The Trinity of PICO; unearthing the mode of action
This podcast will discuss the science, evidence and mode of action supporting the use of PICO 14 sNPWT for chronic wounds.
Welcome to Smith & Nephew's Closer to Zero Podcast. Bimonthly podcast with leading experts in wound care hosted by Smith & Nephew, helping healthcare professionals in reducing the human and economic cost of wounds.
Hello, I'm Ruth Timmins from Smith & Nephew and it's my pleasure today to host this podcast discussing the science behind the use of PICO 14 for chronic wounds. Our special guest today is scientist Runi Brownhill, who is pivotal in the research program to identify the mode of action of PICO. So welcome, Runi. Thanks for joining us today all the way from the UK. Why don't you tell us a little bit about yourself and your role and what you do.
Thank you, Ruth. My name is Runi Brownhill. I'm a scientist in the AWM, R&D business. My expertise is in the field of wound biology and interventions needed to improve patient outcomes. I have a PhD in pharmacology and I have been at Smith & Nephew for over 11 years now. I was born in Sri Lanka, I was educated in a range of countries, and now my parents actually live in New Zealand. So working with the APAC ANZ teams makes it feel like home. So thank you, Ruth.
Oh, it's great for you to join us today and it's a fascinating title, 'The Trinity of PICO', unearthing the mode of action in our podcast today. So, firstly, can you help us understand, you know, we know probably PICO is used in the closed-incision wound type but it's also being promoted for chronic wounds. Can you sort of just discuss that a little bit with us?
Ruth, you're absolutely right. To date, we have been using PICO very successfully on closed incisions with great outcomes. But as a scientist representing the R&D community, when we designed this product, we designed it in such a way that it can be used not just in closed incisions but also on chronic wounds. So let me give you some evidence of its use in chronic wounds. You guys must be aware of our recent Kirsner (1) study by now, which was designed to show exactly that. Can PICO work on chronic wounds? And here, we compared PICO to traditional negative pressure wound therapy.
Well, we were expecting non-inferiority. We wanted to show PICO was the same as traditional negative pressure wound therapy, but what we actually saw was quite unprecedented. PICO was actually superior to traditional negative pressure wound therapy. The results showed a greater than 50% relative increase in wound closure rates with PICO (1). This is quite outstanding. So, yes, PICO was not only designed for chronic wounds, it can actually work superior to traditional negative pressure in these wounds.
OK. So, Runi, if you think about open wounds, they have exudate which needs managing. So, as we know, PICO has a dressing, not a canister. So how does it do the same job as a device with a canister?
Ruth, it sounds magic, doesn't it? Let me take you back to the use of negative pressure for wounds. We know that it has a rich history which dates back to ancient times. The idea was to remove this unpleasant substance coming out of the wound, the exudate, and lock it away from the wound to allow the healing to occur. So it meant having a canister and a pump to do the job. But by virtue of having a canister and a pump meant that the system was quite bulky. So there was a lot of innovation that went on in this space for quite a while where the focus was all around miniaturising the pump and the canister to make the device smaller and portable.
But here's the thing, Smith & Nephew were the first to think outside this box. We thought we can actually ditch the canister altogether. Instead, we replaced it with a dressing and a smaller pump, and this was the birth of PICO. Let's think about the PICO dressing. It has a silicone interface. It has a layer that transmits the pressure, the AIRLOCK™ technology. This is a non-compressible. And even if it's wet, it allows continuous transmission of negative pressure. It also has a super absorbent core to lock the exudate away from the wound. And on top of all of that, it has a top film. This is where some of this magic happens. It allows evaporation of up to 80% of the absorbed exudate. So this is the reason why we can use a dressing instead of a canister. Let me use an analogy to explain this further. Think of a tree. It absorbs the water from the roots and the leaves evaporate it. So like that, our dressing absorbs the exudate into super absorbent core and then the chemistry of the top frame allows evaporation. So the dressing can keep absorbing and keep going.
That's a really great analogy there explaining how the dressing works. So typically, we know that traditional negative pressure is using the -125mm of mercury but PICO delivers the -80. So why is that and how does that work?
When you look at the literature, there's a huge therapy range. Data show it can be anything from -50 to -150. But when the pressure is lower to, let's say, -25, therapy becomes ineffective. In some comparative studies, they actually show no differences in the wound area after treatment with either -50, -75, or -125. Also, a blood flow study has shown that the effect is optimal at -80 and it's not further increase going higher to -125. But if you lower it to -40, you only see half the effect. And preclinical studies showed that maximum biological effect can be seen at -80. Also, the latest European Wound Management report on negative pressure summarises that between -75 and -125 to be clinically effective.(2) Typically, you need a higher suction pressure when you need to remove the exudate into a canister. But when we have a dressing that helps absorb the fluid, you don't need high pressures. So the key is PICO is effective at -80.
So now we know the dressing can handle the exudate without a canister and the negative pressure setting in PICO is effective, but you mentioned the Kirsner study and it gave unexpected results showing PICO to be more effective than traditional negative pressure(1). So how can that be?
Now, I'm getting very excited. You're asking about a topic that I have been living and breathing over the last year or so. This question was given to R&D as a challenge. So we took it on. We conducted a series of investigational studies to establish the mechanism of action of PICO and compare it to traditional negative pressure. We used a range of models. We used ex vivo tissue models as well as a pig wound healing study. This gives an ideal system to investigate healing mechanism.
The overall message from all of these studies led to the conclusion that this superiority of PICO can be put down to three key attributes(3-5). Firstly, PICO provides undisturbed healing because it can be used without a filler and also without frequent dressing changes. Because of this, it allows the wound to granulate, it allows the granulated tissue to mature, and it also allows the wounds to re-epithelialise and bring about closure.
Secondly, PICO provides a wider zone of therapy due to the unique construction of the dressing with this AIRLOCK™ technology. So it gives benefits, not just at the wound site, but over a wider area to support the wound and the surrounding skin. Finally, PICO demonstrated complete portability and simplicity. This allows patients to be fully compliant with the therapy, which means it can be used effectively throughout.
So I like to think of these attributes as the trinity of PICO, the undisturbed healing, the wider zone of therapy, and the portability and simplicity. All three working together is what makes PICO superior.
OK. So that's really interesting. So maybe you could give us a bit more detail into each of those attributes. So, you mentioned undisturbed healing. So, you know, how does that work?
Yeah, sure. Let's first talk about the undisturbed healing benefits. In the Kirsner clinical study, over 80% of the wounds treated with PICO didn't use a filler and they also had significantly less dressing changes compared traditional negative pressure wound therapy(1). We mirrored this in the pig wound healing study to explore the mechanisms.
And here, we saw that PICO treated wounds contracted in a similar manner to the traditional negative pressure groups. But PICO wounds went on to re-epithelialise and achieve faster closure. When we looked at the granulation tissue through microscopic analysis, we saw that even though the traditional negative pressure-treated wounds fill faster, the quality of this tissue was very different. The tissue was more advanced in the PICO treated wounds. What I mean is that it had more collagen. And not only that, it was a more mature form of collagen.
So you can say that these wounds in the PICO group were at a more advanced stage of healing. Not only that, the microscopic images of the granulation tissue identified trapped filler material when treated with traditional negative pressure. This led to foreign body reactions, which meant there were lots of inflammatory cells in this tissue. So when the wounds were treated with traditional negative pressure, it can be more inflamed. But when we treat it with PICO, you don't get that.
We also looked at what was happening during the dressing changes in the pig study. Again, there was differences between the therapies, where there was a lot of trauma and damage to the wound surface during traditional negative pressure use. But this wasn't the case with PICO. So to your question, Ruth, what does undisturbed healing mean and how is it beneficial?
What we're saying is that when we treat PICO indicated wounds like the ones in the Kirsner(1) study such as DFUs and VLUs, we can reduce dressing changes, we can provide a more mature granulation tissue, we can provide less inflammatory tissue, we can reduce the trauma at dressing change, and ultimately, re-epithelialise the wound and close it.
OK. So could you explain a little bit more about the wider zone of therapy benefits of PICO? You mentioned that term, and maybe some people aren't familiar with that concept.
When we did CT X-ray imaging and pressure mapping of ex vivo pig tissue, we obtained these wonderful images that showed how the tissue underneath the dressing was behaving. What we saw was, under the PICO dressing, there is tissue compression and this extends beyond the wound. But with traditional negative pressure, the tissue displacement is fairly localised to the wound site. So this wider distribution of therapy with PICO can help us with providing benefits that go beyond the wound.
An example of this is the ability to reduce oedema. We have seen this with the application of PICO in patients, for example, after spinal surgery. Typically, here, a lot of bruising to the surrounding skin from the use of tissue spreaders can happen. But after PICO application, the surrounding skin looked very similar to the normal skin with no real oedema or bruising. Now, let's consider the interface where the dressing contacts the skin. This is also very important. In our pigs study, we show that the skin surrounding the wound remains uncompromised with PICO therapy. The skin barrier obtained through TEWL measurements was similar to normal skin. TEWL stands for Transepidermal Water Loss, and it's a measure to look at the barrier functionality of the skin. The skin moisture was also not elevated unlike with traditional negative pressure applications. The erythema and redness surrounding the skin was also not elevated.
Overall, the skin surrounding the wound under PICO remains uncompromised. And this means this region may be less likely to undergo damage or maceration. So let me summarise the wider zone attributes of PICO as, A, it provides tissue compression that goes beyond the wound. So it can help with, for example, reducing oedema. B, it provides an uncompromised skin surrounding the wound thereby reducing the risk of damage and maceration.
OK. That's really helped to explain that attribute. And you also mentioned about portability and simplicity, can help. So could you elaborate a little bit more on that attribute?
Sure, Ruth. This is something very easy to visualise because if you put the PICO dressing next to traditional negative pressure systems, it is obvious, PICO looks simple and portable. And not only that, it's less scary. And this is very important, not only to the patient, but also to the caregiver because they can simply pick it up and use it. So how does portability and simplicity of PICO work in improving chronic wound outcomes? The Kirsner study showed that there was fewer dressing applications which meant that the dressing had longer wear times. The exit interviews with the patients in the Kirsner study also reported significantly greater satisfaction with PICO where improvements were seen with comfort mobility and sleep(1). Also, a large community evaluation in Canada showed positive patient and nurse experiences with PICO, with both parties reporting satisfaction and confidence with the device and the dressing performance. So all this means is that the portability and simplicity element of PICO offer advantages at a patient and nurse level. This leads to greater acceptability of the therapy, which means it can go onto improving patient outcomes.
Yes, and we know it's really important that the patient is on board with the therapy. And if it helps with things like sleep and their daily living, then that's really, really key, isn't it? So, wow, that's a lot of data that supports PICO and the mode of action. But, I guess, how would you sort of summarise the key messages of PICO therapy, please, Runi?
So this trinity of PICO, the three attributes, this is very powerful. So if I were going to summarise the three attributes, I would say, firstly, PICO provides an improved environment that enables healing to occur in an undisturbed manner whilst allowing re-epithelialisation. Secondly, this is aided by the PICO dressing with the AIRLOCK™ technology and deliver negative pressure throughout the dressing. And because of that, you can achieve therapy benefits across a wider area extending beyond the wound. And finally, the portability and simplicity of PICO offer benefits to both patients and clinicians. So all of this leads to improving clinical outcomes.
Well, thank you, Runi. That's given us some fantastic insights into the science that supports PICO, and particularly in its use in chronic wounds. So thank you so much, again, for joining us today and thank you to our listeners, and be sure to join us for our next podcast.
At Smith & Nephew, we are proud to provide you with continued innovations in negative pressure wound therapy. Our latest technology, the PICO 14 single-use negative pressure wound therapy system with AIRLOCK™ technology, has been designed with a pump duration of up to 14 days and is aimed for hard to heal and deep wounds. Early intervention with PICO has shown a 94% success rate in healing versus standard dressings 6. For more information on how PICO can kick start the healing trajectory of your chronic wounds, contact your local Smith & Nephew representatives or email us at firstname.lastname@example.org.
The information presented in this podcast is for educational purposes only. It is not intended to serve as medical advice. Products listed and outline of care are examples only. Product selection and management should always be based on comprehensive clinical assessment. For detailed product information including indications for use, contraindications, precautions, and warnings, please, consult the product's applicable instructions for use prior to use. Helping you get closer to zero delay in wound healing.
- Kirsner R, Dove C, Reyzelman A, Vayser D, Jaimes H. A Prospective, Randomized, Controlled Clinical Trial on the Efficacy of a Single‐use Negative Pressure Wound Therapy System, Compared to Traditional Negative Pressure Wound Therapy in the Treatment of Chronic Ulcers of the Lower Extremities. Wound Repair Regen 2019; 27:519-29.
- Reference: EWMA Document: negative pressure wound therapy. Journal of Wound Care, Vol 26 No. 3, Supplement EWMA Document 2017
- Brownhill etal., 2019. Pre-clinical Assessment of a No-canister, Ultra-portable, Single-use Negative Pressure Wound Therapy (sNPWT) System in a Porcine Model of Wound Healing: Unlocking the Mechanism of Action, SAWC Spring Meeting Abstract
- Watkins & Huddleston, 2019. Unlocking the Mode of Action: Why Might a No-canister, Ultra-portable, Single-Use Negative Pressure Wound Therapy (sNPWT) Device Be Clinically Superior to Traditional Negative Pressure Wound Therapy (tNPWT)? SAWC Spring Meeting Abstract
- Dowsett C, et al. Use of PICO◊ to improve clinical and economic outcomes in hard-to-heal wounds. Wounds International. 2017;8:53–58
Senior Scientist Manager
Smith + Nephew Advanced Wound Management
Research & Development, Hull UK.
Runi Brownhill is a recognised scientific expert in the field of Wound Biology and the interventions needed to improve patient outcomes. She provides strategic direction to the Research and Innovation programme through the application of deep domain knowledge in Human Biology & Disease relevant to the business. She has an extensive knowledge of appropriate model systems to investigate the mechanisms of action of various therapies and wound-targeted strategies. Runi additionally provides a broad scientific expertise in order to identify and source innovative new technologies, lead technology scouting and drive product development through to proof of concept.
Runi has a PhD in Pharmacology with a background in the Bio Pharma Sector. Runi has been at S&N for over 11.5 years working as part of the Wound Management R&D division.
Runi was pivotal in the research programme to identify the mode of action of PICO sNPWT.
Runi is based in the UK but her parents live in New Zealand!