Thickened Liquids and Dysphagia (2020)

INTRO: Hello and welcome to Clinical Nutrition Notes – a podcast where we speak with guest experts and opinion leaders about the art and science of clinical nutrition – brought to you by Nestle Health Science Canada. This podcast is intended for health care professionals, for education purposes.

I am your host, Bethany Hopkins, Medical Affairs Manager with Nestle Health Science.

Today we will be talking with Julie Cichero about the use of thickened liquids in the management of dysphagia.

Dr. Julie Cichero, is a speech-language pathologist who for 28 years has worked clinically and conducted research into feeding and swallowing disorders from infancy to old age. Julie has contributed to the evidence base for diagnostic use of swallow-respiratory sounds, characterisation of thick fluids and complexities associated with pill swallowing difficulties. Julie is Co-Chair for the Board of the International Dysphagia Diet Standardisation Initiative; Research Compliance Manager at Mater Research (Australia) and honorary affiliate with the University of Queensland and the Queensland University of Technology. Julie is based in Brisbane, Australia.

Hopkins: Thank you for joining us Julie.

You’ve published reviews around the use of thickening agents in the management of individuals with dysphagia which have included considerations for the practicing clinician who’s interested in balancing safety, nutrition and quality of life. Today we will address some of these current thoughts around the use of thickened liquids.

To begin, can you briefly describe why swallowing of liquids can be problematic for some individuals with dysphagia?

Cichero: I think the think about liquids is that they’re actually a lot more complex than people imagine. We need to move them from the front to the back of the mouth really quickly, and we coordinate our breathing. We briefly stop it when that happens. For a whole range of reasons, whether it’s because of a muscular problem, or a physiologic problem, or a stroke or dementia, any of those types of things, it can really upset the very fine balance between breathing and swallowing, and people can end up taking the liquid down into their lungs because it’s moving too quickly. There are so many little trap doors, if you like, opening and closing, lots of muscles that need to be coordinated for swallowing to work effectively with breathing. Obviously when it doesn’t work, people end up coughing and that can be really distressing for them. One of the reasons that we use thickened liquids then is to manage that.

Hopkins: And that really leads into what I was going to ask you next Julie, in terms of the complexities that you’ve described, and the trap door analogy. It seems that swallowing liquids is something that we take for granted, and often think that it should be very easy to do, when in fact, it may not be. So when should a clinician consider the use of thickened liquids to help manage dysphagia for their patients?

Cichero: I think anytime you’ve got someone who’s distressed with coughing when they’re having thin liquids in particular, some people think that that’s normal unfortunately and it’s not until they try thickened liquids and realize that they’re not coughing all the time, that they recognize that they’re not expending all of that energy, they’re not exhausted, they’re not distressed by it. But also when people have chest infections consistently that are unexplained, and that is where possible aspiration pneumonia comes in, so we want to be checking in on that, to make sure that they’re not quietly aspirating little bits of thin liquids or even saliva as well, where it can be carried down, and there are other things that we need to make sure that people can maintain their safety with drinking, but also avoid aspiration pneumonia as well. Just coming back on the trap door side of things as well, I’m referring there to the epiglottis. One of the things we know about that is it doesn’t quite work like a trap door unfortunately. It doesn’t give a nice clean seal to the top of the airway, which is what we’d really like. In fact, it works more like a rock in a stream. It helps to divert liquids around the opening to the airway. It is actually quite easy for thin liquids to get down into the larynx, underneath the epiglottis, then down into the airway. Whether or not people have got those receptors in place, for a coughing reflex to be triggered, and that may part of their disease pathology at that point in time. So they may not be responding… so we’ve got those two different scenarios, ones where the cough reflex is really working very hard, and those people are exhausted from the coughing, and they’re using a lot of expenditure of energy as well, which increases their nutritional needs too. Then we’ve got the other group, where it is just quietly, silently moving into their airways and making them quite unwell, and for those things we need an instrumental assessment and then to try the different levels of thickened liquids to work out what’s going to work best for them.

Hopkins: And really looking at an individualized approach, when you’re getting down to the assessment. Julie, with that said, are there data to support the efficacy of using thickened liquids?

Cichero: Yes, they’re absolutely are. So we’ve got a couple of recent systematic reviews published in 2015/2016, and the beauty of these is that they were done in different parts of the world, almost simultaneously, and they came up with the same results, which was really good. What they came down to was that thickened liquids do help people who aspirate thin liquids. Secondly though, they also found that liquids can be too thick, and this is where residue can begin to accumulate in the pharynx or the throat, and what that suggests to us for the first time I guess, is that there is an upper therapeutic thickness level, so a point where making it too thick, and that’s been the mantra in the past, that thicker is better, may not actually be the case. There will be times when for some people they’ll need it a bit thinner so it’s not always going to the same go-to level of thickness. The other thing that both of those reviews picked up is that we need more research to determine exactly what those therapeutic thickness boundaries are.

Hopkins: Thank you for that background Julie, and it is interesting to see, in practice, in talking to clinicians, the concept of thickening just enough, by prescribing the minimal level of thickness required to swallow safely. We’re really seeing that evolution in practice, where people are adopting that, which is really nice to see and based on the evidence that you’re talking about.

Cichero: That’s exactly right. And it is great to see that change in practice. When I first started practicing as a clinician back in the early 90’s, it was very much a case of we start with the thickest liquid possible and work our way backwards. Whereas, we’re certainly seeing a reversing trend where people are starting at just thickening enough and taking it to the point where their addressing symptoms if you like, and managing those symptoms, not by immediately going to the very thickest liquids.

Hopkins: I agree. It’s wonderful to see that that is happening. In terms of changes in practice, and questions people have brought up over the years with respect to thickening liquids, some clinicians have questioned ‘should we be using thickened liquids at all? Should we be using other strategies like free-water protocols, or posture changes?’ I’d be interested in your thoughts on that Julie.

Cichero: I think with this, there can be a real polarization where people either think it’s an all or nothing approach. I think we’re better to look at it from the point of view that they all complement each other, they each have a roll. So that yes, the free-water protocols are really important. We need to make sure that people have a really clean mouth. I think that one of the other really big learnings we had that was from the work that Susan Langmore did, again back in the early 90’s, looking at what causes aspiration pneumonia, and it really comes back to the pathogenic state of the oral cavity. If we’ve got people who don’t have good oral hygiene, either because they can’t clean their mouth, or for a whole range of reasons, then that sets up a change in the composition of the bacteria in their mouth and when you aspirate that, and it can go down on liquids, on food, on saliva, it’s that that’s setting up the pneumonia, if you like. Regardless if you’re having thickened liquids or water, you really need to have a clean mouth, really good oral hygiene, to reduce the impact of the development, or the risk of developing a pneumonia. For the free-water protocol, what’s good about them, is that people get the sensation of mouth wetness, and they don’t feel thirsty. So that’s a really important thing, particularly for people who are on thick liquids for a long period of time. They really miss that feeling of thirst quenching if you like. It’s also an opportunity to increase their hydration. Now postural changes, again, these are not an all or nothing thing. We can’t put a chin tuck in for every single person, because we now know that when people have got poor higher laryngeal excursion, where there’s poor deflection at the epiglottis for example, that that’s actually a contraindication for using a chin tuck. There is no one size fits all. It would be the same as saying we should give everyone thick liquids, but I think, when you’ve got a clinician who is actively looking at the person in front of them and working out what’s best for them, so it might be a posture change in addition to free-water, in addition to thick liquids with meal times for example, then that’s what we’re looking for. It shouldn’t actually be a this is better than that. They all have a role to play.

Hopkins: I really like the concept that you mentioned Julie. It’s not an all or nothing approach, and I think that’s really important for everyone to keep in mind and when we’re thinking about patient-centered care, and what works for that individual in front of us, it could be a wide range of strategies, and the combination may vary from person to person.

Cichero: That’s exactly right.

Hopkins: Another question Julie that arises from time to time is around the bioavailability of the water in thickened liquids. Can you comment on this and what we know from the literature?

Cichero: For sure Bethany, it is a really common question and I think a lot of it comes back to this concept of patients telling us that they still feel thirsty. I was fortunate enough to be involved in some research, again a number of years ago, where we looked specifically at the bioavailability of water when it was mixed with a whole range of different thickening agents - starches, gums, xantham gum, and guar gum. We did a study that was both in an animal model, as well as in a human model, and we decided to look at if you’re going to see an impact of bioavailability, we will make it nice and thick, so it was the equivalent pudding-thick back then, or of IDDSI level 4 now, or extremely thick. So we used blood and saliva sampling, we had the rats consuming titrated thickened liquids, and our human subjects consumed deuterium oxide and sodium bromide to label the waters so these were really quite intricate studies. What the results found was that the water was really rapidly absorbed and it was equilibrated within 60 minutes, and that the water absorption exceeded 95% of the administered dose. It didn’t matter whether you were having starch or gum, they were assessed against pure water and those rates of absorption were actually identical. So that was really good. There was another study that was done by Hill et al, not long after we published ours, and they did a slightly different methodology where they used a stable isotope method and urine sampling. They also found that the bioavailability was unaffected by water thickened with, this time a gum, to pudding thick, or IDDSI level 4, extremely thick liquids. So we’re seeing some very consistent results on some quite sound science. Come back to, well, why is it that our patients will tell us that they’re still feeling thirsty then? And it’s because when you don’t have that feeling of mouth wetness then that’s the body’s natural response. There’s another study that was done where they had people hydrated using a drip and they knew their hydration levels were perfect. But people hadn’t been given anything to drink. So there was no mouth wetness and those people still felt really thirsty. One of the takeaways that we’ve got from that is that there are opportunities to use something like potentially a water atomizer to lightly spray using an aerosol method inside of the oral cavity, again making sure that the inside of the mouth is nice and clean. So you can have your thick liquids, and then after that, spray the inside of the oral cavity with a little aerosol of water or a pump action, to provide them with that feeling of mouth wetness. Thinking also here, so for any of our patients who might be tube fed for example, people sometimes can forget that oral hygiene is really important for those people as well and making sure that we do that, and also making sure that we address those issues of mouth wetness in them as well.

Hopkins: It’s, I think, reassuring for clinicians to know that the bioavailability of water is there when they’re using thickened fluids and then also strategies to help manage that feeling of thirst and what people can do with respect to the oral cavity that can make a big difference potentially for those individuals who are on texture-modified diets, or as you said may be NPO and being tube fed.

Cichero: That’s right Bethany, because, as I mentioned before, this concept of really looking at the person in front of you, so it means that we can keep them safe by having thick liquids, but we can also address those feelings of thirst, which can be one of the barriers that sometimes we face with compliance with thick liquids too.

Hopkins: I would think it would have a big impact on quality of life as well.

Cichero: Yes, for sure.

Hopkins: Julie, in terms of thickening agents, we know that not all thickening agents are the same, and they each have specialized and complex properties. Now currently, starches and gums are the most widely used thickeners in practice, and I’m just wondering, can you comment for a moment on the differences between starches and gums, and the clinical implications for use of these agents?

Cichero: That’s a great question Bethany. For years we started with starches and they’ve had a great purpose in terms of being able to thicken. Sometimes they impart a starchy quality, sometimes there is thickening over time. You’ve also got the gums, which are fantastic from a point of view that they’re very stable, and this is one of the elements that lead to their development, because you have the stability of them over time, so once you mix them in. But also with temperature as well. Looking also now at the gums, there’s less of the gums that you need to use when you’re thickening a product as opposed to the starches, which you typically use a little bit more. We’ve got differences in the feel of them, so a slightly grainy feel with the starches to a more slippery feeling with the gums. We’ve had patients that have said to us who have texture preferences inside the oral cavity where they might not particularly like either the grainy feeling or other that don’t particularly like the slippery feeling, so again, not necessarily a one size fits all, to what people will find works best for them.

Hopkins: Do you find Julie, that amylase resistance is a feature that’s important in clinical practice, when looking at different agents?

Cichero: I think it has a place. I think that comes back to really the amalyse resistance is looking at our patients with a really significant dysphagia where they would be keeping the liquid in their mouth for quite a period of time. So yes, certainly in those circumstances your gums are particularly important for use there because of their amylase resistance.

Hopkins: And we hear sometimes from clinicians as well of individuals having assistance with eating, and their using a spoon and helping with eating, and they’ll notice even the transfer of saliva in that process can sometimes make a difference in terms of breaking down the starch.

Cichero: Yes, you’re exactly right about that. There have been a number of studies where they’ve shown that process does occur. So that yes, the saliva going back into the cup is just, over time, thinning out the liquid so that they’re not actually getting the same thickness level that you first started out with.

Hopkins: Now Julie, we talked a little bit about different types of thickeners and some of the properties, what do you see on the horizon regarding advances in thickeners from a clinical perspective.

Cichero: I think we can expect to see an evolution of thick liquids and liquid types particularly as well. So where we’ve seen that evolution from using the starch-based thickeners across to the xantham gum, I think we can potentially see future changes. One of the things that we’re noticing, I’m going to delve into the rheology just for a moment, and then show how it links back to clinical practice. A lot of the formal testing is being done with rheometers, where they’ve looked at the shear rate of the thickened liquids. What we’re starting to look at now is extensional rheology. So when you swallow, if you can imagine the swallowing process, it goes over the back of the tongue and then down the throat. With the extensional rheology, what they’re looking at there is the ability of a liquid to hold together in that process as it goes horizontal and then vertical if you like. So the better the ability of that liquid to hold together in that space rather than fracturing as it comes down potentially. The better the likelihood, is the hypothesis that it will flow down into the esophagus, as opposed to potentially fracturing as it comes down, and breaking to go down into the airway. So potentially we may see some developments in the future around the liquids ability to hold together and that may change things. We might see a real evolution there. I wanted to backtrack a moment if I could as well Bethany, around one of the things that we’re seeing how things are changing. We’ve got these changes also to do with terminology. With thickened liquids, and when we were talking earlier on about the evidence base for thickened liquids a lot of people will come back to randomized control trials which have been completed around thickened liquids. We’ve got Joanne Robbins study, which was quite prolific at the time for the 2008 study, where her conclusion was that, protocol 201 it was, that individuals on honey-thick liquids had poorer outcomes than individuals on nectar-thick liquids. It wasn’t until we started to dig down into the methodology where they included the measurements, that the honey-thick liquids that they were talking about measured 3000 centipoise. Now coming back to the old National Dysphagia Diet terminology, 3000 centipoise is not honey-like. It’s in fact, spoon-thick. Spoon-thick is anything over 1750 centipoise. Their nectar-thick was about 300 centipoise. Now that did fit into the national dysphagia diet nectar-like category. So in fact, there was an error in the way it was reported and what it should have read was that individuals on spoon-thick liquids had poorer outcomes than individuals on nectar-thick liquids. One of the benefits we have with the development of the International Dysphagia Diet Standardisation Initiative literature and framework is that we’ve got some testing methods that allow people, and it doesn’t matter whether you’re in the U.S., Canada, Australia, Egypt or the U.K., where the testing methods we’ve got, with flow tests, allow us all to be talking the same language, and it means when I talk about mildly thick, or slightly thick, that you’re also, you know the measurements can be done so that we are in fact talking about the same thickness levels. That’s got to be good for our practice going forward in building an evidence base, we can develop those therapeutic thickness levels. So that’s the other area that I see as a really exciting area of development coming forward in the future.

Hopkins: That’s a great example of the Robbins study of how having consistent terminology and everyone reading from the same song sheet, so to speak, with respect to what these different viscosities are, can really make a difference, because that particular study was interpreted in very different ways by different people and led to quite a bit of confusion in the dysphagia community.

Julie, thank you for your insights and for providing us with an update on current thoughts around use of thickened liquids in dysphagia management. As the population continues to age, the prevalence of dysphagia is expected to increase, and the demand for dysphagia treatment – which underscores the need for sound management strategies.

On that note, we will conclude this podcast.

I would like to thank you Julie for joining us and thank all of our listeners.

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