Hybrid argon plasma coagulation for the treatment of Barrett’s esophagus:A prospective,multicenter study

BACKGROUND The incidence of Barrett’s esophagus(BE)in China is lower compared to the Western populations.Hence,studies conducted in the Chinese population has been limited.The current treatment options available for BE treatment includes argon plasma coagulation(APC),radiofrequency ablation and cryoablation,all with varying degrees of success.AIM To determine the efficacy and safety of HybridAPC in the treatment of BE.METHODS The study cohort consisted of patients with BE who underwent HybridAPC ablation treatment.These procedures were performed by seven endoscopists from different tertiary hospitals.The duration of the procedure,curative rate,complications and recurrent rate by 1-year follow-up were recorded.RESULTS Eighty individuals were enrolled for treatment from July 2017 to June 2020,comprising of 39 males and 41 females with a median age of 54 years(range,30 to 83 years).The technical success rate of HybridAPC was 100%and the overall curative rate was 98.15%.No severe complications occurred during the operation.BE cases were classified as short-segment BE and long-segment BE.Patients with short-segment BE were all considered cured without complications.Thirty-six patients completed the one-year follow-up without recurrence.Twenty-four percent had mild dysplasia which were all resolved with one post-procedural treatment.The mean duration of the procedure was 10.94±6.52 min.CONCLUSION Treatment of BE with HybridAPC was found to be a simple and quick procedure that is safe and effective during the short-term follow-up,especially in cases of short-segment BE.This technique could be considered as a feasible alternative ablation therapy for BE.

Long-term follow-up after complete ablation of Barrett's esophagus with argon plasma coagulation

AIM: To report the long-term outcome of patients after complete ablation of non-neoplastic Barrett's esophagus (BE) with respect to BE relapse and development of intraepithelial neoplasia or esophageal adenocarcinoma. METHODS: In 70 patients with historically proven non neoplastic BE, complete BE ablation was achieved by argon plasma coagulation (APC) and high-dose proton pump inhibitor therapy (120 mg omeprazole daily). Sixty-six patients (94.4%) underwent further surveillance endoscopy. At each surveillance endoscopy four-quadrant biopsies were taken from the neo-squamous epithelium at 2 cm intervals depending on the pre-treatment length of BE mucosa beginning at the neo-Z-line, and from any endoscopically suspicious lesion. RESULTS: The median follow-up of 66 patients was 51 mo (range 9-85 mo) giving a total of 280.5 patient years. A mean of 6 biopsies were taken during surveillance endoscopies. In 13 patients (19.7%) tongues or islands suspicious for BE were found during endoscopy. In 8 of these patients (12.1%) non-neoplastic BE relapse was confirmed histologically giving a histological relapse rate of 3% per year. In none of the patients, intraepithelial neoplasia nor an esophageal adenocarcinoma was detected. Logistic regression analysis identified endoscopic detection of islands or tongues as the only positive predictor of BE relapse (P= 0.0004). CONCLUSION: The long-term relapse rate of non neoplastic BE following complete ablation with high-power APC is low (3% per year).

Endoscopic ablation of Barrett's esophagus using high power setting argon plasma coagulation: A prospective study

AIM: This prospective study evaluated the effectiveness of 90 W argon plasma coagulation (APC) for the ablation of Barrett's esophagus (BE) that is considered to be the main risk factor for the development of esophageal adenocarcinoma.METHODS: The results from 25 patients, observed at the First Department of General Surgery, University of Verona, Italy, from October 2000 to October 2003, who underwent APC for histologically proven BE were prospectively analyzed.RESULTS: The ablation treatment was completed in all the patients but one (96%). The mean number of APC sessions needed to complete ablation was 1.6 (total number: 40). The eradication was obtained in the majority of cases by one session only (60%), two sessions were required in 24% of the cases and three or more in 16%.About 43% of the sessions were complicated. Retrosternal pain (22.5%) and fever (17.5%) were the most frequent symptoms. Only one major complication occurred, it was an hemorrhage due to ulcer formation on the treated esophagus that required urgent endoscopic sclerosis and admission. The follow-up was accomplished in all the patients with a mean period of 26.3 mo and 20 patients (84%) with a follow-up period longer than 24 mo. Only one patient showed a relapse of metaplastic mucosa 12 mo after the completion of ablation. The patient was hence re-treated and now is free from recurrence 33 mo later.CONCLUSION: High power setting (90 W) APC showed to be safe and effective. The effects persist at a mean follow-up period of two years with a comparable cost in term of complications with respect to standard power settings. Further studies with greater number of patients are required to confirm these results and to assess if ablation reduces the incidence of malignant progression.

Epinephrine plus argon plasma or heater probe coagulation in ulcer bleeding

AIM:To compare the effectiveness of argon plasma coagulation (APC) and heater probe coagulation (HPC) in non-variceal upper gastrointestinal bleeding.METHODS:Eighty-five (18 female,67 male) patients admitted for acute gastrointestinal bleeding due to gastric or duodenal ulcer were included in the study.Upper endoscopy was performed and HPC or APC were chosen randomly to stop the bleeding.Initial hemostasis and rebleeding rates were primary and secondary end-points of the study.RESULTS:Initial hemostasis was achieved in 97.7% (42/43) and 81% (36/42) of the APC and HPC groups,respectively (P < 0.05).Rebleeding rates were 2.4% (1/42) and 8.3% (3/36) in the APC and HPC groups,respectively,at 4 wk (P > 0.05).CONCLUSION:APC is an effective hemostatic method in bleeding peptic ulcers.Larger multicenter trials are necessary to confirm these results.

Role of argon plasma coagulation in treatment of esophageal varices

With the development of endoscopic therapy,argon plasma coagulation(APC)has been widely used by endoscopists.It has many advantages,such as simple to operate,low cost,and minimal invasiveness.Because of its capability of lesion ablation and hemostasis,APC has several indications in the gastrointestinal tract.One of them is esophageal varices.The aim of this review is to summarize the research on APC in this field to provide a reference for clinical practice.

Endoscopic resolution and recurrence of gastric antral vascular ectasia after serial treatment with argon plasma coagulation

To evaluate long-term endoscopic resolution and recurrence rate of gastric antral vascular ectasia (GAVE) after argon plasma coagulation (APC) treatment. METHODSThis was an IRB-approved retrospective single center study that included patients endoscopically treated for GAVE between 1/1/2008 to 12/31/2014. The primary and secondary end points of the study were rate of endoscopic resolution of GAVE after APC treatment and recurrence rate of GAVE after endoscopic resolution, respectively. Endoscopic resolution of GAVE was defined as no endoscopic evidence of GAVE after treatment with APC. Recurrence of GAVE was defined as endoscopic reappearance of GAVE after prior resolution. RESULTSTwenty patients met the study criteria. Median age (range) of the patients was 59.5 years (42-74 years). GAVE was associated with underlying cirrhosis in 16 (80%) patients. Indications for initial esophagogastroduodenoscopy (EGD) included hematemesis and/or melena (9/20, 45%), iron deficiency anemia (6/20, 30%), screening or surveillance of varices (4/20, 20%), and occult gastrointestinal bleeding (1/20, 5%). The patients were treated with a total of 55 APC sessions (range 1-7 sessions). Successful endoscopic resolution of GAVE was achieved in 8 out of 20 patients (40%). There was no correlation between number of treatment sessions and GAVE treatment success (P = NS). Recurrence of GAVE was noted on a subsequent EGD in 2 out of 8 patients (25%) with prior endoscopic resolution of GAVE. Median follow-up period for the study population was 627 d (range 63-1953 d). CONCLUSIONEndoscopic resolution rate of GAVE was low (40%) with a 25% recurrence rate after treatment with APC. These rates suggest that APC treatment of GAVE may not be optimal in many circumstances.

Acute bleeding after argon plasma coagulation for weight regain after gastric bypass: A case report

BACKGROUND Roux-en-Y gastric bypass(RYGB) is the most commonly performed surgical procedure used to treat obesity worldwide. Despite satisfactory results in terms of weight loss, over time many patients experience weight regain. There are many factors that contribute to weight regain after RYGB, including the diameter of the gastric-jejunal anastomosis(GJA). One of the most commonly performed endoscopic procedures for weight regain after RYGB is argon plasma coagulation(APC). We report a case of hematemesis after outlet revision with APC. We highlight several treatment modalities that can be used to treat this complication.CASE SUMMARY A 45-year-old female with a history of weight regain after RYGB was referred for possible endoscopic treatment for weight regain. On endoscopic evaluation, the diameter of the GJA was 22 mm. Due to the dilated GJA, treatment with APC was performed. Several months later she reported a return of poor satiety and an increased appetite. A repeat endoscopy was then performed. The GJA was approximately 15 mm and was incompetent. APC was performed. One day post procedure she had four episodes of hematemesis. An endoscopy was performed and a large ulcer with a visible arterial vessel was visualized at the GJA.Coagulation was attempted using a Coagrasper and after initial contact with the vessel, the vessel started oozing. Due to fibrosis and the depth of ulceration in the area, clips and repeat APC could not be used. Therefore, an attempt to inject epinephrine injection was made. However, persistent oozing was noted. As a result, hemostatic powder was applied to the region of the bleeding vessel.Subsequently, no more bleeding was observed. On follow-up, the patient remained hemodynamically stable and a second look endoscopy was not performed. The patient was discharged three days later.CONCLUSION APC revision of the GJA is known to be a relatively safe and effective strategy to manage weight regain post RYGB. Anastomotic site bleeding is an infrequent and potentially life-threatening complication associated with this therapy. Endoscopic management is the first line therapy used to achieve hemostasis in these cases.

Endoscopic ablation of Barrett's esophagus using the second generation argon plasma coagulation:a prospective randomized controlled trail

Objective：To investigate the efficacy and safety of the second generation argon plasma coagulation（VIO APC） in the ablation of Barrett＇ s Esophagus. Methods：A total of 35 patients with uncomplicated Barrett＇ s esophagus entered into a prospective, randomized, unblinded study comparing the treatment VIO APC combined with a proton pump inhibiter with a proton pump inhibiter administered alone. VIO APC was performed at a power setting of 40W, and argon gas flow at 1.5-2.0 L/min, and＂ forced＂ mode. Ablative treatment was repeated until either no Barrett＇ s epithelium remained or a maximum of 5 treatment sessions occurred. Results：In the ablation group, macroscopic complete ablation was achieved in 14 of 18 patients, and complete ablation confirmed by histology in 12 of 18 patients （P 〈 0.01）. Buried glands were observed in 2 patients who had achieved macroscopic ablation. The Barrett＇s mucosa averaged a reduction of 65%（range 50-75%） in the remaining 4 patients. In the control group, only 2 patients had partial regression, median 30%（range 20-40%）. In the ablation group, post-treatment 4 patients had transient retrosternal pain, and 3 patients had mild epigastric discomfort. One patient had a small hemorrhage during the procedure, which ceased after norepinephrine and thrombosin were administered through the endoscope biopsy channel. No adverse events were observed in the control group. During 11.8（4-15） months follow-up, patients who had achieved the complete ablation have no evidence of relapse of Barrett＇ s esophagus. Conclusion：VIO APC with a relatively low power setting can effectively ablate the Barrett＇ s mucosa. No severe adverse events were observed. Long-term follow-up is needed to assess cancer prevention and the durability of the neo-squamous epithelium.

Argon plasma coagulation for superficial esophageal squamous-cell carcinoma in high-risk patients

AIM: To evaluate the usefulness and safety of argon plasma coagulation (APC) for superficial esophageal squamous-cell carcinoma (SESC) in high-risk patients. METHODS: We studied 17 patients (15 men and 2 women, 21 lesions) with SESC in whom endoscopic mucosal resection (EMR), endoscopic submucosal dissection (ESD), and open surgery were contraindicated from March 1999 through February 2009. None of the patients could tolerate prolonged EMR/ESD or open surgery because of severe concomitant disease (e.g., liver cirrhosis, cerebral infarction, or ischemic heart disease) or scar formation after EMR/ESD and chemoradiotherapy. After conventional endoscopy, an iodine stain was sprayed on the esophageal mucosa to determine the lesion margins. The lesion was then ablated by APC. We retrospectively studied the treatment time, number of APC sessions per site, complications, presence or absence of recurrence, and time to recurrence.RESULTS: The median duration of follow-up was 36 mo (range: 6-120 mo). All of the tumors were macroscopically classified as superficial and slightly depressed type (0-Ⅱc). The preoperative depth of invasion was clinical T1a (mucosal cancer) for 19 lesions and clinical T1b (submucosal cancer) for 2. The median treatment time was 15 min (range: 10-36 min). The median number of treatment sessions per site was 2 (range: 1-4). The median hospital stay was 14 d (range: 5-68 d). Among the 17 patients (21 lesions), 2 (9.5%) had recurrence and underwent additional APC with no subsequent evidence of recurrence. There were no treatment-related complications, such as bleeding or perforation. CONCLUSION: APC is considered to be safe and effective for the management of SESC that cannot be resected endoscopically because of underlying disease, as well as for the control of recurrence after EMR and local recurrence after chemoradiotherapy.

Particle Densities of the Atmospheric-Pressure Argon Plasmas Generated by the Pulsed Dielectric Barrier Discharges

Atmospheric-pressure argon plasmas have received increasing attention due to their high potential in many industrial and biomedical applications. In this paper, a 1-D fluid model is used for studying the particle density characteristics of the argon plasmas generated by the pulsed dielectric barrier discharges. The temporal evolutions of the axial particle density distributions are illustrated, and the influences of changing the main discharge conditions on the averaged particle densities are researched by independently varying the various discharge conditions. The calculation results show that the electron density and the ion density reach two peaks near the momentary cathodes during the rising and the falling edges of the pulsed voltage. Compared with the charged particle densities, the densities of the resonance state atom Arr and the metastable state atom Arm have more uniform axial distributions, reach higher maximums and decay more slowly. During the platform of the pulsed voltage and the time interval between the pulses, the densities of the excited state atom Ar＊ are far lower than those of the Arr or the Arm. The averaged particle densities of the different considered particles increase with the increases of the amplitude and the frequency of the pulsed voltage. Narrowing the discharge gap and increasing the relative dielectric constant of the dielectric also contribute to the increase of the averaged particle densities. The effects of reducing the discharge gap distance on the neutral particle densities are more significant than the influences on the charged particle densities.

Rectal ulcer:Due to ketoprofen, argon plasma coagulation and prostatic brachytherapy

Prostatic brachytherapy with permanent seed implants is a recent and safe radiation therapy technique associated with radiation-induced digestive disease.Argon plasma coagulation procedure is a validated modality in the management of haemorrhagic radiation proctitis,which is known to occasionally induce chronic rectal ulcers.We report here an original case report of an acute painful rectal ulcer as a consequence of the combination of shortterm therapy with non-steroidal anti-inflammatory drugs therapy,prostatic brachytherapy with malposition of seed implants and argon plasma coagulation procedure in a patient with haemorrhagic radiation proctitis.The description of this clinical observation is essential to recommend the discontinuation of non-steroidal anti-inflammatory drugs therapy and the control of the position of seed implants in case of prostatic brachytherapy before argon plasma coagulation for radiation-induced proctitis.

Langmuir Probe Measurements of an Expanding Argon Plasma

In this work,we studied the effects of the discharge current,gas flow rate and vessel pressure on the electron temperature and density of Ar plasma by Langmuir probe measurement.The argon plasma was created by a one-cathode arc source.The experimental results show that with increasing discharge current and gas flow rate,the electron temperature and density increase.It is found that when the discharge current is 70 A,90 A and HO A at an argon flow rate of2000 seem,the electron densities at about 0.186 m distance from the nozzle are 13.00×10^18 m^-3,14.04×10^18 m^-3 and 15.62×10^18 m^-3,and the electron temperatures are 0.38 eV,0.58 eV and0.71 eV,respectively.The positive I-V characteristic is explained.

Ablation of Barrett’s esophagus using the second-generation argon plasma coagulation

Objective To investigate the efficacy and safety of the second-generation argon plasma coagulation (VIO APC) in ablation of Barrett’s esophagus. Methods Eighteen patients with Barrett’s esophagus (12 males, median age of 55 years, median length of 2.1 cm,1 low-grade dysplasia, 13 cases of short segment Barrett’s esophagus) received VIO APC, which was performed at a power setting of 40W and argon gas flow at 1.5-2.0 L/min, "forced" mode, in 1-3 sessions (mean 1.3). All the patients received treatment with high-dose proton pump inhibitors. The main complaints before ablation were upper abdominal pain in 12 patients (66%), sour regurgitation in 14 patients (77%), and dysphagia or odynophagia in 7 patients (38%). Two patients (11%) had esophageal hiatal hernia. Results The percentage of patients in whom ablation was endoscopically achieved proximal to the gastroesophageal junction was 77.8% (14/18), and histologically achieved in 66.7% (12/18). Berried glands were observed in 2 patients who had achieved endoscopic ablation, the areas of Barrett’s mucosa were reduced by more than 60% in the other 4 patients. After treatment, 4 patients had transient retrosternal pain and 3 patients had mild epigastric discomfort. One patient had small amounts of hemorrhage during the process, and it ceased after norepinephrine and thrombosin were administered through endoscope biopsy channel. No esophageal stricture or other severe adverse events was observed. During 11.8 (4-15) months’ follow-up, the patients who had achieved the complete ablation had no evidence of relapse of Barrett’s esophagus. Conclusion VIO APC with a relatively low power setting can effectively ablate the Barrett’s mucosa with special intestinal metaplasia when standard APC has been done. No severe adverse events were observed. Long-term follow-up is needed to assess cancer prevention and the durability of the neo-squamous epithelium.

Numerical study of atmospheric-pressure argon plasma jet propagating into ambient nitrogen

A 2D axial symmetry fluid model is applied to study the features of an atmospheric-pressure argon(Ar) plasma jet propagating into ambient nitrogen(N_(2)) driven by a pulsed voltage,emphasizing the influence of gas velocity on the dynamic characteristics of the jet. The results show that the Ar jet exhibits a cylindrical-shaped channel and the jet channel gradually shrinks with the increase in propagation length. The jet propagation velocity varies with time. Inside the dielectric tube, the plasma jet accelerates propagation and reaches its maximum value near the nozzle. Exiting the tube, its velocity quickly decreases and when approaching the metal plane,the decrease in jet velocity slows down. The increase in gas speed results in the variation of jet spatial distribution. The electron density presents a solid structure at lower gas flow speeds,whereas an annular structure can be observed under the higher gas flow velocity in the ionization head. The jet length increases with the flow velocity. However, when the flow velocity exceeds a critical value, the increase in the rate of the plasma jet length slows down. In addition, the gas velocity effect on the generation and transport of the reactive particles is also studied and discussed.

Simulation of propagation of the HPM in the low-pressure argon plasma

The propagation of the high-power microwave（HPM） with a frequency of 6 GHz in the lowpressure argon plasma was studied by the method of fluid approximation.The two-dimensional transmission model was built based on the wave equation,the electron drift-diffusion equations and the heavy species transport equations,which were solved by means of COMSOL Multiphysics software.The simulation results showed that the propagation characteristic of the HPM was closely related to the average electron density of the plasma.The attenuation of the transmitted wave increased nonlinearly with the electron density.Specifically,the growth of the attenuation slowed down as the electron density increased uniformly.In addition,the concrete transmission process of the HPM wave in the low-pressure argon plasma was given.

Efficacy and complications of argon plasma coagulation for hemorrhagic chronic radiation proctitis

BACKGROUND Chronic radiation proctitis(CRP) is a complication which occurs in 1%-5% of patients who undergo radiotherapy for pelvic malignancies. Although a wide range of therapeutic modalities are available, there is no literature to date showing any particularly appropriate therapeutic modality for each disease stage. Argon plasma coagulation(APC) is currently recommended as the firstchoice treatment for hemorrhagic CRP, however, its indication based on longterm follow-up is still unclear. On the hypothesis that the long-term efficacy and safety of APC are not fully understood, we reviewed APC treatment for patients with hemorrhagic CRP from a single center.AIM To assess the long-term efficacy and safety of APC for hemorrhagic CRP.METHODS This is a retrospective study of consecutive patients treated with APC for hemorrhagic CRP from January 2013 to October 2017. Demographics, clinical variables, and typical endoscopic features were recorded independently. Success was defined as either cessation of bleeding or only occasional traces of bloody stools with no further treatments for at least 12 mo after the last APC treatment.We performed univariate and multivariate analyses to identify factors associated with success and risk factors for fistulas.RESULTS Forty-five patients with a median follow-up period of 24 mo(range: 12-67 mo)were enrolled. Fifteen(33.3%) patients required blood transfusion before APC.Successful treatment with APC was achieved in 31(68.9%) patients. The mean number of APC sessions was 1.3(1-3). Multivariate analysis showed that APC failure was independently associated with telangiectasias present on more than50% of the surface area [odds ratio(OR) = 6.53, 95% confidence interval(CI): 1.09-39.19, P = 0.04] and ulcerated area greater than 1 cm^2(OR = 8.15, 95%CI: 1.63-40.88, P = 0.01). Six(13.3%) patients had severe complications involving rectal fistulation. The only factor significantly associated with severe complications was ulcerated area greater than 1 cm^2(P = 0.035).CONCLUSION The long-term efficacy of APC for hemorrhagic CRP is uncertain in patients with telangiectasias present on > 50% of the surface area and ulceration > 1 cm^2.

Pulsed microwave-driven argon plasma jet with distinctive plume patterns resonantly excited by surface plasmon polaritons

Atmospheric lower-power pulsed microwave argon cold plasma jets are obtained by using coaxial transmission line resonators in ambient air.The plasma jet plumes are generated at the end of a metal wire placed in the middle of the dielectric tubes.The electromagnetic model analyses and simulation results suggest that the discharges are excited resonantly by the enhanced electric field of surface plasmon polaritons.Moreover,for conquering the defect of atmospheric argon filamentation discharges excited by 2.45-GHz of continued microwave,the distinctive patterns of the plasma jet plumes can be maintained by applying different gas flow rates of argon gas,frequencies of pulsed modulator,duty cycles of pulsed microwave,peak values of input microwave power,and even by using different materials of dielectric tubes.In addition,the emission spectrum,the plume temperature,and other plasma parameters are measured,which shows that the proposed pulsed microwave plasma jets can be adjusted for plasma biomedical applications.

Trimming of a migrated metal stent for malignant colonic stricture using argon plasma coagulation

We report the first case of trimming of a migrated metal colonic stent for stent induced severe anorectal pain. We present a case of a 54-year-old female with history of metastatic colorectal carcinoma who had stent placement secondary to obstruction. Subsequent distal migration of the stent caused ulcerations into the rectal mucosa and excruciating anorectal pain. We used argon plasma coagulation (APC) to successfully trim the exposed distal portion of the metal stent and rat tooth forceps to retrieve the stent fragments. The use of APC for trimming metallic stents is an effective procedure that can be used to trim migrated rectal stents that result in significant rectal pain. To date, few studies have been published that use APC to trim metallic stents placed in the gastrointestinal tract. To the best of our knowledge, ours is the only known case in which the indication for stent trimming was severe stent induced rectal pain. The procedure resulted in complete relief of patient symptoms. Therefore, APC is a safe and effective way to trim colo-rectal stents to definitively relieve the symptom of stent induced rectal pain in patients who have experienced distal stent migration and mucosal ulceration.

Transmission properties of microwave in rectangular waveguide through argon plasma

To study the impact of plasma generated by microwave breakdown on the propagation properties of microwave in high power microwave(HPM) devices, a three-dimensional(3-D) fluid model of argon plasma slab in rectangular waveguide is established and calculated by the finite-difference-time-domain(FDTD) method. A rectangular waveguide with a breakdown chamber filled with argon is set as the physics model, and HPM with frequency of 3–50 GHz propagates through this physics model. The time evolutions of the breakdown process are investigated, the reflection, transmission, and absorption coefficients of HPM are calculated, and the influences of some important parameters, including the thickness of the plasma slab and the microwave frequency on the propagation properties of the microwave are shown. Results of this work can offer theoretical instructions for suppressing the influence of breakdown to the performance of HPM devices, and for the use of microwave breakdown, such as the design of plasma limiter or absorber in HPM devices.

Study of Propagation of Ion Acoustic Waves in Argon Plasma

The properties of small amplitude acoustic waves (IAW) in unmagnetised plasma have been discussed in detail. An experimental set up to study the propagation of IAW in argon plasma has been descried. The speed of IAW under different conditions of discharge current and pressure has been measured from the time-of flight technique. From these measurements, electron temperatures have been calculated. The results have been compared with those obtained by single probe method, and were found to be in good agreement with each other so IAW speeds can be used to calculate plasma parameters.