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Introduction

I started working on the design and manufacturing of nasal plugs which will aim to increase nasal resistance, increase airflow velocity and therefore increase WSS and ultimately nasal sensation. For the moment I have designed and manufactured a first fairly small prototype, the cylinders are 4 mm in diameter so that it can enter my nasal cavity. I am currently working on other shapes and other sizes which I will present later in the article.

The choice of the material

I have 3 constraints for the choice of materials.

So after a lot of research I found this material.
It is a biodegradable material made with oyster shell powder, it is certified endocrine disruptors free and it has a shore hardness of 93A which is flexible but still a bit hard. But it is not certified for contact with mucosa yet, I asked Nanovia about that and they said that they have not the certificate but it is possible to have it certified if I want and I pay for that.
I'm still searching a softness material certified biocompatible, but it is not easy to find.

The shape

I designed two different shapes, one cylindrical and the other oblong.

The oblong shape aims to fill more space of the nasal cavity while maintaining the possibility of entering in it. Indeed the anterior part of the nasal cavity can be narrow.

The sizes

For each shape I designed 2 sizes, one in 4 mm of diameter and a length of the tips of 12 mm.
The other with the diameter of 5 mm and the length of the tips of 20 mm. So 4 versions in total. But of course I can design what I want. It is just the the beginning of the project.

The first nasal plug

Nasal obstruction and its treatments

Nasal obstruction is caused by turbinates inflammation or other diseases that can swell turbinates or a deviated septum.

Nowadays, the first line of treatment to reduce nasal obstruction is by medication and if that doesn’t help, surgical procedures are considered. Here is a list of the common interventions:

Temporary medical treatments: nasal decongestant, antihistamine, allergy desensitization, nasal expander.
Permanent surgical interventions (from least invasive to most invasive): radiofrequency, septoplasty, bipolar probe, submucosal resection, turbinoplasty, turbinectomy.

The timeline of surgical interventions usually starts with bipolar probe or radiofrequency which are less invasive procedures under local anesthesia that can reduce the size of the turbinate. If these methods prove unsuccessful, other surgical procedures (submucosal resection, turbinoplasty, septoplasty, turbinectomy) are usually proposed. However, they are more invasive and often performed under general anesthesia. All surgical procedures on the turbinates hold a risk of causing ENS.
Let alone the risks of ENS, we know that cutting turbinates even partially is not the solution for nasal obstruction. Indeed the reduction of turbinate volume necessarily negatively affects their functions which are the following: sense of airflow, humidification, and heating of inhaled air, and adaptation of nasal resistance according to oxygen consumption. Burning them with laser or radiofrequency devices destroys the mucosa, and cutting with a scissor destroys everything. Even sub-mucosal reduction can affect nerves and damage the mucosa.

Luckily, another surgical procedure exists that has become increasingly common in recent years: it is called MSE (Maxillary Skeletal Expansion). In essence, this procedure expands the nasal cavity instead of cutting the turbinates. Think “pushing the walls of the room instead of removing the furniture”. We give an overview of this procedure in the present article.

Why do we have small nasal cavities along with underdeveloped jaws and airways?

Before we take a close look at the MSE procedure, let’s take a step back and understand the likely causes of our small nasal cavities.
In modern western societies, most of us suffer from craniofacial dystrophy. In a nutshell, this means elongated faces, deviated septums, small nasal cavities, narrow and high-arched palates, crooked teeth, small and recessed jaws… In the throat, the airway is small because our recessed jaws push the tongue backward. This is why sleep apnea is becoming increasingly prevalent.

The main causes of craniofacial dystrophy according to the book Jaws which comprises over 200 scientific references are:

For more details about this topic, we invite you to read this article in BioScience and this book.

Why is expanding the maxilla the solution?

Instead of cutting the lower turbinates to create space in the nasal cavity which disturbs the delicate physiology of the nose, another solution has become increasingly popular in recent years: maxillary expansion. The maxilla is the bone in the middle of the face, and maxillary expansion refers to the expansion of this bone through the palatal suture.

The hard palate which is a part of the maxillary bone serves as the base of the nasal passage. Consequently, by expanding the hard palate, the nasal passage gets wider. A wider nasal passage allows for more air to flow in the nose – no more obstruction! This avoids destroying mucosa with radiofrequency or cutting it off with scissors… In fact, expansion can even create some mucosa on the nasal floor.

The hard palate presents a suture that starts to fuse around puberty and becomes increasingly tight until about age 25 when it becomes tightly fused and hard to break apart. Therefore, the suture must be surgically cut prior to starting the expansion in adults. While this might sound just as invasive as turbinectomy, it is far from it because the turbinates play an essential role in breathing and nasal physiology, while the palate’s only role is structural – to be the roof of the mouth and the floor of the nasal cavity. With palate expansion, no tissue is cut off with scissors, a cut is made on the suture which can be done under local anesthesia and remains rather painless. Turbinectomy usually requires general anesthesia and multiple days or even weeks without being able to breathe through the nose because of nose plugs and crust build-up. Maxillary expansion on the other hand can require orthodontic treatment because as the palate expands, the teeth separate temporarily creating a diastema. In some cases, the diastema closes by itself without orthodontic treatment, but it depends on the type of expander used.

Methods for expanding the Maxilla

Some orthodontists have tried to split the suture without prior surgical assist, and while this can work on younger patients or on women who have a less tightly fused suture, it comes at the risk of failing to split the suture, pushing teeth out of the alveolar bone and asymmetric expansion. Therefore, in most cases, maxillary expansion takes place with a surgical assist.

Traditionally, expansion was done in conjunction with a Lefort 1 cut which is the cut of the maxillary bone above the roots of the teeth as shown in this slide from Dr Coppelson’s presentation. Please understand the Lefort 1 cut and the palatal suture cut are two different cut. The Lefort 1 is horizontal while the palatal suture is vertical.

However, the problem with MSE that combines the Lefort 1 cut is that expansion will not enlarge the nasal cavity, it will simply enlarge the dental arches to create a wider smile and more tongue space. To increase the width and therefore volume of the nasal cavity, there should be only a cut of the palatal suture, no Lefort 1 cut - this procedure is referred to as MARPE, and it is the one we suggest.

This decision tree shows a comprehensive overview of all the available types of expansion. It is explained in more detail in the video, but below is a short explanation of each procedure for your reference

Dentoalveolar: related to the alveolar bone in which rooted the teeth
SFOT: grafting bone in front of the root of the teeth to allow more teeth movement during
orthodontic treatment.
Orthodontic expanders: various types of usually acrylic expanders to widen the dental arches. It
might also widen the maxilla and therefore the nasal cavity in children. For this, see the work of
the “Orthotropics” community comprised of orthodontists like Dr Mike Mew and Dr Simon Wong.
Skeletal/Basal Bone: the bone most of the maxilla is composed of, that is not in contact with the teeth.
Traditional: related to the traditional methods of expanding the maxilla with a Lefort 1 cut.
Miniscrew-Assisted Rapid Palatal Expansion (MARPE): maxillary expansion with a prior cut
of the palatal suture. These are the procedures that we think are better.
Simple MARPE: MSE with a cut of the suture through the mouth
Corticopuncture: multiple holes in the suture to facilitate the split (risks of failure to split).
EASE: a cut of the suture through the nose or mouth. Created by Dr Kasey Lee.
MIND: a cut of the suture above the teeth as shown in the photo above. Created by Dr
Coppelson.

In adults, MARPE is usually performed by a maxillofacial surgeon in conjunction with an orthodontist because it requires the surgical cutting of the maxillary suture, although some orthodontists perform the cut themselves under local anesthesia. This procedure is certainly more expensive than any other ENT intervention because it usually requires an orthodontic treatment (although not always). However, it can be partially or totally covered by insurance if you have sleep apnea or severe nasal obstruction which are often correlated. Unfortunately, many doctors are not aware of this procedure or think it’s too invasive and will prescribe classic ENT procedures as a first line of treatment. MSE is indeed a heavy treatment, but if you have the time and resources, we as ENS patients think that it is better to do MSE before any ENT procedure on your nose. If your nasal cavity has been properly expanded, you should not need turbinate reduction.

We hope this article has shed light on these practices and help you make the right decision for your health. Breathing is our most basic function, and everything else depends on it.

This article is co-written by Alexander CHALZ and Aurélien RUMIANO.
Main illustration by JawHacks, YouTube channel.

Introduction

For decades, teams of researchers around the world have been trying to find ways to extend lifespan and slow aging. Recently billions of dollars are injected into the research and some wealthy people are trying to do all they can to slow their aging process.
Bryan Johnson is one of them, he spends 2 millions dollars per year and has a team of 30 doctors for  his health.
So what is the link with ENS? Some of the techniques and products developed for “anti-aging” can maybe help us with ENS symptoms.

Blueprint project website all of his program is detailed here.

Can skin health be transposed to mucosa health?

The answer is I don’t know but we can say that mucosa and skin are similar tissues. For skin Bryan are using different creams, light therapy, fat injection…

Nasal creams

Those vitamins and compounds are interesting, maybe using some nasal creams with all these ingredients can improve the health of the mucosa in the long run.

Light therapy

Bryan also uses light therapy on the skin with different wavelengths, duration etc… It seems pseudo-science but some studies suggest that it can help in many ways [3].
532 (green)  and 1064 nm (infrared) pulsed and around 650 nm (red) for 12 minutes two times a week. Some studies show that red light therapy (650nm) can improve mitochondrial function And so the tissue function.
It is not easy to do pulsed light therapy in the nasal cavity but non-pulsed red light therapy is feasible. I built a little device that can do that. I follow what power and lengthways were used the most and the less dangerous. I exclude the 800nm+ wavelength because it is an infrared ray and it heats the tissues. So I choose 670nm LEDs that have the power to obtain radiation of around 50mW/cm². For the exposition time, I’m using around 5 minutes which is a common duration used in studies.

Little red therapy device

Fat, PRP injections

In his video (at 28 min), we see that he had allograft (from donor) fat injection under the skin in order to rejuvenate it. But skin and turbinates are not comparable because fat is naturally present under the skin but not in the turbinate and in the nasal cavity in general. It is why fat injection seems to have a big absorption rate in the nasal cavity. But some persons can have improvement of their ENS symptoms with several fat injections.
He also uses PRP (platelet rich plasma) (at 43 min) for hair growth, it is used for over 10 years for ENS without great success. It can improve a bit if the turbinectomy was not too aggressive.

Conclusion and warning

I don't know if all these things can improve ENS symptoms, so be careful and do your own research.

Bleprint program video

References

  1. Topical niacinamide reduces yellowing, wrinkling, red blotchiness, and hyperpigmented spots in aging facial skin D. L. Bissett, K. Miyamoto, P. Sun, J. Li and C. A. Berge
  2. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring Pinar Avci, MD, Asheesh Gupta, PhD, Magesh Sadasivam, MTech, Daniela Vecchio, PhD, Zeev Pam, MD Nadav Pam, MD and Michael R Hamblin, PhD
  3. Efficacy of a New Topical Nano-hyaluronic Acid in Humans S. Manjula Jegasothy, MD,a Valentina Zabolotniaia, MD,b and Stephan Bielfeldt, DIPL. BIO.-INGc


Introduction

In the precedent article, I performed a virtual surgery by adding implants. I redid a virtual surgery keeping the previous implants and adding one on the left side. This is the side where the airflow is most poorly distributed between the middle meatus and the inferior meatus. So I would like to improve that with this new implant.

Virtual implant placement

Flowgy® www.flowgy.com

This cut is made a little after the anterior part, in blue is represented the previous implant, and in red is the one that I have just added. I designed this implant to try to better respect the rule that I had written in the previous article which is to have between 1.5 and 3 mm between the walls everywhere in the nasal cavity. And we can clearly see that this was not the case here.

Results

Streamlines

Before

Flowgy® www.flowgy.com - left side - streamlines - maximum velocity 3,12 m/s

After

Flowgy® www.flowgy.com - left side - streamlines - maximum velocity 3,25 m/s

In the area circled in red, we can see an increase in airflow (more streamlines). It's not huge but significant.

Velocity

Before

Flowgy® www.flowgy.com - maximum velocity 2,5 m/s (red)

After

Flowgy® www.flowgy.com - maximum velocity 2,5 m/s (red)

In the central illustration, we can see that after the virtual implant at the level of the inferior meatus an area changes from light blue to green, but it is quite subtle. It is a very minor change.

Wall Shear Stress

Before

Flowgy® www.flowgy.com - maximum WSS 0,1 Pa (red)

After

Flowgy® www.flowgy.com - maximum WSS 0,1 Pa (red)

We can see that in the first view where the virtual implant is placed there is an increase in WSS (red arrows). It is not surprising because the implant has moved the wall closer to the airflow. On the other hand, it is quite disappointing to see no change in the inferior meatus, the increase in airflow has not translated into an increase in WSS. I think the increase in airflow is not high enough to see a significant change in terms of WSS.

Nasal resistance and airflow symmetry

Discussion

I already talked about it in the previous article, I think it's very important to restore the "ideal" distance (from 1.5 to 4 mm) between the walls. And that's what I tried to do with this new virtual implant. From my point of view, this ideal distance must be restored everywhere in the nasal cavity. I think it's one of the best strategies to improve several key points:

This is exactly what the body does after a rapid change in the anatomy of the nasal cavity, for example after a deviation of the septum. Indeed there is a correlation between the deviation of the septum and the formation of a concha bullosa [1]. In this study, the authors say:

"We also found that there was a strong relationship between the presence of a concha (unilateral or a dominant concha) and deviation of the nasal septal convexity away from the concha (P < .0001). We also found, however, that there was always maintenance of the nasal air channel between the medial aspect of the concha (unilateral or dominant concha) and the adjacent surface of the nasal septum"

Examples of concha bullosa

Source [1]
Source [1]

The interpretation that we can have is that the "body" does this in order to restore the ideal distance between the walls. And if he does that, there is surely a certain utility.

Conclusion

Adding this virtual implant did not drastically change the airflow, however, I think this optimization is useful. Note that I have not talked about nasal resistance and airflow symmetry in the article because the change is minor after this virtual implant.

References

  1. The Incidence of Concha Bullosa and Its Relationship to Nasal Septal Deviation and Paranasal Sinus Disease, Jamie S. Stallman, Joao N. Lobo and Peter M. Som

Introduction

In this article, I will compare many parameters before and after the virtual implants to see if there are improvements. But before I would like to explain the causes of ENS because before finding solutions it is necessary to understand the problem correctly. In the second paragraph, I will define goals. What parameters do I think I can improve with these virtual implants.

In the article I will speak about different regions in the nasal cavity, to be clear here is an illustration.I
n red the anterior part which is the beginning of the nasal cavity, in green the middle meatus, it is where the middle turbinates are and finally in blue the inferior meatus where the inferior turbinates are.

Nasal cavity regions
Source [1]

Causes of ENS

The Empty Nose Syndrome can be caused by a partial or a complete cut of the inferior or middle turbinates. It can even be caused by a burn of the mucosa. The cut causes a loss of volume, that's to say an increase in emptiness and a reduction in the mucosa surface. The burn affects negatively the health of the mucosa. All of this has many effects:

Goals of the virtual implants

The thing that seems not possible to do with implants is to increase the mucosa surface, an implant just moves the mucosa. In some cases, it can create a bit of a mucosa surface by stretching it but it can't be a major increase.
What it is possible to do is to decrease the emptiness, so decrease the cross-sectional area. The goal is to design the implants in order to:

Virtual implants placement

Virtual implants appear in red, we can say that there are 3 implants in the left nasal cavity, one on the floor, one in the nasal wall, and a small one in the septum. On right it is a pretty big implant, note that I don’t know if this implant is possible to do because it is placed behind my existing implant and the shape that I have designed is huge.
What I tried to do by designing these implants is to restore the "ideal" distance between the walls. Let me explain what I call the “ideal” distance between walls. When we see a healthy nasal cavity CT-SCAN we can see that the distance between two walls is almost the same everywhere. I measured it, it's between 1.5 and 3 mm. So I designed these implants to tend to these values without reaching them everywhere due to technical constraints. I tried to respect what could be done in terms of implantation with a big doubt about the right implant.

Illustration of the “ideal” distance between walls on a healthy subject

Change of the cross-sectional area

After the virtual implant, it is not surprising that the cross-sectional area has decreased and it is a little more regular throughout the nasal cavity.
Note that the values of the control groups are pulled from this study [6], but I measured myself some healthy CT-SCANs and I found values between 250 and 300 mm² of total cross-sectional area instead of the 200mm² in the study. So I don’t know what the normal values are. Maybe it is a range between 200 and 300 mm², I don’t know. The area also depends on body position and physical activity but I assume almost all ct-scans are done while lying down. The values obtained are therefore comparable.

Results

Streamlines

Before virtual implants

Flowgy® www.flowgy.com - left side - streamlines - maximum velocity 3,24 m/s
Flowgy® www.flowgy.com - right side - streamlines - maximum velocity 3,24 m/s

In the previous article I had not shown the right side, we can see that there is a bit better distribution of the airflow on this side.

After virtual implants

Flowgy® www.flowgy.com - left side - streamlines - maximum velocity 3,24 m/s
Flowgy® www.flowgy.com - right side - streamlines - maximum velocity 3,24 m/s

We can see that there is almost no change in the airflow distribution. Maybe in the left side view, there is a bit more streamlines in the inferior meatus. But it is not a huge improvement.

Flowgy® www.flowgy.com - before virtual implants
Flowgy® www.flowgy.com - after virtual implants

Velocity

Before virtual implants

Flowgy® www.flowgy.com - maximum velocity 2,5 m/s (red)

After virtual implants

Flowgy® www.flowgy.com - maximum velocity 2,5 m/s (red)

All surfaces that have an airflow velocity greater than 2.5 m/s are in red. The peak is at 3,24 m/s.
Same thing here no real improvement in velocity.

Wall Shear Stress

Before virtual implants

Flowgy® www.flowgy.com - maximum Wall Shear Stress 0,1 Pa (red)

After virtual implants

Flowgy® www.flowgy.com - maximum Wall Shear Stress 0,1 Pa (red)

All the walls that have a greater WSS than 0,1 Pa are in red. The peak is at around 0,9 Pa.
We can see a real change here, in the areas where the virtual implants are placed the walls are more “colored”. Which means that the WSS is higher.

Flowgy® www.flowgy.com - before, cut at 30 mm from nostrils
Flowgy® www.flowgy.com - after, cut at 30 mm from nostrils

In these cuts, we can clearly see that the virtual implant has increased the WSS. Now there is blue and even yellow color, which means that the WSS has increased from almost 0 Pa to values between 0,025 and 0,07 Pa.

Flowgy® www.flowgy.com - before, cut at 40 mm from nostrils
Flowgy® www.flowgy.com - after, cut at 40 mm from nostrils

Same thing here, there is more WSS, especially on the right side. What I can say is that it is really a positive change, concretely this improvement of the WSS should improve the feeling of the airflow in the inferior meatus. The virtual implants simply moved the walls closer to the airflow. I think it's a good strategy to adopt, identify the airflow and then bring the walls closer to the airflow in order to increase the WSS while respecting the minimum distance between the walls (1,5 - 3 mm).

Airflow humidity

Before virtual implants

Flowgy® www.flowgy.com - minimum humidity 70% (blue)

After virtual implants

Flowgy® www.flowgy.com - minimum humidity 70% (blue)

We can see that there is almost no change in the airflow humidity.

Airflow temperature

Before virtual implants

Flowgy® www.flowgy.com - minimum temperature 300°K (blue)

After virtual implants

Flowgy® www.flowgy.com - minimum temperature 300°K (blue)

There is a little bit less green and yellow in the last slice which means that the airflow temperature is a bit higher after the virtual implants. The temperature in the scalebar is in Kelvin so you need to subtract 273 to obtain the temperature in Celcius. And also you need to multiply by 100 before that. So for example in red the temperature is equal to 3,096*100= 309,6°K and then 309,6 - 273 = 36,6°C.

Nasal resistance and airflow symmetry

Flowgy® www.flowgy.com - resistance and airflow symmetry graph

If your CFD results are in the green square you have a high probability of having normal nasal resistance and normal airflow symmetry. The resistance R is on the horizontal axis and the airflow symmetry theta (𝚹) is on the vertical axis. You can see how these indicators are calculated in this study here [7].

Airflow symmetry

Before virtual implants, the flow rate is at 7 l/min on the left and 7,3 l/min on right. This corresponds to a 𝚹 of 1,028 which is very good, the flow is almost the same in the right nasal cavity than in the left. After virtual implants, the flow rate is at 6,9 l/min on the left and 7,68 l/min on right. This corresponds to a 𝚹 of 1,097 which is a bit less good but it’s still normal according to Flowgy. So if I wanted to correct this I would have to design a smaller implant on the right or a bigger one on the left.

Nasal resistance

Nasal resistance R is calculated based on several parameters like the difference of pressure between the environment and the pharynx (delta P), the flow rate, the density of air, and the area of the nostrils. When the air passes through the nasal cavity, it undergoes a loss of pressure due to the friction on the walls, it is the delta P.
Before virtual implants, the value is 4,7 and after 6,94, it is not surprising that the value has increased because the virtual implants have decreased the cross-sectional area in certain regions of the nasal cavity.
This is rather a good thing because according to the graph the value was barely within the norm. After the implants, the values have progressed a bit in the right direction. But note that the absolute value of R is not very precise because it depends on a lot of parameters in the simulation. It's just an indicator to see if the virtual surgery has changed the value in the right direction. Also, this value seems to have no impact on the ENS symptoms as I mentioned in the “goals” paragraph. But I still think it's a good thing to be in the norm because nasal resistance is useful for normal lung function [8].

Conclusion

One of the goals was not achieved, the airflow distribution did not improve. I don't really know how to improve it, especially on the left side where it is particularly bad.
However, the virtual implants have greatly improved the WSS which is a positive thing. Also, the airflow temperature and the nasal resistance are a bit higher.
So I think that this kind of implant can be useful, especially for the airflow sensation.


References

  1. Investigation of the abnormal nasal aerodynamics and trigeminal functions among empty nose syndrome patients, Chengyu Li, PhD, Alexander A. Farag, MD, Guillermo Maza, MD, Sam McGhee, Michael A. Ciccone, Bhakthi Deshpande, MA, Edmund A. Pribitkin, MD, Bradley A. Otto, MD, and Kai Zhao, PhD
  2. Empty Nose Syndrome Pathophysiology: A Systematic Review, Jeanie Sozansky BS, Steven M. Houser MD,
  3. Submucosal glands, Wikipedia
  4. The nasal cycle in health and disease, J. Hanif
  5. Sataloff's Comprehensive Textbook of Otolaryngology: Head & Neck Surgery, Robert T Sataloff, chapter 19, p 286
  6. Computational fluid dynamics and trigeminal sensory examinations of empty nose syndrome patients, Chengyu Li , Alexander A Farag , James Leach , Bhakthi Deshpande, Adam Jacobowitz , Kanghyun Kim , Bradley A Otto , Kai Zhao 
  7. Robust nondimensional estimators to assess the nasal airflow in health and disease, E. Sanmiguel-Rojas M. A. Burgos C. del Pino M. A. Sevilla-García F. Esteban-Ortega
  8. Surgery of the turbinates and “empty nose” syndrome, Marc Oliver Scheithauer, paragraph 8

Introduction

First of all, what is Flowgy? Flowgy is a software dedicated for CFD of the nasal cavity with tools for virtual surgery. In this article, I will compare the results that I got with my industrial software (Onshape and Simscale) and the results with Flowgy. I would like to thank Pr Manuel Burgos for loaning me the software and answering all my questions.

Simscale - streamlines - left side
Flowgy® www.flowgy.com - streamlines - left side

I set the max speed at 3,25 m/s in both software. We can see the same thing, most of the airflow passes through the middle meatus. Note that on Flowgy I just showed the airflow in the left nasal cavity to see more clearly what is going on.

Cuts - Velocity

Simscale - cuts view - max velocity 3,5 m/s (red)
Flowgy® www.flowgy.com - cuts view - max velocity 2,5m/s (red)

The main difference in the two views is the max speed, it is set at 3,5 m/s in Simscale and 2,5 m/s in Flowgy because I was not able to set 3,5m/s in Flowgy. But we can roughly see the same thing, the speed of the airflow is very lower in the inferior meatus. It's reassuring to see the same thing because it means that the 3d model I drew of my nasal cavity was quite accurate.

Wall Shear Stress

Now the really interesting thing in Flowgy is that there are other data available, one of them that is particularly interesting in the ENS context is the Wall Shear Stress (WSS). I already mentioned WSS in other articles. I will explain a bit more about what WSS is and why it is particularly interesting data in the ENS context. WSS is the pressure exerted by the airflow to the walls, the unit is the Pascal (Pa). The higher the gradient of velocity near the wall the higher the WSS. It is an important value because it is the WSS that gives the airflow sensation.

Flowgy® www.flowgy.com - left side - Wall Shear Stress - max pressure 1 Pa (red)
Flowgy® www.flowgy.com - cuts view - Wall Shear Stress - max pressure 1 Pa (red)

The pressure higher than 1 Pa is represented in red. We can see that the max WSS is located mostly in the anterior part and also in the middle meatus which corresponds to the velocity of the airflow. So we want to have a better distribution of the WSS between the middle and inferior meats. This is what I will try to do with virtual implants in the next article.

Airflow humidity

Flowgy® www.flowgy.com - cuts view - mini humidity 70% (blue)

In this view is represented the humidity of the airflow, we can of course see that it increases as it passes through the nasal cavity. We can see that part of the airflow is at 92% humidity in the last cut. The values are certainly not very precise. By default in the simulation parameters, the mucosa is at 100% humidity which is a little optimistic given that we often have the mucosa dry because of the ENS. At the same time, the value of the inspired air is set to 20% humidity which is pessimistic because often the outside air is more humid than this. What will be interesting is the comparison before/after the virtual implants so the input parameters are not so important.

Airflow temperature

Flowgy® www.flowgy.com - cuts view - mini temperature 300°K (blue)

Same thing here with the temperature of the airflow, in the simulation parameters the mucosa is set at 309,65°K which is 36,65°C. The inhaled air is set at 21,15°C. The temperature of the mucosa is also maybe a little optimistic in the context of ENS. I think the entrance to the nose is colder than that due to the lack of mucosa. But I can't quantify it and it will depend on the aggressiveness of the turbinectomy. In this illustration, the minimum temperature is set at 300°K (27°C) in blue.

Conclusion, what’s next?

Flowgy gives us really interesting data which will be valuable to compare before and after the addition of virtual implants. I'll talk about it in the next article, but I think it's no longer possible to do nose surgery in 2022 without first having done a virtual surgery to see what it will give in terms of airflow, WSS, etc …
Now I will try to design virtual implants in order to improve airflow distribution, WSS distribution, etc …

Introduction

As planned I designed virtual implants in my nasal cavity in order to improve airflow distribution and decrease cross-sectional area to tend toward a healthy nose.

Virtual implants placement

Virtual implants

In red are the virtual implants that I designed, you can see that I added a lateral wall implant behind the existing one on the right side. It measures approximately 30 mm long, 10mm high, and 5mm thick.
On the other side, we can say that it is two implants, a floor, and a lateral wall implant.
The floor implant measures approximately 35 mm long, 6mm wide, and 3 mm thick.
And the lateral wall implant is 35 mm long, 10 mm high, and 2 mm thick.
So I don't know if it is even possible to add an implant behind the existing one but I think that it is a good idea to keep the cross-sectional area constant all along the right side.
On the left side, I added two implants which aim to reduce the space between the existing inferior turbinates and the walls.

Cross-sectional area change

We can see that the change starts at 40 mm from the nostrils until 70 mm. And now we reach a maximum of around 400 mm² instead of 500 mm², but it is still far from a healthy nose. So we can already say that the implants are not big enough. But my first goal was to try to have a better flow distribution and a constant cross-sectional area.

Results

Left side
Right side

We can quickly see that there is almost no change in the airflow distribution and velocity. There is maybe a bit more airflow in the inferior meatus but it is not a crazy change.

Before virtual implant

After virtual implant

Slices

In the slice view If we compare before and after virtual implants, we also do not see any significant difference in airflow velocity.

Before virtual implants
After virtual implant

I made a slice with the same distance from the nostrils of the two 3d models (before and after virtual implants). And I placed a dot to measure the velocity at the same location. After virtual surgery, the velocity is around twice higher 0,26 m/s instead of 0,14 m/s in the post-virtual surgery 3d model. But it is just a little area, we can see the color change and it is twice higher yes but 0,26 m/s is still a very low velocity to the 2 m/s in green for instance. So I speculate that this change is almost not perceptible in terms of airflow feeling.

Conclusion and next step

So what I can say with those data is these virtual implants have almost changed nothing in the velocity and the airflow distribution. It's possible that if these implants were done in reality I would feel almost no improvements. But one thing, ENS symptoms are not just due to airflow problems, there is also the health of the mucosa, the nasal cycle which is almost dead with cutted turbinates and maybe others things to take into account.

What is the next step?

Find better implants placement, also maybe bigger implants to decrease cross-sectional area … I don't know.
Recreate true turbinates… Ok it is not possible in reality.

Introduction

Finally, I was able to make a 3d model of my nasal cavity usable with a CFD software.
For those who don't know what is CFD, it just mean Computational Fluid Dynamics which is the study of fluids, in our case the air.
I took 15 l/min for the flow rate and I did not apply temperature conditions on the walls.
Just for information each nostril has a surface of around 68 mm² and the beguining of my pharynx 420 mm². And you can see my cross-sectional area here, in my precedent article.

Results

Right side view

In this view, the airflow is represented by tiny tubes. We can see that almost all the airflow passes through the middle meatus at a velocity between 1,5 and 2 m/s. On the opposite in the inferior meatus zone, there is almost no airflow and the velocity is very low, less than 0,5 m/s. Near the nostrils, in some areas, the velocity is pretty high around 3 m/s.

Left side view

Same thing for the left side.

Slices view

In this view, the nasal cavity is sliced, at the left of the illustration it is near the nostril, and at the right near the pharynx. We just see the velocity not the quantity of airflow, and we can see the same thing that in the other views, very low velocity in the inferior meatus despite my right nasal wall implant.

Results interpretation

The results are not very surprising, some studies come to the same conclusion about the airflow distribution. In this study for instance they showed the same thing, an important reduction of the airflow in the inferior meatus (25.8% ± 17.6%) . They also showed a reduction in wall shear stress (WSS) in the inferior meatus area, which is the force of friction on the walls of the mucosa. Less shear stress means less airflow sensation. And I'm not sure but less airflow quantity and less velocity mean less wall shear stress. In my simulation, I was not able to measure the wall shear stress due to software limitations but since the velocity and the airflow are very low in the inferior meatus then we can say that the WSS too. And according to this same study, the symptoms "of "suffocation" and "nose feels too open" were also found to be significantly correlated with peak WSS around the inferior turbinate. So in others words less WSS in the inferior meatus zone mean more symptoms of suffocation and the feeling of the nose too open.

Investigation of the abnormal nasal aerodynamics and trigeminal functions among empty nose syndrome patients

Conclusion and next step

Now that we clearly see that one of the problem in ENS is the airflow distribution, I will try to fix that with some virtual implants placed in differents area. The goal of course is to tend towards the same airflow distribution of a heathy nose.

Limitations

Just to be clear, I'm not a reasearcher nor a CFD specialist, so the results can be wrong due to many things. If you see an error in the conditions or the reasoning, please can contact me.

I designed a simplified 3d model of a nasal cavity (just one side) to test different scenarios such as adding an implant. You can see that I grouped the superior turbinate and the middle turbinate in order to simplify the model. I need a simple model because it is better to make future geometry change.

The model is simpler but it respects the cross-sectional area of my real nasal cavity, you can see my post about the cross-sectional area measurements that I have written here. Also as you can see it simulates a pretty large inferior turbinectomy and a total turbinectomy in the middle section area. For the flow I took 7.5l/min, it is the respiratory flow at rest. Here are the first results I get...

The airflow in the area of the absent inferior turbinate swirls and is very slow (less than 0.6m/s) unlike the airflow in the area of the middle turbinate (about 3m/s). This is not very surprising, it can be seen in quite a few CFD studies on empty nose syndrome. The speed values also match which means that my 3d model and the flow rate value taken are pretty accurate.

In the coronal section view, we can see that the velocity is higher between the middle turbinate and the septum but also in the zone at the bottom of the middle turbinate.

Now what I can say about these results is that too low airflow velocity greatly reduces sensations in the area of the absent inferior turbinate (inferior meatus). This is one of the big problems of the ENS.

In future articles, I will simulate an implant in the inferior meatus zone to see the change in airflow.

First of all, I found this study that compares the cross-sectional area of a control group with an ENS group. I found this interesting so I do the same for myself, and here are the results.

We can see that there is no doubt that my nasal cavity (in blue) is more empty than the control group. The information about the control group is pulled from the study cited at the beginning of this article.
At a distance of 20 mm from the nostrils, my nasal cavity is more empty than the control group but not too much. But after 40 mm the value explodes and it reaches up to 2.5 times the control value at a distance of 50 mm to the nostrils. So clearly I need more volume from 40mm to 70mm.

I think it is better to have a stable cross-sectional area all along the nasal cavity even if a little higher than normal rather than reaching the normal value at the beginning of the nasal cavity and then leaving a big hole afterward. Of course, the ideal would be to be able to reach the value of the control group all along the nasal cavity.

I made a second graph that compares the cross-sectional area from the right and left nasal cavity in order to see the imbalance.

Here we can see that the area until 40 mm from the nostrils of the right nasal cavity is pretty stable thanks to my lateral wall implant. After this value, the area explodes and reaches more than 200 mm². Which is more than 2 fold the control group. I don't have the cross-sectional area data from the right and left nasal cavities of the control group, only the two together. But we can speculate that the nasal cavities of the control groups are balanced so about 100 mm² each. The left side is worse, it reaches almost 300 mm² at a distance of 50 mm, which is almost 3 times the control value! However, this is the side where I have almost 50% of the turbinate left, but it is also the side where I have never had an implant or injections.

However, although my left nasal cavity is emptier than the right, I don't feel that it is worse. First because on the left I still have 50% of the turbinate while on the right nothing. Thanks to the half of the turbinate still present on the left, the surface of the mucosa is not the same between the two nasal cavities. This is what we will see in this third graph.

We can therefore see that the perimeter of the mucosa is greater on the left than on the right. We are talking about perimeter here because these are slices in 2 dimensions but it reflects the value of the surface of the mucosa. So we can clearly see on the graph that the surface of the mucosa is higher on the left than on the right thanks to the remaining half of the turbinate. So although my left side is emptier than the right I don't feel it is worse.
Note that the larger the mucosa surface, the more blood vessels, TRPM8 sensors there are, and the larger the exchange surface between the air and the mucosa.

To conclude this article, I think that the cross-sectional area and the surface of the mucosa are interesting information that can help to know where to place an implant. And also it's I think interesting to quantify the lack of volume.

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