IAS Visiting Fellow Viviana Shiffman MSc delivers a seminar on their research –
Viviana Shiffman will present a unique approach involving the utilization of an oesophageal balloon catheter – an instrument that measures oesophageal and gastric pressures along with electromyography of the diaphragm. The present methodology provides distinct advantages in data collection and measurement of physiological variables. The application of this technique in exercise physiology research will be elucidated, highlighting its potential contributions to advancing our understanding of the respiratory system.
Viviana is a researcher at the University of British Columbia. She has studied exercise-induced arterial hypoxemia in female masters athletes. Her current research investigates the impact of inspiratory muscle training on the respiratory muscle metaboreflex and how this is moderated by age and sex.
For more information about the IAS, please visit – https://www.lboro.ac.uk/research/ias
Thank you um so I’m just here to introduce Biana um she’s a respiratory physiology researcher from the University of British Columbia um and she’s been with her us for a few weeks so uh we’re interested in breathing pattern research here and we’ve been benefiting from giana’s uh experience
And expertise in in sight um into this particular methodology DS’s balloon catheter um and uh she will be showing a a video but just to reassure anybody who’ve not sort of seen it before there are a number of people here who have had who have participated in this uh
Procedure over the course of the past couple of weeks and are still here to tell the tale so uh it’s uh it’s quite painless um she’s uh has a particular expertise though in in some of in the sort of methodology and particularly in the measurements that you can take from
It and the insights that you can gain from the particular procedure um and that’s what she’s here to share today um and we’ve had a preview of this yesterday and it was absolutely fascinating so I’m going to hand over to vivana now and I’m sure she’ll meet
You thank you s for that intruction thank you to the team as well for having me I’ve had such a great time uh being over here oh I have yeah okay so today this is a bit of an outline of what we’ll go through we’ll start with looking at the
Respir muscles as well as the mechanics of breathing uh followed by using the esophageal balloon uh and then some of the applications um and at the end what my research uh looks like right now at DC so spal muscles are usually thought of as locomot muscles or limb muscles
That are used to run ski cycle or hike but often times s you don’t think of them as muscles that do these carefully coordina contractions for us to breathe but respirate muscles are scal muscles and we’ve had 63 of them documented with the role of breathing which is about 20%
Of our human SK muscle system but how do we measure what these muscles are doing well we can look at muscle shortening as a change in volume that that restory muscle does to particular particular structure so for example a change in the rib cage volume or a change in the AB
You can look at velocity shortening of this muscle based on the change in flow so our inspiratory flow when you breathe in versus our exory flow o and lastly how we measure force is a change in pressure oop sorry a change in pressure that the uh bre muscles generate during
Um while they breathe so throughout this presentation we’ll look at these three variables of volume flow and pressure and how we use those to collect data on the rest muscles so a bit of background on the left side or on on the right side or I
Guess your left and and on this side we have our inspiration and expiration so the main primary uh muscle for inspiration is our diaphragm it’s interated by the frenic nerve and during quiet breathing it only moves about 1 cm there’s two section of sections of it
The costal part and the plural area but during a heavy exercise diaphragm can move up to 10 cm so if you do a force inspiration or Force expiration that diaphragm will displace up to 10 cm another important muscle for inspiration is the external intercostals they’re going to help increase the volume of the
Thoracic cage and then we have two accessory muscles as an example they Cy mastoids and the scalings sorry realize I’m not showing on the um the stoom mastoids and the scalings here those are accessory muscles and we don’t really use them at rest but as we start to increase intensity of exercise and
Increase our ventilation they become really important in lifting our ribs and our sternum however if you go on to the expiration side usually at rest uh during quiet breathing it’s passive because when you inspire you’re moving away your lung and chest wall elastic equilibrium away away from its eum and
At expiration you’re bringing it back towards it however when you start to exer ex size um you expiration becomes an active process and you end up using these muscles over here so you have your rectus abdominis your external and internal obliques as well as your transverse abdominis to really decrease
The abdominal um volumes and then you also have these internal and intercostals to help decrease the rib cage volume so overall you have an increase in thoracic volume with inspiration and you have a decrease in thoracic volume with expiration so here in this diagram we have a lung
Inside a jar with a pressure pump and a speter to measure volume and then what we do when we change it will’ll show you on the graph on the right where is your pressure along the x-axis and the volume change on the Y so with this pressure
Pump if you decrease the pressure within it sub atmospheric you’ll see an increase in volume as the lung expands so that’s sorry I should really use that so that’s this curve here the first one so decreasing the pressure you’re increasing the volume because the lung is expanding and then as you decrease
Back the pressure towards zero or I guess increase it um you’re bringing it you’re bringing the volume back down so if you look at this curve you can see there it’s nonlinear and that’s because of a component called hysteresis which is because the lungs visol lastic components and the surface tension
Um cause this difference in inflation and deflation when you look at the actual uh respiratory system you can’t just look at the pressure volume relationship of the lung tissue you also need to consider what the chest wall is doing so in this graph we have pressure on the x-
Axis and then volume as a percent of total lung capacity on the Y uh and then just understand that the pressure is zero in the middle here with negative and then positive the first uh line we’ll go through is the pressure volume relationship of the
Lung here you can see that the lung uh tissue is at equilibrium at about 20% of their total lung capacity and that’s why our lungs tend to want to recoil inward all the time the other line that we’ll look at is and that’s at point B the
Other line we’ll look at is the pressure ballum relationship of the chest wall which is this gray line here and it’s at equilibrium at about 70% of TLC and that’s why our chest wall always wants to have to be expanded outwards but these two relationships work together and we have our uh
Pressure volume relationship of our total respiratory system which is this green line and at this point here at 01 this is functional residual capacity also known as F FRC and that is when our chest wall um tendency to want to Spring out is balanced by the lung elastic
Recoil want to recoil in and that’s where we usually end our normal breath out so if you’re breathing quietly and you take an expiration and you want to stop that’s where you are at at F FRC so your muscles are going to have to work with or against these um uh
Pressure volume relationships of the chest wall as well as the lung so at F FRC we’re at one and we’re at equilibrium but let’s say we increase our volume um up to about 70% TLC these arrows are represent in what the respiratory muscles have to work against
So at here the respiratory muscles are going to work against the inward recoil of the long elasticity but so they’re trying to push outwards to create this volume but because they’re in line with the equilibrium of the chest wall they don’t have to worry about what the the
The forces of the chest wall at this point but if we increase up to three here now we’re away from both the equilibriums of the chest and the lung so these per muscles now have to work against both of them now if we decrease our volume towards residual volume our
Muscles are going to have to work to maintain a positive pressure as our chest wall tensing wants to go outwards so on top of the elastic uh forces we also have to think about the airway and tissue resistance so tissue resistance um isn’t doesn’t take a big
As a component as our Airway resistance unless you have a disease so we’re really going to focus on the airway resistance uh so resistance can be calculated by the viscosity is proportional by the viscosity and the length and inversely proportional by the radius to the fourth power so radius
Becomes a really important factor when you’re looking at resistance for flow through it two so here if you look at the first graph here in a you can see the trachea and then it starts to Branch out and this is the airway slowly branching out into more and more
Generations as they Branch out these Airways get smaller and smaller and smaller and if you look at the second part you have our Airway generation from zero to 25 and then s stands for cross-sectional area so as you increase the airway generation you see a greater and greater cross-sectional area and you
Would think that last Airway generation because their diameter is so small that’s probably where the greatest resistance is but it’s actually the opposite where you see on the last panel we have the resistance on the Y AIS instead an airway generation on the X the resistance is much is the highest um
At the first generations and drops down when you get to the smaller um parts of the airway tree and this is because you have a greater cross-sectional area so oh wait um so the method that we use uh is called is well the method you use um to
Look at these differences the the respir muscles are doing to um is using an esophageal balloon catheter so here on the left side you have a picture of an esophageal balloon catheter in the middle is an animation um where the Sagal balloon catheter gets inserted through the nose down to the esophagus
And into the stomach it has two balloons one that sits in the esophagus and one that sits in the gastric with EMG coils in between and so it’s really important that that diaphragm is sitting between the two balloons here I have a video so here I’m inserting an esophageal balloon catheter
Into one of our participants I’m asking them to take sips and swallows as they um have a catheter placed in them because we want their glotus to open to let the balloon in so we have them uh slowly slipping and swalling and we’re feeding it in I sped this up by two
Times so it takes about two times um the time for it to come the for the placement to occur and so the Sagal balloon will measure a sophal pressure the gastric balloon will measure the pressure in the stomach and our EG coils will measure the the electromyography or
EMG of the diaphragm so why we measure esophageal pressure um you can see that from the picture in the right here this is a transverse plane cut through the lung and the Red Dot is where you place the esophageal balloon in the esophagus you can see how close the proximity is
Uh to to the plural pressure right here uh the plural pressure yeah the proximity plural pressure so we use a sophal pressure as a surate for plural pressure on the left here is an example of what the esophageal pressure Trace looks like so you have a sophal pressure
Here on the Y and this first part here is what the pressure swings look like at rest this one right here is a big inspiration and then the positive one is a big expiration in the middle here is that 60% Max intensity and so you have uh you
Can see that these esophageal pressure swings are becoming more frequent and also larger in this last section right here this is at 100% Max intensity so now you can see how much more frequent these esophageal pressure swings occur as well as how much larger they become the other pressure we get is gastric
Pressure and what’s really great um with getting both of these is now we can look at diaphragmatic pressure which is an index of how much pressure that diaphragm is creating so if you look at this picture here the difference between esophageal and gastric is the pressure
Of the diaphragm will be creating so the last measure uh you can get from this balloon is EMG so in between those two balloons you have 10 coils the first one is a ground and then the last nine here create five pairs um of EMG electrodes and it’s really important that we have
Five instead of two because as I was saying the diaphragm can move up to 10 cm within the chest wall cavity and so it’s important that we can collect activity no matter where it is within um the cavity so this is an example of what the EG uh activity looks like during
Exercise you have EMG um activity on the y axis here with 60 to 80 to 100% of peak ventilation and you can see that the inactivity increases with an increase in ventilation so as you start to exercise you want to be able to maintain your blood gas homeostasis and you do this by
Increasing your ventilation right um but increasing your ventilation comes with a mechanical cost uh to breathing and we usually look at uh mechanical cost or work as force times distance but because we use a change in pressure as force and a change in volume as our distance we
Can calculate work of Brey based on that and with those two components that we spoke about earlier we have a resistive component from the Airways and we also have a visol elastic component from those pressure volume relationships so there’s two components to work of breathing resistive which is the work
Done in overcoming the resistance to turent flow as well as Vis elastic which is the work done and overcoming the resistance offered by lung tissue to deformation so this is how we calculate your mechanical cost of work of breathing so this is a pressure volume Loop you have volume on the x-axis and
Esophageal pressure on the y e LV stands for end inspiratory lung volume so at the top of your inspiration and end expiratory lung volume uh stand or yeah elv stands for end X lung volume which is at the end of your expiration when you plot those on your
Pressure volume Loop you get this line here and this slope is your compliance which is the change in volume over the change pressure you then take uh the iso pressure of e LV across and you take an ISO volume of end in TR long volume up
To make this right angle triangle so now we have three sections within our pressure volume curve the first section here is the inspiratory resistive work that the respir muscles have to overcome we have our inspiratory elastic work and then we have our total expiratory work
At the top so here we’re able to discern between elastic and resistive on the inspiratory side but here we put total expiratory um work in one section oh um yeah so here’s the graph here and we know how we’re getting our esophageal pressure but how are we
Getting our volume so there’s two ways one um is you can just integrate flow from what you get uh yeah from your flow Trace another way is you can use a motion capture system where you have where it look at the change in shape of the abdominal and rib cage wall using
Reflective markers so you have 89 to 90 reflective markers put onto um the chest wall and you can make different compartments so in this example they have two compartments the first one is blue here which is our rib cage compartment and then we have a sorry a um abdominal compartment in green here
Now if you look at the bottom the left side is their cycling mod modality and on the right side is a running modality the first panels are volume um over time then you have a sopal pressure over time and gastric pressure over time so we’ll focus on the first section here of
Volume the black Trace is the volume changes we’re getting from the motion capture system and the red one is what we’re getting through the flow integration and you can see that they match quite well whether it’s during cycling or during running another way to measure your work
Of breathing or at least calculate it um is using modified Campbell diagrams so it’s very similar to what we just saw with the pressure volume move but now the axes are flipped so you can see that esophageal pressure is on the x- axis and volume is on the y axis you can uh
Pinpoint where your inspiration is here and then you expire on this side so you take a composite average of your pressure volume loops and plot those you then find your end inspiratory lung volume so the top of your breath and and expiratory lung volume at the bottom of
Your breath very similar to the other one where you will find the slope between those two and that’s your lung compliance but we also have our chest wall compliance which you can calculate with an equation and then plot it based on your functional residual capacity right that’s where you’re at at a normal
Breath out where those com um the lung and chest wall elas are at their are at their equilibrium so you can see here there’s four sections so we have our inspiratory resistive in this section our inspiratory elastic and then our expiratory resistive and expiratory elastic so we’re able to now discern
Between in our expiratory work what is elastic and what is resistive so does this work of breathing defer based on sex so in this study they did an incremental exercise test with instrumented esophagal balloon catheter um we have minute ventilation on the x- axis as well as work of breathing and jewels per
Minute on the y axis and you can see about after 50 to 60 lers a minute women have a greater work of breathing than men um and just to note that this line did get extrapolated over to 200 liters a minute so they would be equal but this
Line um originally wasn’t there up to that point so they wondered why was the work of breathing higher well you can look at it based on those components that we went through so we have male on the left and female on the right and just visually you can see that the Fe
The female pressure volume Loops are much larger than the ones in the male now these two participants had comparable ventilations at 100 liters a minute a comparable title volume of 2.2 and a breathing frequency of 50 breaths per minute and you can see visually one’s larger than the other and that’s
Correct because the total work breathing is almost double in a in this female and why is that well we can see it’s because of the inspiratory resistive sides and the inspiratory um or sorry the resistive uh expiratory side as well you see those two are much larger where the visco elastics are very
Comparable so to understand why the resistive part of breathing is larger in females you have to come back to this idea of D synapsis which comes dis from unequal and anopexy from growth it’s this idea that you can have disproportionate growth within uh two parts of an organ so in our example
We’re using Airways as well as lung tissue and so to measure this we need to find a variable that’s sensitive to Airway size and a variable sensitive to lung size so what we use is Vmax 50 which is the flow rate at at 50% of your vital capacity and you use vital
Capacity as your sensitivity to lung size now we are dividing out the um this variable which is your long elastic recoil at 50% of your vital capacity because your expiratory flow rates uh depend on Airway size but also it can also depend on your elasticity of your
Lung so we divide that out so we can really narrow down just what Airway size is looking at and with this um Dr me found that fully mature lungs of men appear to have Airways that are approximately 177% larger in diameter than are the Airways of
Women so with this concept in mind one of my uh lab mates their doctoral research was looking at differences in Airway size uh using optical coherence tomography so here they came into an incremental exercise test they had an assage balloon uh instrumented to look at the total work of breathing but then
Also divide into its components of resistive and elastic they then went to the hospital you can see here they’re semi sedated and we put this probe which is 58 microns um around a plastic sheath which is 900 microns this goes into the biopsy Port of a bronos scope and we
Slowly feed oh sorry we slowly feed it through uh until it gets wedged into the Airways and once it’s wedged in the Airways we have a motor system on it and so it slowly pulls back and as it pulls back this probe has a camera on it and
It’s videotaping um in a circle as it gets pulled back so an image a snapshot of what the video looks like is here and with that we can calculate the luminal area which is our yeah our L our luminal area and we did that with four to the
Fourth to eth generations of the lung when you associate the luminal area with work of breathing you can see here are Airway Generations from 4 to 8 on the x- axis and Lumin area is on the Y AIS the females are in the white dots whereas
The males are in the black dots you can see in generation four through six the luminal area is larger in males compared to females but it’s also good to appreciate that there is some overlock and so this difference in luminal area was associated with our resistive component of work of breathing
So you can see at the top here the total work of breathing is larger in females than males and it’s really explained because of that resistive component because the visco elastic Point are very similar in females and males and that is because with resistance when we change that diameter
A large factor is that radius because it’s power the four power of to the fourth power so how about aging well a lot of things happen as you age you have a decre um a lot of of your systems start to deteriorate but the main ones I want
To focus on here with your mechanical work of breing is with aging you have a decrease in chest wall compliance as well as an increase in the lung tissue compliance so your lungs become floppy so in this study they had younger and older uh females and males doing incremental exercise test with these
Esophageal balloon catheters placed um and they compared them at their minute ventilation in liters per minute to the work of breathing so here we can see very similar relationship the blue line is the younger females whereas the red line are the younger males and now if we
Plot the older individuals we see the same relationship with the younger part participants but it’s shifted upwards so with aging there’s a greater work of breathing but because of that increase in um elastic work of breathing so we looked at how we can look the mechanical cost of breathing
But what about the oxygen cost of breathing so in this study the participants came in they did a day one they did an incremental exercise test with sage Geo balloon catheter they came in another day they wore the same clothes they sat on the same bike here and they mimicked
Their ventilation that they did during exercise and how are they able to mimic it well because they looked at this screen here they had a pressure volume Loop to follow and an a flow volume Loop also so they were mimicking uh what their ventilation looked like during incremental exercise
Test and how well did they mimic it well you can see the first top panel here is their pressure volume Loops during exercise the bottom ones are their pressure volume Loops as they were mimicking what their exercise ventilation look like well Seated on that bike and you can see from 45% all
The way to 100 on both of them and you can see that these Loops look very similar in size and shape so they were able to mimic quite well what their ventilation look like when you plot it for males versus females with ventilation on the xois and
V2 RM as their V2 um for the respiratory muscles you can see females have a lar higher oxygen cost of breathing compared to males but overall it the V2 of the respiratory muscles take about 9 15% of full body uh V2 which is a large um
Portion so a bit of a summary we can use these Sagal balloon catheters to measure aagal pressure as well as gastric pressure uh these changes in pressure are used to calculate our mechanical work of breathing and when we exercise we increase this ventilation to maintain our homeostasis but obviously comes with
This mechanical cost um and at Absolute ventilation the work of breathing is going to defer based on sex and age and these mechanical work breathing comes as well with an oxygen cost to breathe which also differs based on SE so the last variable um that you can
Get from these balloons is the EMG of the diaphragm so usually what they used to do is they put the electro pairs on the outside on the skin it’s not a great way because the diaphragm isn’t right there it’s more um and it also moves so
Here in this study they look at EMG of the diaphragm using that esophageal balloon caler but they also look at the EMG with surface electrodes of the scaling and the sternomastoid because remember as we exercise they become more and more important to our ventilation so here’s
An example of what it looks like between the muscles so we have EMG on the first section for the diaphragm then the scalin and the sternomastoid with an increase in work rate and you can see that the CMG activity increases with increasing work rate um another way you can apply EMG um
Or collecting EMG of the diaphragm is with changing or manipulating the work of breathing so you can use a proportional assist ventilator also known as a path to reduce the mechanical work of breathing and so that means the respiring muscles don’t have to work as
Hard and then we have our panels here so this is a participant before they’re on the path while they’re normally exercising you can see their flow is up here this is their esophageal um swings or esophageal pressure swings they dimatic pressure swings and their EMG once they go on the proportional
Cyst ventilator so it’s aiding them to breathe you can see that these esophagal pressure swings decrease you can also see the pressure of the DI that the diaphragms generating also decreases and Visually you can see that these EMG activity bursts are lower so you can use this to manipulate how much uh mechan
The how much the work of breathing is in a participant so what I’m looking at um currently in my PhD is this phenomena called respiratory muscle metab reflux so when you have high diaphragmatic uh fatiguing or high fatiguing diaphragmatic contractions of the diaphragm but as well as other respiratory muscles you’ll
Have an increase in metabolites within the muscles and that’s going to activate our group four frenic afference this is going to induce a reflex where see an increase in sympathetic basoc constriction activity within those limb muscles that are working so this reflex has been characterized in females males young and
Old by using a procedure that isolates respiratory muscles they sit they listen to a metronome that tells them when to inspire and expire and they’re breathing on a mouthpiece and this mouthpiece has a weight on it so they have to be able to lift the weight to bring it
Inspiration in and so they’re following how much pressure they’re generating in and they have to hit that goal so when you look at a young female versus a young male so the first section here and you have mean arterial pressure on the y axis females um right here have a
Decrease or an attenuated metabol reflex compared to young males but when you look at an older female and older male that sex difference is no longer present and they have a higher reflex compared to younger um their younger counterparts but can we train this reflex can we
Lower or attenuate it so in this study they had two training groups one that was a sham and one that actually used inory muscle training for five weeks um to hopefully Train The metabol Reflex the black dot are the first panels are mean arterial pressure and
The bottom ones are heart rate you have um from minute 1 2 and three up until failure and you can see in the train group that after training the white dots there’s an attenuated response to um the respiratory muscle metabol reflux so what I’m interested in looking
At is can we use inpr Muscle training uh in females and old older adults and see that we or and see the similar effects I also want to look at does this inory muscle train uh training change the EMG activity of the diet and the mechanics of
Breathing and I also want to see if after five weeks of draining post IMT how much of the changes were made so um that’s my presentation I want to thank everyone um that has helped me at UBC as well as uh at this University uh and Happy Valentine’s Day
1 Comment
👏🏻