Bio-Mechanical Development of The Gastro-Mechanical Analyser By: George Oppong-Addae (B.Eng. Mech; Grad. Dip Mngt) 1/14/2015 Page 1 DESCRIPTION 1. Introduction To gain a functional understanding of the bio-mechanical process in the feeding of humans, there has to be clarity of the motion & flow of food substances as they travel through the GI Tract and finish at the rectum. The digestion process of these food and fluid substances, usually involves stimulation of the nasopharyngeal passage as the first point of contact. This generates increased secretion of saliva in the mouth and also hydrochloric acid into the stomach. Chyme formation starts in the stomach during digestion, and it is a thick semi-fluid mass of partially digested food and digestive secretions which assists with flow of the food substances. Other secretions from the pancreas, gallbladder, liver, and glands; in the intestinal wall add to the total volume of chyme and protects the membrane lining of the digestive system from gastric ulcers (e.g. peptic & duodenal ulcers) caused by the highly acidic gastric juice (1). Muscular contractions of the stomach walls help mix food and digestive substances together in forming chyme. As particles of food become small enough, they are passed at regular intervals into the small intestine. Once in the intestine, more enzymes are added and mixing continues. When food particles are sufficiently reduced in size and composition, they are absorbed by the intestinal wall and transported to the bloodstream. As chyme passes through the stomach and intestine, it picks up cellular debris and other types of waste products. Some food material is passed from the small intestine to the large intestine, or colon. In the colon, chyme is acted upon by bacteria that break down the proteins, starches and some plant fibres not totally digested by the other organs. In both the small and the large intestine, water is normally absorbed so the chyme gradually gets thicker. When all of the nutrients have been absorbed from chyme, the remaining waste material passes to the end of the large intestine, the sigmoid colon and rectum, to be stored as fecal matter until it is ready to be excreted from the body (2). Page 2 2. Development This project aims to demonstrate how the above process in the human digestive system may be understood and better controlled in average healthy humans and in people who require EN aids and applications. In particular the study will be formulated around the following stages of feeding through to emptying of the gastric system. Preparandial Gastric Analysis: a. Measure gastric system pressure, vital signs, age, gender body mass index, abdominal girth and health. b. Measure the temperature, viscosity and volume of the food/fluid substances to be ingested. Parandial Gastric Analysis: a. Estimate the required time to be taken for feeding. b. Monitor variations in gastric system pressure and flow of food/fluid substances into the system (i.e. peristaltic or turbulent movement of food/bolus in oesophagus and churning of chyme in the stomach). Postparandial Gastric Analysis: a. Assess the system stability. b. Observe the characteristics of the gastric system's motility (i.e. by monitoring the churning of chyme in the stomach). c. Ensure that there are regular bowel outputs, and micturition. The methods that will be used to analyse the above, and to provide vital answers, will include a careful and thorough examination of what the inputs to the system are in comparison to the outputs. The bio-mechanical characteristics, performance and condition of the human feeding and digestive system will be studied with the aim of providing an insight into the optimum pressure, fluid viscosity, PH and volume that can be tolerated by specific individuals during the process. This study will require 3-D modelling of the fluid dynamics in the GI Tract to gain an insight into food ingestion, digestion and excretion. Results of these investigations should be quantifiable to assist in formulating dietary needs with respect to EN aids; e.g. PEG Feeding and J-Tube, currently being used for people who require such applications, due to their inability to have feed via the oesophagus. It has been established that feeding through to excretion processes, can be represented by a closed loop mechanical control system. Existing research focuses on sections of the GI Tract and analyse it as an open loop control system with no feedback. An open loop control system is illustrated below. Page 3 An open loop control system Advantages . Sensors are not needed to measure variable as feedback is absent. . It is easier to build and less expensive. . It is more stable as feedback is absent. Disadvantages * It has no accuracy. * If non-linearity is present in the input then it cannot be reduced because of the absence of feedback. * More sensitive to system parameter variation. * Transient response and steady state response cannot be controlled effectively. Examples * An automatic faster * Control of furnace for coal heating * An electric washing machine This research proposal aims to analyse the entire GI Tract, during pre-feeding, feeding and post feeding, by simulating its characteristics using a closed loop control system. This is explained briefly below. The governing equation for analyses determines the roots of the characteristic polynomial and it is defined as: T(s) =....KG(s)...... 1+KG(s) H(s) Where: T(s) - The Closed Loop Transfer Function (CLTF) K - The Controller-Forward Path Gain (A system parameter that is to be varied) G(s) - System Characteristics H(s) - Sensor in the Feedback System A closed loop control system Advantages . It gives more accuracy. . If non-linearity is present in the input then it is reduced by the feedback. . It is less sensitive to system parameter variation. . Transient response and steady state response can be controlled more conveniently. Page 4 Disadvantages * Sensors are needed as feedback is present. . It is very difficult to build. . It is comparatively less stable. Examples . Pressure control system * Speed Control System . Robot Control System The requirements for a good control system are: Accuracy, Sensitivity, Noise Attenuation, Stability, Bandwidth, Speed and Oscillation. The transfer function(s) will be set up mathematically and the efficiency of the system will be determined for the three stages of feeding, digesting and emptying. It is also hoped that through these analyses a better understanding of system stability will evolve. Furthermore the analysis will provide answers to whether there is a direct correlation between the rate of feeding and gastric comfort levels. Gastric comfort levels will be benchmarked against the theoretical stability of the individual's system where there is no disturbance of concern; e.g. any diarrhoea or constipation. 3. Design Proposal The proposed bio-mechanical device to be developed as a result of this study will be called a Gastro-MechanicalAnalyser. It will be capable of data logging and measuring where practical all of the following parameters: a. PH measurements in the gut. b. Intra Gastric Pressure (IGP). c. Viscosity of the food/fluid d. Temperature of the client as well as the food e. Flow Rate Although most of the data may be able to be captured automatically by the analyser, there will still be a requirement for some data to be manually entered into it to facilitate analyses. The analyser may be used in an array of gastric mechanics applications and will have specific use in support of Enteral Nutritional needs of people who are unable to feed normally by oral ingestion through the GI Tract. The device will be capable of performing complex gastro-mechanical system analyses using bio-mechanical control algorithms and will provide meaningful results which will assist specialists and medical professionals in making beneficial decisions and recommendations on: * GI Tract system stability conditions. * GI Tract system efficiencies with regard to inputs and outputs through the system. Page 5 * GI Tract system motility control factors, taking into consideration set bio-kinetic performance criteria developed scientifically. * GI Tract system tolerance levels by analysing the relationship between feeding and digestive comfort levels specific to the individual. 4. Existing Research on Aspects of the GI Tract "Despite recognition of the importance of enteral nutrition, evaluation of the efficacy of formula delivery is more limited. "('3). Delivery of formula is intrinsically associated with accommodation and gastric comfort levels. The argument on hand centres on how a gastric system can cope when these EN feeding applications are in use, particularly for people who are unable to ingest food/fluids via the oesophagus. Gastric tone measurement "The standard to determine gastric accommodation is the gastric barostat. This technique detects changes in muscle tone by measuring volume changes of an intragastric balloon that is kept at a constant pressure. There is however important drawbacks associated with the technique: the inflated balloon distends the proximal stomach, might exaggerate gastric accommodation, and hampers physiologic responses to food intake (6) It remains a fact that further insight into the IGP is required when feeding to help establish nutrient loads experienced during the administration of EN applications. This will ascertain quantitatively gastric accommodation capacities particularly for conditions which lead to failure to thrive, such as cerebral palsy, cystic fibrosis, malignancies, metabolic disorders and various major congenital abnormalities. 5. Demand Analysis Referral patterns by patient clinic (Home Enteral Nutrition Service Database, W&CH) Breakdown of patients by age (Home Enteral Nutrition Service Database, W&CH) Full analysis of the Market Segment for which the Gastro-Mechanical Analyser will be of relevance is beyond the scope of this preliminary proposal. An appreciation of the nature and potential size of this market is presented below. "Approximately 14% of the Australian population are aged 65 years or over, representing almost two million people who may require additional health care as time progresses. Consequently, early intervention may save considerable financial resources in addition to increasing the number of healthy, as opposed to frail, aged people" (4). It is envisaged that this device will provide specialists with a detailed understanding of how the entire GI Tract may be controlled to benefit clients as well as facilitate Bio-Mechanical Research and the Health Care Industry in the use and application of bio-mechanical devices for EN needs. Page 6 6. Conclusion The paper has found that there is an underpinning requirement to pursue much needed bio-mechanical research in the mechanics of the GI Tract with respect to EN pre-feeding, feeding and post-feeding processes. It is also necessary to be able to have a device which can predict and monitor the condition, characteristics and performance of the GI Tract with respect to ingestion, digestion and excretion of food and fluid substances that may be taken in by average healthy humans and by people who require EN devices to assist them feed comfortably, and to prevent disturbances that may prompt them to pull out or dislodge these devices. Therefore there is a need for a Gastro-Mechanical Analyser capable of ensuring the holistic bio-mechanical care of the GI Tract is maintained. This project aims to develop the analyser to support specialists and medical professionals by providing them critical information that will facilitate beneficial decisions, recommendations and conclusions to do with EN feeding needs of people. 7. References A. Ferrua MJ, Marra F, Singh RP. PIV analysis of the flow within a closed system that simulates the peristaltic movement of the stomach wall. 2009. IFT Annual Meeting. Anaheim, California. Nr09-A-2619-IFT. 1. Written by: The Editors of Encyclopedia Britannica - Last Updated 3-10-2014. 2. Written by: The Editors of Encyclopedia Britannica - Last Updated 3-10-2014. 3. Dieticians Association of Australia. Enteral nutrition manual for adults in health care facilities. Dieticians Association of Australia; 2011. Available from: http://daa.asn.au/wp--content/uploads/20 1 1/1 /Enteral-utrition-manual-Oct 2011.pdf. Accessed July 4, 2014. 4. Baines S.K, Roberts D. C. K, Department of Nutrition and Dietetics, School of Health Sciences, 2001:24:113-5; Newcastle University, Newcastle, New South Wales. 5. Wright D, - (RN, BNg, Grad. Cert. Health (CCAFHN) Clinical Nurse 1996:83 Home Enteral Nutrition Service Women's and Children's Hospital, Adelaide. 6. Carrasco M, Azpiroz F, Malagelada JR. Relations among intragastric pressure, postcibal perception, and gastric emptying. Am J Physiol 1993; 264: G1112-7. Page 7