 So, hi guys, I'm Krishanu here and a little bit of background of mine, I have been working as a mechanical engineer for 11 years, more than 11 years now and most of my work has been across in the medical industry, although I have worked in other sectors also quite a bit but majority of my work has been in the medical devices sector and in the amount of time I spent in the medical devices sector I spent a majority of it working on ventilators and that's that's why I'm here today just to take every one of you through through the basics of ventilator and understanding the nitty gritties of it and why it is a difficult very difficult engineering challenge to have right so so to begin with let's let's start from the agenda here on so so we are basically gonna look at the types of ventilators that are there in the market so this is gonna be a very broad perspective of ventilators we're not looking at ambulatory or transport ventilators here just just the kind of ventilators you would find in a regular hospital and after that we're gonna look at the ventilators that would be needed in the current COVID situation and and what are what are the problems that you you face and then how you could be treated for that right and then we'll take a deeper drive into the working of the ICU ventilators very we are gonna take you through how each module works and why is it needed and stuff like that and then we will go through the different mechanical ventilation modes in which you will have the kind of modes that a ventilator needs to run on and the kind of sensors that are needed for it and how an electronic control needs to be in to handle all these modes and most importantly last but not the least the lung trauma that is caused by ventilators so this is gonna be a very basic overview of the kind of damage a ventilator can do to the lungs and anybody who's even thinking of making a ventilator should have this as one of their you know most prior you know highest priority information and they need to be very wary of how a ventilator can damage lungs so going on from here so the if you go back in history ventilation started from something known as a mapleson circuit a lot of you guys find the Ambu bag or the Gamma bag everybody talks about right now and this mapleson circuit is nothing but a just an elaborate balloon with a couple of NRVs and you have a fresh gas inlet if you can see here so fresh gas is nothing but a combination of oxygen, air and a little bit of anesthetic agents if needed so this circuit is primarily used when a patient is you know fully in coma and cannot breathe at all or anesthesia induced coma is there so he cannot at all breathe so you they pump fresh gas in to ensure that the coma state is always there and the Ambu bag is expressed by the respiratory therapist or whom I was doing it and this is the state where a patient cannot breathe at all so from here the ventilators basically graduated to the anesthesia ventilators that you can see in the right side so so most of these anesthesia ventilators are a better version of the mapleson circuit and they basically are used to ventilate patients who are you know under anesthesia so as as the word says right that the anesthesia ventilators will use will be used on patients who are completely on in coma or undergoing surgery and they they have no breath of their own at all and they have all pressure monitoring volume monitoring and all the other essential monitoring systems that an OT needs to have and it ensures that the right percentage of anesthesia keeps going into the patient during surgery and the anesthetist home seller is there can sit on on the table that you can see there and have a look at all the parameters and keep the patient alive during during the surgery so that's that's basically the job of this ventilator it's it's to ensure that the patient is always you know in coma during the surgery and also to ensure that the patient is alive by checking all the vitals and with everything is fine or not right and the most advanced version of it the broad spectrum of the most advanced version of it is the right most you let you see they're called ICU ventilators and these ventilators are used on in your regular ICU where you see either a patient can breathe completely or they're there they basically give assist to breathe to a lot of patients so these these ventilators basically even detect and understand how a patient is breathing and try to mimic their breath and I try to ensure that a patient can be weaned out of a ventilator so basically a lot of patients would be in coma and they would take time to to first they will take ventilator support and slowly slowly slowly they have to be removed removed from the ventilator so the it's it's only this ICU ventilator that is capable of that kind of a functionality in ventilators so coming to the next topic what kind of ventilator is needed for this current COVID situation right so a lot of patients whom you see are tested for COVID positive and need ventilation nowadays COVID usually induces something called as ARDS which is acute respiratory distress syndrome and that can be mostly tackled with an ICU ventilator and the other the Mapleson circuit and anesthesia ventilators can only be used in case of these patients being sedated under anesthesia and you induce coma and then you give them that ventilator but however if you if you have to get them out which is a like which is the most amount of time so when you say date a patient and give them anesthesia ventilator or the Mapleson circuit after you get you take him out of sedation you have to slowly bring him to full consciousness and he should be able to breathe 100% on his own so so when this phasing out of the ventilator comes you need to always ensure that the ICU ventilator is the one that can do it because that will be the one that will be tracking and monitoring the breath and changing its mode as per as per what the patient needs so I think I pretty much covered the assisted ventilation here in my previous discussion over here and weaning patients of the ventilators is just what I'm saying so ICU ventilator is something that is needed to ensure that you can you know you can take patients off off of a ventilator after that the next very important requirement from patients for patients suffering from ARDS is a requirement of peep so peep stands for positive and expiratory pressure so this is the amount of pressure that is always kept inside the lung when you're doing when you're getting mechanical ventilation this is this is very important for ARDS patients so that the lung walls and the alveoli walls do not shut in on themselves and if they do it becomes very difficult to to reopen them because the lungs and the the lung walls and the alveoli walls also will have some percentage of edema some amount of edema and that edema is usually sticky and the moment both walls of the lung and the alveoli come together what happens is it is very difficult to reopen them again and you need a very high requirement of peep in case of ARDS subsequent slides will give you more of an understanding of the alveoli and why peep is needed especially for ARDS the next point over here is this ventilator ICU ventilator needs to have some amount of intelligence and some amount of sensing sensing the reaction of the patient and when a patient gives gives breathing effort right so whenever the patient gives breathing effort this day this ventilator should be able to sense it and also try to synchronize his breath with with the breaths given by the ventilator if you don't do that you you you induce a lot of other kind of problems in the lung majorly barotrauma and volutrauma that you're gonna again I'll explain this in one of the next slides so we need to be very very careful and these with these ventilators are are designed to be very sensitive to what patient is doing and only then they can respond and not only that this whole ventilation circuit that goes goes into a lung it needs to be completely leak proof that's that's why you see those who are those who need ventilation of this level usually they need something known as an invasive ventilation where they have an ET tube and they basically put a tube down your trachea and then and then there's a balloon that blows up close to your lung and what what that ensures is there's whatever amount of gas exchange is happening this gas exchange happens in a completely leak leakage freeway leakage is the enemy of any ventilator and it it always throws off calculations by by a long time by by really far and it causes a lot of damage in in the patient's lungs so we need to be very careful and there are a lot of standards to ensure that that whatever circuits that are there and the internal circuits that are there they are completely leak proof so that the ventilator sensors work in a very in a way that is reliable and then last but not the least this the particular standard for critical care ventilators is ISO 8061 dash 2 dash 12 and this is a particular standard for the ventilator and you need you need to follow this standard to get to get into to get Europe you marking a CE marking and even FD Clare certification also right now in the Indian market if you look at ventilators are not a regulated product and this standard right now is not needed to call out to make a ventilator but it is in the works and ventilators in India which will become regulated and if they put this standard as a minimum requirement then it would make a lot it would make ventilators a lot more complicated and it would need a lot more safety safety precautions to ensure that whatever ventilation happens happens safely so if you can see on the right top of the slide over here you can look at lung capacity and tidal volume inspirators volume expiratory residual volume so before we go on to our next slides just to give you a little background these these are terms that you will use you will see me or hear me use pretty regularly so the total lung capacity is pretty straightforward you know the total volume that a lung can carry during normal operation right and a part of that total lung capacity would be residual volume that will be when the lung completely collapses and completely excels there'll be some amount of volume of air still in the lungs so that is what is called as residual volume and then you have expiratory volume so from the residual volume to the amount of volume that you need to inside to keep hold of peep that you can see your positive end expiratory pressure is called the expiratory reserve volume and on top of it you have the inspiratory reserve volume where you say the amount of buffer of ventilation keeps ventilator keeps knowing that your knowing that your inspiratory reserve volume starts you know buffer that a ventilator keeps so basically then we go on to the tidal volume right so this is something that you listen to a lot of ventilator manufacturers and designers always talk about so tidal volume is the volume per breath that a ventilator can give to a patient and this tidal volume necessarily is never the complete lung capacity or it's not even the total lung capacity minus minus the residual volume this this is always less than the reserve lung capacity just to ensure and reduce the chances of volume trauma on the patient and the tidal volume is always prescribed by a respiratory therapist or a pulmonologist or whosoever is the expert in that field so let's get into one of the workings of the ventilator over here you can see the ventilator predominantly has two inlet lines one is air and another is oxygen and both of them get filtered before they enter the ventilator and both of them need to be hundred percent dry so the major this is the major requirement for any ICU ventilator and I think why it needs to be clean is very you know understandable to anyone but why they need to be dry is because any amount of humidity is gonna hamper the working of any of the electronic sensors that you see along the line and these sensors mind you need to be very very very very sensitive so the air and oxygen enters through the filter and knee they usually enter at a pressure pressure of 60 psi and they need to be dropped down to a pressure of around 50 to 60 centimeter of H2O now from 60 psi to 50 to 60 centimeter of H2O is less than one psi so it's a huge drop in pressure and from industrial standpoint from sensing standpoint sensing anything less than one psi is very difficult and getting very very accurate sensors is very very difficult in that range so the you can also see there would be an electronic pressure sensor before the regulation happens so that that basically connects to your to your micro to your microcontroller or your electronic circuits to ensure that if the pressure inlet pressure drops below a certain amount of limit it shuts down the ventilator and ventilator throws up an alarm that a there's no enough pressure not enough pressure in the line and you know we cannot ventilate the patient with the amount of pressure you're giving so once the pressure regulator brings it down to 50 to 60 centimeter of water usually there's no regulator that can accurately bring that can accurately bring down the pressure from 60 psi to 50 centimeter of H2O sub one psi in one stage so you usually have to two pressure regulators working in tandem so one of them brings it from 60 to 2 psi and another one brings it from two to sub one psi so the usually the later regulator is more expensive since those those pressure ratings are not seen in the market and you do not have enough demand and also they're bigger and clunkier and more difficult to manufacture there those regulators would be more expensive after that once you've regulated the pressure to a certain level you need to get into flow control where you've basically control the amount of flow that is going into into the patient so in both of these cases you need very high fidelity valves and these valves also can you know can control the flow in in millilitres per second in less than millilitres like or some of them will have very low resolutions like of 0.5 ml per second or something like that so when when you have such high resolutions that are needed for these valves these valves also can can get incredibly expensive and impossible to manufacture in in in many setups so they would need clean rooms and they would need very high finishing to be to get that kind of a fidelity after that you get a flow sensor a flow sensor here is nothing but to all mechanical engineers out there they would know it's just a venturi and it measures differential pressure it have got pressure sensors in two different places and it and it detects minute change in pressure and then based on Bernoulli's theorem it can calculate the amount of flow that is happening through the ventilator after that this comes into something known as a both oxygen and air comes comes into something known as a mixing block this mixing block is where the mixing of course happens between air and oxygen and there is some amount of challenges involved over here as well so this here basically the problem is the specific weight of ventilator of air and oxygen are very different and the specific gravity sorry the specific gravity of air and oxygen are very different and they do not want to mix that easily so when you put although you put air and oxygen it it doesn't form a homogeneous mixture it forms a heterogeneous mixture and the danger of this being that there may be times when the first I mean if you get if you give the patient 10 breaths maybe three of them would be 50 60% oxygen and three and remaining seven of them would be like very low less than oxygen so both cases are not good I think sending less less oxygen will ensure that the parent the patient you know I mean he doesn't get enough oxygen and he gasps and if you have more oxygen going to the patient that also leads to a lot of medical complications and they end up you know burning your trachea or the bronchi and they they cause a lot excess amount of oxygen also cause a lot of damage to the human body so once you have ensured that in the mixing block that both air and oxygen are mixed homogeneously you send it through a pressure oxygen cell and the oxygen cell is also known as an FiO2 cell and the FiO2 cell essentially measures the percentage of oxygen that is there and ensures that the flow control happens in such a way that the amount of oxygen that the that the doctor suggests is the amount of oxygen that's going to the patient so this is one and then the final piece is the emergency pressure relief so this is a mechanically set valve which is which has no you cannot set that valve this is preset by the manufacturer and left so this is there always to ensure that if there's any problem in in the whole ventilator and it's if any of the electronics fail there you should never have more pressure getting into the patient lung which would you know lead to a lot of lung damage and even death so this pressure relief always ensures that you know if there's a software as a bug or the electronics have malfunctioned any of the valves are malfunctioned that whatever it basically releases all the pressure and gives only what is acceptable to the patient and no surgeon or no doctor can can even get access to this valve on it's neither settable by them so from here it goes to the patient and when the patient inhales and then he exhales out these gases so when this when the gases get exhaled you come to the orange side so you have it comes to the exhalation valve and and from the exhalation valve this exhalation valve is majorly responsible for ensuring peep as what I told in your preview in the previous slide so this inch this exhalation valve allows how much ever pressure above the set peep to go out and the gas to go out but as soon as the peep is reached by the patient the pressure that is supposed to be there within the lungs this exhalation valve basically stops the breath and doesn't let the patient exhale fully and the flow sensor here musically measures the amount of air that goes out and the exhalation pressure sensor also measures the amount the pressure at which the patient is breathing out and based on that you can see there's some amount of small amount of air that is taken from the input airline and this is controlled with the right right valves to ensure that whatever peep is set by the doctor is executed on the patient so you would have a you'd have a diaphragm and you just have a diaphragm and one side of it you have patient pressure and another side of it you have the pressure given and set by the doctor so as soon as the lung can overcome the pressure set by the doctor this valve basically just leaks out and then also starts blocking once the pressure set by the doctor and the pressure and the patient lungs are same you basically stop the breath so after this we get on to the breathing modes here there we go so there are predominantly four modes here so you so you can see there is volume assist and control mode so in volume assist mode you you have a preset tidal volume and only that is what is an input taken from the doctor and other pressure curves and pressure in pressures are not controlled by the doctor the ventilator sets the pressure to ensure that at what respiratory rate if you can see that sir what what what I mean by respiratory rate is the number of breaths per minute and what breath for minute is maintained is maintained to give that amount of volume to the lungs of the patient and also complete the breath so it basically only controls the volume that goes into the patient and does not it just monitors the pressure and checks for safety against excessive pressure but it does not control the pressure at all the second mode here is called the pressure assist control mode so this is basically inverse of the volume assist control mode so what happens here is you basically control the pressure and only pressure is controlled here and volumes are not controlled here so as soon as the lung reaches some amount of pressure your you know the ventilator switches to an exhalation mode and let's let's the patient exhale the air so the next mode that we come across over here is called pressure support mode and pressure support mode is large is largely also done by ICU ventilators and also there are machines in the market called bipap or CPAP that can do this kind of ventilation so this basically just supports whatever breath you're doing that it basically only gives you some pressure that when a patient can breathe so this this basically just eases the method of breathing that he the patient doesn't need to do too much effort to have a breath last but not the least I think synchronized intermittent mandatory ventilation along with pressure support so that this is usually called SIMV along with PS in the medical fraternity and why this mode is very very important is this is the mode where the ICU ventilator basically synchronizes synchronizes with the breath of the patient and then it it lets the it it lets the patient breathe breathe and gives mandatory breaths to the patient as decided by the doctor so a doctor can basically say okay that I would give five mandatory breaths in a minute through the ventilator and the other breaths will be taken by the patient itself and the patient would be taking and this this mode over here will be basically monitoring all the breathing characteristics of the patient and synchronize the breath as given by the ventilator to the patient so in all of these ventilation modes let's let's get get into each of these in a little bit of detail over here the next slides so if you can see the first mode over here is controlled ventilation and this control ventilation can be both pressure control and volume control like I'd said in the last slide and this is something that you would seek very commonly in an anesthesia ventilator as well so you would see that in volume control mode you you would have a preset flow and the flow would keep increasing inside a ventilator till it reads reaches some amount of peak and then and then the flow direction basically reverses that flow starts dropping here and then the flow comes comes back to normal when the breath is completed and similarly if you look at the pressure here if you see volume control ventilation you can see that both the pressure curves are different so the pressure here is not monitored at all you can see the first pressure would read some amount beyond which the safety would cut it off and the next breath the same pressure is not reached but in volume control mode you can see that the volumes are always maintained and the tidal volume given to the patient is always always the same across two to three breaths and once one tidal volume is met it allows the patient to exhale out and again the tidal volume goes up and then again it allows the patient to exhale out in pressure control ventilation as well you can see the same thing happens but here you can see your pressure is always constant whatever the doctor has said but the volume keeps changing the tidal volume that goes into the patient keeps keeps changing and before I go on to the next slide I would just want to say that this these slides are you know pretty much into the medical medical domain and electronic domain and I'm not an expert in that domain so I have basically referred to Dr. Lokesh Tiwari here whom you can see on LinkedIn and taken these slides from one of his presentations and then we can get on to assist control ventilation so the problem with the control ventilation before I go on to the assist is is that it is only time driven you can see that you know here the breaths that are given that is just given to a particular time duration that is set by the doctors with the number of breath per minute so if the doctor is said set it to like 20 breaths per minute well the ventilator will give the patient 20 breaths per minute so this control ventilation is always used when the patient is completely sedated and or in coma and cannot breathe at all however when you come to the next stage of ventilation it is called assist control ventilation some anesthesia anesthesia ventilators have it but most I but it is this this this feature is mostly there for ICU ventilators and you can see here in assist control ventilation here the here the ventilator keeps monitoring the breathing mechanics of the lung and once it keeps monitoring the breathing and realizes that when a patient needs a breath and only gives a breath when the patient needs it so the doctor cannot you know set number of breath per minute or something like that here the patient will only be the ventilator will only you know respond to the effort of a patient so if you can see here on the assist control ventilation pressure you can see PT triggered so you basically have a trigger you have a breath trigger so the more amount the moment the sensor of the lungs in that that is sensing the pressure in the lungs detect that there's a drop in lung pressure beyond a certain limit which is maybe 25 percent of the P it basically decides that okay this is not the amount of breath that a patient needs to have and it starts giving a breath to the patient as against a time triggered one which basically doesn't take that any any input from the lungs so here also I would say that this this is not used regularly on a patient who is fully conscious this is used on a patient who's basically serrated or coma are in coma and or is trying to get out of coma so this this is used in this mode is used in those cases more often than not after that let's come on to pressure support ventilation so when you come to pressure support ventilation it is pretty evident that this if you can see the name itself says this is just support so this ensures that your patient is just breathing breathing normally and this just aids it so if you can see here on this pressure support ventilation slide slide you can see that whenever the patient exhales and then inhales this pressure support ventilation just enhances the amount of inhalation that a patient does and then the patient doesn't breathe even the pressure even the pressure support doesn't do any work and then patient exhales again and then when again he inhales he he he inhales a lot more than what what he would do normally with his own effort so this this happened this is used when a patient is not having enough energy or as long as not functioning enough to take in the amount of breath that is needed for him to complete breathing cycle and ensure that his body is oxygenated enough and although he can take breaths but the breaths is taking a lot of effort and he's not able to you know oxygenate his body enough so that is where this pressure support ventilation is is used and they are typically they are even given to homes these kind of machines they are called three paps and my paps as i told you earlier if you can go if you can see the first uh first image that i have over here i don't know if you can see it properly but if you can see here during during the pressure breaths given by the ventilator you can see small breaths being taken by the patients over here so here if you can see uh the patient is trying to take a breath but the ventilator is not helping and you can see a condition here where the ventilator is forced him to give a breath whereas the patient was trying to take a breath as well so these are conditions where you basically end up damaging a patient's lungs because either he's trying to breathe differently that leads to barotrauma and also it leads to a lot of distress in the muscles around around the lungs of the patient and because the patient is forced to breathe despite all efforts of the muscles around his lungs so this is where a need for synchronous ventilation comes in that when a patient is trying to breathe you only basically give a breath then and you do not give a breath otherwise that is what synchronous ventilation means and coming to the next slide you have something called as simv so synchronous intermediate mandatory ventilation so here you can see where a doctor can do a trade-off right with pressure support so when a patient is breathing you you just aid his breath with pressure support but during one of his breaths maybe whatever the patient says doctor says you know you need five breath a minute or eight breath a minute the ventilator synchronizes with the breath of the patient and gives a major breath with the help of the ventilator and then he and then the ventilator keeps quiet and keeps monitoring the breath of the patient again for the next couple of breaths and again it it goes only when a patient is trying to breathe so this mode doesn't come into you know picture otherwise this mode is also used with patients who have asthma and diseases like that where they have a lot of effort to breathe they have to give a lot of effort to breathe and they keep breathing and this ventilation just helps them with the effort so coming to the trauma caused by the ventilators on the lungs so you have first of all ARDS right so if you go back this is the same condition of the lungs that that is caused by even COVID and even a ventilator can introduce ARDS as well the next one is volume trauma if you can borrow sorry barrel trauma so if you can see the right two images the top and bottom images on the right you can see that if the alveoli over here is closed completely and you're you're just giving him too much pressure giving it too much pressure you would see that the bronchi of the lungs would would start breaking in different it would bulge and just pop out or it would just you know share out in this case and this this amount of damage on the bronchi would also would ensure that there'd be more edema in the lung because the body will try to repair this by giving it some blood and energy to heal quickly so that is what happens and on the left side over here you can see how an alveoli works basically so you can see air comes in and the alveoli is is the sac around here and then you can see impure blood coming in and as soon as the air comes in there is a osmosis happening here and the air basically goes sorry not osmosis diffusion diffusion happening here so air which has higher concentration of oxygen the oxygen gets into your blood cells impure blood cells and they get oxygenated and the impure blood cells let out CO2 which get into the alveoli and it's sent out to the during exhalation so it's it's it's in this alveoli where basically oxygen exchange happens and whenever you're maintaining you're giving mechanical ventilation it is of primal importance that this alveoli is always you know is all is is not damaged because these these cell walls are very thin and these walls that causes diffusion are very very thin there you can see and because of that if you give excessive pressure or excessive volume they would rupture within no time so coming to volume trauma over here volume trauma is something that that happens over here if you can see right so if you if you give this alveoli too much of volume so you basically it's like a balloon and it you give it too much volume it it expands it expands it expands after sometime it just pops open and this pretty much affects the membrane of the of the alveoli and also it gives a lot of stress to the lungs and the lungs have many alveoli and I think a few of them get I mean if not taken care all of them can get damaged with volume trauma and also there's atlect trauma which is if you if you let the alveoli wall stick like in this case and then you force it open multiple times even then this wall gets this wall gets damaged and that is where the requirement of peep comes into the picture that I discussed earlier and to ensure that that that doesn't happen you need to have some amount of peep and in ARDS the amount of peep is usually higher and you ensure that your alveoli walls do not you know collapse onto themselves completely like like what is shown in this image and they always have some amount of air inside them and lastly that the amount the ventilator can also cause pneumonia in patients and the primary response the primary thing that happens over here is because the internal circuits of the ventilator are out of you know patient or sterilization requirements you put filter in front of them to ensure that that circuit doesn't get infected or or germs don't live there but however no matter how many filters you put there are something that escapes and because of this it is very difficult to clean the inlet airway pressure but however the exhalation ports that deal with more patient output are can be sterilized separately that you know detachable and they can be sterilized separately but however in ventilator you have to be very very careful just to avoid cross infection I think that's that's it from my side if you if anyone has any questions you can ask before I guess we compile any questions from people okay to me this is like space tech right like literally too many complexities involved too many sensors and this is a complex setup that's out there and as you said that things can fail in any place and you have the safety wall at the end which just ensures in case of failure it just stops so like I see it's complex and how even to make one how long does it actually take to make one of these and how how much of money is usually does it cost so if you if you're looking at development of a ventilator it it'll easily go into years right if you're trying to start from scratch if you're if you're reverse engineering something or you have the design already it will take you less amount of time to make it but the cost involved will be very high you will you will have to source valves and you'll have to make valves and manifolds and the amount of you need to have proper industry machines and proper setup and also have good source of these valves because these valves are traditionally very difficult to make and they because primarily because of most of these valves are made by hand right so the most critical valves here are basically finished by hand and then sent out so even the companies that are manufacturing them have a manufacturing limit to the amount of valves they can make and then when they send it out to to the companies and then they need to assemble it properly in a manifold and have a very good clean room setup where these valves get manufactured and the setup cost and and the the manufacturing cost of these will be will be very high it it would go into crawls even you know if you're trying to develop this okay uh what do you think about this whole open source ventilators that people are trying to develop with right so most of alternative centers yeah so most of these open source ventilators if i come back here they would work on any one of these control ventilation kind of setup right and they can work very well if the patient is sedated completely or is in coma and you have to keep him alive and there is no lung function at all and you just keep him alive so you have either lung volume control or you have pressure control so most of these low cost ventilators would do would essentially stop in this mode over here and if if you want to go beyond anything beyond this mode like you know maybe an simv mode or a assist mode you would need like we are talking about pressure sensors over here that that uh that typically sense around one centimeter of h2o kind of pressure and in engineering we know right that if you're trying to measure something it needs to be one tenth its least count needs to be around one tenth to one fifth of what you're measuring otherwise what will happen is if your least count is more than one centimeter of water you would never get accurate and reliable values because your error is more than what you're trying to measure so you would never get good values so you need to get that those particular sensors with around 0.1 to 0.2 centimeter of water accuracy to be able to measure these kind of values and getting those sensors would be would would be tremendously cost expensive and also time consuming most importantly okay so some of these ventilators that people are trying to build will only be helpful in specific scenarios but COVID in itself may not be not no no in it it i would just say it would not help in ARDS okay in fact if not careful these ventilators will cause ARDS essentially damage to the lung yes yeah interesting uh i guess there are not many questions out there maybe we'll redirect people to the comments if anybody has questions post the event you can actually post in the comment section of the page and we will redirect them to Prashanu okay i guess we'll end it here it was a really interesting talk i i guess i'm not sure how many people in India are actually developing this but i do come across people trying to post images saying we're trying to do it like right so i i see a lot of efforts around the world even in India i see a lot i hear a lot of people even contacting me but i just want to say this right so if if you're planning to make a ventilator i will not discourage you it's you know the more manufacturers of ventilator the better it is for humanity but it is you need to be be into it in the net for the long you know it's it's not something that you can turn around in a couple of months yeah so i mean we have this startup space in Telangana called t-hub so there's some it's kind of a maker space i guess they have this hardware division called t works uh so there are a bunch of folks who were developing one and they developed a prototype i guess they're testing it with the doctors but so yeah i guess how do you test these i mean right so when you test one of these ventilators you need the first thing you need to do is you need to buy a lung simulator so any of the high-end like any of the ventilator manufacturers have a lung simulator and if i if i can get back to the slide right there's this iso standard over here right the iso standard calls for you to test it on that simulator and when you buy that simulator and test all your modes on that lung simulator and ensure that all lung compliances and all lung conditions are uh the ventilators behaving to is proper and acceptable only then you can sell this ventilator in the market right so without a lung simulator i uh even if you say a doctor is you know testing this untested ventilator on a patient it is basically unethical you should not be doing it uh i mean do we usually have lung simulators and like educational hospitals i don't think so because it's a very expensive uh piece of equipment most of them most people think test lungs are lung simulators but it's not uh a lung simulator is a machine that can easily cost upwards of 10 lakh rupees and then it's very difficult to maintain because you have to send it out every year to calibrate uh to the us or to whomsever is a manufacturer of the simulator and then it goes to them and then they calibrate it and then they send it back every year year on year and uh it's very expensive to keep and it's very expensive to maintain as well so that's that's that's how you've got to test a ventilator and it's very difficult like uh designing a ventilator can take you between you know a couple of years or three years and then you when you figure out the testing that will take another year or so okay quite time so i have one question from the audience he was like uh there are these new uh ventilators splitters like mask oh yeah yes yes where they're providing one ventilator for multiple patients uh how how does that work so same synchronized breathing so long and short short of it is in most cases it does not work right so let me let me be very clear here but however there are few cases under which they work so if i can come come down here uh if you go to volume control and pressure control in these cases also they will work provided one of these splitters have some kind of a valve which which controls the amount of volume that gets into difference see basically when you put two different patients you've got two different lung compliances and uh if you're trying to do synchronized intermittent breathe breath on them it is impossible because a ventilator would not know which lung is behaving in which way at which lung is trying to breathe so it will become very difficult to do simv on them uh pressure support is possible is one of few things that's possible pressure control is possible but pressure assist is not and volume assistant control is also out of the picture but pressure assistant pressure control is possible with the condition that both of these lungs have the same pressure and both and compliance and then whatever the splitter is can give two different volumes to the size of the lungs otherwise you will need to look for lungs that will need same tidal volumes and when it needs the same tidal volume if you if you have a like if you have 10-15 patients you will not even get a single patient who has a who need who needs the same amount of pressure and who needs the same amount of tidal volume it's statistically very low so they would not help you in any way so these are very few conditions where you can use these splitters okay so it's it will help provided you have have these kind of ventilators and where you're also you you are controlling the flows yeah which means me to the question like how train should a medical professional be to actually operate this right so respiratory therapy is a field of paramedical in itself you you need a BSE or MSC to do it and even the pulmonologist and all they have to do your mbbs and have to do your complete you know masters and other things to be trained enough to understand enough to be able to handle a ventilator so even nowadays in hospitals right the people those are nurses and all do not set a ventilators these doctors those who do they come and set it and then these ventilators I need to bring up one more point over here most of these ventilator handles patients for weeks and weeks and months even years we've always heard of patients who are there in the ICU for a year or two years or three years in coma and then you know the payoff family you know cannot pay for the ventilator anymore and stuff like that but this ventilator is supposed to be doing that so can you imagine the amount of reliability that a machine needs to have to ensure that you know in a year you can imagine this gives 20 breath in in one minute in one one and a half years how many breaths this machine gives and all these breaths should be reliable all the time even if one breath goes wrong it kills the patient right so that much amount of reliability needs to be built into these ventilators and that's that's what's very important for us over here it's it's it brings out that most of this is like a very complex problem both in terms from a health care perspective and even from a tech perspective whether it's mechanical engineering perspective rather i don't want to call it tech per se in terms of both mechanical and electrical so i would want to bring you know one more thing into consideration over here making the low-cost ventilators is not something new right if if people are thinking right now oh covid has come and we have to make low-cost ventilators no it's it's not something that is new engineers have been trying for tens of tens of years to try to make something low-cost and something more uh accessible but it's not possible many of the african countries few of them don't even have a single ventilator and they have dealt with pandemics like ebola and like for example nigeria nigeria has one ventilator right and it's it's people are trying to make it for a long long time now and this is where you hit a roadblock where you say oh okay this this is what the laws of physics allows me to do this is what laws of physics doesn't allow you to do you know it's you cannot go more than the speed of light right i mean that's that's what it is it's it's a physical boundary that you are fighting against over here okay on that note uh thank you so much krishanu for explaining these basics of how ventilators work i hope people understand what they are trying to do when they are attempting to build some of these and hope uh more than be more people also learn about this and more medical doctors are also trained on these and we'll end it here if you have any more questions please comment on our page and we will ensure that they reach krishanu and we'll see we can get it applied for you okay thank you thank you