DIY solutions for NPWT in low-resource settings

If you are not familiar with the basics of NPWT, we advise you to read through the other chapters on NPWT first. DIY- solutions for NPWT require some experience and sound knowledge of NPWT in general.

 

NPWT is a powerful modality for wound healing. Used correctly in the right type of wound there is no other modality in wound care with the same capabilities. However, commercially available NPWT pimps and kits are expensive, and usually not available in areas with limited health resources. Even the simpler commercial pumps, which use a spring-laden mechanism to achieve a negative pressure, are often too expensive for these areas in Africa.

 

There are many cheap workaround solutions for NPWT.   Before you embark on using an improvised method for NPWT be aware that you are doing so on your own responsibility. One of the significant advantages of modern NPWT pumps is that they have sensitive alarm systems, which alert the patient and caregiver of leaks, blocked tubes, low batteries, and other adverse events. If we use an improvised homemade system we do not have these alarm mechanisms and it is extra important to follow the treatment with vigilance. While NPWT is generally a very safe treatment method, a blockage of the tubes or failure of the suction mechanism can lead to severe infection within a few hours. As we have mentioned in several other chapters- an NPWT dressing is an airtight system- if there is no suction it behaves like a greenhouse for bacteria! For this reason, it is recommended to change the dressing if the suction has not been working for 2-3 hours.

Until about 15 years ago, even some university hospitals in western countries used homemade solutions for NPWT- some hospitals sterilized mattress foam as wound fillers, and commonly wall suction was used to establish a negative pressure. That was then, today most clinics in western countries use commercially available products.

DIY NPWT can be made from simple items for as little as a few dollars. You will need the following ingredients:

Transparent adhesive plastic film (occlusive drape)

 

An NPWT dressing is an airtight environment. To achieve this, you need adhesive plastic film. There is no perfect work-around solution for this. If you check around at different suppliers, you will find substantial price differences for these products. It is important that you use plastic film intended for use on humans – i.e., that it will not cause any skin reactions upon application. If you can only get hold of smaller sizes like 10x15 cm, that is fine; you can easily patch several smaller sheets to cover a larger skin area.

 

We know that some caregivers use cling wrap ( the kitchen product) for this. Be aware that it is necessary to wrap several layers of cling wrap around the area to be treated. There is a significant danger of wrapping it too tightly, which can harm the patient! You will also have to extend the cling wrap quite far, distally, and proximally from the area to be treated to achieve a good seal. We have found cling warp to be quite hard to work with, while others use this regularly. If you click on the image below, you get to an article published in Ghana, where cling wrap is routinely used with sterilized mattress foam as a wound filler.

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Figure 1 In this article by Nsaful and Gentil,2021 the authors describe a homemade NPWT method using sterilized nmatress foam and clingwrap.  Click in the image above to get to the oritnal article published at medcraveonline.com opyright: https://medcraveonline.com/IPMRJ/IPMRJ-06-00279.pdf

Especially for NPWT on hands and feet, single-use surgical gloves can be used to create an airtight environment. If you click on the images below it will luink you to an article by Gopal and Salomon, 2019 who explain this technique further and have illustrative examples of their results. The authors used a regular urinary catheteras tubing and wall suction as the source of negative pressure.

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Figure 2 Using a surgical glove to create an airtight environment for NPWT treatment. The authors used a urinary catheter as tubing and wall suction as the source of negative pressure. The glove mustn't be too tight not to impair blood circulation. It is also essential to place a good layer of padding underneath the course of the catheter to prevent pressure injury. Click on the image above to get to the original article. Copyright: https://onlinelibrary.wiley.com/doi/full/10.1111/iwj.13002

Wound filler

In commercial NPWT kits, the wound filler is usually a polyvinyl foam or cotton gauze.Commonly the gauze is impregnated with PHMB for antibacterial properties. Many kits contain a gauze calle Kerlix AMD. It sounds reasonable to have an antibacterial agent in a gauze.Gauze tends to collapse somewhat more under suction, and slimy exudate easily gets trapped in the gauze. Having an antibacterial agent in the gauze may inhibit bacteria from thriving within the gauze material, thus reducing the chances of infection. However, you can use regular cotton gauze for this purpose , but you need to follow the treatment closely.You can make antibacterial gauze yourself by soaking cotton gauze in 1% gentian violet solution and letting this dry, before application to the wound.Ideally the wound filler should be sterile- it is cheap and easy to sterilize cotton gauze in an autoclave.We have no experience as to sterilizing cotton impregnated with gentian violet – will the antibacterial properties of gentian violet be deactivated by autoclaving?

 

Concerning foam as a wound filler it is possible to make this from sterilized mattress foam. This type of foam is not identical to commercial NPWT foam.Matress foam is usually polyurethane foam (PVU) while commercial NPWT foam is polyvinyl foam ( PVA).However, PVU foam works well as a wound filler.Prior to using it it needs to be sterilized.Commercial NPWT are sterilized usinggas (EtO) or gamma radiation. This type of sterilization method is most likely not available to you. Both PVU and PVA foams do not tolerate high heat- in our experience most foams will, however, tolerate steam sterilization at 121 Celsius.You will have to test different foams available to you and check how they feel after sterilization.Some advanced autoclaves have low temperature sterilization settings, but these are special autoclaves that are most likely not available to you.

 

Some years ago we routinely used the foam from surgical sterile brushes ( used when surgeons are scrubbing in) as a wound filler for NPWT.These can usually be bought quite cheaply. The foam is easily torn off the back of the brush and can be used directly in the wound and cut to shape.The disadvantage is that they are small in size and are not convenient for more extensive wounds.

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Figure 3 Sterile surgical scrubbing brushes have soft foam on one side. This foam can easily be torn off and works very well as a wound filler for NPWT.

Tubing

The wound needs to be connected to a suction pump- for this purpose; you obviously need tubing. The tubing diameter depends on the connections- a 16 French tube is usually a good choice, though smaller diameters also van work if the exudate is not too viscous. Use a tube material that does not kink too easily. Tubes from iv lines can work reasonably well for this. Nasogastric feeding tubes are also a good alternative. Urinary catheters will also work- basically, any rubber tube can be utilized for this purpose. The end of the tube that lies over the wound filler should be perforated at multiple sites. You can easily cut small perforations using a fine scissor.

Exudate collector

Unless you use a bellow for suction or a syringe, you will need a collector for exudate so that the fluid will not enter the pump. A jar with a metal lid can function well if you get a good seal around the tubes entering and exiting the jar. The problem is often that the exudate may accidentally enter the exit tube if the jar is turned upside down or is very full. If you fill the jar halfway with cotton wool, this can work as an absorbent preventing the fluid from moving around freely. 

Sealant

It is very useful to have a sealing agent at hand. Stoma paste with high viscosity is suitable for this, and we do not know of any skin-friendly substitutes for this. Do not use industrial type silicone used for sealing edges in bathrooms- these types of silicones often contain additives that may cause significant irritation on the skin!

A suction mechanism

The biggest challenge for DIY NPWT is finding a suitable suction mechanism. Here we have several alternatives:

Bellow NPWT pump

 Bellows are usually quite cheaply available also in Africa. TIn many low-resource regions of the world bellows are used as NPWT devices. There are a few commercially available bellow systems specifically designed for NPWT. As with the syringe systems we cannot be sure as to how much the exact negative pressure is exerted when using a bellow – but usually this is somewhere around -50 mmHg depending on the bellows size, material and how much it is compressed upon activation. The bellow collects exudate aswell and should be emptied at least once daily. The use of a bellow for NPWT is very straight forward and is really the recommended choice for DIY NPWT.

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Figure 4 A PhD candiadte at the Massachusets Institute of Technology developed this commercially available bellow NPWT device. It costs about 3 US Dollars to make. Click in the image above to get to an article about this device. Copyright:  Zurovcik, Danielle R., Gita N. Mody, Robert Riviello, and Alex Slocum. “Simplified Negative Pressure Wound Therapy Device for Application in Low-Resource Settings.” Journal of Orthopaedic Trauma 29 (October 2015): S33–S36.

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Figure 5 Most bellows used for surgical exudate management will provide adequate suction for NPWT. They have many advantages. They are cheap, do not require an electrical supply or maintenance, and allow the patient to ambulate freely. The bellow may be carried around in a small shoulder bag.

Syringe method

A syringe can be used as an NPWT pump. A 50 ml syringe is very suitable for this. The suction pressure will depend on the syringe volume and how much force you have used to pull back the piston. In reality, you don't have any way of knowing how much suction you have applied. In some papers, we read that pressures of around -250 mmHg have been measured from syringes when the piston is pulled back. This is a much higher negative pressure than we use with regular pumps. However, for some reason, this works fine nevertheless. We plan to do some more research on this and do some pressure readings with different sizes of syringes. To be on the safe side: as you pull back the piston, feel the resistance- once you have "reasonable" resistance, stop here and lock the piston with a hairpin, as shown below. 

 

Having a three-way connector is very useful: initially, as you start the "syringe pump" by drawing back the piston, you may have sucked out so much air ( especially if it is a large wound) that the syringe is full of air – then you can use the three-way connector to expel the air and then with the next pull on the piston you will achieve negative pressure. Tubing form iv lines with a Luer lock are helpful for these connections.

Once the piston is withdrawn and you notice resistance, pull back a few millimeters more and lock the piston into place with a hairpin ( bobby pin) or something similar- see image below. You will have to drill ( or burn) a small hole in the piston stem beforehand. Drill the hole once you have established how far you will pull the piston back. In other words- do a trial first- pull the piston back, and when you notice resistance, you mark the area where to drill the hole for the pin. 

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Figure 6 This technique was explained by Watson and McFadden in an article in Todays Veterinary Practice. It involves creating suction with a syringe and then locking the piston with a hairpin or something similar. Click on the image above to get to the original article. Copyright: https://todaysveterinarypractice.com/soft-tissue-surgery/surgical-drains-indications-types-and-complications/

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Figure 7 A three-way connector ( three-way stop cock) is useful when using a syringe as a suction pump for NPWT.  It makes it slightly neasier for the patient to empty the syringe from accumaulated exudate and to restart the suction, without having to disconnect anything.

The syringe also works as a canister for exudate, and the exudate should be emptied from the syringe dialy or even several times daily if there is a lot of exudate. Here again the three way connector is very useful as exudate can be expelled through this. All NPWT dressings have some leakage. If you have a commercial pump this will compensate for some leakage. Using a syringe does not compensate for much leakage. It is crucial to instruct then patient on how to  re-activate the syringe pump several time daily and always before going to bed.

When using the hairpin ( bobby pin) method the negative pressure will gradually decrease in the course of a few hours due to minute leakages which are unavoidable. If we want to make a more advanced NPWT from a syringe we have to incorporate some sort of spring mechanism that exerts a constant pull on the piston, thus compensating for minor leakages. We have experimented with this – the challenge is to make or buy a spring of  a suitable size for this purpose. Most hardware shops in Africa should have springs in different sizes available, but even a corner shop mechanic may be able to make this out of a clothes hanger or other metal wire.

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Figure 8 Using a custom-made spring to fit behind the syringe's piston, a reliable suction device can be made. The advanatge of this method is that it maintains a more constant suction force as compared to the syringe/hairpin method described earlier. Click on the image to get to the original article. Copyright: Igwe et al 2016, science direct: International Journal of Surgery Case Reports Volume 20, 2016, Pages 30-32 creative commons attribution: non-commercial

Another method is to fasten the syringe to a stand- the syringe's piston pointing to the floor. A suitable weight is then attached to the piston providing a constant pull on the piston. It is usually enough with 200-300g of weight to achieve a constant force on the piston. Incidentally, it is possible to combine two syringe pump methods: During the day when the patient is ambulating and performing chores they can sue the hairpin method – at night the patient can use the latter method to ensure that there is sufficient negative pressure during the entire night.

A pitfall of the syringe method is that sometimes the rubber on the piston becomes less flexible in the course of a few days- especially in cheap syringes. This can cause the piston not to glide easily and when using the syringe or weight method this can lead to failure of the suction mechanism.

The advantages of the syringe method is that it is a very cheap method, the downsides are that it has some pitfalls and it requires a high level of vigilance during the treatment.   If there is a lot of leakage, it will not work well- the patient should not be required to re-activate the syringe every half hour. If you have achieved a good seal the syringe should not nedd re-activation more than about three times a day.

Using wall suction

In modern institutions, there is usually a system for central suction available. Commonly each patient room should have a connector for suction available. Before our institution purchased NPWT, we used wall suction for NPWT treatment. The downside is that the patient is "chained" to the bed; depending on the length of the tubing, they cannot ambulate more than around the bed.

From our experience, most hospitals in Africa do not have functioning wall suction due to technical breakdowns that have never been fixed.  

When using wall-suction, you need a container to collect exudate between the patient's wound and the wall connection. You also need a manometer to know what pressure you are operating with. Wall suction can generate very high pressures that can harm the patient. When using NPWT, we want the pressure to be around 50-130 mmHg.   Be aware that many manometers have other units in the display – often bar, psi, or kPa! Sometimes the gauge is in inches Hg, not mmHg. So check the gauge carefully and instruct your colleagues to read the meter correctly.    We have had cases where a patient was treated with wall suction where the wall suction accidentally was turned onto maximal effect, resulting in a negative pressure of over 250 mmHg!

Other suction pumps used at hospitals

If you are working at a hospital, check around whether there are any old models of aspiration suction pumps that have been taken out of service. These make suitable NPWT pumps but are, of course, dependent on a power supply.

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Figure 9 Older models of surgical aspiration/suction pumps taken out of service will still work perfectly as an NPWT pump. 

Modification of other pumps

If you google " air suction pump" or vacuum pump," you will find a multitude of pumps that can be modified to use as an NPWT pump. Aquarium pumps, for example, can make an excellent NPWT pump. They are usually cheap and small in size. Turning an aquarium pump into an NPWT requires some slight modifications. The video below from the Phnom Penh children's hospital in Vietnam explains the modification process.

Video 1 A video by the Phnom Penh Children's hospital explaining how an inexpensive aquarium pump can be converted into an NPWT pump with only slight modifications. 

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Figure 10 A link to an article showing the results of NPWT using a modified aquarium pump. 

Using a large industrial air vacuum pump to treat several patients simultaneously

The safest is to start with NPWT when the patient is admitted to an institution, as you can monitor closely how the wound Is performing. If you often have patients who will benefit from NPWT but do not have commercial NPWT pumps or wall suction available, you can invest in a regular air suction pump used for industrial purposes. These pumps are powerful so that they can treat multiple patients simultaneously. So if you dedicate one room at your institution to NPWT treatment, you can easily manage this with only one such suction pump. These pumps are usually available from about 100 US Dollars and upwards. 

Each patient will be connected to the pump with their own tubes, and there has to be a fluid collecting canister for each patient separately. There is no/little risk of cross-contamination as the pump only has suction.   We have drawn a  simple diagram below for a possible setup with this type of pump. You will need several connectors/adapters for this setup, which can usually be obtained from most hardware shops. If you are using NPWT regularly in patients, you could even place the pump in a separate room to avoid having a noisy pump in the patient room. With basic plumbing skills, you can then lay a central line into the patient room as we have for wall suction in modern hospitals. The downside of this system is that it relies on electricity. In most areas of Africa, power shortages are a common problem, and if your hospital does not have a functioning diesel generator, you will have to have emergency measures available. You could, for example, connect the patient to suction bellows when there are power cuts. Another downside is that the patients are "chained" to the room when using this

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Figure 11  An industrial air suction pump can be purchased relatively cheaply, sometimes as cheap as about 100 US Dollars. This type of pump is strong enough to simultaneously treat many patients with NPWT. This can be a good alternative if you are working at an off-the-grid hospital where you do not have access to air suction built into the walls. To avoid having a noisy patient pump in the room, the pump can be placed in another room as long as you have long enough tubes. Be aware that each patient needs to have their own exudate collection canister and this needs to be emptied regularly to avoid contaminated exudate from reaching the pump.

DIY NPWT with irrigation

Once you have mastered making a DIY NPWT dressing, it is very easy to adapt this to make an irrigation dressing. NPWT with irrigation/dwell time is also termed NPWTid.  This means we can let saline or an antibacterial solution enter the wound filler, let it dwell there for some time, and then suck the fluid up when the suction is switched on again. The most advanced pumps can do this in an automated process. When we do not have the resources to buy such a pump, we have to do the process manually. 

NPWTid is undoubtedly the most effective NPWT method available- by far. The regular irrigation of the wound reduces the bacterial load very well, allowing us to deal with quite complicated wound situations. Using NPWTid also allows us to extend the shift intervals, sometimes up to 7 days. Overall, it appears that wounds granulate better using NPWTid than using regular NPWT. 

 

NPWTid works best when we use foam as a wound filler as opposed to gauze. It is usually sufficient to irrigate the wound about every third hour. The dwell time depends on how clean the wound is, how heavy the bacterial burden appears to be and what type of irrigation fluid we are using. The volume used to irrigate the wound is usually equal to 50% of the volume of the wound filler. If we, for example, have a piece of foam that is about 3 x 4x 3cm, then this is equivalent to a volume of 30 ml- we should install at least 15 ml of irrigation fluid at each irrigation cycle. Today, there is no general consensus on how often wounds should be irrigated, recommended dwell times, and which irrigation fluid to use. Our knowledge about this today comes from personal experience and expert opinions. 

 

So how do we go about making a DIY NPWTid dressing? There are several ways to do this. A simple method is to use an iv cannula, stick this into the foam, discard the needle, and secure the plastic cannula with adhesive tape. Every third hour or so we can let the irrigation solution drip into the wound filler. The suction is stopped during this process. The drip line is clamped at the end of the dwell time, and suction is started again. An even simpler method is to inject the required volume with a syringe into the wound filler and then seal the tiny puncture hole with a small piece of transparent adhesive film. 

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Figure 12  Using an iv cannula to puncture the NPWT dressing for irrigation and dwell treatment. The iv line can be clamped and the iv cannula left in place when suction is started again.

Another solution is to attach a three way connector to the suction tube. In this way the connector can be closed towards the suction side while the irrigation/dwell process is taking place. This variant is a good solution when the patient is treated at home. The patient himself or family members can easily be taught how to carry out the irrigation/dwell procedure when using the three-way connector. 

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Figure 13  Using a three-way connector ( also known as a three-way cock) for irrigation and dwell treatment. 

Another solution is to have two tubes inserted into the NPWT dressing- one is for suction, the other is for irrigation/dwell.  The video below is an example of this technique.  In the video the authors refer to the technique of installing irrigation solutions as ChemoVac. 

Video 2 In this video, Dr. Glass explains making a simple irrigation NPWT dressing. In the video the technique is termed "Chemovac Dressing" indication that chemotherapeutics like antibacterial solutions and other therapeutic irrigation solutions can be applied by this method. copyright: www.drglass.org

Getting hold of used commercial NPWT pumps

 

Many institutions in western countries dispose of their NPWT at 5-10 years intervals. Some discard the pumps, others return them to the producers. If you have any network to wound care institutions in western countries you can ask them if you can get these pumps once they are taking out of service. In most cases these pumps are still fully functional. Most NPWt are very solidly built. We still have some of the earliest BlueSky Medical pumps form 20 years ago and they still work well.   If you have some financial resources you can also buy used pumps at places like ebay. The costs of NPWt pumps here is about a third of a new pump. Be aware however, that for most pump models you have to buy a canister that only fits for that specific model. These canisters are often surprisingly expensive. However, as always, there are also work-around solutions for this – with some homemade connectors you can use a commercial pump with  another collection chamber for the exudate.

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Figure 14  Buying pre-owned NPWT devices on sites like ebay is an alternative if you have the resources.  Used NPWT will usually come at a fraction of the original price.  Be aware that you will have to buy expensive exudate canisters for these types of pumps but you can modify the connections to fit DIY exudate collectors.  However, unless you can afford the single use cannisters, we do not recommend you to buy these pumps. 

Leasing pumps

In many western countries, institutions lease the pumps for “ free” and pay for the pumps indirectly by purchasing the single use NPWT dressing kits and canisters. If you are working at an institution where the initial investment of purchasing a pump is too daunting for the finance department, a leasing model may be something they will accept.

Looking for some inspiration?

Read the article in AlJazeera about a small hospital in Cameroon that has established a wound clinic where NPWT is also offered. Click on the image below to get to the original article:

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Figure 15  An inspiring article about the Balaveng Hospital in Cameroon specializing in wound treatment. NPWT is part of the wound treatments offered here. Click on the image above to get to the article. Copyright: https://www.aljazeera.com/gallery/2018/10/25/the-hospital-in-cameroon-trying-to-heal-old-wounds