Harry F. Tibbals

Biomechanical Properties of The Vaginal Wall: Effect of Pregnancy, Elastic Fiber Deficiency, and Pelvic Organ Prolapse

OBJECTIVE The purpose of this study was to identify pregnancy-induced changes in biomechanical properties of the vaginal wall and to compare these with fibulin-5 knockout mice (Fbln5(-/-)) with and without prolapse. STUDY DESIGN Mid-vaginal segments of nonpregnant and late-pregnant wild-type mice, Fbln5(-/-) with prolapse mice and Fbln5(-/-) mice without prolapse were studied. Tissue length at failure, maximal strain, maximal stress, and tissue stiffness were determined. RESULTS Compared with nonpregnant mice, vaginas of pregnant and Fbln5(-/-) (with prolapse) mice exhibited decreased maximal stress, increased distensibility and strain, and decreased stiffness. Tissues from Fbln5(-/-) mice without prolapse were similar to nonpregnant wild-type animals. CONCLUSION Pregnancy confers remarkable changes in the vaginal wall that include increased distensibility and decreased stiffness and maximal stress. Elastinopathy alone is insufficient to cause significant changes in these properties, but prolapse confers additional alterations in distensibility and stiffness that are similar to those changes that have been observed in pregnancy. These changes may contribute to the poor durability of many restorative surgical procedures for prolapse.

An Implantable, Batteryless, and Wireless Capsule With Integrated Impedance and pH Sensors for Gastroesophageal Reflux Monitoring

In this study, a device for gastroesophageal reflux disease (GERD) monitoring has been prototyped. The system consists of an implantable, batteryless and wireless transponder with integrated impedance and pH sensors; and a wearable, external reader that wirelessly powers up the transponder and interprets the transponded radio-frequency signals. The transponder implant with the total size of 0.4 cm ×0.8 cm ×3.8 cm harvests radio frequency energy to operate dual-sensor and load-modulation circuitry. The external reader can store the data in a memory card and/or send it to a base station wirelessly, which is optional in the case of multiple-patient monitoring in a hospital or conducting large-scale freely behaving animal experiments. Tests were carried out to verify the signal transduction reliability in different situations for antenna locations and orientation. In vitro, experiments were conducted in a mannequin model by positioning the sensor capsule inside the wall of a tube mimicking the esophagus. Different liquids with known pH values were flushed through the tube creating reflux episodes and wireless signals were recorded. Live pigs under anesthesia were used for the animal models with the transponder implant attached on the esophageal wall. The reflux episodes were created while the sensor data were recorded wirelessly. The data were compared with those recorded independently by a clinically used wireless pH sensor capsule placed next to our implant transponder. The results showed that our transponder detected every episode in both acid and non-acid nature, while the commercial pH sensor missed events that had similar, repeated pH values, and failed to detect pH values higher than 10. Our batteryless transponder does not require a battery thus allowing longer diagnosis and prognosis periods to monitor drug efficacy, as well as providing accurate assessment of GERD symptoms.

An implantable batteryless wireless impedance sensor for gastroesophageal reflux diagnosis

A new method for long term monitoring of gastroesophageal reflux is presented. The impedance of the reflux in the esophagus can be determined remotely without the need of a battery in the sensor implant. The implant includes an energy harvesting circuit, sensing electrodes, an antenna and an impedance to frequency converter. An external reader provides power to the implant and measures the impedance values simultaneously. A prototype with an overall size of 0.5×1×3.1cm3 was made with a printed circuit board and discrete components, and packaged in polydimethylsiloxane. In vivo experiments were conducted in pig cadavers. The results show good correlation between impedance and pH values of the acid solutions flushed into the esophagus, and good signal-to-noise ratios with the transducer inside the body. The impedance sensor can detect nonacid materials due to the frequency shift differences between air and solutions. The batteryless wireless impedance sensor is able to detect every reflux episode, either acid or non-acid, which provides more accurate diagnosis for the gastroesophageal reflux disease.

Effect of periurethral denervation on function of the female urethra

OBJECTIVE The purpose of this study was to determine the effect of periurethral denervation on contractile function of the female rat urethra. STUDY DESIGN Periurethral nerve transection or sham operation was performed in 16 young female rats. After 2 weeks, contractile function of the external urethra sphincter (EUS) and longitudinal smooth muscle was determined. Inhibitors of nitric oxide (NO) signaling were used to evaluate the role of nitric oxide in nerve-mediated relaxation. Statistical comparisons were conducted by Student t test. RESULTS Periurethral nerve transection resulted in gross evidence of urinary retention and bladder distention. In normal and sham-operated rats, nerve-mediated relaxation of urethral smooth muscle was inhibited by L-nitroarginine and oxadiazolo quinoxalin-1-one (ODQ), and this relaxation response was impaired significantly after periurethral nerve injury. Relaxation responses to the NO donor sodium nitroprusside remained intact. Contractile function of the EUS was not altered by periurethral nerve injury. CONCLUSION Neurons surrounding the urethra contain NO and innervate smooth muscle of the inner urethra. Periurethral denervation results in impaired urethral smooth muscle relaxation with no appreciable effect on contractility of the external striated sphincter.

Development of an Implanted RFID Impedance Sensor for Detecting Gastroesophageal Reflux

A new method to detect gastroesophageal reflux is presented. Based on passive RFID principles, the impedance of the refluxate can be determined. We have designed and fabricated planar coils integrated with electrodes on flexible substrates using standard photolithography processes. The device can be implanted in the esophagus using currently available clinical techniques. In vitro experiments with simulated stomach acid were conducted. An approach to integrate the sensor with RFID systems is proposed. This device can help diagnose gastroesophageal reflux disease effectively.

Blood detection in wireless capsule endoscopy using expectation maximization clustering

Wireless Capsule Endoscopy (WCE) is a relatively new technology (FDA approved in 2002) allowing doctors to view most of the small intestine. Other endoscopies such as colonoscopy, upper gastrointestinal endoscopy, push enteroscopy, and intraoperative enteroscopy could be used to visualize up to the stomach, duodenum, colon, and terminal ileum, but there existed no method to view most of the small intestine without surgery. With the miniaturization of wireless and camera technologies came the ability to view the entire gestational track with little effort. A tiny disposable video capsule is swallowed, transmitting two images per second to a small data receiver worn by the patient on a belt. During an approximately 8-hour course, over 55,000 images are recorded to a worn device and then downloaded to a computer for later examination. Typically, a medical clinician spends more than two hours to analyze a WCE video. Research has been attempted to automatically find abnormal regions (especially bleeding) to reduce the time needed to analyze the videos. The manufacturers also provide the software tool to detect the bleeding called Suspected Blood Indicator (SBI), but its accuracy is not high enough to replace human examination. It was reported that the sensitivity and the specificity of SBI were about 72% and 85%, respectively. To address this problem, we propose a technique to detect the bleeding regions automatically utilizing the Expectation Maximization (EM) clustering algorithm. Our experimental results indicate that the proposed bleeding detection method achieves 92% and 98% of sensitivity and specificity, respectively.

Nanofabricated Sensing Electrodes in a Batteryless Endoluminal Sensing Telemeter for Diagnosis of Gastroesophageal Reflux Disease (GERD)

Gastroesophageal reflux disease (GERD) is recognized the primary risk factor associated with esophageal cancers. Therefore, monitoring GERD symptoms accurately is important for early diagnosis of such cancers. In this work, interdigitated impedance sensing electrodes and nanofabricated IrOx-based pH sensing electrodes were made on the flexible substrates that can be easily embedded into an implantable device. The dual sensor electrodes were integrated into a batteryless wireless capsule packaged with biocompatible material for implant applications. The proposed sensing system has been tested with stimulated solutions of different pH values recording modulated sensor data in terms of frequency shifts to verify its performance. The experimental results showed that the impedance electrodes responded to ion content variations and the pH electrodes identified the pH values of various pH solutions. Our sensing system has demonstrated the ability to detect gastroesophageal reflux activities more accurately, which could help doctors to provide precise treatment methods, consequentially lowering the risks of esophageal cancer development.Copyright

Optimizing function distribution in a terminal network

Abstract By lowering cost restraints, microprocessors have enabled functions to be implemented on distributed hardware in a terminal network, where such distribution reflects and enables the distribution inherent in the logical design and operation of the network. The degree of distribution in this application is represented by the level of function executed on distributed terminal handlers, versus a single centrally located handler, and by the number of terminals clustered on each distributed handler. A design model is used to illustrate the variation of the optimum point in the tradeoff between central and distributed designs, based on hardware costs as the major variable.