Keith L. Obstein

Association Between Model for End-Stage Liver Disease and Spontaneous Bacterial Peritonitis

OBJECTIVE:To determine whether a greater Model for End-Stage Liver Disease (MELD) score is associated with a greater risk of spontaneous bacterial peritonitis (SBP).METHODS:Our retrospective case-control study enrolled 271 consecutive patients with cirrhosis and ascites who underwent diagnostic paracentesis upon hospital admission (2002–2005). After excluding immunosuppressed patients, those recently exposed to antibiotics, those with a potential confounding etiology for ascites, and those with a prior history of SBP, 111 were included in the study. SBP was defined as a paracentesis yielding ≥250 neutrophils/mL ascites fluid. Multivariable logistic regression was performed to determine the odds ratio for the development of SBP associated with MELD score and grouped MELD score (≤15, 16–24, ≥25). Potential confounders assessed included age, diabetes mellitus, gender, race, alcohol use, serum sodium, and etiology of liver disease.RESULTS:Twenty-nine of 111 hospitalized patients with cirrhosis were found to have SBP. Patient characteristics were similar between groups with and without SBP. The mean MELD score for patients with SBP was 24 and for those without 18 (P = 0.0003). The odds ratio for developing SBP by each MELD point was 1.11 (1.05–1.19, P = 0.001). Patients with MELD ≥25 had an odds ratio of 9.67 (2.35–39.82, P = 0.002) for SBP, compared to subjects with MELD ≤15. None of the potential confounders substantially altered the relationship between MELD and SBP.CONCLUSIONS:Increasing MELD score is independently associated with a greater risk of SBP. For every point increase in the MELD score, the risk of developing SBP increases by 11%. Our finding has important implications for increasing the suspicion of SBP in patients with elevated MELD scores.

The Efficacy of Proton Pump Inhibitors for the Treatment of Asthma in Adults: A Meta-analysis

BACKGROUND Gastroesophageal reflux disease occurs frequently among patients with asthma. Therapy with proton pump inhibitors (PPIs) to improve asthma control remains controversial. We sought to evaluate the efficacy of PPIs in treatment of asthma using objective and subjective outcome measures. METHODS A literature search was undertaken using MEDLINE (1950-January 2010), PubMed (1950-January 2010), EMBASE (1980-January 2010), and Cochrane Central Register of Controlled Trials (through January 31, 2010). Randomized, placebo-controlled trials evaluating the efficacy of PPIs for treatment of asthma in adults were selected. The primary outcome of interest was morning peak expiratory flow (PEF) rate. Secondary outcomes included objective (evening PEF rate and forced expiratory volume in 1 second) and subjective (asthma symptoms score and Asthma Quality of Life Questionnaire score) measures. Influence of study characteristics on outcomes was examined by subgroup analyses and meta-regression. RESULTS Eleven trials (2524 patients) met inclusion criteria. Overall, patients had a higher mean morning PEF rate after treatment with PPIs compared with placebo (mean difference, 8.68 L/min [95% confidence interval, 2.35-15.02]). No significant single large-study effect, temporal effect, or publication bias was seen. Subgroup analysis revealed a trend toward a larger improvement in morning PEF rate in studies enrolling only patients with gastroesophageal reflux disease (mean difference, 16.90 L/min [95% confidence interval, 0.85-32.95]). Analyses of secondary outcomes (asthma symptoms score, Asthma Quality of Life Questionnaire score, evening PEF rate, and forced expiratory volume in 1 second) showed no significant difference between PPIs and placebo. CONCLUSIONS Proton pump inhibitor therapy in adults with asthma results in a small, statistically significant improvement in morning PEF rate. The magnitude of this improvement, however, is unlikely to be of meaningful clinical significance. There is insufficient evidence to recommend empirical use of PPIs for routine treatment of asthma.

Wireless Insufflation of the Gastrointestinal Tract

Despite clear patient experience advantages, low specificity rates have thus far prevented swallowable capsule endoscopes from replacing traditional endoscopy for diagnosis of colon disease. One explanation for this is that capsule endoscopes lack the ability to provide insufflation, which traditional endoscopes use to distend the intestine for a clear view of the internal wall. To provide a means of insufflation from a wireless capsule platform, in this paper we use biocompatible effervescent chemical reactions to convert liquids and powders carried onboard a capsule into gas. We experimentally evaluate the quantity of gas needed to enhance capsule visualization and locomotion, and determine how much gas can be generated from a given volume of reactants. These experiments motivate the design of a wireless insufflation capsule, which is evaluated in ex vivo experiments. These experiments illustrate the feasibility of enhancing visualization and locomotion of endoscopic capsules through wireless insufflation.

Assessment of competency in endoscopy: establishing and validating generalizable competency benchmarks for colonoscopy

BACKGROUND AND AIMS The Mayo Colonoscopy Skills Assessment Tool (MCSAT) has previously been used to describe learning curves and competency benchmarks for colonoscopy; however, these data were limited to a single training center. The newer Assessment of Competency in Endoscopy (ACE) tool is a refinement of the MCSAT tool put forth by the Training Committee of the American Society for Gastrointestinal Endoscopy, intended to include additional important quality metrics. The goal of this study is to validate the changes made by updating this tool and establish more generalizable and reliable learning curves and competency benchmarks for colonoscopy by examining a larger national cohort of trainees. METHODS In a prospective, multicenter trial, gastroenterology fellows at all stages of training had their core cognitive and motor skills in colonoscopy assessed by staff. Evaluations occurred at set intervals of every 50 procedures throughout the 2013 to 2014 academic year. Skills were graded by using the ACE tool, which uses a 4-point grading scale defining the continuum from novice to competent. Average learning curves for each skill were established at each interval in training and competency benchmarks for each skill were established using the contrasting groups method. RESULTS Ninety-three gastroenterology fellows at 10 U.S. academic institutions had 1061 colonoscopies assessed by using the ACE tool. Average scores of 3.5 were found to be inclusive of all minimal competency thresholds identified for each core skill. Cecal intubation times of less than 15 minutes and independent cecal intubation rates of 90% were also identified as additional competency thresholds during analysis. The average fellow achieved all cognitive and motor skill endpoints by 250 procedures, with >90% surpassing these thresholds by 300 procedures. CONCLUSIONS Nationally generalizable learning curves for colonoscopy skills in gastroenterology fellows are described. Average ACE scores of 3.5, cecal intubation rates of 90%, and intubation times less than 15 minutes are recommended as minimal competency criteria. On average, it takes 250 procedures to achieve competence in colonoscopy. The thresholds found in this multicenter cohort by using the ACE tool are nearly identical to the previously established MCSAT benchmarks and are consistent with recent gastroenterology training recommendations but far higher than current training requirements in other specialties.

Small-bowel endoscopy core curriculum.

This is one of a series of documents prepared by the ASGE Training Committee. This curriculum document contains recommendations for training, intended for use by endoscopy training directors, endoscopists involved in teaching endoscopy, and trainees in endoscopy. It was developed as an overview of techniques currently favored for the performance and training of small-bowel endoscopy and to serve as a guide to published references, videotapes, and other resources available to the trainer. By providing information to endoscopy trainers about the common practices used by experts in performing the technical aspects of the procedure, the ASGE hopes to improve the teaching and performance of small-bowel endoscopy.

Advanced endoscopic technologies for colorectal cancer screening

Colorectal cancer is the third most common cancer in men and the second most common cancer in women worldwide. Diagnosing colorectal has been increasingly successful due to advances in technology. Flexible endoscopy is considered to be an effective method for early diagnosis and treatment of gastrointestinal cancer, making it a popular choice for screening programs. However, millions of people who may benefit from endoscopic colorectal cancer screening fail to have the procedure performed. Main reasons include psychological barriers due to the indignity of the procedure, fear of procedure related pain, bowel preparation discomfort, and potential need for sedation. Therefore, an urgent need for new technologies addressing these issues clearly exists. In this review, we discuss a set of advanced endoscopic technologies for colorectal cancer screening that are either already available or close to clinical trial. In particular, we focus on visual-inspection-only advanced flexible colonoscopes, interventional colonoscopes with alternative propulsion mechanisms, wireless capsule colonoscopy, and technologies for intraprocedural bowel cleansing. Many of these devices have the potential to reduce exam related patient discomfort, obviate the need for sedation, increase diagnostic yield, reduce learning curves, improve access to screening, and possibly avert the need for a bowel preparation.

Image partitioning and illumination in image-based pose detection for teleoperated flexible endoscopes

OBJECTIVE Colorectal cancer is one of the leading causes of cancer-related deaths in the world, although it can be effectively treated if detected early. Teleoperated flexible endoscopes are an emerging technology to ease patient apprehension about the procedure, and subsequently increase compliance. Essential to teleoperation is robust feedback reflecting the change in pose (i.e., position and orientation) of the tip of the endoscope. The goal of this study is to first describe a novel image-based tracking system for teleoperated flexible endoscopes, and subsequently determine its viability in a clinical setting. The proposed approach leverages artificial neural networks (ANNs) to learn the mapping that links the optical flow between two sequential images to the change in the pose of the camera. Secondly, the study investigates for the first time how narrow band illumination (NBI) - today available in commercial gastrointestinal endoscopes - can be applied to enhance feature extraction, and quantify the effect of NBI and white light illumination (WLI), as well as their color information, on the strength of features extracted from the endoscopic camera stream. METHODS AND MATERIALS In order to provide the best features for the neural networks to learn the change in pose based on the image stream, we investigated two different imaging modalities - WLI and NBI - and we applied two different spatial partitions - lumen-centered and grid-based - to create descriptors used as input to the ANNs. An experiment was performed to compare the error of these four variations, measured in root mean square error (RMSE) from ground truth given by a robotic arm, to that of a commercial state-of-the-art magnetic tracker. The viability of this technique for a clinical setting was then tested using the four ANN variations, a magnetic tracker, and a commercial colonoscope. The trial was performed by an expert endoscopist (>2000 lifetime procedures) on a colonoscopy training model with porcine blood, and the RMSE of the ANN output was calculated with respect to the magnetic tracker readings. Using the image stream obtained from the commercial endoscope, the strength of features extracted was evaluated. RESULTS In the first experiment, the best ANNs resulted from grid-based partitioning under WLI (2.42mm RMSE) for position, and from lumen-centered partitioning under NBI (1.69° RMSE) for rotation. By comparison, the performance of the tracker was 2.49mm RMSE in position and 0.89° RMSE in rotation. The trial with the commercial endoscope indicated that lumen-centered partitioning was the best overall, while NBI outperformed WLI in terms of illumination modality. The performance of lumen-centered partitioning with NBI was 1.03±0.8mm RMSE in positional degrees of freedom (DOF), and 1.26±0.98° RMSE in rotational DOF, while with WLI, the performance was 1.56±1.15mm RMSE in positional DOF and 2.45±1.90° RMSE in rotational DOF. Finally, the features extracted under NBI were found to be twice as strong as those extracted under WLI, but no significance in feature strengths was observed between a grayscale version of the image, and the red, blue, and green color channels. CONCLUSIONS This work demonstrates that both WLI and NBI, combined with feature partitioning based on the anatomy of the colon, provide valid mechanisms for endoscopic camera pose estimation via image stream. Illumination provided by WLI and NBI produce ANNs with similar performance which are comparable to that of a state-of-the-art magnetic tracker. However, NBI produces features that are stronger than WLI, which enables more robust feature tracking, and better performance of the ANN in terms of accuracy. Thus, NBI with lumen-centered partitioning resulted the best approach among the different variations tested for vision-based pose estimation. The proposed approach takes advantage of components already available in commercial gastrointestinal endoscopes to provide accurate feedback about the motion of the tip of the endoscope. This solution may serve as an enabling technology for closed-loop control of teleoperated flexible endoscopes.

Controlled colonic insufflation by a remotely triggered capsule for improved mucosal visualization

BACKGROUND AND STUDY AIMS Capsule endoscopy is an attractive alternative to colorectal cancer screening by conventional colonoscopy, but is currently limited by compromised mucosal visibility because of the lack of safe, controlled colonic insufflation. We have therefore developed a novel system of untethered, wireless-controlled carbon dioxide (CO2) insufflation for use in colonic capsule endoscopy, which this study aims to assess in vivo. MATERIAL AND METHODS This observational, nonsurvival, in vivo study used five Yorkshire-Landrace cross swine. A novel insufflation capsule was placed in the porcine colons, and we recorded volume of insufflation, time, force, visualization, and a pathologic assessment of the colon. RESULTS The mean (standard deviation [SD]) diameter of insufflation was 32.1 (3.9) mm. The volume of CO2 produced successfully allowed complete endoscopic visualization of the mucosa and safe proximal passage of the endoscope. Pathologic examination demonstrated no evidence of trauma caused by the capsule. CONCLUSIONS These results demonstrate the feasibility of a novel method of controlled colonic insufflation via an untethered capsule in vivo. This technological innovation addresses a critical need in colon capsule endoscopy.

Capsule endoscopy of the future: What's on the horizon?

Capsule endoscopes have evolved from passively moving diagnostic devices to actively moving systems with potential therapeutic capability. In this review, we will discuss the state of the art, define the current shortcomings of capsule endoscopy, and address research areas that aim to overcome said shortcomings. Developments in capsule mobility schemes are emphasized in this text, with magnetic actuation being the most promising endeavor. Research groups are working to integrate sensor data and fuse it with robotic control to outperform todays standard invasive procedures, but in a less intrusive manner. With recent advances in areas such as mobility, drug delivery, and therapeutics, we foresee a translation of interventional capsule technology from the bench-top to the clinical setting within the next 10 years.

A Platform for Gastric Cancer Screening in Low- and Middle-Income Countries

Gastric cancer is the second leading cause of cancer death worldwide and screening programs have had a significant impact on reducing mortality. The majority of cases occur in low- and middle-income countries (LMIC), where endoscopy resources are traditionally limited. In this paper, we introduce a platform designed to enable inexpensive gastric screening to take place in remote areas of LMIC. The system consists of a swallowable endoscopic capsule connected to an external water distribution system by a multichannel soft tether. Pressurized water is ejected from the capsule to orient the view of the endoscopic camera. After completion of a cancer screening procedure, the outer shell of the capsule and the soft tether can be disposed, while the endoscopic camera is reclaimed without needing further reprocessing. The capsule, measuring 12 mm in diameter and 28 mm in length, is able to visualize the inside of the gastric cavity by combining waterjet actuation and the adjustment of the tether length. Experimental assessment was accomplished through a set of bench trials, ex vivo analysis, and in vivo feasibility validation. During the ex vivo trials, the platform was able to visualize the main landmarks that are typically observed during a gastric cancer screening procedure in less than 8 min. Given the compact footprint, the minimal cost of the disposable parts, and the possibility of running on relatively available and inexpensive resources, the proposed platform can potentially widen gastric cancer screening programs in LMIC.