Esophageal diameter and the treatment of achalasia

Mechanical strength and gastric residence time of expandable fibrous dosage forms

The expandable, gastroretentive dosage forms are promising for precise control of drug concentration in blood. So far, however, short gastric retention times and safety considerations have precluded their use. In this work, to mitigate the above limitations, expandable fibrous dosage forms were investigated for mechanical strength and gastric retention time in dogs. The fiber formulation consisted of ibuprofen drug; water-absorbing, high-molecular-weight hydroxypropyl methylcellulose (HPMC) excipient; strengthening, enteric methacrylic acid-ethyl acrylate excipient; and barium sulfate, a gastrointestinal contrast agent. The fibers were coated either with a hydrophilic sugar coating, or with the strengthening enteric excipient. Upon administration to a dog, in the stomach the dosage form with sugar-coated fibers expanded to 1.7 times its initial radius in 50-100 minutes, and disintegrated after 4.8 hours. The dosage form with the enteric-excipient-coated fibers, by contrast, expanded to 1.6 times the initial radius in 5 hours. Eventually, after 31 hours the dosage form fractured due to cyclic loads applied by the contracting stomach walls. The fragments passed into the small intestine where they dissolved in less than 2-3 hours. Diametral compression tests and models of fatigue failure show that the substantial increase in gastric residence time is due to strengthening of the fibers by the enteric-excipient coating. Because the enteric excipient is a rubbery semi-solid in the acidic gastric fluid and dissolves in the pH-neutral intestinal fluids, safety concerns should be minimal. Thus, the expandable fibrous dosage forms can be designed for prolonged, safe gastric retention.

Challenges and Recent Progress in Oral Drug Delivery Systems for Biopharmaceuticals

Routes of drug administration and the corresponding physicochemical characteristics of a given route play significant roles in therapeutic efficacy and short term/long term biological effects. Each delivery method has favorable aspects and limitations, each requiring a specific delivery vehicles design. Among various routes, oral delivery has been recognized as the most attractive method, mainly due to its potential for solid formulations with long shelf life, sustained delivery, ease of administration and intensified immune response. At the same time, a few challenges exist in oral delivery, which have been the main research focus in the field in the past few years. The present work concisely reviews different administration routes as well as the advantages and disadvantages of each method, highlighting why oral delivery is currently the most promising approach. Subsequently, the present work discusses the main obstacles for oral systems and explains the most recent solutions proposed to deal with each issue.

Ingestible hydrogel device

Devices that interact with living organisms are typically made of metals, silicon, ceramics, and plastics. Implantation of such devices for long-term monitoring or treatment generally requires invasive procedures. Hydrogels offer new opportunities for human-machine interactions due to their superior mechanical compliance and biocompatibility. Additionally, oral administration, coupled with gastric residency, serves as a non-invasive alternative to implantation. Achieving gastric residency with hydrogels requires the hydrogels to swell very rapidly and to withstand gastric mechanical forces over time. However, high swelling ratio, high swelling speed, and long-term robustness do not coexist in existing hydrogels. Here, we introduce a hydrogel device that can be ingested as a standard-sized pill, swell rapidly into a large soft sphere, and maintain robustness under repeated mechanical loads in the stomach for up to one month. Large animal tests support the exceptional performance of the ingestible hydrogel device for long-term gastric retention and physiological monitoring.

A pH-responsive supramolecular polymer gel as an enteric elastomer for use in gastric devices

Devices resident in the stomach-used for a variety of clinical applications including nutritional modulation for bariatrics, ingestible electronics for diagnosis and monitoring, and gastric-retentive dosage forms for prolonged drug delivery-typically incorporate elastic polymers to compress the devices during delivery through the oesophagus and other narrow orifices in the digestive system. However, in the event of accidental device fracture or migration, the non-degradable nature of these materials risks intestinal obstruction. Here, we show that an elastic, pH-responsive supramolecular gel remains stable and elastic in the acidic environment of the stomach but can be dissolved in the neutral-pH environment of the small and large intestines. In a large animal model, prototype devices with these materials as the key component demonstrated prolonged gastric retention and safe passage. These enteric elastomers should increase the safety profile for a wide range of gastric-retentive devices.

Some control-related issues in mini-robotics for endoluminal surgery

This paper introduces some issues related to the development of robotics for endoluminal surgery from control point of view. Endoluminal surgery are incisionless procedures performed through natural orifices within the natural pathways. New devices are then required to achieve these new surgical procedures. Besides the development of new devices, control issues arise in both technological and theoretical aspects. The paper presents some of them and we propose a teleoperation architecture that has already been tested for needle insertion that could be used for teleoperated endoluminal surgery especially for instance for biopsies or anastomoses.

Numerical analysis of pouch filling and emptying after laparoscopic gastric banding surgery

BACKGROUND

Previous studies have indicated that pouch volume and stoma size are two important factors related to weight loss after laparoscopic gastric banding in morbid obese patients. We hypothesized that there was association among the wall stress, pouch volume, and stoma size in a model for the filling and emptying phases of the pouch.

METHODS

A numerical pouch model with variable pouch volume and stoma size was generated. Uniaxial tensile testing was performed on fundus strips from fresh pig stomach and the mass flow of filling and emptying of the pouch was simulated numerically.

RESULTS

There was an overall qualitative agreement on the volume change between the simulated results and the clinical recording. Increasing the pouch volume size from 22 to 105 ml caused a decrease of the maximum circumferential stress from 14.14 to 11.80 kPa and the maximum longitudinal stress from 9.87 to 6.70 kPa in the pouch wall at the same degree of filling. Decreasing the stoma diameter from 27 to 10 mm caused an increase of the maximum circumferential stress from 11.46 to 12.78 kPa and a decrease of the maximum longitudinal stress from 10.34 to 8.69 kPa.

CONCLUSION

Both the pouch volume and stoma size are important determinants of mechanical wall stress, wall strain, and pouch emptying and hence may affect satiety and weight loss. This information may be important in understanding the mechanical behavior of pouches and for the development of more advanced numerical models in the clinical management of the surgery.

Meal area index: a new technique for quantitative assessment in achalasia by ambulatory manometry during eating

Ambulatory non-perfused oesophageal manometry was used to study oesophageal body function during consumption of a full meal in patients with achalasia. A measure of oesophageal body activity (the meal area index) was developed by calculating the total area under the pressure curve during eating, above the preprandial baseline oesophageal pressure, per meal minute. Untreated patients with achalasia (n = 13) were compared with normal subjects (n = 42), patients with benign stricture (n = 9) and patients with achalasia who had undergone Heller's myotomy (n = 17). The results showed a high meal area index in achalasia, due to a rise in baseline oesophageal pressure and frequent high-amplitude contractions during eating. This was not seen in normal subjects or patients with stricture. The high meal area index was abolished by successful Heller's myotomy but remained in two patients with persisting dysphagia. Sustained high intraoesophageal pressure is generated during consumption of a solid meal in untreated achalasia, resulting in a unique manometric profile. Manometry during eating using the meal area index permits quantitative assessment of oesophageal body function in achalasia and may aid in the assessment of response to treatment.

Achalasia of the cardia: long-term results of oesophagomyotomy and posterior partial fundoplication

Forty-eight patients with achalasia of the cardia were treated by Heller's myotomy with a posterior fundoplication of approximately 270 degrees, suturing the gastric fundus to the edges of the myotomy. The mean(s.d.) postoperative follow-up period was 5.4(2.8) years. The clinical results were good to excellent in 44 cases (92 per cent) and fair in four cases (8 per cent) (two with residual dysphagia and two with gastrooesophageal reflux). Barium studies showed a decrease in oesophageal diameter and disappearance of distal narrowing but normal oesophageal emptying did not occur. Postoperative manometric studies (29 patients) revealed a significant decrease in lower oesophageal sphincter pressure and a significant increase in the length of the infradiaphragmatic segment. In the oesophageal body a recovery of peristaltic waves in the proximal third was seen in ten of the patients (34 per cent). Twenty-four-hour pH monitoring showed pathological reflux in only three of 25 patients studied, and one of these was asymptomatic. This technique is effective, improving oesophageal symptoms and controlling long-term reflux.

Effects of total fundoplication on function of the esophagus after myotomy for achalasia

Twelve patients underwent distal esophageal myotomy for achalasia. After denuding the esophageal mucosa over 50 percent of its circumference, a short (2 cm) total fundoplication was performed over a size 56 mercury bougie. Clinical evaluation showed marked symptomatic improvement. Obstructive symptoms are minimal, and no reflux symptoms were noted. Manometric documentation showed a significant decrease in resting esophageal and lower esophageal sphincter pressure. Contraction pressure was also lowered, and peristalsis returned in 36 percent of the waves in the proximal esophagus. Radiologic and scanning documentation revealed slow emptying without evidence of significant reflux. Endoscopic evaluation revealed no esophagitis after 19 months' follow-up.

Achalasia of the esophagus. A reappraisal of esophagomyotomy vs forceful pneumatic dilation

56 patients with achalasia of the esophagus were reviewed in a retrospective study to compare the results of a forceful pneumatic dilation with those of a Heller esophagomyotomy. 22 of 33 patients treated with forceful dilation (67%), showed relief of dysphagia and reduction in the average esophageal diameter by barium swallow during the follow-up period (mean = 6.5 years). In 2 patients (6%), forceful dilation was complicated by esophageal perforation, promptly diagnosed, and successfully treated at surgery in both patients. 21 out of 23 patients who underwent esophagomyotomy (91%) showed permanent relief of symptoms and improvement by endoscopic and radiographic criteria. There were no significant postoperative complications during the follow-up period ranging between 1.5 and 10.0 years. The results of this study indicate that esophagomyotomy constitutes a more effective therapeutic modality than forceful dilation (P less than 0.05). Although esophageal dilation has a place in the treatment of early achalasia, esophagomyotomy appears to be a safer and a more successful form of treatment, of particular value in advanced esophageal disease and in those instances where pneumatic dilation fails to result in immediate clinical improvement.