Design of Low cost Negative Pressure Wound Therapy

Transcription

1 International Journal of Engineering Science, Advanced Computing and Bio-Technology Vol. 8, No. 4, October December 2017, pp Design of Low cost Negative Pressure Wound Therapy *M.Kalayarasan 1, S.Mohanraj 2, T.Dineshmurugan 3, R.Sruthi 4, A.Naveen 5 PSG College of Technology, Coimbatore , India * mech.kalai@gmail.com, 2 bsrmohan@gmail.com, 3 tdineshmurugan74@gmail.com, 4 rpsruthi96@gmail.com, 5 navinmech905@gmail.com Abstract: The main objective of this project is to design a Negative Pressure Wound Therapy (NPWT) with an optimum cost. The existing model of Negative Pressure Wound Therapy has a problem that it is economically cost effective and the life span of the device is not more than 7 days. The reverse engineering is made on the current NPWT and the various parts are analysed. The Pressure regulation is analysed and evaluated. The material chosen for dressing has been analysed. The Bulb Vacuum System has been analysed and the possibility of combining with NPWT has been take into account. The parameters which have to be considered in developing the low cost Negative pressure wound therapy have been analysed. Key words: Negative Pressure Wound Therapy, reverse engineering, Bulb Vacuum System, cost effective, Parameters. 1. Introduction: Chronic wounds in India s increasingly diabetic and geriatric population are proving to be a daunting challenge for doctors, resulting in productivity and financial losses for patients. The Negative Pressure Wound Therapy (NPWT) System can be used to manage difficult wounds. It was originally developed as an alternative treatment for debilitated patients with chronic wounds and has rapidly evolved into an accepted treatment of chronic and acute wounds, as well as wound complications from failed operations. NPWT uses subatmospheric pressure to promote healing by (1) Maintaining a moist wound healing environment while removing stagnant wound fluid that may contain pro-inflammatory mediators (2) Optimizing wound perfusion (3) Mechanical stretching of the cells, this results in increased vessel formation and granulation tissue formation. (4) Managing the bacterial colonization in the wound. NPWT can also be used for wound bed preparation and bolstering grafts, incisions, and living skin equivalents. The Negative Vacuum Pressure Wound Therapy (NPWT) is a device used to heal the wounds at a much faster rate. The NPWT device used in KOVAI MEDICAL CENTRE & HOSPITAL, Coimbatore costs approximately INR 20,000 and the life span of the device is not more than 7 days. The simplified NPWT design in use does not draw fluid out at the wound site to keep it clean and sanitary but requires disassembly of the wrapping in order to clean the wound. Although it provides a strong negative pressure vacuum, some of this Received: 10 August, 2017; Revised: 02 September, 2017; Accepted: 14 October, 2017 *Corresponding Author DOI: /ijesacbt/2017/49245

2 224 International Journal of Engineering Science, Advanced Computing and Bio-Technology power could be sacrificed for a decrease in size and an increase in portability. The major concern with this device is the cost and life span of the device. 2. Working of NPWT: Negative Pressure Wound Therapy is a treatment that aids in the healing of wound injuries by increasing blood flow to the target area and promoting the formation of granulation tissue. Italso helps in removing and draining fluid and prevents leakage, decreasing both the amount and rate of infection and bacterial growth, assisting in closure, and providing protection from the surrounding environment. Such a device typically is comprised of: 1) A gauze or wound dressing to fill the cavity 2) A drainage tube held near the area of injury, sometimes inside of the dressing 3) An adhesive sealant placed at the top of the dressing to create an air- tight seal, 4) A container or outlet for the fluid drained from the injured area, and 5) A low-pressure (around 40 to 200 mmhg, depending on severity and depth) vacuum to create negative pressure. The dressing of the wound is likely to last no more than three days and thus requires frequent replacement. According to the Food and Drug Administration, NPWT is proven to provide aid to chronic wounds, burns, diabetic and pressure ulcers, acute wounds, traumatic wounds, and dehisced wounds. In terms of clinical proof, NPWT has been shown to increase the rate of healing by 300% and, in some cases, even more. This study aimed to simplify current negative pressure wound therapy systems and to significantly improve upon simplified versions that already exist for potential application in underdeveloped countries and in domestic first- aid kits. 3. Methodology: The methodology for the design of low cost Negative pressure Wound Therapy is to first identify the Healing process of wounds followed by reverse engineering on the device, then to study the functionality of the existing component. After this compare the working of bulb system and NPWT by finding the pressure of the bulb vacuum system. In order to develop into a working model study the parameters. This methodology helps to build a low cost NPWT device. 4. Reverse Engineering: The first step towards the design of low cost Negative Pressure Wound Therapy is to study the currently available NPWT device. The Power ON/OFF button is the indication for wrong dressing (i.e.,) in case of air leakage from the dressings and OK signal if everything is set well

3 Design of Low cost Negative Pressure Wound Therapy 225. Figure4.1: Outer cover On performing the reverse engineering process on the device, the components involved have been analysed. There is a pressure regulator which is connected to the inlet of the suction which helps to maintain the region within a desired pressure (i.e., 75mm of mercury). The device also consists of a PCB board which helps to maintain the desired pressure throughout the process of healing. On other words there will not be either rise or fall of desire value of pressure. Figure4.2: Inner portion of NPWT Figure4.3. PCB Board Setup

4 226 International Journal of Engineering Science, Advanced Computing and Bio-Technology The PCB board setup consists of a very Complex Circuit, which contains resistors, capacitors, microprocessor etc. The tube which is connected to the dressing is made as an inlet to the Suction unit (i.e., Micro-diaphragm pump). The micro diaphragm pump runs at 3A current and DC 3V. The Pump is eccentrically connected to the rotor of the motor. The Power Source for the motor is generated from the battery. The tube from the dressing is connected to the inlet of the pump and the outlet is made as free to the outside environment (atmosphere). 5. Cost Analysis: After completion of the Reverse engineering process we started studying on the major cost contributing components and it is shown in the following table. DESCRIPTION COST USD Vacuum pump & Motor $23.51 INR 1410 Dressing $25 INR 1500 SUM INR 2910 Total cost of the device $333 INR PCB Board and other Miscellaneous cost RUPEE INR INR 2910 = INR As the cost of the pump and motor and dressing is comparatively less than the PCB board and other miscellaneous cost. The ultimate aim is to eliminate the need of PCB board or to find the alternative to function the PCB board properties with minimal cost. 6. Bulb Vacuum System: The bulb vacuum system consists of a bellow plunger head which helps to create the suction in the desired region. Figure 6.1: Simplified NPWT

5 Design of Low cost Negative Pressure Wound Therapy 227 A. Pressure Calculation: Method 1: Using Flow sensor the ultimate aim is to measure the suction pressure of the bellow type plunger. In Sensorics Lab with the help of flow sensor, the pressure was found to be 0.2 Bar or 150 mm of Mercury and 6 lpm. Figure 6.2: Pressure measurement using Flow sensor In this method, we externally applied pressure to the Bulb Vacuum system and measured the pressure. For further verification of the pressure, we go for pressure measurement using Manometer principle. Method 2: Using Manometer To confirm the pressure the U- Tube Manometer principle has been used. The catheter itself was made into a U- Shaped tube. Before that the capillarity of the catheter is to be checked. Capillarity: It is the ability of a liquid to flow in narrow spaces without the assistance or even in opposition to, external forces like gravity. It is observed that the tube has no capillarity effect and is well suited for undergoing the manometer process of pressure measurement. Figure 6.3: Capillarity effect The following figure 6.4 shows the procedure for performing the pressure measurement using U- Tube manometer. The bulb is initially in the expanded form; we then compress it to the maximum level and close the regulator valve.

6 228 International Journal of Engineering Science, Advanced Computing and Bio-Technology Figure 6.4: Manometer principle When the measurement is to be made the regulator valve is opened so that air can get inside the Bulb and make it expand. While air gets into the Suction chamber there will be a difference in the water level between the tubes. Figure 6.5: Procedure for pressure measurement We have to measure the pressure by determining the difference in the water level in both the tubes of the U-tube manometer Figure 6.6: Water level inside the tubes

7 Design of Low cost Negative Pressure Wound Therapy 229 The difference gives us the pressure head h. From this we can measure the pressure by using the formula P = ϱ * g *h. As the fluid get enters into the extension tube, the difference in the height could not be determined and it is difficult to measure. P = ϱ *g*h Where H cannot be determined, as it get enters into the suction chamber. Figure6.7: Back Flow of fluid into the Chamber B. Drawback: The size of U- tube manometer has to be taken to into consideration for accurate measurements (i.e., the length and diameter of the U-tube Manometer) C. Specification: Wall thickness mm Outer diameter mm Inner diameter mm Length of the tube - 345mm Using this length of the tube, the water gets into the suction unit and hence it is not suitable to measure the pressure. 7. Parameters: The parameters to be considered for the development of low cost negative pressure wound therapy are, 1. Dressing 2. Pressure sensor and regulator 3. Vacuum pump and motor 4. Micro controller The following information gives more knowledge on the parameters. Dressing:

8 230 International Journal of Engineering Science, Advanced Computing and Bio-Technology The dressing has to be selected based on the size of the wound. The dressing contains three layers. It has been assumed that it may contain a chemical layer with silica gel, fine tissues (cotton fibres + papers). The dressing bottom layer should have high hydrophilic property. The top layer of the dressing should have a property of water repellent. A dryness fraction test has to be conducted on the dressing. The dressing may also be made of Hydrogel. The hydrogel can be of synthetic (cheap) or Natural (costly).it also has a property to absorb liquid 400% of its weight. The pressure sensor, regulator and the pump, motor setup can be mounted on the Arduino board. Figure7.1: Arduino board MEGA 2560 The procedure for using the Arduino board is, 1. Get an Arduino board(mega 2560) and USB cable 2. Download the Arduino Software (IDE) 3. Connect the board Connect the Arduino board to your computer using the USB cable. The green power LED (labeled PWR) should go on. 4. Install the drivers 5. Launch the Arduino application 6. Select your board You will need to select the entry in the Tools -> Board menu that corresponds to your Arduino.

9 Design of Low cost Negative Pressure Wound Therapy Select your serial port 8. Upload the program A few seconds after the upload finishes, you should see the pin 13 (L) LED on the board start to blink (in orange). 9. Conclusion: Classical electric NPWT pumps require a consistent power source to supply a vacuum. System inefficiencies, such as air leaks, require a greater input of power for the desired function (200 watt maximum, Hz electrical supply). Also, current battery life in the portable units is well below 24 hours. The foremost dilemma is cost. This high cost may be partially attributed to digital readout screens, microprocessors to regulate vacuum strength in compensation of air leaks, and the need for a trained medical professional to apply the system. Even in the developed world, NPWT devices are widely considered to be too expensive for the treatment of minor wounds. Prior studies indicate that a pertinent NPWT issue is associated with changing dressings and patient mobility. Thus a simpler light weight design focusing on patient mobility and low cost is taken into consideration. The current pressure measured is averaged to be 150 mm of mercury but the requirement for the effective functioning of the device is to maintain the pressure at 75 mm of mercury. So a further study is required on the use of Arduino board incorporating all the controllable parameters, the dressing to be used and finally make it a better replacement for the existing Negative Pressure Wound Therapy device. Acknowledgement: The authors offer sincere thanks to Dr. Shegu Gilbert and KMCH for being a source of strength and support throughout the course of this project. References: [1]. Higley HR, Ksander GA, Gerhardt CO, Falanga Extravasation of macromolecules and possible trapping of transforming growth factor-beta in venous ulceration. [2]. Barrick B, Campbell EJ, Owen CA. Leukocyte proteinases in wound healing: roles in physiologic and pathological processes. Wound Repair Regen [3]. Agosti J. Negative pressure wound therapy. [4]. AHRQ, Technology assessment. Negative pressure wound therapy devices. [5]. Dorafshar AH, Franczyk M, Gottlieb LJ, Wroblewski KE, Lohman RF. A prospective randomized trial comparing sub atmospheric wound therapy with a sealed gauzedressing and the standard vacuum-assisted closure device. Ann Plast Surgery

10 232 International Journal of Engineering Science, Advanced Computing and Bio-Technology [6]. Henderson V, Timmons J, Hurd, T, Deroo K, Maloney S, Sabo S. NPWT in everyday practice made easy. Wounds International 2010 [7]. Mendonca D Drew PJ, Harding KG, Price PE. A pilot study on the effect of topical negative pressure on quality of life. J Wound Care [8]. Authors Profile: M. Kalayarasan presently is working as Assistant Professor in PSG College oftechnology, Coimbatore. He completed his Master s degree in Engineering Design from Kongu Engineering College. He received his Bachelor s degree in Mechanical Engineering. His research interests are computational biomechanics, Machine tool Vibration and FEM. He has published several conference and journal papers related to this topic. S Mohanraj presently is working as Assistant Professor in PSG College of Technology, Coimbatore. He completed his Master s degree in Computer Integrated Manufacturing from PSG College of Technology. He received his Bachelor s degree in Mechanical Engineering. His research interests are High speed Machining, Machine Tool vibration, Finite Element Method. T.Dineshmurugan is an Under Graduate student doing his Bachelor Degree in Mechanical Engineering (SW) from PSG College of Technology. His area of interests is Design for Manufacture and Assembly, Manufacture and Inspection of Gears. R.Sruthi is an Under Graduate student doing her Bachelor Degree in Mechanical Engineering (SW) from PSG College of Technology. Her area of interests is Finite element analysis, Strength of Materials. A.Naveen is an Under Graduate student doing his Bachelor Degree in Mechanical Engineering (SW) from PSG College of Technology. His area of interests is CAD Modeling, Tribology.