Does the patch fit the stoma? A study on peristoma geometry and patch use in laryngectomized patients.

OBJECTIVE: To determine the geometry of (peri)stomas of laryngectomized patients in relation to patch use. This data will enable improvement of tracheostoma interfaces, specifically addressing patients currently unable to use stoma patches. The low use of Heat-and-Moisture-Exchange (HME) filters and (hands-free) speech valves, although very important to the quality of life of laryngectomized patients, is mainly attributed to poor fit of the adhesive patches to the stoma site. Current patch shapes are not based upon an objective (peri)stoma geometry because this geometry is unknown. DESIGN: Observational anthropometric study of the (peri)stoma of laryngectomized patients. SETTING: Ten hospitals or institutes in eight countries. PARTICIPANTS: About 191 laryngectomized patients, at least 1 year post operative. MAIN OUTCOME MEASURES: (Peri)stomas were photographed and measured. Patients completed a questionnaire on patch-use. Concavity of commercially available patches was measured. RESULTS: In countries with a financial reimbursement system 58% of the patients use patches, compares to only 9% in other countries. Patches stay in situ for an average of 33.3 h. Patch and non-patch users differ on five out of ten measured geometrical parameters. Most striking differences are that patch users have much shallower peristomas (13 versus 18 mm), and stomas far more parallel to the anterior neck plane. The deepest commercially available patch is only 7 mm deep. CONCLUSIONS: This study provides detailed (peri)stoma geometry data of a divers population, and for the first time in relation to patch-use. It reveals a serious mismatch between patients and patches. With these data new patches can be developed that could dramatically improve rehabilitation after laryngectomy.

Surface properties of Indonesian-made narrow dynamic compression plates.

The enormous need of orthopaedic (surgical) implants such as osteosynthesis plates is difficult to be fulfilled in developing countries commonly rely on imported ones. One of the alternatives is utilization of local resources, but only after they have been proven safe to use, to overcome this problem. Surface properties are some of the determining factors of safety for those implants. We have succeeded in developing prototype of osteosynthesis plate and the results indicate that Indonesian-made plates need improvement with regards to the surface quality of physical characterization.

Difficulties in the fixation of prostheses for voice rehabilitation after laryngectomy.

In most patients with advanced or recurrent laryngeal or hypopharyngeal cancer, total laryngectomy is indicated. This means the loss of three main functions: phonation; respiration; and the prevention of aspiration during deglutition. Laryngectomy patients have various options to restore phonation: an oesophageal voice; an electrolaryngeal voice; or a tracheo-oesophageal voice. In the last case a silicone rubber shunt valve is placed in the tracheo-oesophageal wall and phonation is generated when exhaled air is forced through the oesophagus and neopharynx. This method is widely applied in Western Europe. In this paper we review the literature on fixation problems with shunt valves, tracheostoma valves and heat and moisture exchange (HME) filters. Tracheo-oesophageal speech without a valve is not considered. Despite 22 years of experience with the implantation of tracheo-esophageal shunt valves and many improvements in the design, problems still remain, such as biofilm formation with subsequent leakage through the valve, the need for frequent and inconvenient replacements, fistula enlargement leading to leakage around the device and reduced fixation, and infections. The high cost of shunt valves is a drawback to their use worldwide. To enable hands-free speech, different types of tracheostoma valve have been developed. These valves are fixed to the skin or to the tracheostoma by means of an intra-tracheal device. An HME filter is used to protect the airway and maintain physiological balance. Such devices are only suitable for a selected group of patients as fixation to the skin or trachea can be a major problem. Speaking and coughing cause pressure increases, which often result in mucous leakage and disconnection of the valve and/or HME filter. Recommendations are made for future improvements in fixation techniques.

Redesign of Indonesian-made osteosynthesis plates to enhance their mechanical behavior.

Mechanical properties determined by fatigue strength, ductility, and toughness are important measures for osteosynthesis plates in order to tolerate some load-bearing situations caused by muscle contractions and weight-bearing effects. Previous study indicated that Indonesian-made plates showed lower mechanical strength compared to the European AO standard plate. High stress under load-bearing situations often starts from surface of the plate; we therefore refined the grain size of the surface by using shot peening and surface mechanical attrition treatment (SMAT). Single cycle bending tests showed that shot-peened and SMAT-treated plates had significantly higher load limit and bending stress compared to the original plates (p<0.05). Weibull analysis confirmed the improvement of proportional load limit of SMAT-treated plates. Fatigue limit also increased upon shot-peening and SMAT treatment (improvement ratio 18% and 27%, respectively). Significant improvement ratio of fatigue tests can be observed in SMAT-treated plates compared to the untreated and shot-peened plates. Fatigue performance demonstrated equivalent results between SMAT-treated and standard plate. These designated that mechanical properties of Indonesian-made plates can be improved upon SMAT treatment leading to significant enhancement of mechanical strength thus is comparable to the standard plate. Our findings highlight the benefits of SMAT treatment to improve mechanical strength of Indonesian-made osteosynthesis plates.

Animal models for tracheal research.

Tracheal research covers two main areas of interest: tracheal reconstruction and tracheal fixation. Tracheal reconstructions are aimed at rearranging or replacing parts of the tracheal tissue using implantation and transplantation techniques. The indications for tracheal reconstruction are numerous: obstructing tracheal tumors, trauma, post-intubation tissue reactions, etc. Although in the past years much progress has been made, none of the new developed techniques have resulted in clinical application at large scale. Tissue engineering is believed to be the technique to provide a solution for reconstruction of tracheal defects. Although developing functional tracheal tissue from different cultured cell types is still a challenge. Tracheal fixation research is relatively new in the field and concentrates on solving fixation-related problems for laryngectomized patients. In prosthetic voice rehabilitation tracheo-esophageal silicon rubber speech valves and tracheostoma valves are used. This is often accompanied by many complications. The animal models used for tracheal research vary widely and in most publications proper scientific arguments for animal selection are never mentioned. It showed that the choice on animal models is a multi-factorial process in which non-scientific arguments tend to play a key role. The aim of this study is to provide biomaterials scientists with information about tracheal research and the animal models used.

Functional buckling behavior of silicone rubber shells for biomedical use.

BACKGROUND: The use of soft elastic biomaterials in medical devices enables substantial function integration. The consequent increased simplification in design can improve reliability at a lower cost in comparison to traditional (hard) biomaterials. Functional bi-stable buckling is one of the many new mechanisms made possible by soft materials. The buckling behavior of shells, however, is typically described from a structural failure point of view: the collapse of arches or rupture of steam vessels, for example. There is little or no literature about the functional elastic buckling of small-sized silicone rubber shells, and it is unknown whether or not theory can predict their behavior. Is functional buckling possible within the scale, material and pressure normally associated with physiological applications? An automatic speech valve is used as an example application. METHOD OF APPROACH: Silicone rubber spherical shells (diameter 30mm) with hinged and double-hinged boundaries were subjected to air pressure loading. Twelve different geometrical configurations were tested for buckling and reverse buckling pressures. Data were compared with the theory. RESULTS: Buckling pressure increases linearly with shell thickness and shell height. Reverse buckling shows these same relations, with pressures always below normal buckling pressure. Secondary hinges change normal/reverse buckling pressure ratios and promote symmetrical buckling. All tested configurations buckled within or closely around physiological pressures. CONCLUSIONS: Functional bi-stable buckling of silicone rubber shells is possible with adjustable properties in the physiological pressure range. Results can be predicted using the proposed relations and equations.

Mechanical properties of Indonesian-made narrow dynamic compression plate.

Osteosynthesis plates are clinically used to fixate and position a fractured bone. They should have the ability to withstand cyclic loads produced by muscle contractions and total body weight. The very high demand for osteosynthesis plates in developing countries in general and in Indonesia in particular necessitates the utilisation of local products. In this paper, we investigated the mechanical properties, i.e. proportional limit and fatigue strength of Indonesian-made Narrow Dynamic Compression Plates (Narrow DCP) as one of the most frequently used osteosynthesis plates, in comparison to the European AO standard plate, and its relationship to geometry, micro structural features and surface defects of the plates. All Indonesian-made plates appeared to be weaker than the standard Narrow DCP because they consistently failed at lower stresses. Surface defects did not play a major role in this, although the polishing of the Indonesian Narrow DCP was found to be poor. The standard plate showed indications of cold deformation from the production process in contrast to the Indonesian plates, which might be the first reason for the differences in strength. This is confirmed by hardness measurements. A second reason could be the use of an inferior version of stainless steel. The Indonesian plates showed lower mechanical behaviour compared to the AO-plates. These findings could initiate the development of improved Indonesian manufactured DCP-plates with properties comparable to commonly used plates, such as the standard European AO-plates.

Geometry of the intervertebral volume and vertebral endplates of the human spine.

Replacement of a degenerated vertebral disc with an artificial intervertebral disc (AID) is currently possible, but poses problems, mainly in the force distribution through the vertebral column. Data on the intervertebral disc space geometry will provide a better fit of the prosthesis to the vertebrae, but current literature on vertebral disc geometry is very scarce or not suitable. In this study, existing CT-scans of 77 patients were analyzed to measure the intervertebral disc and vertebral endplate geometry of the lumbar spine. Ten adjacent points on both sides of the vertebrae (S1-superior to T12-inferior) and sagittal and transverse diameters were measured to describe the shape of the caudal and cranial vertebral planes of the vertebrae. It was found that the largest endplate depth is located in the middle or posterior regions of the vertebra, that there is a linear relationship between all inferior endplate depths and the endplate location (p < 0.0001) within the spinal column, and that the superior endplate depth increases with age by about 0.01 mm per year (p < 0.02). The wedge angle increases from T12-L1 to L5-S1. The results allow for improvement of the fit of intervertebral disc-prostheses to the vertebrae and optimized force transmission through the vertebral column.

Development of a double-membrane sound generator for application in a voice-producing element for laryngectomized patients.

For voice rehabilitation after total laryngectomy a shunt valve is usually placed in the tracheo-esophageal (TE) wall, thereby enabling the production of a TE voice. Some patients, however, are unable to produce a voice of sufficient quality. Furthermore, the TE voice is low pitched, which presents a problem especially for female laryngectomized patients. The voice quality after laryngectomy might be improved by introducing a voice-producing element (VPE) into the TE shunt valve. In this study a sound generator was developed that is suitable for application in such a VPE. This sound generator consists of two elastic membranes placed parallel inside a circular housing. A substitute voice source is created when the membranes start to vibrate via a constant flow of air passing between them. To determine the optimal membrane configuration for proper functioning under physiological conditions, up-scaled physical VPE models with different membrane geometries were evaluated using in vitro experimental tests. For certain membrane geometries the tests showed that a basic sound, containing multiple harmonics, could be successfully produced under physiological air pressure and airflow conditions. The fundamental frequency (60-95 Hz) and sound pressure level (57-78 dB, at 15 cm microphone distance) were regulated via changes in the driving pressure, thereby enabling the possibility of intonation in laryngectomized patients' speech. The obtained frequency range is considered appropriate for producing a substitute voice source for female patients. The geometry considerations in this study can be used for the development of a true scale VPE that can be evaluated clinically, to eventually replace the voice after laryngectomy.

The Groningen hypothermic liver perfusion pump: functional evaluation of a new machine perfusion system.

To improve preservation of donor livers, we have developed a portable hypothermic machine perfusion (HMP) system as an alternative for static cold storage. A prototype of the system was built and evaluated on functionality. Evaluation criteria included 24 h of adequate pressure controlled perfusion, sufficient oxygenation, a maintained 0-4 degrees C temperature and sterile conditions. Porcine livers were perfused with pump pressures that were set at 4 mmHg (continuous, portal vein) and 30/20 mmHg, at 60 BPM (pulsatile, hepatic artery). Control livers were preserved using the clinical golden standard: static cold storage. In the HMP group, pressure, flow and temperature were continuously monitored for 24 h. At time-points t = 0, 2, 4, 8, 12, and 24 h samples of University of Wisconsin machine preservation solution were taken for measurement of partial oxygen pressure (pO(2)) and lacto-dehydrogenase. Biopsies in every lobe were taken for histology and electron microscopy; samples of ice, preservation solution, liver surface, and bile were taken and cultured to determine sterility. Results showed that temperature was maintained at 0-4 degrees C; perfusion pressure was maintained at 4 mmHg and 30/20 mmHg for portal vein and hepatic artery, respectively. Flow was approximately 350 and 80 ml/min, respectively, but decreased in the portal vein, probably due to edema formation. Arterial pO(2) was kept at 100 kPa. Histology showed complete perfusion of the liver with no major damage to hepatocytes, bile ducts, and non-parenchymal cells compared to control livers. The machine perfusion system complied to the design criteria and will have to demonstrate the superiority of machine perfusion over cold storage in transplant experiments.