multivariate model were malignancy (odds ratio [OR]: 3.0, P<0.001) or neurologic disorder (OR: 2.69, P=0.0005). Validation revealed our model had a sensitivity of 60.4% and specificity of 69.9%. Our study shows that patients who are more likely to have a temporary IVC filter kept permanent are more likely to be older males with a history of malignancy, neurologic condition, or VTE. These factors are also predictive of permanence and can be used in our predictive model to provide insight into the significant preoperative risk factors that should play into the decision-making process.

Temporary and Permanent Inferior Vena Cava Filters in the Oncology Population

BackgroundThe use of both temporary and permanent inferior vena cava (IVC) filters continues to rise yet randomized data regarding efficacy and complication rates are limited, especially in cancer patients. Temporary IVC filters are associated with higher costs and can have more long-term complications than permanent IVC filters. In this study, we examined the use of temporary and permanent IVC filters in the cancer population, a group at high risk for venous thromboembolism (VTE) as well as complications of anticoagulation.MethodsThis single-institution study included patients with active malignancy receiving adjuvant chemotherapy or considered for future chemotherapy that received an interventional radiology (IR) placed temporary (N=179) or permanent (N=207) IVC filter from 2009 to 2013. Patients were followed prospectively from the time of filter placement. The database included patient demographics, type of malignancy, indication for filter placement, time to filter retrieval, complications of placement/retrieval, rates of VTE recurrence and cause of death (if applicable).ResultsPatient demographic information is shown in Table 1. The most common reasons cited for filter placement included a contraindication to anticoagulation from bleeding (36%), recent or upcoming procedure (19%), thrombocytopenia (17%), and surgical prophylaxis (8%). 21% of filters were placed in patients with no contraindication to anticoagulation or failure of anticoagulation. Of these, 35% of the temporary filters were not removed. IVC filters were most frequently placed in patients with underlying hematologic malignancies (22%), gastrointestinal malignancies (22%) and lung cancer (16%). The majority of patients had stage III or IV cancer (62%).Of the 179 temporary filters placed, 60% were not retrieved. The most common reasons for failure of filter retrieval included: progressive disease/clinical deterioration (51%), continued contraindication to anticoagulation (23%) and loss of follow-up (8%). Only 2% of filters could not be removed because of mechanical reasons. Of the 81 attempted filter removals, 5 had in-filter thrombus, 4 had surrounding fibrin sheaths, 4 had filter tilt, 1 had IVC in-growth, 1 had broken struts and 1 had a procedure-related infection.The rate of recurrent VTE in all patients studied was 23% (21% in temporary filter group, 24% in permanent filter group), including 20 pulmonary emboli (PE) and 14 thromboses within the IVC filter. The majority of recurrences occurred off of anticoagulation (58%). Only 34% could be maintained on therapeutic anticoagulation. By study end, 72% of patients had died, most commonly due to progressive cancer. Median time from filter placement to death was 2.9 months (range: 0.1-64.7 months). Seventy-five patients (19%) died within 30 days of filter placement. They were more likely to have stage IV disease (78% vs. 54%). Of these 75 patients, three experienced recurrent VTE, two with lower extremity DVTs and one with an IVC thrombus. Data on filter costs were also collected. Costs were attributable to the placement and retrieval procedures when applicable ($10,983.00 and $8,824.00, respectively) as well as the device itself ($1,576.00).ConclusionsMalignancy-associated thrombosis is common and associated with a high rate of recurrence. While most recurrent VTE after IVC filter placement were deep vein thromboses, a relatively large number of PE's occurred after filter placement as well. A significant number of patients with malignancy-associated thrombosis who underwent IVC filter placement had no contraindication to anticoagulation or recurrent VTE while on anticoagulation. Better prospective studies are needed to assess the safety and efficacy of IVC filters in the setting of hemodynamic compromise, extensive clot burden or for surgical prophylaxis, especially in the oncology population. In this cohort, the majority of filters were placed in patients with advanced cancer with likely short life expectancies, suggesting the patient selection for filter placement could be optimized. Finally, the cost of filter placement and retrieval is substantial, further emphasizing the need for better prospective data to identify the subset of patients who will derive the most benefit from filter use. [Display omitted] DisclosuresStein:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Lewandowski:Cook Medical: Consultancy; Boston Scientific: Membership on an entity's Board of Directors or advisory committees.

Estimating the State in Stiff Continuous-Time Stochastic Systems within Extended Kalman Filtering

This paper studies performance of the well-known extended Kalman filtering method for estimating continuous-time stochastic mathematical models with discrete measurements. The mentioned continuous-discrete stochastic systems arise naturally in applied science and engineering and constitute the basic simulation means in such diverse topics of research as target tracking, navigation, stochastic control, chemistry, finance and so on. Therefore developing effective tools for their numerical treatment is an important task of study nowadays. Our paper focuses on so-called stiff stochastic systems in the sense that the stiffness of the drift coefficient in stochastic differential equations feeds into severe problems with state estimation of such systems by existing extended Kalman filtering methods. We expose that the majority of filters are not effective for stiff stochastic systems, including those attributed to solving such mathematical models. So, the task of designing efficient methods for treating stiff co...

Temporary Vena Cava Filters in Oncology Patients

BackgroundWhile inferior vena cava (IVC) filter placements continue to exponentially increase, the long-term complications from these devices are progressively more recognized. Randomized data on the efficacy of filters is sparse and focuses mainly on outcomes following permanent filter placement; however, the majority of filters placed currently are retrievable. Placement and removal of these filters are more expensive than permanent filters and have more long-term complications. In this study, we analyzed the use of retrievable filters in the cancer population, a group at very high risk for incident and recurrent venous thromboembolism (VTE).MethodsThis is a single-institution study. All patients with a history of malignancy or active malignancy that received an interventional radiology (IR) placed temporary IVC filter from 2009 to 2013 were logged into a database. Patients were followed prospectively from time of device placement. Recorded data included demographics, type of malignancy, indication for filter placement, time to filter retrieval, complications of placement/retrieval, rates of VTE recurrence and cause of death (if applicable). Final data analysis (n=179 filter placements) was only performed on patients that had an active malignancy or were receiving adjuvant therapy for a recent active malignancy.ResultsThe most common indications cited for filter placement included a contraindication to anticoagulation (69%), surgical prophylaxis (17%) and concern for cardiopulmonary collapse from a pulmonary embolism (PE) (6%). IVC filters were most frequently placed in patients with underlying hematologic malignancies (28%), gastrointestinal malignancies (17%) and gynecologic malignancies (15%). The majority of patients had stage III or IV cancer (61%). Internal medicine providers were most likely to order filter placements (36%) followed by hematologists/oncologists (26%) and gynecologic oncologists (17%). 35% of filters were not placed due to a contraindication to anticoagulation or failure of anticoagulation, and of these filters placed, 20% were not removed. Of the 179 temporary filters placed, 60% remained permanent. The most common reasons stated for failure of filter removal included: progressive disease/clinical deterioration (51%), continued contraindication to anticoagulation (23%) and loss of follow-up (7%). Only 2% of filters were unable to be removed because of mechanical reasons. Of the 81 attempted filter removals, 5 had in-filter thrombus, 4 had surrounding fiber sheaths, 4 had filter tilt, 1 had IVC in-growth, 1 had a procedure related infection and 1 had broken struts. The rate of recurrent VTE in all patients studied was 20% (predominantly deep vein thromboses), with the majority of recurrences occurring in patients that had the filter in place and were not maintained on anticoagulation. By the end of the study, 59% of patients had died, most commonly due to progressive cancer. Median time from filter placement to death was 5.25 months. Additionally, we gathered data on filter costs. Costs were attributable to the device ($1576.00), placement ($10,983.00) and removal ($8,824.00), totaling over $2 million dollars for placement of IVC filters in this cohort.ConclusionsA significant number of cancer patients who have an IVC filter placed have no contraindication to anticoagulation or evidence of recurrent VTE on anticoagulation. Better prospective data is needed regarding the safety and efficacy of IVC filter placement for prophylactic purposes or in the setting of a large VTE burden as these are commonly cited indications for placement. Additionally, consideration for permanent filter placement should be made in cancer patients as the majority of temporary filters are not removed and may carry higher risks of complications. Notably, our filter removal rate was significantly higher than the retrieval rate at most centers (<20%). IVC filters are commonly placed in patients with advanced malignancy and low expected survival, raising particular questions regarding their role in this patient population. Finally, the cost of filter placement and removal is markedly high, further emphasizing the need for better prospective data to clearly delineate those patients who will derive the most benefit from their use. DisclosuresLewandowski:Cook Medical: Consultancy; Boston Scientific: Membership on an entity’s Board of Directors or advisory committees. Stein:Incyte Corporation: Honoraria, Speakers Bureau; Sanofi Oncology: Honoraria.

Penetration of the inferior vena cava and adjacent organs after filter placement is associated with retrievable filter type and length of time in place.

Concern over local complications of inferior vena cava (IVC) filters exists, but little long-term data are available. Referrals for filter penetrations on computed tomography (CT) have increased with no standards for management. We reviewed postfilter CT findings in our institution. All patients receiving IVC filters between January 1, 2006 and December 31, 2009 with a postfilter CT were reviewed. Penetration was graded with a previously published scale. Filter indication, type, and subsequent encounters for abdominal or back pain were recorded. A total of 591 patients had a filter during the study period. Of these, 262 had an adequate postfilter CT, comprising the study group. Indications were prophylaxis in 16.4% and venous thromboembolism in 83.6%. Of filters placed for venous thromboembolism, indications were absolute (inability/failure of anticoagulation) in 44.7% and relative in 55.3%. Retrievable filters made up 92.7% of the filters, and 7.3% were permanent type. Of the retrievable filters, 1.6% were retrieved. One hundred twenty (45.8%) filters had grade 2 or 3 penetration. Another 38.2% (100) had struts immediately adjacent to the external aspect of the IVC, which may represent tentingof the cava. Grade 2 or 3 penetration occurred in 49.0% of retrievable filters but only 5.3% of permanent filters(P=.0001). Grade 2 or 3 penetration occurred in 18.2% of filters less than 30days old but in 57.3% of filters 30days old or older (P< .0001). Thirty-two patients had subsequent encounters for abdominal or back pain, but none was conclusively related to penetration. A majority of filters were placed for prophylaxis or relative indications and were retrievable type. Retrieval rate was low. Penetration of the IVC and adjacent organs was common and associated with retrievable type and length of time in place. It is unclear if most penetrations cause problems. Monitoring of penetrations with CT may be important to understand the natural history of this condition.

Reporting the impact of inferior vena cava perforation by filters

Perforation of the inferior vena cava by filters struts is a known complication. The goal of our review is to assess the impact of inferior vena cava perforation by filters based on an open, voluntary national database. We reviewed 3311 adverse events of inferior vena cava filters reported in Manufacturer and User Facility Device Experience database from January 2000 to June 2011. Outcomes of interest were incidence of inferior vena cava perforation, type of filter, clinical presentation, and management of the perforation, including retrievability rates. Three hundred ninety-one (12%) cases of inferior vena cava perforation were reported. The annual distribution of inferior vena cava perforation was 35 cases (9%), varying from seven (2%) to 70 (18%). A three-fold increment in the number of adverse events related to inferior vena cava filters has been noted since 2004. Wall perforation as an incidental finding was the most common presentation (N = 268, 69%). Surrounding organ involvement was found in 117 cases (30%), with the aorta being the most common in 43 cases (37%), followed by small bowel in 36 (31%). Filters were retrieved in 97 patients (83%) regardless of wall perforation. Twenty-five (26%) cases required an open procedure to remove the filter. Neither major bleeding requiring further intervention nor mortality was reported. Inferior vena cava perforation by filters remains stable over the studied years despite increasing numbers of adverse events reported. The majority of filters involved in a perforation were retrievable. Filter retrieval, regardless of inferior vena cava wall perforation, is feasible and must be attempted whenever possible in order to avoid complications.

Indications, Complications and Management of IVC Filters in 952 Patients At An Academic Hospital with a Level 1 Trauma Center

Abstract▪2285▪This icon denotes a clinically relevant abstract Introduction:Inferior vena cava (IVC) filters are frequently placed for the treatment and prevention of venous thromboembolism (VTE). Despite limited data to support their safety and efficacy, filter use has increased over the last three decades at our institution, as it has in hospitals throughout the United States. Boston Medical Center (BMC), a 500-bed academic institution with more than 30,000 admissions per year, is the largest and busiest Level 1 Trauma Center in New England. This study investigated the indications for IVC filter placement at BMC and examined outcomes including filter complications, management of anticoagulation, and follow up. Methods:A search was performed after obtaining IRB approval using Current Procedural Technology (CPT) codes to determine the number of patients at BMC that had IVC filters placed from August 2003 to February 2011. IVC filters were placed in 978 patients during the study period. Of these, 26 patients were excluded due to incomplete medical records. The remaining 952 charts were reviewed to determine patient demographics, indication for IVC filter placement, complications, post-discharge follow-up, filter retrieval, and use of anti-coagulation. Results:Of the 952 filters for which data were available, permanent filters were placed in 273 patients (29%), with the majority of these placed prior to 2006. Retrievable filters were placed in 679 patients (71%). Seven different types of IVC filters were placed by physicians from multiple departments, in decreasing order of frequency: interventional radiology, trauma surgery, vascular surgery, cardiology, and cardiothoracic surgery. Filters were successfully placed in the IVC in all patients except one, in whom a portion of the filter entered the renal vein and could not be extracted. The majority of filters were placed due to perceived immediate contraindication to anticoagulation (recent trauma, bleeding, or surgery). Five hundred and four patients (53%) had VTE at the time of filter placement with almost half of these, 237 patients (25% of all patients), received therapeutic anti-coagulation prior to discharge. A median of three days (range 0–32) elapsed between the date of trauma and filter insertion, with 174 (37%) being inserted five or more days after trauma. Only 31 patients (3%) sustained a VTE while on therapeutic anticoagulation. There was no protocol in place for routine imaging after filter placement or retrieval. Of the patients referred for subsequent imaging (approximately half) due to symptoms of VTE or other indications, 73 had VTE that developed after filter placement. Twenty-six of these events occurred during the index hospitalization. The majority of patients had follow-up at BMC within one month, although 207 patients had no documented follow-up at our institution. An attempt was made to remove 71 (10.5%) of the retrievable filters placed. Retrieval was successful in 58 of the 71 patients. Retrieval attempts failed in thirteen patients (18%) for the following reasons: filter embedded in the IVC, a clot in the filter, or a filter protruding through the blood vessel. The median retrieval time was 122 days (range 2 to 1931 days). The patient with retrieval at 1931 days had a fractured IVC filter removed with one prong extracted from a pulmonary artery. Conclusion:These data report on the largest single institution review of IVC filter placement and follow-up. Nine hundred and fifty-two filters were placed during the study period and 679 were filters designed for retrieval, yet only 58 retrievable filters (8.5%) were successfully removed. Unsuccessful retrieval occurred in 18% of attempts, making this a common and under-recognized problem. A significant proportion of filters placed for trauma were inserted after the period of highest bleeding risk had subsided, when anticoagulation may have been more appropriate. While many of these filters were placed under the generally accepted guideline of an existing contraindication to anticoagulation, 237 patients were discharged on therapeutic doses of anti-coagulation. Data are critically needed regarding indications for filter placement, risks and benefits of retrieving filters, and short and long-term complications of leaving filters in place. Disclosures:Sloan:Acetylon Pharmaceuticals: Consultancy; Millenium: Consultancy.

Hepa Filter Replacement Experience in a Biological Laboratory

Integrity tests on 969 HEPA filters filtering air to and from rooms and laboratories have been done annually for 13 years. Filter replacements were analyzed by supply or exhaust air system, area serviced, primary or secondary situations and cause for replacement. The average annual filter replacement rate for installations filtering either supply or exhaust air, or vented gases were 2.9%, 1.9%, or 3.0% respectively. Initially, most failures occurred in the filter medium or the gasket seal. However, in recent years, there has been a general increase in filter reliability with filter blockage being the major reason for replacement. The replacement rates for exhaust filters in laboratory, animal room or other plant rooms were similar. This study has shown that the critical biocontainment function of HEPA filters in this biological laboratory has been exceptionally reliable with little deterioration in performance over 13 years of service. Because a majority of filters (up to 78% for exhaust systems) have never been replaced, it was not possible to determine a meaningful life expectancy for filters.

A NOVAL APPROACH TO SPEECH ENHANCEMENT USING ADAPTIVE MULTI-BAND LOGARITHMIC ENVELOPE EXPANSION TECHNIQUE

The speech enhancement problem covers a broad spectrum of constraints, applications and issues. The principal application areas of speech enhancement are noise reduction for human listening, preprocessing for recognition systems and preprocessing for linear predictive coding. This paper introduces a modified technique based on Multi-band envelope expansion technique called adaptive multi-band logarithmic envelope expansion technique. In this technique a threshold level varying according to the change of input signal-to-noise ratio is used, and the nonlinear function used to expand the envelope is a logarithmic function. In addition, the use of non-uniform frequency spacing gives better enhancement since the majority of filters are concentrated in the actual speech band ( up to 1.5 KHz ) with few filters in the remaining band 1.5 up to 4 KHz ). The simulation results show that the new technique gives a high dynamic range of input signal-to-noise ratio ( up to - 8db ), and a high improvement factor. The intelligibility of the proposed technique is considered as a subject for further investigation.