Glycerol as a precursor for hepatic de novo glutathione synthesis in human liver.

BACKGROUND: Glycerol is a substrate for gluconeogenesis and fatty acid esterification in the liver, processes which are upregulated in obesity and may contribute to excess fat accumulation. Glycine and glutamate, in addition to cysteine, are components of glutathione, the major antioxidant in the liver. In principle, glycerol could be incorporated into glutathione via the TCA cycle or 3-phosphoglycerate, but it is unknown whether glycerol contributes to hepatic de novo glutathione biosynthesis. METHODS: Glycerol metabolism to hepatic metabolic products including glutathione was examined in the liver from adolescents undergoing bariatric surgery. Participants received oral [U-13C3]glycerol (50 mg/kg) prior to surgery and liver tissue (0.2-0.7g) was obtained during surgery. Glutathione, amino acids, and other water-soluble metabolites were extracted from the liver tissue and isotopomers were quantified with nuclear magnetic resonance spectroscopy. RESULTS: Data were collected from 8 participants (2 male, 6 female; age 17.1 years [range 14-19]; BMI 47.4 kg/m2 [range 41.3-63.3]). The concentrations of free glutamate, cysteine, and glycine were similar among participants, and so were the fractions of 13C-labeled glutamate and glycine derived from [U-13C3]glycerol. The signals from all component amino acids of glutathione - glutamate, cysteine and glycine - were strong and analyzed to obtain the relative concentrations of the antioxidant in the liver. The signals from glutathione containing [13C2]glycine or [13C2]glutamate derived from the [U-13C3]glycerol drink were readily detected, and 13C-labelling patterns in the moieties were consistent with the patterns in corresponding free amino acids from the de novo glutathione synthesis pathway. The newly synthesized glutathione with [U-13C3]glycerol trended to be lower in obese adolescents with liver pathology. CONCLUSIONS: This is the first report of glycerol incorporation into glutathione through glycine or glutamate metabolism in human liver. This could represent a compensatory mechanism to increase glutathione in the setting of excess glycerol delivery to the liver.

Demographic factors as determinant of selection of sleeve gastrectomy or gastric bypass for surgical weight loss.

INTRODUCTION: Use of sleeve gastrectomy (SG) for weight loss has grown exponentially; however, clear indications for SG versus Roux-en-Y gastric bypass (RNYGB) are lacking. Certain populations may be more likely to undergo SG due to its simpler technique and without clear clinical indications. We aim to examine underlying predictors of patients undergoing SG vs RNY across a single state. METHODS: We queried the Colorado All Payers Claim Database for patients undergoing laparoscopic SG or RNY. Patient-level variables included patient demographics, comorbidities, distance traveled for surgery, and distressed communities index (DCI), a zip code-based measure of socioeconomic status. Hospital-level variables included annual bariatric surgery volume, academic status, and whether hospitals were a bariatric Center of Excellence. We performed mixed-effects logistic regression adjusting for demographics, insurance coverage, and comorbidities to compare odds of undergoing SG vs RNY, with a random effect for hospital. RESULTS: 5,017 patients were included with 3,042 (60.6%) undergoing SG and 1,975 (39.4%) undergoing RNY. On multivariable analysis, patients with a high DCI were not more likely to undergo a SG (OR 1.18, CI 0.89-1.55, p = 0.25). However, patients who underwent surgery at hospitals serving the greatest proportion of those from highly distressed communities were significantly more likely to undergo SG (OR 4.22, CI 1.38-12.96, p = 0.01). Patients managed at Bariatric Centers of Excellence were less likely to undergo SG (OR 0.22, CI 0.07-0.62, p = 0.005). Patients with higher BMI, diabetes, or GERD were all more likely to undergo RNY. CONCLUSION: While patients with high DCI were more likely to undergo SG on univariate analysis, these associations disappeared after addition of a hospital-level random effect, suggesting that disparities may be due access to surgeons or systems with preference for one procedure. However, hospitals serving a higher proportion of high-DCI patients are more likely to utilize SG.

Prospective assessment of fibrinolysis in morbid obesity: tissue plasminogen activator resistance improves after bariatric surgery.

BACKGROUND: Morbid obesity is associated with an increased risk of thrombotic events, which has been attributed to increased thrombotic activity. Multiple mechanisms have been proposed to explain this increased risk, including an inflammatory state with upregulation of procoagulant and antifibrinolytic proteins. We therefore hypothesize that patients with morbid obesity are hypercoagulable and will revert to normal after bariatric surgery. OBJECTIVES: To evaluate changes in the hypercoagulable state after bariatric surgery. SETTING: University Hospital, Bariatric Center of Excellence, United States. METHODS: Thromboelastography (TEG) data were collected on 72 subjects with morbid obesity, with 36 who had 6 months of follow-up after bariatric surgery. TEG data of 75 healthy subjects (HS) without obesity, recent trauma or surgery, acute infection, or chronic conditions (e.g., liver, cardiovascular, or kidney disease; cancer; diabetes; autoimmune or inflammatory disorders; and disorders of coagulation) were used for comparison. TEG was performed alone and with the addition of 75 and 150 ng/mL tissue plasminogen activator (tPA) to quantify fibrinolysis resistance (tPA-challenged TEG). RESULTS: The bariatric surgery cohort had a median age of 40.5 years, a median body mass index of 44.6 kg/m2, and 90% female patients. Median body mass index reduced significantly 6 months post surgery but remained elevated compared with the HS group (31.4 versus 25.4 kg/m2, P < .0001). At 6 months post surgery, subjects had longer reaction time (mean difference, 1.3; P = .02), lower maximum amplitude (-2.4, P = .01), and increased fibrinolysis with low-dose (3.1, P < .0001) and high-dose tPA-challenged TEG (9, P < .0001). Compared with HS, the postsurgery TEG values were still more likely to be abnormal (all P < .05). CONCLUSIONS: Patients with morbid obesity form stronger clots more rapidly and are more resistant to fibrinolysis than subjects without obesity. Bariatric surgery significantly improved the hypercoagulable profile and fibrinolysis resistance of morbid obesity.

Comparison of surgical versus diet-induced weight loss on appetite regulation and metabolic health outcomes.

Bariatric surgery is associated with significant and sustained weight loss and improved metabolic outcomes. It is unclear if weight loss alone is the main mechanism of improved metabolic health. The purpose of this trial was to compare indices of appetite regulation, insulin sensitivity and energy intake (EI) between participants achieving 10 kg of weight loss via Roux-en-Y Gastric Bypass (RYGB) or dietary restriction (DIET); intake of a very low calorie liquid diet (800 kcal/d; 40% protein, 40% fat, 20% carbohydrate that matched the post-RYGB dietary protocol). Adults qualifying for bariatric surgery were studied before and after 10 kg of weight loss (RYGB [n = 6]) or DIET [n = 17]). Appetite (hunger, satiety, and prospective food consumption [PFC]), appetite-related hormones, and metabolites (ghrelin, PYY, GLP-1, insulin, glucose, free fatty acids [FFA], and triglycerides [TG]) were measured in the fasting state and every 30 min for 180 min following breakfast. Participants were provided lunch to evaluate acute ad libitum EI, which was similarly reduced in both groups from pre to post weight loss. Fasting ghrelin was reduced to a greater extent following RYGB compared to DIET (P = 0.04). Area under the curve (AUC) for ghrelin (P = 0.01), hunger (P < 0.01) and PFC (P < 0.01) increased after DIET compared to RYGB, following 10 kg weight loss. Satiety AUC increased after RYGB and decreased after DIET (P < 0.01). Glucose and insulin (fasting and AUC) decreased in both groups. FFA increased in both groups, with a greater increase in AUC seen after RYGB versus DIET (P = 0.02). In summary, appetite-related indices were altered in a manner that, if maintained, may promote a sustained reduction in energy intake with RYGB compared to DIET. Future work with a larger sample size and longer follow-up will be important to confirm and extend these findings.

Intermuscular adipose tissue directly modulates skeletal muscle insulin sensitivity in humans.

Intermuscular adipose tissue (IMAT) is negatively related to insulin sensitivity, but a causal role of IMAT in the development of insulin resistance is unknown. IMAT was sampled in humans to test for the ability to induce insulin resistance in vitro and characterize gene expression to uncover how IMAT may promote skeletal muscle insulin resistance. Human primary muscle cells were incubated with conditioned media from IMAT, visceral (VAT), or subcutaneous adipose tissue (SAT) to evaluate changes in insulin sensitivity. RNAseq analysis was performed on IMAT with gene expression compared with skeletal muscle and SAT, and relationships to insulin sensitivity were determined in men and women spanning a wide range of insulin sensitivity measured by hyperinsulinemic-euglycemic clamp. Conditioned media from IMAT and VAT decreased insulin sensitivity similarly compared with SAT. Multidimensional scaling analysis revealed distinct gene expression patterns in IMAT compared with SAT and muscle. Pathway analysis revealed that IMAT expression of genes in insulin signaling, oxidative phosphorylation, and peroxisomal metabolism related positively to donor insulin sensitivity, whereas expression of macrophage markers, inflammatory cytokines, and secreted extracellular matrix proteins were negatively related to insulin sensitivity. Perilipin 5 gene expression suggested greater IMAT lipolysis in insulin-resistant individuals. Combined, these data show that factors secreted from IMAT modulate muscle insulin sensitivity, possibly via secretion of inflammatory cytokines and extracellular matrix proteins, and by increasing local FFA concentration in humans. These data suggest IMAT may be an important regulator of skeletal muscle insulin sensitivity and could be a novel therapeutic target for skeletal muscle insulin resistance.

Pharmacokinetic and Pharmacodynamic Evaluation of a Weight-Based Dosing Regimen of Cefoxitin for Perioperative Surgical Prophylaxis in Obese and Morbidly Obese Patients.

The objective of this study was to determine the pharmacokinetics and pharmacodynamics (PK/PD) of a weight-based cefoxitin dosing regimen for surgical prophylaxis in obese patients. Patients received a single dose of cefoxitin at 40 mg/kg based on total body weight. Cefoxitin samples were obtained over 3 h from serum and adipose tissue, and concentrations were determined by validated high-performance liquid chromatography. Noncompartmental pharmacokinetic analysis was performed, followed by Monte Carlo simulations to estimate probability of target attainment (PTA) for Staphylococcus aureus, Escherichia coli, and Bacteroides fragilis over 4-h periods postdose. Thirty patients undergoing bariatric procedures were enrolled. The body mass index (mean ± standard deviation [SD])was 45.9 ± 8.0 kg/m(2) (range, 35.0 to 76.7 kg/m(2)); the median cefoxitin dose was 5 g (range, 4.0 to 7.5 g). The mean maximum concentrations were 216.15 ± 41.80 µg/ml in serum and 12.62 ± 5.89 in tissue; the mean tissue/serum ratio was 8% ± 3%. In serum, weight-based regimens achieved ≥90% PTA (goal time during which free [unbound] drug concentrations exceed pathogen MICs [fT>MIC] of 100%) for E. coli and S. aureus over 2 h and for B. fragilis over 1 h; in tissue this regimen failed to achieve goal PTA at any time point. The 40-mg/kg regimens achieved higher PTAs over longer periods in both serum and tissue than did the standard 2-g doses. However, although weight-based cefoxitin regimens were better than fixed doses, achievement of desired pharmacodynamic targets was suboptimal in both serum and tissue. Alternative dosing regimens and agents should be explored in order to achieve more favorable antibiotic performance during surgical prophylaxis in obese patients.

Intestinal Manometry Force Sensor for Robotic Capsule Endoscopy: An Acute, Multipatient In vivo Animal and Human Study.

GOAL: Development of a new medical device class generally termed robotic capsule endoscopes (RCE) is currently being pursued by multiple research groups. These maneuverable devices will allow minimally invasive diagnosis and treatment of intestinal pathologies. While the intraluminal pressures related to the migrating motor complex (MMC) are well understood, no previous study has measured the active contact forces exerted by the human small bowel wall on a solid, or near solid bolus such as an RCE. Understanding and quantifying the active contact force are critical for the advancement of RCE technology. METHODS: In this study, the authors develop a novel manometric contact force sensor for human studies and validate the feasibility of the design, sterilization method, and minimally invasive surgical procedure in a multianimal study, followed by a multihuman study. RESULTS: Four porcine tests of the sensor were conducted. The mean porcine myenteric contact force measured using the new sensor is 1.20 ± 0.08 N·cm-1. The mean myenteric contact force recorded for all five human test subjects is 0.18 ± 0.33 N·cm-1. CONCLUSION: This study demonstrates the feasibility of operating an MMC force sensor in a live human with a minimally invasive surgical technique and presents force data necessary for RCE design. SIGNIFICANCE: This study represents the first known myenteric contact force measurements on a solid bolus in the human small intestine.

Laparoscopic sleeve gastrectomy: long-term weight loss outcomes.

BACKGROUND: Laparoscopic sleeve gastrectomy (LSG) has become an increasingly popular stand-alone weight loss surgery, but there is a paucity of long-term efficacy data. OBJECTIVE: To determine long-term outcomes for patients undergoing LSG. SETTING: Tertiary care university hospital in the United States. METHODS: This study presents a case series of the first 16 patients undergoing LSG at our institution. Inclusion criteria were accepted indications for bariatric surgery, and exclusion criteria were any prior bariatric surgery, gastrectomy, substance abuse, uncontrolled psychiatric illness, end-stage organ disease, or advanced-stage cancer. Patients were followed for 7 years. Outcomes included percent excess weight loss (%EWL), percent weight loss (%WL), resolution of co-morbidities, and major and minor complications. RESULTS: Patients enrolled in this study had a mean body mass index (BMI) of 43.5 kg/m(2) and a mean age of 49, and 14 of 16 patients were women. Fourteen of 16 patients had 7-year follow-ups with a mean %WL of 29.6%±8.95 and a mean %EWL of 59.6%±89.9%. At 7 years, 11 of 14 patients achieved>50% EWL. One-year follow-up data revealed a mean EWL of 72%±20%, which was significantly greater than the %EWL at 7 years (P = .005). Complications included 1 partial obstruction at the gastric incisura angularis and 1 subacute leak; both were managed endoscopically. There were no reoperations and no deaths. Five of 14 patients experienced new-onset gastroesophageal reflux disease. CONCLUSIONS: At 7 years postoperative, the LSG remained a durable and successful operation.

Tissue storage ex vivo significantly increases vascular fusion bursting pressure.

INTRODUCTION: Harvested biological tissue is a common medium for surgical device assessment in a laboratory setting; this study aims to differentiate between surgical device performance in the clinical and laboratory environments prior to and following tissue storage. Vascular tissue fusion devices are sensitive to tissue-device temperature gradients, tissue pre-stretch in vivo and tissue water content, each of which can vary during tissue storage. In this study, we compare the results of tissue fusion prior to and following storage using a standardized bursting pressure protocol. METHODS: Epigastric veins from seven porcine models were subject to identical bursting pressure protocols after fusion. One half of each vein was fused in vivo, harvested and immediately analyzed for burst pressure; the remainder was stored (0.9% Phosphate Buffered Saline, 24h, 4 °C) and then analyzed ex vivo. Histological slides were prepared for qualitative analysis of in versus ex vivo fusions. RESULTS: Bursting pressures of vessels fused ex vivo (514.7 ± 187.0 mmHg) were significantly greater than those of vessels fused in vivo (310 ± 127.7 mmHg, p = 2.06 E-10). Histological imaging of venous axial cross-sections indicated the lamination of adventitia and media layers ex vivo, whereas in vivo samples consisted only of adventitia. CONCLUSION: These findings suggest that the fusion of porcine venous tissue ex vivo may overestimate the clinical performance of fusion devices. Prior work has indicated that increased tissue hydration and the lamination of tissue layers both positively affect arterial fusion bursting pressures. The bursting pressure increase observed herein may therefore be due to storage-induced alterations in tissue composition and mechanics of the fusion interface. While harvested tissue provides an accessible medium for comparative study, the fusion of vascular tissue in vivo may avoid storage-induced biomechanical alterations and is likely a better indicator of fusion device performance in a clinical setting.

The effect of Medicaid status on weight loss, hospital length of stay, and 30-day readmission after laparoscopic Roux-en-Y gastric bypass surgery.

BACKGROUND: Patients with Medicaid are much less likely to undergo bariatric surgery compared to those with commercial insurance. The aims of this study were to compare outcomes after laparoscopic Roux-en-Y gastric bypass (LRYGB) for patients covered by Medicaid, other (non-Medicaid) government insurance, and commercial insurance. METHODS: This was a retrospective cohort study of all eligible patients who underwent LRYGB between July 2004 and October 2011 at a single university hospital (n = 450). Multivariable regression analysis was used to compare percent weight loss (PWL), absolute weight loss (AWL), hospital length of stay (LOS) ≥3 days, and 30-day readmission rates. Analyses were adjusted for appropriate covariates. RESULTS: There was a nonsignificant increase in PWL in Medicaid patients at 2 months (p = 0.08), 6 months (p = 0.09), and 12 months (p = 0.17) compared to commercial insurance patients. Similarly, there was a nonsignificant increase in AWL in Medicaid patients at 2 months (p = 0.054), 6 months (p = 0.08), and 12 months (p = 0.14) compared to commercial insurance patients. Medicaid patients had similar PWL and AWL compared to those with other government insurance (p ≥ 0.29 at all time points). Medicaid patients were more likely to have a hospital LOS ≥ 3 days (OR 2.03; 95 % confidence interval (CI) 1.09-3.77) and a hospital readmission within 30 days of discharge (odds ratio (OR) 2.84; 95 % CI 1.15-6.96) compared to commercial insurance patients. CONCLUSIONS: These data should be considered as states expand Medicaid and make decisions regarding treatment of severe obesity. Interventions to decrease hospital LOS and the 30-day readmission rate, particularly in Medicaid patients, should be explored.

Wireless tissue palpation for intraoperative detection of lumps in the soft tissue.

In an open surgery, identification of precise margins for curative tissue resection is performed by manual palpation. This is not the case for minimally invasive and robotic procedures, where tactile feedback is either distorted or not available. In this paper, we introduce the concept of intraoperative wireless tissue palpation. The wireless palpation probe (WPP) is a cylindrical device (15 mm in diameter, 60 mm in length) that can be deployed through a trocar incision and directly controlled by the surgeon to create a volumetric stiffness distribution map of the region of interest. This map can then be used to guide the tissue resection to minimize healthy tissue loss. The wireless operation prevents the need for a dedicated port and reduces the chance of instrument clashing in the operating field. The WPP is able to measure in real time the indentation pressure with a sensitivity of 34 Pa, the indentation depth with an accuracy of 0.68 mm, and the probe position with a maximum error of 11.3 mm in a tridimensional workspace. The WPP was assessed on the benchtop in detecting the local stiffness of two different silicone tissue simulators (elastic modulus ranging from 45 to 220 kPa), showing a maximum relative error below 5%. Then, in vivo trials were aimed to identify an agar-gel lump injected into a porcine liver and to assess the device usability within the frame of a laparoscopic procedure. The stiffness map created intraoperatively by the WPP was compared with a map generated ex vivo by a standard uniaxial material tester, showing less than 8% local stiffness error at the site of the lump.

Biocompatibility and tissue integration of a novel shape memory surgical mesh for ventral hernia: in vivo animal studies.

Approximately 400,000 ventral hernia repair surgeries are performed each year in the United States. Many of these procedures are performed using laparoscopic minimally invasive techniques and employ the use of surgical mesh. The use of surgical mesh has been shown to reduce recurrence rates compared to standard suture repairs. The placement of surgical mesh in a ventral hernia repair procedure can be challenging, and may even complicate the procedure. Others have attempted to provide commercial solutions to the problems of mesh placement, but these have not been well accepted by the clinical community. In this article, two versions of shape memory polymer (SMP)-modified surgical mesh, and unmodified surgical mesh, were compared by performing laparoscopic manipulation in an acute porcine model. Also, SMP-integrated polyester surgical meshes were implanted in four rats for 30-33 days to evaluate chronic biocompatibility and capacity for tissue integration. Porcine results show that the modified mesh provides a controlled, temperature-activated, automated deployment when compared to an unmodified mesh. In rats, results indicate that implanted SMP-modified meshes exhibit exceptional biocompatibility and excellent integration with surrounding tissue with no noticeable differences from the unmodified counterpart. This article provides further evidence that an SMP-modified surgical mesh promises reduction in surgical placement time and that such a mesh is not substantially different from unmodified meshes in chronic biocompatibility.

A quantitative comparison of soft tissue compressive viscoelastic model accuracy.

Viscoelastic models are generally considered a good option for modeling biological tissue due to tissue time-dependency. However, although various forms of viscoelastic models have been developed, only a few have shown a good balance between model mathematical simplicity and experimental fit accuracy. Starting from a basic Standard Linear Solid (SLS) model, a systematic modification of the viscoelastic model leading to a more accurate tissue model is presented. A five-element model family, with a Double Maxwell-arm Wiechert (DMW) representative model, is selected for its mathematical simplicity and mathematical loading accuracy. This DMW model is then used to fit experimental data collected from stress relaxation indentation tests performed on fresh porcine liver and spleen. The results show that this DMW model provides a closer fit with the experimental liver (SLS R(2)=0.731, DMW R(2)=0.991) and spleen (SLS R(2)=0.720, DMW R(2)=0.981) data, compared to an SLS model, while maintaining appreciable mathematical simplicity by using only five model elements, compared to seven-element models. Thus, any model from this five-element model family can be used as a base compressive model for complex soft tissue with an approximate 35% improved model fit over SLS. Finally, model element parameters for in vitro fresh porcine liver and spleen are determined from the associated indentation tests.

Measurements of the contact force from myenteric contractions on a solid bolus.

The development of robotic capsule endoscopes (RCEs) is one avenue presently investigated by multiple research groups to minimize invasiveness and enhance outcomes of enteroscopic procedures. Understanding the biomechanical response of the small bowel to RCEs is needed for design optimization of these devices. In previous work, the authors developed, characterized, and tested the migrating motor complex force sensor (MFS), a novel sensor for quantifying the contact forces per unit of axial length exerted by the myenteron on a solid bolus. This work is a continuation, in which the MFS is used to quantify the contractile strength in the small intestine proximal, middle, and distal regions of five live porcine models. The MFSs are surgically implanted in a generally anesthetized animal, and force data from 5 min of dwell time are analyzed. The mean myenteric contact force from all porcine models and locations within the bowel is 1.9 ± 1.0 N cm(-1). Examining the results based on the small bowel region shows a statistically significant strengthening trend in the contractile force from proximal to middle to distal with mean forces of 1.2 ± 0.5, 1.9 ± 0.9, and 2.3 ± 1.0 N cm(-1), respectively (mean ± one standard deviation). Quantification of the contact force against a solid bolus provides developers of RCEs with a valuable, experimentally derived parameter of the intraluminal environment.

Small intestine mucosal adhesivity to in vivo capsule robot materials.

Multiple research groups are investigating the feasibility of miniature, swallowable, in vivo, untethered robots that are capable of traversing the small intestine for the purpose of acquiring biometrics and performing simple surgical procedures. A mathematical model of the intraluminal environment will speed the development of these so-called Robotic Capsule Endoscopes (RCEs), and to this end, the authors, in previous work, initiated a comprehensive program for characterizing both the active and passive forces exerted by the small intestine on an RCE-sized solid bolus. In this work, forces due to adhesivity between RCE materials and the mucosa are investigated. The experimental factors are adhesive modality (peel and tack), material (polycarbonate, micropatterned polydimethylsiloxane, stainless steel, and mucosa), and bowel region (proximal, middle, and distal). The mucosa is excised from a fasting pig, stored in lactated ringer's solution at 3 °C, and then tested at room temperature within 43 h of excision. The results show the mean tack strength of the mucosa to engineering materials was 0.198±0.070 mJ cm⁻². The mean peel strength was 0.055±0.016 mJ cm⁻². This study marks the first time, to the authors' knowledge, that adhesivity between small intestinal mucosa and RCE engineering materials has been measured. The adhesivity values acquired from this study will provide a valuable input into analytical and numerical models of the gastrointestinal tract, specifically models that account for the interfacial properties of the tissue.

Characterization and experimental results of a novel sensor for measuring the contact force from myenteric contractions.

The intraluminal pressures and traction forces associated with the migrating motor complex are well understood; however, the contact forces directly exerted by the bowel wall on a solid, or near solid, bolus have not previously been measured. Quantifying contact forces is an important component to understanding the net force experienced by an in vivo robotic capsule endoscope. In this paper, we develop a novel sensor, the migrating motor complex force sensor (MFS), for measuring the contact force generated by the contracting myenteron of the small intestine. The MFS consists of a perfused manometer connected to four torus-shaped balloons custom formed of natural latex rubber and embedded with temperature and pressure sensors. Force exerted on the balloon causes sensor pressure change. In vivo, the MFS measures the magnitude and axial location of contact pressure exerted by the myenteron. The device is tested in vivo in a live porcine model on the middle small bowel. The mean total force per centimeter of axial length of intestine that occurred over a 16-min interval in vivo was 1.04 N·cm (-1) in the middle region of the small intestine; the measured force is in the range of theoretical values.

Surgical evaluation of a novel tethered robotic capsule endoscope using micro-patterned treads.

BACKGROUND: The state-of-the-art technology for gastrointestinal (GI) tract exploration is a capsule endoscope (CE). Capsule endoscopes are pill-sized devices that provide visual feedback of the GI tract as they move passively through the patient. These passive devices could benefit from a mobility system enabling maneuverability and controllability. Potential benefits of a tethered robotic capsule endoscope (tRCE) include faster travel speeds, reaction force generation for biopsy, and decreased capsule retention. METHODS: In this work, a tethered CE is developed with an active locomotion system for mobility within a collapsed lumen. Micro-patterned polydimethylsiloxane (PDMS) treads are implemented onto a custom capsule housing as a mobility method. The tRCE housing contains a direct current (DC) motor and gear train to drive the treads, a video camera for visual feedback, and two light sources (infrared and visible) for illumination. RESULTS: The device was placed within the insufflated abdomen of a live anesthetized pig to evaluate mobility performance on a planar tissue surface, as well as within the cecum to evaluate mobility performance in a collapsed lumen. The tRCE was capable of forward and reverse mobility for both planar and collapsed lumen tissue environments. Also, using an onboard visual system, the tRCE was capable of demonstrating visual feedback within an insufflated, anesthetized porcine abdomen. CONCLUSION: Proof-of-concept in vivo tRCE mobility using micro-patterned PDMS treads was shown. This suggests that a similar method could be implemented in future smaller, faster, and untethered RCEs.

Single-port-access surgery with a novel magnet camera system.

In this paper, we designed, built, and tested a novel single-port access laparoscopic surgery (SPA) specific camera system. This device (magnet camera) integrates a light source and video camera into a small, inexpensive, portable package that does not compete for space with the surgical tools during SPA. The device is inserted through a 26-mm incision in the umbilicus, followed by the SPA port, which is used to maintain an insufflation seal and support the insertion of additional tools. The camera, now in vivo, remains separate from the SPA port, thereby removing the need for a dedicated laparoscope, and, thus, allowing for an overall reduction in SPA port size or the use of a third tool through the insertion port regularly reserved for the traditional laparoscope. The SPA camera is mounted to the abdominal ceiling using one of the two methods: fixation to the SPA port through the use of a rigid ring and cantilever bar, or by an external magnetic handle. The purpose of the magnet camera system is to improve SPA by: 1) eliminating the laparoscope SPA channel; 2) increasing the field of view through enhanced camera system mobility; and 3) reducing interference between the camera system and the surgical tools at the port, both in vivo and ex vivo.

Preliminary mechanical characterization of the small bowel for in vivo robotic mobility.

In this work we present test methods, devices, and preliminary results for the mechanical characterization of the small bowel for intra luminal robotic mobility. Both active and passive forces that affect mobility are investigated. Four investigative devices and testing methods to characterize the active and passive forces are presented in this work: (1) a novel manometer and a force sensor array that measure force per cm of axial length generated by the migrating motor complex, (2) a biaxial test apparatus and method for characterizing the biomechanical properties of the duodenum, jejunum, and ileum, (3) a novel in vitro device and protocol designed to measure the energy required to overcome the self-adhesivity of the mucosa, and (4) a novel tribometer that measures the in vivo coefficient of friction between the mucus membrane and the robot surface. The four devices are tested on a single porcine model to validate the approach and protocols. Mean force readings per cm of axial length of intestine that occurred over a 15 min interval in vivo were 1.34 ± 0.14 and 1.18 ± 0.22 N cm(-1) in the middle and distal regions, respectively. Based on the biaxial stress/stretch tests, the tissue behaves anisotropically with the circumferential direction being more compliant than the axial direction. The mean work per unit area for mucoseparation of the small bowel is 0.08 ± 0.03 mJ cm(-2). The total energy to overcome mucoadhesion over the entire length of the porcine small bowel is approximately 0.55 J. The mean in vivo coefficient of friction (COF) of a curved 6.97 cm(2) polycarbonate sled on live mucosa traveling at 1 mm s(-1) is 0.016 ± 0.002. This is slightly lower than the COF on excised tissue, given the same input parameters. We have initiated a comprehensive program and suite of test devices and protocols for mechanically characterizing the small bowel for in vivo mobility. Results show that each of the four protocols and associated test devices has successfully gathered preliminary data to confirm the validity of our test approach.

An integrated port camera and display system for laparoscopy.

In this paper, we built and tested the port camera, a novel, inexpensive, portable, and battery-powered laparoscopic tool that integrates the components of a vision system with a cannula port. This new device 1) minimizes the invasiveness of laparoscopic surgery by combining a camera port and tool port; 2) reduces the cost of laparoscopic vision systems by integrating an inexpensive CMOS sensor and LED light source; and 3) enhances laparoscopic surgical procedures by mechanically coupling the camera, tool port, and liquid crystal display (LCD) screen to provide an on-patient visual display. The port camera video system was compared to two laparoscopic video systems: a standard resolution unit from Karl Storz (model 22220130) and a high definition unit from Stryker (model 1188HD). Brightness, contrast, hue, colorfulness, and sharpness were compared. The port camera video is superior to the Storz scope and approximately equivalent to the Stryker scope. An ex vivo study was conducted to measure the operative performance of the port camera. The results suggest that simulated tissue identification and biopsy acquisition with the port camera is as efficient as with a traditional laparoscopic system. The port camera was successfully used by a laparoscopic surgeon for exploratory surgery and liver biopsy during a porcine surgery, demonstrating initial surgical feasibility.