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The standard method for qualitatively evaluating the dynamic response is to see if the gain of the amplitude spectrum curve approaches 1 (input signal = output signal) over the frequency band of the blood pressure waveform. In a previous report, Watanabe reported that Gardner’s natural frequency and damping coefficient, which are widely used as evaluation methods, do not reflect the dynamic response of the circuit. Therefore, new parameters for evaluating the dynamic response of pressure monitoring circuits were desired. In this study, arterial pressure catheters with length of 30, 60, 150, and 210 cm were prepared, and a blood pressure wave calibrator, two pressure monitors with analog output and a personal computer were used to analyze blood pressure monitoring circuits. All data collection and analytical processes were performed using step response analysis program. The gain at 10 Hz was close to 1 and the systolic blood pressure difference was small in the short circuits (30 cm, 60 cm), and the gain at 10 Hz was 1.3–1.5 in the 150 cm circuit and over 1.7 in the 210 cm circuit. The difference in systolic blood pressure increased in proportion to the length of the circuit. It could also be inferred that the gain at 10 Hz should be less than 1.2 to meet a clinically acceptable blood pressure difference. In conclusion, the gain at 10 Hz is sufficiently useful as an indicator to determine the correct systolic blood pressure.

PurposeThe dynamic response of pressure monitoring circuits must be evaluated to obtain true invasive blood pressure values. Since Gardner’s recommendations in 1981, the natural frequency and the damping coefficient have become standard parameters for anesthesiologists. In 2006, we published a new dynamic response evaluation method (step response analysis) that can plot frequency spectrum curves instantly in clinical situations. We also described the possibility of the defect of the standard parameters. However, the natural frequency and the damping coefficient are considered the gold standard and are even included in a major anesthesiology textbook. Therefore, we attempted to clarify the issues of these parameters with easy-to-understand pressure waves and basic numerical formulae.MethodsA blood pressure wave calibrator, a single two-channel pressure amplifier, and personal computer were used to analyze blood pressure monitoring circuits. All data collection and analytical processes were performed using our step response analysis program.ResultsWe compared two different circuits with almost the same natural frequency and damping coefficients. However, their amplitude spectrum curves and input/output pressure values were significantly different.ConclusionsThe natural frequency and the damping coefficient are inadequate for the dynamic response evaluation. These parameters are primarily obtained from the phase spectrum curve and not from the amplitude spectrum curve. We strongly recommend an evaluation using the amplitude spectrum curve with our step response analysis method. It is crucial to maintain an amplitude gain of 1 (input amplitude = output amplitude) in the pressure wave frequency range of 0–20 Hz.

BackgroundEndoscopic retrograde cholangiopancreatography (ERCP) in patients with surgically altered anatomy is technically difficult. Extensive training is required to develop the ability to perform this procedure.AimsTo investigate the learning curve of single-balloon-assisted enteroscopy ERCP (SBE-ERCP).MethodsWe conducted a retrospective, observational case series at a single center. We evaluated the SBE-ERCP procedures between April 2011 and February 2021. The main outcomes were the rate of reaching the target site and the success rate of the entire procedure. These parameters were additionally expressed as a learning curve.ResultsA total of 687 SBE-ERCP procedures were analyzed. The learning curve was analyzed in blocks of 10 cases. In this study, seven endoscopists, experts in conventional ERCP, were included. The overall SBE-ERCP procedural success rate was 92.2% (634/687 cases). Combining all data from individual endoscopists’ evaluation periods, the insertion and success rates of the SBE-ERCP procedures gradually increased with increased experience performing SBE-ERCP. The insertion success rates for the number of SBE-ERCP cases (< 20, 21–30, > 30) were 82.9%, 92.9%, and 94.3%, respectively; the procedure success rates were 74.3%, 81.4%, and 92.9%, respectively. The endoscopists who had performed > 30 SBE-ERCP cases had a success rate of ≥ 90%.ConclusionsOur results suggest that performing > 30 cases is one of the targets for conventional ERCP experts to become competent in performing SBE-ERCP in patients with a surgically altered anatomy.

Objectives The safety and effectiveness of propofol in more complex endoscopic procedures, such as endoscopic retrograde cholangiopancreatography, remain unknown. Thus, we aimed to evaluate propofol sedation during endoscopic cholangiopancreatography, ultrasound‐guided intervention, and gastroduodenal stenting and examine risk factors for excessive sedation. Methods We retrospectively analyzed data from 870 patients who underwent endoscopic treatment with propofol sedation for biliary and pancreatic disease between October 2020 and September 2021. Sedation included propofol and fentanyl, with continuous monitoring of vital signs and the bispectral index. The assessed risk factors included age, complications, body mass index, treatment duration, and specialty. Results Distal bile duct treatment (n = 367), hilar bile duct treatment (n = 197), post‐small‐intestinal reconstruction treatment (n = 75), endoscopic ultrasound‐guided intervention (n = 140), and gastrointestinal obstruction treatment (n = 91) were performed. The rates of excessive sedation, hypoxemia, and hypotension were 7.8%, 6.0%, and 1.8%, respectively. Post‐small‐intestinal reconstruction treatment had the highest incidence rate of excessive sedation (16%), whereas endoscopic ultrasound‐guided intervention had the lowest incidence rate (4.3%). Multivariate analysis revealed significant associations between excessive sedation and comorbid sleep apnea, obesity, and prolonged procedural time. Conclusions Obesity, sleep apnea syndrome, and prolonged procedure time are risk factors for excessive sedation related to propofol use. Thus, sedation techniques should be tailored for these patients.

Tissue sampling in biliary tract cancer (BTC) is generally performed through transpapillary biopsy (TPB) or endoscopic ultrasound-guided tissue acquisition (EUS-TA). For the first time, we compared the suitability of specimens obtained using TPB and EUS-TA to determine the optimal tissue-sampling method for comprehensive genome profiling (CGP) analysis in patients with unresectable BTC (UR-BTC). Pathology precheck criteria for CGP analysis comprised the OncoGuide NCC Oncopanel System (NCCOP) and FoundationOne CDx (F1CDx). Seventy-eight patients with UR-BTC (35 TPB and 43 EUS-TA) were included. The NCCOP analysis suitability achievement rate was higher in EUS-TA specimens than in TPB specimens (34.9% vs. 8.6%, p = 0.007), whereas that of F1CDx was 0% in both groups. EUS-TA was identified as an independent factor that contributed to the suitability of the NCCOP analysis. The suitability of the NCCOP analysis of EUS-TA specimens showed a tendency to be higher for mass lesions (43.8% vs. 9.1%, p = 0.065), especially for target size ≥ 18.5 mm, and lower for perihilar cholangiocarcinoma (0% vs. 41.7%, p = 0.077). In TPB, papillary-type lesions (66.7% vs. 3.2%, p = 0.016) and peroral cholangioscopy-assisted biopsies (50.0% vs. 3.3%, p = 0.029) showed better potential for successful NCCOP analysis. EUS-TA is suitable for NCCOP analysis in UR-BTC and may be partially complemented by TPB.

IntroductionPreoperative biliary drainage (PBD) is often required for patients with pancreatic cancer accompanied by biliary obstruction to ensure the safe administration of neoadjuvant chemotherapy or to manage cholangitis and jaundice. Although endoscopic retrograde cholangiopancreatography (ERCP) is the standard approach for PBD, it carries a significant risk of post-ERCP pancreatitis. Endoscopic ultrasound-guided biliary drainage (EUS-BD), particularly via hepaticogastrostomy (EUS-HGS), offers a promising alternative that avoids papillary manipulation. However, the clinical utility of EUS-BD as primary drainage for PBD remains unclear due to a lack of prospective studies. This multicentre prospective trial aims to evaluate the safety and efficacy of EUS-HGS as primary drainage for PBD in patients with resectable or borderline resectable pancreatic cancer.Methods and analysisThis multicentre prospective study involves seven institutions in Japan. Eligible patients will undergo EUS-HGS using a 7Fr plastic stent. The primary endpoint is clinical success, defined by improvements in bilirubin or liver enzyme levels within 14 days postprocedure. Secondary endpoints include technical success rate, adverse event incidence, stent patency and surgical outcomes. A total of 30 patients will be enrolled, considering an expected clinical success rate of 90% and a 10% dropout allowance.Ethics and disseminationThis study has been approved by the National Cancer Center Institutional Review Board (Research No. 2024-084). The results of this study will be reported at an international conference and published in an international peer-reviewed journal.Trial registration numberUMIN ID: 000055173.

Objectives Hilar cholangiocarcinoma often results in repeated early stent dysfunction and difficult‐to‐control cholangitis after drainage using endoscopic retrograde cholangiopancreatography (ERCP). In this study, we evaluated the effectiveness of additional drainage using endoscopic ultrasound‐guided biliary drainage (EUS‐BD) in patients with hilar cholangiocarcinoma who had difficult‐to‐control cholangitis after transpapillary drainage with ERCP alone. Methods We retrospectively evaluated 20 patients with hilar cholangiocarcinoma who had difficult‐to‐control cholangitis after transpapillary drainage with ERCP at our hospital between 2017 and 2025 and therefore underwent additional drainage using EUS‐BD. We evaluated the time to recurrent biliary obstruction (TRBO) just before and after combined ERCP and EUS‐BD in these patients. Results The Bismuth classification of stenosis was II in four cases (20.0%), IIIa in five cases (25.0%), IIIb in one case (5.0%), and IV in 10 cases (50.0%). The median (95% confidence interval) TRBO biliary obstruction just before and just after additional drainage with EUS‐BD was 16.5 days (7.0–27.0) and 91.0 days (53.0–NR), respectively, and additional drainage with EUS‐BD significantly prolonged stent patency. Conclusions Combining ERCP with EUS‐BD for drainage was effective in patients with hilar cholangiocarcinoma who had stent dysfunction due to cholangitis that was difficult to control using transpapillary drainage with ERCP alone.

Background: Endoscopic retrograde cholangiopancreatography (ERCP) may not provide adequate drainage for patients with malignant hilar biliary obstruction (MHBO). Endoscopic ultrasound-guided hepaticogastrostomy (EUS-HGS) is a salvage method for malignant distal biliary obstruction (MDBO); however, its effectiveness for MHBO remains unclear. Objectives: We aimed to evaluate the short- and long-term outcomes of EUS-HGS for MHBO. Design: This was a single-center retrospective cohort study. Methods: Unresectable patients who underwent initial EUS-HGS because of ERCP failure were recruited. Distal biliary stenosis or Bismuth types I and II–IV were defined as MDBO and MHBO, respectively. We defined EUS-HGS for MDBO as the control and analyzed the outcomes for MHBO. Results: The MDBO group (n = 208) was treated using EUS-HGS alone. In the MHBO group (n = 63), EUS-HGS alone (unilateral drainage, n = 26), EUS-HGS with bridging (EUS-HGSB, bilateral drainage, n = 21), and ERCP + EUS-HGS (bilateral drainage, n = 16) were performed. In EUS-HGS (MDBO), EUS-HGS (MHBO), EUS-HGSB, and ERCP + EUS-HGS, the technical success rates were 98.6%, 96.3%, 95.5%, and 94.1%; clinical success rates were 88.5%, 76.9%, 85.7%, and 75.0%; adverse event rates were 19.7%, 15.4%, 9.5%, and 25.0%; and non-recurrent biliary obstruction (RBO) rates at 180 days were 45.5%, 19.8%, 61.9%, and 68.4%, respectively. In multivariate analysis of the MHBO group, EUS-HGSB tended to have a lower risk of RBO (adjusted hazard ratio (aHR), 0.39; p = 0.09), and ERCP + EUS-HGS showed a significantly lower risk (aHR, 0.25; p = 0.03) compared to EUS-HGS alone (unilateral drainage). Conclusion: ERCP + EUS-HGS followed by EUS-HGSB, providing bilateral drainage, can offer preferred palliation for MHBO. These drainages may serve as potential salvage options in the management of MHBO.

IntroductionThe current endoscopic treatment for postoperative benign hepaticojejunostomy anastomotic stricture (HJAS) has a high technical success rate and is highly effective in the short term. However, long-term results have shown a high rate of stenosis recurrence, which indicates an insufficient response to treatment. Three prospective studies on fully covered self-expandable metallic stent (FC-SEMS) treatment for benign HJAS used the stenosis resolution rate as the primary endpoint, and no study has yet used the long-term non-stenosis rate (at 12 months) as the primary endpoint.Methods and analysisWe launched the ‘saddle-cross study’, which will be conducted as a multicentre, prospective intervention of endoscopic treatment using two modified FC-SEMSs (BONASTENT️ M-Intraductal) that have been improved for benign stenosis in patients with benign HJAS, with the long-term non-restenosis rate (at 12 months) as the primary endpoint. This study aims to evaluate the long-term non-restenosis rate (at 12 months) and safety of the saddle-cross technique for benign HJAS. We plan to enrol 50 participants.Ethics and disseminationThis study has been approved by the Certified Review Board of the National Cancer Center, Japan (CRB3180009). The results will be reported at various conferences and published in international peer-reviewed journals.

Objectives Self‐expandable metal stents (SEMS) may become embedded because of tissue hyperplasia or tumor ingrowth, making their removal challenging. The stent‐in‐stent (SIS) method, which involves placing another SEMS inside to compress the tissue and aid removal, is a known rescue approach for stent removal. However, its efficacy across anatomical routes, optimal timing of removal, and predictors of difficult stent removal remain unclear. Methods We retrospectively reviewed 17 patients treated between April 2018 and May 2025. Embedded stents were placed via the transpapillary route, endoscopic ultrasonography‐guided hepaticogastrostomy (EUS‐HGS), or choledochojejunal anastomosis. Technical success rates and adverse events were evaluated. Results The overall technical success rate was 76.5%, with rates of 80.0%, 100%, and 33.3% for the transpapillary route, EUS‐HGS, and choledochojejunal anastomosis, respectively. Three of the four failures occurred when removal was attempted within 4 weeks of the second stent placement. Stent removal was successful in 100% of the hyperplasia cases but in 60% of the ingrowth cases. Cholecystitis occurred in one case after the second stent placement. Conclusions The SIS method is feasible for the transpapillary route and EUS‐HGS but may show limited efficacy in choledochojejunal anastomosis. Stent removal 4 weeks after the second stent placement improves the success rate. The SIS method may be less effective in cases of malignant ingrowth. The stent‐in‐stent technique involves placing another fully covered metal stent inside an irremovable embedded stent to compress tissue and enable safe removal. In this study of 17 patients, the overall technical success rate was 76.5%, with higher efficacy via EUS‐guided hepaticogastrostomy (100%) and transpapillary routes (80%). Delaying removal for over 4 weeks has the potential to improve outcomes, and the effectiveness may be lower in cases with malignant ingrowth (60%) or choledochojejunal anastomosis (33.3%).