Understanding safety-critical interactions with a home medical device through Distributed Cognition

As healthcare shifts from the hospital to the home, it is becoming increasingly important to understand how patients interact with home medical devices, to inform the safe and patient-friendly design of these devices. Distributed Cognition (DCog) has been a useful theoretical framework for understanding situated interactions in the healthcare domain. However, it has not previously been applied to study interactions with home medical devices. In this study, DCog was applied to understand renal patients’ interactions with Home Hemodialysis Technology (HHT), as an example of a home medical device. Data was gathered through ethnographic observations and interviews with 19 renal patients and interviews with seven professionals. Data was analyzed through the principles summarized in the Distributed Cognition for Teamwork methodology. In this paper we focus on the analysis of system activities, information flows, social structures, physical layouts, and artefacts. By explicitly considering different ways in which cognitive processes are distributed, the DCog approach helped to understand patients’ interaction strategies, and pointed to design opportunities that could improve patients’ experiences of using HHT. The findings highlight the need to design HHT taking into consideration likely scenarios of use in the home and of the broader home context. A setting such as home hemodialysis has the characteristics of a complex and safety-critical socio-technical system, and a DCog approach effectively helps to understand how safety is achieved or compromised in such a system

Design and modeling of a portable hemodialysis system

Research to improve artificial renal replacement therapies is varied across the many different parts of a hemodialysis system. Work largely focuses on developing a better dialyzer - the component that is directly responsible for removing wastes from the blood - but less study is devoted to the entire hemodialysis system. This work seeks to improve hemodialysis in two ways: by proposing a new renal replacement therapy that does not rely on traditional hemodialysis components, and by investigating the feasibility of adapting current hemodialysis practices to a portable format. While an alternative renal replacement therapy may be the best solution to today's dialysis problems, this work further focuses on reducing hemodialysis to a portable format through systematic engineering design. In that process, a detailed system model is made in Simulink that can account for the large number of inputs of such a system - the blood flow rate, dialyzer size, treatment time, etc. - allowing for detailed exploration of the design space. Once the model is completed, it is verified through in vitro experiments carried out with porcine blood. Additionally, the model is verified against published human hemodialysis data. After model verification, hemodialysis concepts are generated that allow for maximum portability under different patient conditions.M.S.Committee Chair: Rosen, David; Committee Member: Ku, David; Committee Member: Paredis, Chri

Study on the Premarket Safety Evaluation of Hemodialysis System

早大学位記番号:新7547早稲田大

Estimation of dialysis treatment efficiency by means of system identification

When treating patients suffering from renal failure with hemodialysis, an obvious point of interest is the actual blood cleaning efficiency of the dialyzer (artificial kidney). This efficiency is called clearance or dialysance. The method currently used for estimating clearance is based on doing a step-change on the process. Due to the nature of the process, this method is slow and has a relatively large output spread. This master thesis investigates a new method of finding clearance by means of system identification. The dialyzer is modelled as a discrete-time system, and perturbed by use of a pseudo-binary random sequence. The input/output-data is then fed into an optimal Kalman filter for parameter estimation. The gain and offset of the identified system is directly related to the dialyzer clearance of the treatment. The method shows promising results, usually converging to good parameters within 15 minutes, and then tracking changes continuously for the rest of the treatment. It also provides better accuracy, with a considerable reduction in spread compared to the old method. Main obstacles stem from variable time-delays in the system and measurement offsets

Destructive Effect of Calcium Hypochlorite against Pseudomonas aeruginosa Biofilm

Background: Pseudomonas aeruginosa is the most common bacteria contaminating the hemodialysis water and has high capability to form a biofilm. The presence of biofilm is hazardous because it becomes a constant source of bacterial and toxin release toward the hemodialysis patient’s blood. Calcium hypochlorite (Ca(OCl)2) is an easily obtained disinfectant. This study was aimed to detect the destructive effect of Ca(OCl)2 against P. aeruginosa biofilm and the optimal disinfectant concentration required to achieve significant effect.Methods: This experimental study was conducted in six replicates from September to October 2015 in Microbiology Laboratory of Faculty of Medicine Universitas Padjadjaran Bandung. A modified tissue culture plate method was performed to grow P. aeruginosa biofilms which were subsequently treated with Ca(OCl)2 in various chlorine concentrations, namely 20, 30, 40, and 500 parts per million (ppm). The data was analyzed using Welch Analysis of Variance (ANOVA) and Games-Howell post-hoc tests and presented in tables.Results: Data were obtained from 36 flat-bottomed polystyrene wells. There was a statistically significant mean difference between groups [F(4, 11.92)= 91.198, p<0.001)]. All of the tested chlorine concentrations caused significant decreases in biofilm optical densities (p = 0.027 for 20 ppm and p< 0.001 for 30, 40, and 500 ppm).Conclusions: Ca(OCl)2 with chlorine concentrations of 20, 30, 40, and 500 ppm have significant destructive effect against P. aeruginosa biofilm. The mean differences among treated groups were not significant. The most optimum concentration is 30 ppm

Recent Experience with Hemodialysis in Acute Renal Failure, Chronic Renal Disease with Reversible Features, and in Conjunction with Renal Homotransplants

Hemodialysis is a safe acceptable method of treatment for drug intoxication, and acute renal failure. It is also useful in the management of patients with chronic renal disease either on a periodic basis or, intermittantly, for acute exacerbations superimposed on chronic renal insufficiency. The great majority of dialysis at MCV has been done in conjunction with the ongoing renal homotransplantation program. Here dialysis has proven to be an innocuous procedure and has contributed significantly to the success of this program

Determination of vancomycin and gentamicin clearance in an in vitro, closed loop dialysis system

Background\ud The purpose of this study was to evaluate the feasibility of utilizing an in-vitro, closed loop hemodialysis system as a method to assess drug clearance. Secondarily, this study tested the influence of variables (blood flow rate, dialysate flow rate, and type of filter) in the hemodialysis procedure on the clearance of vancomycin and gentamicin.\ud \ud Methods\ud An in-vitro, closed loop hemodialysis system was constructed. The vancomycin (30 mg/L) and gentamicin (25 mg/L) were added to a simulated blood system (SBS). Four conditions (C1-C4) were tested by defining the filter (Polyflux 170H or F180) and the blood and dialysate flow rates (BFR and DFR). All hemodialysis sessions were 3 hours in length and each condition was completed in duplicate. Dialysate effluent was collected in a 50 gallon polyethylene drum. Samples were collected (in duplicate) from the SBS and the dialysate effluent at baseline and at the end of the hemodialysis session. Samples were analyzed for vancomycin and gentamicin with an ultrahigh performance liquid chromatography/tandem mass spectrometry method.\ud \ud Results\ud A total of eight 3-hour hemodialysis sessions were conducted. For all tested conditions (C1-C4), vancomycin was undetectable in the SBS at the end of dialysis. However, total vancomycin recovery in the dialysis effluent was 85±18%, suggesting that up to 15% may have adsorbed to the dialysis filter or tubing. Gentamicin clearance from SBS was >98% in all tested conditions. Average gentamicin recovery in the dialysate effluent was 99±15%.\ud \ud Conclusion\ud Both vancomycin and gentamicin were readily removed by high-flux hemodialysis under all conditions studied. No significant differences in drug clearance were observed between conditions used in this in vitro study. The clinical implications of changing these hemodialysis parameters are unknown

Extracorporeal Delivery of a Therapeutic Enzyme

To remove circulating harmful small biochemical(s)/substrates causing/deteriorating certain chronic disease, therapeutic enzyme(s) delivered via vein injection/infusion suffer(s) from immunoresponse after repeated administration at proper intervals for a long time and short half-lives since delivery. Accordingly, a novel, generally-applicable extracorporeal delivery of a therapeutic enzyme is proposed, by refitting a conventional hemodialysis device bearing a dialyzer, two pumps and connecting tubes, to build a routine extracorporeal blood circuit but a minimal dialysate circuit closed to circulate the therapeutic enzyme in dialysate. A special quantitative index was derived to reflect pharmacological action and thus pharmacodynamics of the delivered enzyme. With hyperuricemic blood in vitro and hyperuricemic geese, a native uricase via extracorporeal delivery was active in the dialysate for periods much longer than that in vivo through vein injection, and exhibited the expected pharmacodynamics to remove uric acid in hyperuricemic blood in vitro and multiple forms of uric acid in hyperuricemic geese. Therefore, the extracorporeal delivery approach of therapeutic enzymes was effective to remove unwanted circulating small biochemical(s)/substrates, and was expected to avoid immunogenicity problems of therapeutic enzymes after repeated administration at proper intervals for a long time due to no contacts with macromolecules and cells in the body

Isolated Bacteria from Hemodialysis Water Distribution Systems in Hemodialysis Centers in Bandung

Background: Despite the advent of water treatment technology for the past few decades, bacterial contamination is still an everlasting issue that requires solid intervention. Many studies across the world have identified myriad of bacteria that colonize the hemodialysis water distribution system. This study was conducted to identify common bacteria that colonized the hemodialysis water distribution systems in Bandung.Methods: This was a descriptive laboratory study conducted at the Department of Microbiology Faculty of Medicine Universitas Padjadjaran in 2014. Sterile bottles were used to collect 16 samples of reverse osmosis water from 2 hemodialysis centers in Bandung. Approximately 15 ml of water volume was collected in each bottle from 7 standard points for water sampling in hemodialysis system. The samples were first inoculated into R2A agar by pour-plate method and colonies were sub–cultured onto MacConkey and blood agar and the identification was based on Gram stain morphology, colony characteristics, and biochemical tests.Results: Micrococcus luteus and Pseudomonas sp. were the two predominant organisms which colonized the hemodialysis water distribution system. In addition, some genus of the Enterobacteriaceae such as Enterobacter aerogenes, Klebsiella pneumoniae, and Yersinia pseudotuberculosis were also isolated from the system and seemed to colonize the entire system.Conclusions: Bacterial contamination in hemodialysis water distribution system in Bandung is still a major problem regardless the efforts taken to minimize it. [AMJ.2016;3(2):259–64] DOI: 10.15850/amj.v3n2.78

Design of a new type of coating for the controlled release of heparin

Thrombus formation at the surface of blood contacting devices can be prevented by local release of heparin. Preferably, the release rate should be constant for prolonged periods of time. The minimum heparin release rate to achieve thromboresistance will be different for various applications and should therefore be adjustable. In this study a new type of heparin release system is presented which may be applied as a coating for blood contacting devices. The system is based on the covalent immobilization of heparin onto porous structures via hydrolysable bonds. This approach was evaluated by the immobilization of heparin onto a porous cellulosic substrate via ester bonds. Cuprophan was used as a model substrate and N,N¿-carbonyldiimidazole as a coupling agent. Heparinized Cuprophan incubated in phosphate buffered saline showed a release of heparin due to the hydrolysis of the ester bonds between heparin and Cuprophan. The release rate could be easily adjusted by varying the amount of coupling agent used during immobilization. Cuprophan with a rather stable heparin coating (release rate: 6.1 mU/cm2·h) and Cuprophan which shows a substantial release of heparin (release rate up to 23.0 mU/cm2·h) could be prepared. Except when the release was relatively high, release rates were constant for at least 1 week. Storage of the release system at ambient conditions up to 6 months or sterilization by means of steam, ethylene oxide exposure, or gamma irradiation did not affect the release properties. It was concluded that this concept for a heparin release system is highly promising to prepare thromboresistant surfaces for various blood contacting devices