Presence Of Leak Research Articles

Duplex ultrasound evaluation of endoluminally treated aortic aneurysms with emphasis on diameter measurement: A comparison with computed tomography

The aim of this study was to determine the accuracy of color Doppler ultrasound (CDUS) for endoleak detection and measurement of the aneurysm diameter after endovascular aortic aneurysm repair. Forty-eight CDUS and computed tomographic angiography (CTA) examinations performed concurrently on 29 patients who were treated with endovascular stent grafts for abdominal aortic aneurysms were included in the study. CTA and CDUS findings were retrospectively compared for aneurysm diameter, patency of the graft, and the presence of leaks in the aneurysm's lumen (the so-called "endoleaks"). The stent graft was patent in all patients. Including the follow-up examinations, endoleaks were detected in a total of 17 CTA studies. The sensitivity, specificity, and positive and negative predictive values for CDUS compared with CTA as the gold standard were 100%, 96%, 94.4%, and 100%, respectively. Kappa statistics showed a high level of agreement between CDUS ant CTA examinations (χ = 0.95). The aneurysm diameters measured with CDUS and CTA were significantly different, but within 5 mm of each other in 83% of patients. Provided that a strict CDUS protocol including spectral analysis of perigraft flow is used, CDUS is comparable to CTA for endoleak detection and measurement of the aneurysm diameter.

Complicaciones postquirúrgicas de la malformación de Chiari tipo I: duroplastia y fístula de líquido cefalorraquídeo

The surgical treatment of Chiari I malformation is to carry out a suboccipital decompression. It is described that postoperative complications may occur, especially if the dura is open and closed using a graft (duraplasty). Among them, one of the most important events due to its difficult handling is cerebrospinal fluid leak through the suture line. To conduct a postoperative review to analyze the outcome of the patients and the occurrence of complications depending on the dural plasty used. A retrospective study was carried out between 1997 and 2008, both inclusive, where we assessed 36 patients. All of them were studied with preoperative and postoperative craniospinal magnetic resonance, and by a thorough clinical examination performed before and after the surgery. The surgical procedure consisted of suboccipital decompression and resection of the posterior arch of C1 or C1 and C2 (depending on the extent of the caudal displacement of the tonsils), followed by duraplasty using either an autologous graft (pericranium) or a synthetic graft (Gore-tex). After a mean follow-up of 2 years, the clinical results were: excellent (55%), if there was a great clinical improvement; good (29%), if there was slight improvement; and bad (16%), if there was no improvement or there was worsening. In the 30 patients given a duraplasty (18 with an artificial graft, 12 with an autologous pericranium graft), 6 cases of cerebrospinal fluid leak appeared, although no significant association between the type of dural plasty and the presence of leak was observed. The best results were obtained for headaches, cervical pain and dizziness. Despite the fact that there were more cases of cerebrospinal fluid leak in patients receiving an artificial graft compared to patients with pericranium graft, there was no significant difference.

Which factors may effect urinary leakage following percutaneous nephrolithotomy?

To evaluate the factors that may effect urinary leakage following percutaneous nephrolithotomy (PCNL). Four hundred and thirty-three patients who underwent PCNL were reviewed retrospectively. The factors that may lead to leakage after surgery were analyzed as categorized into four groups according to individual variables (age, sex, body mass index); renal factors (previous surgery, extracorporeal shock wave lithotripsy history, presence of hydronephrosis); stone burden; and surgical features (access number, type of dilatation, presence of nephrostomy catheter). These data were compared for the presence and duration of urinary leakage. There was no statistically significant correlation between individual factors and both the presence of leak (POL) and the duration of leak (DOL) (P > 0.05). Among renal factors, only presence and degree of hydronephrosis was significantly correlated with POL (P < 0.001) and DOL (P < 0.001). The mean cumulative stone burden neither had impact on POL nor correlated with DOL (P > 0.05). Among surgical factors, dilatation with a Nephromax dilator significantly increased incidence of POL when compared with an Amplatz dilator (P < 0.001), yet did not change DOL. Using an internal ureteral stent significantly decreased incidence of POL and DOL (P < 0.001). DOL increased with catheter diameter and stay time (P < 0.05). Several yet simple factors appear to be effective in postoperative urine leakage from the access sites after percutaneous stone surgery. Precautions may also be simple if these factors are considered preoperatively.

Postoperative Noninvasive Ventilation

Thesemodificationsoftherespiratoryfunctionoccur early after surgery and are more often transient andcould lead to ARF. The clinical result (severity of theARF) is the product of perioperative-related ventilatoryimpairment and severity of the preoperative pulmonarycondition. Maintenance of adequate oxygenation in thepostoperative period is of major importance, especiallywhen pulmonary complications such as ARF occur. Al-though invasive endotracheal mechanical ventilation hasremained the cornerstone of ventilatory strategy for manyyearsforsevereARF,severalstudieshaveshownthatmor-tality associated with pulmonary disease is largely relatedto complications of postoperative reintubation and me-chanicalventilation.Therefore,majorobjectivesforanes-thesiologists are first to prevent the occurrence of postop-erative complications and second to ensure oxygenadministration and carbon dioxide removal while avoid-ing intubation if ARF occurs. Noninvasive ventilation(NIV) does not require an artificial airway (endotrachealtube or tracheotomy), and its use is well established toprevent ARF occurrence (prophylactic treatment) or totreat ARF to avoid reintubation (curative treatment) (fig.1). Studies show that patient-related risk factors, such aschronic obstructive pulmonary disease, age older than 60yr, American Society of Anesthesiologists class of II orhigher, obesity, functional dependence, and congestiveheart failure, increase the risk for postoperative pulmo-nary complications.

Bilevel vs ICU Ventilators Providing Noninvasive Ventilation: Effect of System Leaks: A COPD Lung Model Comparison

Noninvasive positive-pressure ventilation (NPPV) modes are currently available on bilevel and ICU ventilators. However, little data comparing the performance of the NPPV modes on these ventilators are available. In an experimental bench study, the ability of nine ICU ventilators to function in the presence of leaks was compared with a bilevel ventilator using the IngMar ASL5000 lung simulator (IngMar Medical; Pittsburgh, PA) set at a compliance of 60 mL/cm H(2)O, an inspiratory resistance of 10 cm H(2)O/L/s, an expiratory resistance of 20 cm H(2)O/ L/s, and a respiratory rate of 15 breaths/min. All of the ventilators were set at 12 cm H(2)O pressure support and 5 cm H(2)O positive end-expiratory pressure. The data were collected at baseline and at three customized leaks. At baseline, all of the ventilators were able to deliver adequate tidal volumes, to maintain airway pressure, and to synchronize with the simulator, without missed efforts or auto-triggering. As the leak was increased, all of the ventilators (except the Vision [Respironics; Murrysville, PA] and Servo I [Maquet; Solna, Sweden]) needed adjustment of sensitivity or cycling criteria to maintain adequate ventilation, and some transitioned to backup ventilation. Significant differences in triggering and cycling were observed between the Servo I and the Vision ventilators. The Vision and Servo I were the only ventilators that required no adjustments as they adapted to increasing leaks. There were differences in performance between these two ventilators, although the clinical significance of these differences is unclear. Clinicians should be aware that in the presence of leaks, most ICU ventilators require adjustments to maintain an adequate tidal volume.

Water content of delivered gases during non-invasive ventilation in healthy subjects

No clear recommendation exists concerning humidification during non-invasive ventilation (NIV) and high flow CPAP, and few hygrometric data are available. We measured hygrometry during NIV delivered to healthy subjects with different humidification strategies: heated humidifier (HH), heat and moisture exchanger, (HME) or no humidification (NoH). For each strategy, a turbine and an ICU ventilator were used with different FiO(2) settings, with and without leaks. During CPAP, two different HH and NoH were tested. Inspired gases hygrometry was measured, and comfort was assessed. On a bench, we also assessed the impact of ambient air temperature, ventilator temperature and minute ventilation on HH performances (with NIV settings). During NIV, with NoH, gas humidity was very low when an ICU ventilator was used (5 mgH(2)O/l), but equivalent to ambient air hygrometry with a turbine ventilator at minimal FiO(2) (13 mgH(2)O/l). HME and HH had comparable performances (25-30 mgH(2)O/l), but HME's effectiveness was reduced with leaks (15 mgH(2)O/l). HH performances were reduced by elevated ambient air and ventilator output temperatures. During CPAP, dry gases (5 mgH(2)O/l) were less tolerated than humidified gases. Gases humidified at 15 or 30 mgH(2)O/l were equally tolerated. This study provides data on the level of humidity delivered with different humidification strategies during NIV and CPAP. HH and HME provide gas with the highest water content. Comfort data suggest that levels above 15 mgH(2)O/l are well tolerated. In favorable conditions, HH and HMEs are capable of providing such values, even in the presence of leaks.

Prediction of bulk modulus and volumetric expansion coefficient of water for leak tightness test of pipelines

To determine whether any pressure variation in pipeline hydrostatic test is a result of temperature changes or the presence of leaks, the calculation of pressure/temperature changes is required for test sections. In these calculations, bulk modulus and volumetric expansion coefficient of fresh or sea water must be taken into account. In this study, a simple-to-use correlation is developed to predict the bulk modulus and volumetric expansion coefficient of both fresh and sea water as a function of temperature and pressure. The proposed correlation helps to cover the bulk modulus and volumetric expansion coefficient of both fresh and sea water for temperatures less than 50 °C (40 °C for sea water) as well as pressures up to 55,000 kPa (550 bar). The results can be used in follow-up calculations to determine whether any pressure variation in pipeline hydrostatic test is a result of temperature changes or the presence of leaks. The proposed correlation showed promising results with average absolute deviations for volumetric expansion coefficient and bulk modulus of water being around 0.58% and 0.08% respectively. The novel correlation is easy to use and will prove to be of immense value for project engineers to test the critical limits accurately.

Performance of noninvasive ventilation modes on ICU ventilators during pressure support: a bench model study

Noninvasive ventilation (NIV) is often applied with ICU ventilators. However, leaks at the patient-ventilator interface interfere with several key ventilator functions. Many ICU ventilators feature an NIV-specific mode dedicated to preventing these problems. The present bench model study aimed to evaluate the performance of these modes. Bench model study in an intensive care research laboratory of a university hospital. Eight ICU ventilators, widely available in Europe and featuring an NIV mode, were connected by an NIV mask to a lung model featuring a plastic head to mimic NIV conditions, driven by an ICU ventilator imitating patient effort. Tests were conducted in the absence and presence of leaks, the latter condition with and without activation of the NIV mode. Trigger delay, trigger-associated inspiratory workload, and pressurization were tested in conditions of normal respiratory mechanics, and cycling was also assessed in obstructive and restrictive conditions. On most ventilators leaks led to an increase in trigger delay and workload, a decrease in pressurization, and delayed cycling. On most ventilators the NIV mode partly or totally corrected these problems, but with large variations between machines. Furthermore, on some ventilators the NIV mode worsened the leak-induced dysfunction. The results of this bench-model NIV study confirm that leaks interfere with several key functions of ICU ventilators. Overall, NIV modes can correct part or all of this interference, but with wide variations between machines in terms of efficiency. Clinicians should be aware of these differences when applying NIV with an ICU ventilator.

Design of a Lung Simulator for Teaching Lung Mechanics in Mechanical Ventilation

Over the last 10 years, noninvasive ventilation has become a treatment option for respiratory insufficiency in pulmonology services. The technique is currently included in pulmonology teaching programs. Physicians and nurses should understand the devices they use and the interaction between the patient and the ventilator in terms of respiratory mechanics, adaptation, and synchronization. We present a readily assembled lung simulator for teaching purposes that is reproducible and interactive. Based on a bag-in-box system, this model allows the concepts of respiratory mechanics in mechanical ventilation to be taught simply and graphically in that it reproduces the patterns of restriction, obstruction, and the presence of leaks. It is possible to demonstrate how each ventilation parameter acts and the mechanical response elicited. It can also readily simulate asynchrony and demonstrate how this problem can be corrected.

When a leak is unavoidable, preoxygenation is equally ineffective with vital capacity or tidal volume breathing

Ideally, preoxygenation is performed using a tight fitting mask either by breathing normally for three to five minutes or with four to eight vital capacity (VC) breaths in 0.5 to one minute, but in practice leaks are frequent and sometimes unavoidable. This study was designed to determine which breathing method provided the best oxygenation in the presence of leak. Twenty volunteers were instructed to breathe from a circle circuit supplied with 6 L x min(-1) of fresh oxygen. Each subject was tested under four situations selected in random order: 1) normal breathing for three minutes without leak; 2) normal breathing for three minutes with a leak; 3) four VCs in 30 sec without a leak; and 4) four VCs in 30 sec with a leak. The leak was created by a piece of size 18 French nasogastric tube, 5 cm long, taped under the face mask. Inspired and expired O(2) and CO(2) were sampled at the nostrils. In the absence of a leak, the end-tidal oxygen fraction (F(EO(2)) was greater after three minutes of tidal breathing (89 +/- 3%; mean +/- SD) in comparison with the response to four VCs (76 +/- 7%; P < 0.001). Introduction of a leak decreased the F(EO(2)) significantly (P < 0.001). With a leak, the F(EO(2)) was similar with normal breathing (61 +/- 8%) and after four VCs (59 +/- 11%). Preoxygenation with tidal volume breathing for three minutes yields higher F(EO(2)) in comparison to four VCs. If a small leak (4 mm internal diameter) is introduced, the F(EO(2)) decreases significantly with both breathing methods to approximately 60%.

Performance Characteristics of 10 Home Mechanical Ventilators in Pressure-Support Mode

Inspiratory pressure (Pi) support delivered by a bilevel device has become the technique of choice for noninvasive home ventilation. Considerable progress has been made in the performance and functionality of these devices. The present bench study was designed to compare the various characteristics of 10 recently developed bilevel Pi devices under different conditions of respiratory mechanics.Bench model study.Research laboratory, university hospital.Ventilators were connected to a lung model, the mechanics of which were set to normal, restrictive, and obstructive, that was driven by an ICU ventilator to mimic patient effort. Pressure support levels of 10 and 15 cm H(2)O, and maximum were tested, with "patient" inspiratory efforts of 5, 10, 15, 20, and 25 cm H(2)O. Tests were conducted in the absence and presence of leaks in the system. Trigger delay, trigger-associated inspiratory workload, pressurization capabilities, and cycling were analyzed.All devices had very short trigger delays and triggering workload. Pressurization capability varied widely among the machines, with some bilevel devices lagging behind when faced with a high inspiratory demand. Cycling was usually not synchronous with patient inspiratory time when the default settings were used, but was considerably improved by modifying cycling settings, when that option was available.A better knowledge of the technical performance of bilevel devices (ie, pressurization capabilities and cycling profile) may prove to be useful in choosing the machine that is best suited for a patient's respiratory mechanics and inspiratory demand. Clinical algorithms to help set cycling criteria for improving patient-ventilator synchrony and patient comfort should now be developed.

Histopathologic Features of Conjunctival Filtering Blebs

To characterize and compare the histological features of conjunctiva obtained during the repair of trabeculectomy and inadvertent blebs and to assess the effects of antifibrotic agents. We used routine paraffin processing and light microscopy to examine conjunctival specimens from 28 eyes undergoing late bleb revision: 19 leaking trabeculectomy blebs, 5 nonleaking trabeculectomy blebs, and 4 inadvertent blebs. Quantitative analysis of histological characteristics included conjunctival epithelial thickness, stromal vascularity, squamous metaplasia, stromal inflammatory cell infiltrate, and goblet cell density. The type of surgery, presence of leaks, prior topical medication, and antifibrotic use were correlated with histological findings. Trabeculectomy blebs (leaking and nonleaking) showed decreases in overall epithelial thickness (P<.02), goblet cell density (P<.001), and vascularity (P<.001) compared with inadvertent bleb controls. Conjunctiva exposed to antifibrotics had fewer layers of epithelial cells than those with no prior exposure (P<.05). Histological analysis of thin blebs excised following trabeculectomy demonstrated decreases in epithelial thickness and goblet cell density compared with inadvertent blebs. Both leaking and nonleaking trabeculectomy blebs exhibited decreases in localized stromal vascularity and increases in surrounding stromal vascularity compared with normal conjunctiva.

Leak Estimation in Water Distribution Systems by Statistical Analysis of Flow Readings

A new method is presented for detecting the magnitude of leaks in small residential service zones (under 1,000 homes) of a drinking water distribution system. It is assumed that continuous measurements of flow rates through the main supply line into a residential service zone are available during periods of low use. The sample mean and variance from the set of measured flow rates are computed as the set is truncated progressively from below. Trajectories of the sample statistics and their derivatives are plotted versus the level of data truncation. In the presence of leaks, these trajectories diverge from their expected theoretical path when plotted on a standardized graph derived from a mixed truncated normal distribution. The point of departure on the standardized graph indicates where the truncation threshold matches the maximum rate of network leakage. A performance limit for the proposed method is derived to account for network size and time averaging. Several examples, based on observed and simulated pipe flows, demonstrate application of the leak detection method.

Resultados del tratamiento endovascular de los aneurismas de aorta abdominal. Estudio prospectivo de los cambios producidos en el calibre de los aneurismas

Summary Objective To analyse results of endovascular treatment, in terms of calibre variation and evolution of leaks during follow-up. Patients and methods 25 patients, electively treated by means of endovascular devices from May-1998 to Dic-2000. Mean follow up 11 months. Results of treatment on discharge, calibre variation and presence of leaks during follow up are described. Results 48% of treated patients had ASA III-IV surgical risk; mean age 71 years. Epidural anaesthesia was employed in 88% of cases. All procedures were successful, without need of conversion to open surgery. There was no mortality. 3 type IIleaks were observed. Mean postop-erative stay was 3,2 days. No variations were observed in aneurysm neck during follow up (p Conclusions Endovascular treatment of abdominal aortic aneurysm is associated with a low morbi-mortality and reduced post-operative stay. Endovascular treatment causes statistically significant reduction of aneurysm diameter at six months after the procedure. We do not find any relation between the presence of leaks and changes in the diameter of aneurysms.

An experimental evaluation of the vapour compression plant performances in presence of R407C leaks using an electronic expansion valve

Chlorofluorocarbons and hydrofluorocarbons (HFCs) used as working fluids in the vapour compression plants, have to be replaced by new substances because of their ozone depletion potential. Zeotropic mixture of HFCs refrigerants that are environment-friendly substances are often employed. The zeotropic mixtures with a large glide temperature could cause problems in the refrigeration control system when a leak occurs because their composition modifies. This paper presents a comparison of the energetic performances, in presence of leaks, when a thermostatic valve and an electronic expansion valve are used in a refrigeration plant, working with the zeotropic mixture designated as R407C (R32/R125/R134a 23/25/52% in mass)—this is the most suitable substitute of the HCFC22. The vapour leaks are simulated at the inlet of the evaporator and at the liquid receiver. Experimental results show that a good adaptability to mixture leaks is related to the electronic expansion valve, while better energetic performances are obtained using the thermostatic expansion valve as long as it is usable.

Respiratory burst response of peritoneal leukocytes adhering to titanium and stainless steel.

Titanium sheets, made hydrophilic by oxidative cleaning or hydrophobic by treatment with butanol, and stainless steel sheets with different patterns of pores (straight phi = 0.8 mm) were implanted into the peritoneal cavity of mice. The implants were removed after 2 h, and the surface-adhering leukocytes were stained with propidium iodide and fluorescein diacetate to quantitate cell adhesion and to indicate the presence of leaks in the cell membrane. The ability of the surface-adhering leukocytes to mount a respiratory burst response after stimulation with PMA or zymosan was measured by chemiluminiscence. The results show that stainless steel without pores induces membrane leakage in 80% of the surface-adhering leukocytes compared with 65% of cells adhering to porous steel. Hydrophilic titanium induces membrane leakage in 48% of the surface-adhering leukocytes compared with 19% of cells adhering to hydrophobic titanium. The respiratory burst response of the surface-adhering leukocytes stimulated with PMA was attenuated on stainless steel and hydrophilic titanium compared with hydrophobic titanium. Thus, butanol treatment of titanium and pores in stainless steel increase the biocompatibility of the materials.

Role of radiologic contrast studies in the early postoperative period after bariatric surgery.

Radiologic contrast studies have been used routinely to rule out gastrointestinal (GI) leaks and to evaluate gastric emptying after bariatric surgery. The aim of the study was to evaluate the value of this study in the diagnosis of early complications. 100 morbidly obese patients underwent bariatric surgery at our institution in a 7 year period. An upper GI series was routinely performed 48 to 72 hours after surgery. Clinical and radiologic records were reviewed, analyzing demographic characteristics, type of surgery, radiologic findings, and clinical evolution with emphasis on the presence of leaks. Mean age was 36 +/- 10 years; there were 68 women and 32 men. Mean body mass index (BMI) was 48 +/- 10 kg/m2. All radiologic examinations ruled out the presence of leaks and showed adequate gastroesophageal emptying. One patient with normal postoperative x-ray studies developed a small GI fistula after starting liquid diet. Contrast radiologic studies permit good visualization of the gastric anatomy after bariatric surgery. They usually confirm adequate gastric emptying, but might be unable to demonstrate small gastric leaks.

Role of Endoscopic Retrograde Cholangiography and Nasobiliary Drainage in the Management of Postoperative Biliary Leak

In order to assess the role of endoscopic retrograde cholangiography in evaluating the patients with post-operative biliary leak and of endoscopic nasobiliary drainage in its management, 36 patients with biliary leak seen over a period of 9 years were studied. Thirty-two had biliary leak following cholecystectomy, 3 following repair of liver trauma and 1 following choledochoduodenostomy. Patients presented at an interval of 4 days to 210 days (mean ± SEM, 32.4 ± 6.7 days) following laparotomy. Hyperbilirubinemia was noticed in only 13 patients (36.1%), while abdominal ultrasonogram showed ascites or biloma in 24 (66.7%). Endoscopic retrograde cholangiography showed the leak to involve the common bile duct in 55.6%, cystic duct in 33.3% and intrahepatic biliary radicles in 8.3%. Associated lesions included bile duct obstruction due to stricture or accidental ligature in 20%, bile duct stone in 20% and liver abscess in 2.8%. Endoscopic nasobiliary drainage using a 7 Fr pig-tail catheter was attempted in 14 patients and could be established in 12 of them. Bile duct leak sealed in all but one of these 12 patients after an interval of 3 days to 40 days (mean ± SEM, 12.2 ± 3.2 days). A single patient with large defect and a proximal bile duct stricture did not respond and required surgery. Common bile duct stones were removed by endoscopic sphincterotomy in 3 out of 4 patients. One patient with large stone required surgical choledocholithotomy. In conclusion, endoscopic retrograde cholangiography was safe and useful in confirming the presence of leak as well as its site, size and associated abnormalities. Endoscopic nasobiliary drainage proved an effective therapy in post-operative biliary leak and could avoid re-exploration in 71.4% patients.

Separation of fluorocarbons in the fluid systems of the DELPHI Barrel RICH detector

Abstract During the run period 1994 the presence of leaks inside the barrel of the DELPHI RICH detector led to an increased mixing of the two fluorocarbon liquids being used as radiator media (gas radiator, C 5 F 12 ; liquid radiator, C 6 F 14 ). To cope with the potential risk of boiling or condensation, as well as with the varying refractive indices, intervention became indispensable. We report on the methods that allowed us not only to monitor and stabilize the respective contaminations, but also to follow the time dependence of the refractive indices. In the run period 1995 the installation of a dedicated on-line separation plant in the gas radiator system combined with an on-line distillation plant in the liquid radiator system maintained the mixing at a level below 20%. In addition, the use of specially designed vapour pressure cells allow a permanent and precise monitoring of the composition and thereby of the refractive indices of the radiator media.

Compression ratio and leakage through stages in turbomolecular pumps

The presence of leaks through the stages of a turbomolecular pump affects its actual compression ratio. The measured compression ratios are in many instances much lower than calculated ones if this effect is not considered in the calculation. A theoretical evaluation is done for the effect of the leakage from high pressure stages to the low pressure stages. A simple model is developed to calculate the decrease in the compression ratio caused by leakage. Two cases are studied in detail, referring to a particular design of the pump: (1) the conductance in the region between the envelope of the pump and the spacer rings is much larger than the conductance between two adjacent spacer rings; (2) the conductance between two adjacent spacer rings is much larger than the conductance in the region between the envelope of the pump and the spacer rings. In the latter case, compression ratios might be very close to the maximum (without leakage). Above considerations show a way to improve compression ratios in turbomolecular pumps. Finally an experimental verification has been performed, the calculated configurations have been tested, and the experimental and theoretical results are compared.