okay so today we are going to talk about the basics of ventilator we will discuss that how do you put a patient on ventilator how to initiate mechanical ventilation we will discuss the different modes of ventilation including cmv ac simv and spontaneous mode of ventilation we'll discuss that how do you liberate a patient how do you wean a patient off from ventilator first of all what are the indications of mechanical ventilation indications include low gcs score gcs less than 8 the patient has weak breathing effort gcs less than 8 is an indication for mechanical ventilation if the patient has impaired oxygenation despite giving oxygen hundred percent oxygen through oxygen mass the patient is not maintaining the saturation patient is developing co2 retention and the carbon dioxide needs to be washed out that patient must be put on ventilator now if you have seen a patient on ventilator you would have seen a tube like this an ett tube endotracheal tube pass through the patient's mouth and a balloon is inflated in the patient's airway to keep this tube in place then this tube is attached to the tubings of the ventilator and ventilator controls the breathing of the patient ventilator gives certain amount of air a volume of air with each breath and that volume of air with each breath is given with a certain pressure and that volume given with a pressure is given at a certain rate like we normally breathe we breathe at the rate of 15 to 16 breath per minute the same way ventilator gives these breaths give this volume of air with each breath at a certain rate and certain amount of oxygen is given with this air so ventilator is taking control of the patient's breathing giving certain volume of air with certain pressure at a specific rate mixed with oxygen before going into the discussion of the modes of ventilator i'll briefly talk about the correlation of volume and pressure remember on the ventilator you have all the options of setting up the certain amount of volume given to the patient certain pressure with which that volume of air is given the rate at which it is given and the oxygen present in that air but remember between the volume and pressure only one thing can be set constant one thing is to be decided by the doctor the other thing will be decided by the ventilator if doctor decides to control the volume the ventilator will decide the pressure given with each breath if you set up a constant volume if you said that 500 ml of air will be given in each breath you cannot control the pressure now pressure will be decided by the ventilator that how much pressure will the ventilator exert to give that volume of air to the lungs to give 500 ml of air to the lungs how much pressure will be required ventilator is going to decide that you are not going to decide that so between the volume and pressure you can set one thing constant and the other thing will be variable because the other thing will be decided by the ventilator why is it so now you were thinking that why can we not control both of them now just listen to this thing if you reset the volume at 500 ml and you decide that 500 ml of air must be given with each breath now if the patient's lungs are stiff if the patient chest is stiff if the patient is old and the chest wall is stiff now to give this 500 ml of air more pressure will be exerted by the ventilator more pressure will be required to put this 500 ml of air into that lung but if the patient's lungs are compliant if the chest is more compliant that patient will require less pressure to put 500 ml into those lungs so if the patient's chest is stiff patients lungs are stiff more pressure is exerted to fill those lungs with 500 ml of air and if the patient's lungs are compliant chest is compliant less pressure will be exerted by the ventilator to give 500 ml of air so the ventilator is going to decide that i have to give 500 ml because the doctor ordered me to give 500 ml of air with each breath now how much pressure will i have to give to give that 500 ml that will be decided by the ventilator same goes the other way if the doctor sets up a constant pressure if you set up a constant amount of pressure given with each breath the volume of air will be decided by the ventilator now now if you set up the pressure at 10 mm of edgy that with each breath 10 mm of energy pressure must be exerted the volume of air with which the lungs are filled will be decided by the ventilator now we'll see that how does it work if the lungs are stiff if the chest wall is non-compliant and stiff this much amount of pressure will generate low volume of lungs the lungs will not be inflated much the lungs will be inflated with lesser amount of volume the lesser amount of volume of air will enter the lungs with this much pressure because the chest is stiff the lungs are stiff if the if the patient is young and the chest is more compliant in that patient this much amount of pressure will generate more volume it will be easier for the ventilator to inflate these lungs because these lungs are compliant so more volume will be generated so if if you decide a constant volume the pressure will be decided by the ventilator if you decide a constant pressure the volume will be decided by the ventilator now if you understand this concept of volume and pressure we will apply it on the modes of ventilation we have the modes like cmv mode assist control mode synchronized intermittent data ventilation mode spontaneous breathing mode first of all before setting up a mode of ventilation you need to set up the rate at which the breaths are given by the ventilator we normally breathe at the rate of 12 to 20 breaths per minute the same way we set the rate of breathing on the ventilator like the normal physiological breathing of 12 to 20 breaths per minute in obstruction and asthma we keep it on the lower end 12 to 14 and in erds and pneumonia we keep it on the slightly higher normal quarter 18 to 20. decision of keeping the rate high or low depends on the clinical condition of the patient and abg's tidal volume tidal volume is the amount of air the volume of air given with each breath it is given six to eight ml per kg of the ideal body weight ideal body weight is different from the normal weight of the patient ideal body weight is calculated based on the height of the patient there are formulas to calculate ideal body weight in men you take it as 50 kg plus 2.3 into the height of the patient in inches minus 60 and in women 45.5 kg plus 2.3 into height of women in inches minus 60 this gives you the ideal body weight and then i based on that ideal body weight you give the tidal volume 6 to 8 ml per kg of the ideal body weight friction of inspired oxygen normally in the air the fraction of oxygen present in the air in the atmosphere is 21 percent but these patients are already having impaired oxygenation so we usually start from 80 to 90 percent and as the patient improves we slowly gradually bring it down what is positive end expiratory pressure p pressure a very important term positive and expiratory pressure is the pressure exerted by the ventilator at the end of the expiration to keep the alveoli slightly open when the patient expires the alveoli start to collapse as air moves out from the lungs but positive and expiratory pressure does not let the alveoli collapse at the end of expiration it keeps the alveoli slightly open at the end of expiration at the end of expiration positive and expiratory pressure peep keeps the alveoli open it does not let the alveoli collapse at the end of expiration that is called as peep because if you let the alveoli collapse at the end of expiration it will be very difficult for the ventilator to again open up this alveoli and more pressure will be exerted so to avoid that we ask the ventilator that even at the end of expiration just give certain amount of pressure so that the alveoli do not collapse so peep is set as 4 to 5 centimeter of water pressure we increase the peep in ards because in ards the lungs are filled with fluid and we want to keep the alveoli open and we decrease the peep in pneumothorax and increased intracranial pressure now coming to the first mode of ventilation controlled mandatory ventilation cmv mode cmv mode is usually applied to the patients who have very weak breathing effort the patients who cannot breathe by themselves the patient were in a deep comatose state and cannot breathe by themselves those patients are put on the cmv mode and cmv mode takes control of the whole breathing all the breaths are provided by the ventilator in cmb mode there is no spontaneous breathing there is no patient's effort in breathing all the effort is done by the ventilator the patient is sedated the patient is fully paralyzed patient can not take breath even if there is small little activity of breathing in the patient that is paralyzed because we do not want the patient to fight with the ventilator because we want the ventilator to take control of the patient's breathing therefore the patient is sedated the patient is paralyzed and ventilated takes control takes charge of breathing you can set a constant volume a constant rate if you set a constant volume the pressure will be decided by the ventilator that how much pressure is required to fill the that volume of air in the lungs ventilator controls everything patient cannot trigger breathing now in the coming modes we will see that there are certain modes in which the patient is having some little amount of breathing effort and if the patient has some little amount of breathing effort the ventilator will detect it and ventilator will give breaths accordingly but in cmb mode patient cannot trigger breathing because the patient is sedated patient is paralyzed patient cannot trigger breathing all the breaths are timed all the breaths are given at a certain rate with a certain volume and everything is set up by the ventilator the drawback of cmb mode the cmb mode also has a drawback since we have paralyzed and sedated the patient the patient is having no breathing effort and if the patient has prolonged icu stay with prolonged stay on the ventilator there can be a trophy of the respiratory muscles and if we are setting up a constant volume sometime it happens that to produce that certain amount of volume in the lungs to give that certain amount of volume of air to the lungs ventilator has to apply more pressure and if the ventilator has to apply more pressure more pressure can result in the damage of the alveoli in the bursting of the alveoli barotrauma and the most dreadful drawback of cmv mode is accidental disconnection results in depth sometime it happens that the ett tube gets disconnected with the ventilator tubings and ventilator control of breathing is lost because the ett tube is disconnected and the patient is sedated patient is paralyzed that patient will suddenly die so this disconnection will result in death because patient has no breathing effort patient is sedated patient is paralyzed coming to assist control ventilation assist control ventilation and cmv mode they are almost the same they are almost the same except one small difference in assist control mode patient has some breathing effort and patient can trigger breaths you set up a constant volume of air given with each breath and you set up a certain rate at those at that rate the ventilator will give breath but the ventilator will also see that whether patient is trying to take the breath or not the patient will have some breathing effort when the patient tries to take the breath the patient will try to inhale and there will be negative suction pressure developing in the patient's lungs that negative suction pressure will be detected by the ventilator and ventilator will detect that okay the patient wants to take the breath now the end the ventilator will give that set amount of volume of air at that very time when the patient wants to take the breath so patient triggers the breathing patient wants to take the breath patient has some breathing effort and when when the patient tries to take the breath the ventilator detects it and ventilator gives that amount of breath now what if the patient is not breathing at all but what if the patient has no breathing effort or very small breathing effort if the patient breathes two times a minute that is hypoventilation now in that case you also set up a backup rate you also set rate with the volume you set you set a rate on 12 breaths per minute you tell the ventilator that okay whenever the patient wants to take the breath you should give the breath at that time but if the patient does not breathe you should give at least 12 breaths per minute even if the patient is not trying to breathe you must give 12 breaths per minute but if the patient wants to breathe give those breaths at the time when the patient is breathing so this assist control mode is controlling the patient's ventilation but it is also assisting the some breathing effort done by the patient whenever patient wants to take breath ventilator gives the breath ventilator waits for some time that whether patient is going to maintain the rate that is ordered by the doctor or not if the patient is not maintaining that rate the ventilator will give the breaths so that is called as assist control mode now what are the drawbacks to assist control mode in assist control mode we tell the ventilator that you have to maintain this much amount of rate this much amount of breaths per minute whenever patient tries to take breath ventilator gives it the breath but what if the patient is trying to take breathe more rapidly if the patient is breathing rapidly and triggering the ventilator again and again that will result in triggering of the ventilation and if the patient breathes more often the patient the ventilator will give breaths more often and patient will develop a hyperventilation and respiratory alkalosis so the drawback of assist control mode is that if the patient tries to take more breaths trigger more breaths the ventilator will give more breaths and patients will develop hyperventilation and respiratory alkalosis so this is a drawback of assist control mode a simple way to remember the modes is that whichever mode has the word control in it assist control mode controlled mandatory ventilation these modes the major control of ventilation is with the ventilator as we discussed previously in volume and pressure you can control one thing so in ac mode you can either set up a volume control or you can set up a pressure control usually volume control is preferred more than pressure control but in some patients you also go for pressure control now sometime it happens that when you have put the patient on volume control the pressure will be decided by the ventilator but the pressure are exceeding the normal acceptable limits the ventilator is ringing alarm that you have set a constant volume and i am trying to give that constant volume of air to the patient's lungs but i have to exert too much pressure why i have to exert too much pressure the alarms are ringing that there is a high peak pressure you would see alarm of high peak pressure that the pressure exerted by the ventilator to give that certain amount of volume of air to the patient lungs is very high and if the pressures are very high to give that certain amount of volume it can result in barotrauma it can result in damage of the lungs so if if you see high peak pressure alarm then you need to see that what is the problem you need to go from the machine to the patient you need to see that whether sometimes there is water or secretion or blockage in the ventilator tubing so the set amount of volume of air that ventilator is trying to give it is to be given with more pressure because the ventilator is fighting with the water secretions and blockage of the tubes sometime it happens that the patient is chewing the ett tube patient is in deep comatose state and patient is chewing the ett tube and tube is blocked and ventilator is trying to give that set amount of volume to the patient but the fish that volume is to be given with more pressure and ventilator has to exert more pressure so ventilator will ring an alarm that i am trying to give that volume of air to the patient but i have to give so much pressure with it so you need to see that whether the tubings are clear whether the patient is chewing the ett tube or sometime it also happens that there is blockage or kinking of the ett tube or sometimes there is bronchosposum or secretion present in the bronchi and lungs in that case the the set amount of volume that is to be given with each breath is to be given with more pressure by the ventilator and more pressure can result in barotrauma so the ventilator will give you an alarm that okay you decided the volume i have to decide the pressure but the problem is that i have to give so much pressure to give that certain amount of volume so the ventilator will give you an alarm and then you have to see all these things that whether these things are okay or not now coming to the graphs of ventilator on the ventilator you would see certain amount of graphs going on the first one shows the pressure second one shows the flow third one shows the volume if you have set up a constant amount of volume to be given with each breath that volume of air will be given with each breath and flow shows that whether the air is flowing through the tubing or not whether it is going quickly whether that volume of air is going quickly or slowly that is called as flow and pressure with which the that volume of air is being given to the patient that will be seen on the pressure graph so you would see a graph like this on the ventilator where the lowest line is the volume flow and the pressure now coming to synchronize intermittent mandatory ventilation mode simv mode simv mode is basically a weaning of mode a mode in which you are trying to take the patient out from the ventilator in cmv mode in ac mode all the control was with the ventilator but in simv mode the patient is trying to breathe and ventilator will help the patient now in simb mode you set up a constant volume you set up a certain rate and ventilator what ventilator would do is that ventilator would just sit back and see that whether the patient is breathing okay or not patient takes the first breath ventilator does not do anything even though the patient triggers breath the ventilator is not giving any breath patient takes the second breath ventilator is not doing anything but in the third breath ventilator is saying that okay i have to maintain a certain amount of oxygen in you i have to maintain certain amount of carbon dioxide in you i have to maintain a certain rate so the third third breath ventilator will push in the volume of air but then again the ventilator sits back ventilator does not do anything and let the patient breathe once more and then after some time ventilator gives the breath so it is basically a weaning of mode where you are trying that the patient should breathe by himself and ventilator should only help sometimes in cmv mode all the breaths were from the ventilator in a cyst control mode the trigger was from the patient but the breath was from the ventilator but in simv mode the breaths are off the patient and few of the breaths in between are given by the ventilator that is called as simv mode that is a weaning of mode now coming to pressure control ventilation in pressure control ventilation you set up a constant pressure and the volume is decided by the ventilator usually we prefer volume control mode but in some cases if you do volume control the pressures exerted by the ventilator to give that certain amount of volume in some patients are very high and the pressures are peaking and those peaking pressures can cause barotrauma so in those certain types of patients especially in ards patient in airds patients when you set up a constant volume the pressure exerted to inflate those lungs will be very high and that high pressure can even result in barotrauma so in the conditions like ards we cannot set a constant volume because if you set a constant volume the pressures get out of control so in these conditions we make a compromise we said we say that okay fine we we do not want the pressures to go so high we lock the pressures in pressure control mode and we see that okay fine if the volume is generated or not but the patient should not get barotrauma in this condition in these types of condition we set a constant pressure we lock the pressure and we let the volume go up or down so in pressure control ventilation you set a constant pressure and volume generated will be decided by the ventilator in conditions like erds where if you set the constant volume the pressures will exceed the normal limit the pressures will be peaking in that condition what you do is that you lock the pressures at a certain limit you do pressure control and you let the volume go up and down and usually the volume does not go that high volume generated are less by that pressure now there are also drawbacks to pressure control mode if you have locked the pressure and somehow patient has developed secretions bronchospasm are kinking of the tube now since you have locked the pressure the pressures cannot increase and the volume generated the volume with which that air is filled in the lungs will be less so the tidal volume will decrease and patient will develop respiratory acidosis so if there is blockage if there is kinking if there is secretion the pressure is locked at a certain point and you cannot give more pressure the volume will not be generated the patient will have lesser volumes and resulting in respiratory acidosis so whenever the patient is on pressure control mode keep an eye on the expired tidal volume whenever you are using pressure controlled ventilation because if you lock the pressures in conditions like aids the volumes generated will be very less coming to spontaneous mode of ventilation in spontaneous mode of ventilation it is really the last mode after which we want the patient to be out of the ventilator after simv mode we put the patient into spontaneous mode and in spontaneous mode all the breathing effort is by the patient all the trigger is from the patient ventilator just gives some pressure support there is no pressure control in it there is just pressure support in it all the volume inhaled is by the patient ventilator just gives a little amount of pressure so that it's easy for the patient to breathe that is called a spontaneous mode all efforts and breaths are by the patient ventilator just supports each breath by providing a little bit pressure i'll give you an example if you are in gym and every day you lift 20 kg dumbbells 20 kg weights and today all of a sudden you decided that okay i am going to lift 40 kg weights today you ask your trainer to hold those dumbbells while you are trying to lift them just as a support that in case if you drop them if you lose control your gym trainer will hold it so just like that in spontaneous mode patient is breathing patient is breathing all the breaths are provided by the patient all the breaths are by patient the ventilator just provides a support that if patient somehow collapses if the patient somehow ah breathing effort drops it will give more pressure so that is a spontaneous mode usually it's the mode in which you take the patient out from the ventilator now coming to liberation from ventilator weaning off a patient from ventilator as i said first usually patients are put in controlled mechanical ventilation then in assist control then in simv mode and then in spontaneous mode the last mode slowly and gradually you start lifting the sedation the patient was in cmb mode and you slowly and gradually give the patient sedation holiday you start lifting the sedation and you try to put the patient on spontaneous mode you give the patient a trial that whether that patient is able to breathe or not whether that patient is able to leave that 40 kg weight or not and if the patient drops that you hold it with the ventilator and you do abg's regularly you check the ph of the ph is greater than 7.35 pco2 is less than 45 po2 is between 60 and 80 that means that the abg's are fine and patient is doing well that patient can be taken off from the ventilator you also check the mental status you check the secretions that whether that patient will be able to breathe if we take the patient out from the ventilator so these are all the things that you see when you are taking the patient out from the ventilator a simple comparison of cmv ac and siem mode in cmb ventilator controls everything there is no patient trigger patient is traded patient is paralyzed in ac mode patient triggers some breaths but mainly all the breathing is done by the ventilator in simv mode patient triggers the breath ventilator supports a few breaths most of the beds are by the patient but ventilator supports a few of the breaths in summary we talked about the indications of ventilator the volume and pressure control one thing can be set constant how do you set up a mode cmv mode and the drawbacks ac mode and the drawbacks high peak pressures what do you need to check in that case the flow charts and simv mode the pressure controlled ventilation spontaneous mode where you just give pressure support how do you liberate a patient from ventilator how do you wean a patient off so this was all about ventilator if you liked my video please click on the subscribe button and check out my other videos on emergency medicine infectious medicine the link of those videos is given in the description below if you liked my video please leave a nice comment thank you very much