hey guys if smithy coasters perfection a loss for medicine makes perfect sense we continue our playlist pulmonology this video is video number 26 in the series please watch these videos in order in the previous video we started talking about lung physiology we talked about normal quiet breathing inspiration exploration stuff like that today I'll talk about lung pressures we have three types of pressures intrapulmonary pressure transmural pressure and intra plural pressure those are really important for you to remember and let's get started the intra pulmonary pressure is the pressure in the lung or in the alveoli this can be positive or negative the intrapleural pressure is the intrathoracic pressure which is the pressure between the two layers of the pleura and this is always negative we're talking about normal people here transpulmonary also known as transmural pressure is the pressure that actually inflates the lung is the difference between one or two and this is always positive for the pros transpulmonary pressure and intrapleural pressure have the same amount but they have different charges interpreter is always negative transformin airy is always positive translation if the intrapleural pressure is negative six at that same moment the transmural or transpulmonary pressure is going to be positive six same quantity but the sign is different let's talk about intrapulmonary pressure which is the pressure inside your lung or inside your alveolar a-kor according to Boyle's law when you inspire and inhale the volume of your lung increase so the pressure is gonna decrease because according to mr Boyle the relationship between pressure and volume is inversely related so the greater the volume the lower the pressure when you inhale you increase the volume and decrease your pressure when you decrease your pressure it's going to go to negative one what do you mean by negative one I mean that at that moment let's say the atmospheric pressure is zero it's minus one it means it's below atmospheric as you know from physics negative pressure pulls stuff so it's gonna suck the air in that's why you breathe in the opposite happens during expiration when you expire you're decreasing your lung volume so you're increasing the pressure according to Boyle's law therefore your intrapulmonary pressure will rise above the atmospheric pressure when it rises above the atmospheric pressure this pushes the air out at the end of inspiration and at the end of expiration the pressure is atmospheric inside your lungs why because during med inspiration your lung expands the pressure decreases creating a suction force to pull the air in then the air enters into your lung to fill the void because nature hates the ether or the vacuum when the air fills the void it raises the pressure therefore at the end of inspiration your pressure is back to atmospheric from negative one add that mid inspiration to zero at the end of inspiration same thing in exploration during med exploration longer equals decreasing lung volume increasing pressure which pushes the air to the outside as the air exits the pressure decreases till it reaches zero at the end of expiration so met expiration we were positive one end of expiration we are back to atmospheric so before I breathe in or out if I'm atmospheric life now I'm zero I breathe in negative one but at the end of inspiration zero okay then I can breathe out positive one at the end of expression huh zero oh my gosh I hear these graphs shut up and calm your butt down if you understood the previous slide this is gonna be a piece of cake okay so lung volume is here in blue when you inspire we increase your lung volume easy right the lung volume increased to the maximum and then you expire her back to normal is a piece of cake okay the intrapulmonary pressure which we have just talked about which is the pressure inside the lung is here in purple as you breathe in the volume increases according to boil the pressure will decrease like this when the pressure decreases it pushes the air in the air comes in and the pressure starts to normalize because now there is air filling the void until it becomes atmospheric piece of cake now let's expire we are expiring now the lung volume is decreasing the pressure is increasing pushing the air to the outside and now it's back to normal this is the atmospheric so before you begin inspiration the intrapulmonary pressure is atmospheric at the end of inspiration it's atmospheric at the end of expiration its atmosphere the crest and the trough are at the mid inspiration expiration the highest and lowest values are here the greatest deflection is in the mid inspirational expiration fine now we'll talk about intrapleural or intrathoracic pressure calm down it's easy let's talk about intrapleural pressure why is the entropy lower pressure always negative if you remember my words of wisdom because the pressure inside the pleura is balanced on the dynamic harmonious antagonism between that chest wall which wants to expand and the lungs which want to recoil this when two surfaces go away from each other they create a negative charge or a negative pressure in between which prevents them from departing it's like your histology slides bring two glass slides put a drop of water or oil in between them okay now try to not slide but separate them by pulling them apart as you try to pull them apart there are two surfaces moving away from each other getting a negative pressure in between which prevents you from pulling the slides apart it's impossible to pull those slides apart if they have a drop of water in between this is how your pleura works two surfaces parietal pleura and visceral pleura visceral pleura is covering the lung from the outside parietal pleura is lining the thoracic cavity from the inside and they have a very thin pleural fluid in between why does the long tend to recoil it's called surface tension and elasticity why does just wall tend to expand because of elasticity but it has to be like a spiral spring like this okay you know this alright because when you push it okay and leave it it tends to expand same as the chest wall your chest wall is confined in your body it's confined by by your body itself and by the lungs but if you would leave it alone on its own outside of the body it tends to expand okay I get the spiral analogy but I don't think that my chest always like a spiral okay think about you have external intercostal muscles like this and then you have underneath internal intercostal muscles like this and they are kind of perpendicular to each other same thing as the spiral same idea in physics as the lungs wants to recoil and the chest wall wants to expand a negative pressure is created in between called intrapleural pressure which in turn keeps them close together let's talk about intrapleural pressure now we're gonna inhale okay you inhale your chest wall is expanding it's moving away from the lung when two surfaces move away from each other they create in negative pressure that's why the pleural pressure is becoming more negative this negative pressure will help suck the air in and increase the lung volume fine I get it until we go to the end of inspiration now we want to get the air out the lung has recoil tendency the lung has a recoil tendency and when you expire your chest wall is decreasing its dimension as it decreases it comes closer to the lung pressure becomes a little more positive I mean less negative so your entropy Racicot intrapleural pressure is always negative between negative five and negative seven it's always negative it becomes more negative at the end not the mid like this one like the intrapulmonary now at the end of inspiration and then it becomes less negative at the end of exploration we got it so this is intra pulmonary pressure and this is intrapleural pressure the difference between them is called transmural pressure fine and this is the pressure that actually inflates the lungs if you wanna measure from here which is zero to here which is negative seven don't say the distance between here and here is negative seven the distance is not in negative the distance is always positive this is plus seven pressure we mean centimeters of water if you want to measure this transmural pressure between here and here it's gonna be around five so it ranged between five to seven remember I told you intrapleural pressure and transmural pressure have the same amount amount but different charges so five when this is five this is negative five when this is seven this is negative seven let's say that someone stabbed you in the chest so here is your nice chest wall and then there is a stab wound and then there's your chest wall now your pleura is connected to the atmospheric pressure so the pressure becomes atmospheric not negative don't say negative its atmospheric okay and don't say positive either its atmosphere so we get it now what's gonna happen if your intrapleural pressure is not negative the lung tends to recall until it reads relaxation volume which is one liter which is very very little the chest wall tends to expand on centrist relaxation volume which is five liter because the negative intrapleural pressure was due to the dynamic harmonious antagonism between the chest wall which wants to expand and along which wants to recoil but now there is no negative pressure so the lung will tend to recoil and chest-wall will tend to expand okay now let's say tension pneumothorax now tension pneumothorax is different there is actually a valve here you know your tire of your car okay when you inflate your tires with air you you have availed why because the valve lets the air into the tire but it doesn't let the air out of the tire that's why we put a valve on the freaking tire without a valve you inflate the tire it deflates you cannot drive so when you have tension pneumothorax air comes in and for some reason a valve like mechanism exists this valve will allow the air to come into the pleura but not to exit this will raise the intrapleural pressure into a positive not negative not even atmospheric but positive and this is tension pneumothorax that's why the pleura on this side will push the mediastinum towards the negative side and you will have tracheal shift towards the normal side and away from the affected side now let's talk about this negative intrapleural pressure and why do we call it intrathoracic pressure the relation between the pressure and the esophagus do you know you know that the negative pressure in the pleura the pleural pressure is negative we know that therefore negative pressure pulls it pulls on the esophagus and open the esophagus to increase the volume of the esophagus what happens when you increase the volume you decrease the pressure according to Boyle's law which states that the relation between the pressure and volume is inverse provided that the temperature remains constant now the pressure of the esophagus is decreasing until it becomes negative okay now let me ask you this do you think the pressure in the esophagus will be equal to the pleura or slightly more or slightly less now some people may say like maybe there is a teeny tiny variation wrong they are exactly the same the pressure in the esophagus is exactly equal to the pressure in the pleura otherwise let's say that the pleural pressure is more neck the esophagus will keep expanding into an oblivion let's say that the pressure inside the esophagus was like more negative than the floor it's gonna shrink until it collapses to oblivion they have to be the same that's why we call the intrapleural pressure intrathoracic pressure because all of the structures inside of the thorax whether it's esophagus or an artery or a vein or like a lymph tract or whatever lymph duct or whatever all of them are the same and they equal the intrapleural pressure that's why we call the intrapleural pressure intrathoracic pressure now let me ask you a smart question let's say I would like to measure the intrapleural pressure practically in the lab how should I do it a stupid student might suggest Oh insert a needle into the pleura oh oh shut up so let me get that straight do you want to cause pneumothorax just to have the privilege to measure the intrapleural pressure shut up so how do we do it you measure the intra esophageal pressure baby how by an intra esophageal balloon you inserted tube into the patient's mouth or nose and then they go to the esophagus and once in the esophagus they measure the pressure in the esophagus and as you know it has to equal the pressure inside the pleura voila that's why we called intra thoracic pressure fine and thanks to the negativity of the intrapleural pressure it helps with the venous drainage the venous return from your legs up to your heart it's all because of the negative internal pressure it sucks the air in and it sucks the blood up so that it can go to that right side of the heart so that you can pump it again and live happily ever after and that's why patients with severe COPD or patients who have a problem in their pleura and the pressure in the pleura is positive they end up with ankle a dream a baby because now the pleural pressure is not negative it's not pulling the venous return upwards the veinous like the veins are stagnant with pressure and with fluid increased hydrostatic pressure leading to edema is it a transudate or an exudate answer transudate is it pitting edema or non pitting edema answer pitting edema why does that pleural pressure becomes more negative during inspiration because during inspiration the diaphragm descends the intercostal muscles contract especially the external the chest wall expands creating a negative pressure pulls the air in the lung expands the more the lung expands the more it acquires a recoil tendency stored as a potential energy and the more the recoil tendency the more negative the ends of pleura pressure is since the greatest expansion of the lung occurs at the end of inspiration therefore the maximum negative intrapleural pressure occurs at the end of inspiration what's the normal value of the Interpol pressure it's always negative it's negative 5 to negative 7 there is the range negative 5 at the end of expiration negative 7 at the end of inspiration so it's more negative at the end of inspiration can the intrapleural pressure become positive yes with a stab wound this is called pneumothorax you have to say tension pneumothorax because in spontaneous pneumothorax no it's not going to be positive so we have to say tension pneumothorax well solve a maneuver ok during the vacation or matron what do you do you close the glottis and then you contract you decrease your chest walls dimension that's valsalva maneuver so the inter floor pressure is increasing because the two surfaces are coming closer to each other when the entropy or pressure becomes positive you can force the stool or the urine or the baby outside of your body it's actually disgusting to talk about mixture and defecation in the same sentence as childbirth I apologize candy and traveler pressure become less negative yes the healthier the lung the more the recoiled tendency the more negative the entropy or pressure but in emphysema you have decreased recoil you have less negative intrapleural pressure let's talk about the intrapleural pressure normally negative 5 to negative 7 okay can it be less negative yes negative 4 to negative 1 case of emphysema you have less negative therefore less ability to pull the venous return upwards that's why people with severe COPD end up with ankle edema can it be zero yes at the moment of birth so when your age is zero your interpreter is zero or step wound without a valve or a spontaneous pneumothorax in spontaneous pneumothorax a blowout blip blip just ruptured into like an alveolar blip ruptured into the pleural cavity and since the alveoli are connected to the atmospheric pressure this pressure is gonna be atmospheric which is called zero can it be positive yes stab wound with a valve called tension pneumothorax that's why there is mediastinal shift towards the normal side or with valsalva maneuver you close the glottis and you force your chest inwards the two surfaces come closer to each other creating a positive intrapleural pressure forcing the stuff outside of your body please pay attention valsalva maneuver positive interflour pressure therefore decrease the venous return that's going to the heart that's why elderly patient while defecating when they do the valsalva maneuver for a long time they can decrease their venous return and pass out in the bathroom you gotta be careful with the valsalva man it's dangerous let's talk about the transmural pressure which is the actual pressure that inflates and these tends the lung it's the difference between the inter pulmonary pressure and the intrapleural pressure this transmural pressure is a measure of the lung elastic forces which tend to collapse the lung also known as recoil pressure recoil pressure is the same thing as lunk elastic force pressure is the same thing as transmural pressure normal value I said is the difference between intrapulmonary and the interpol so here's the intrapulmonary at the end of inspiration it's atmospheric so zero minus negative 7 which is the interval pressure equals 7 next at the end of expiration so intrapulmonary is 0 into pleura is negative 5 0 minus negative 5 is positive 5 and I've told you before the value of the transmural pressure is the same value as in the intro floor pressure just change the sign Enterprise negative however transpulmonary is positive now let's tell the whole story and get the flip out of here you inspire your lung volume increased as the volume increase the pressure inside the lung decrease this is called Boyle's law okay next air comes in as air comes in to fill the void the interpoma air pressure increases and back to atmospheric then you expert you're decreasing the lung volume and increasing its pressure until the air exits and it becomes atmospheric let's talk about interpret pressure okay you inhale you expand your chest the lung expand the greater the expansion of the lung the greater the potential energy stored inside the lung as recoil tendency this recoil tendency creates a negative Interflora pressure and it becomes more negative as your lung expands as you're filling your lungs with air and as the lung expands the intrapleural pressure is becoming more negative and it reached its peak at the end of inspiration then after that the lung collapses as the lung collapses the recoiled tendency stored as potential energy starts to decrease and the pressure rises to become less negative that's the intrapleural pressure always negative transmural pressure is the difference between intrapulmonary and intrapleural at the end of inspiration between here and here this is the distance is 7 so we call 7 centimeters of water at the end of expiration from here to here and this is 5 baby and this is the centimeter what which pressure is the pressure that actually expands the lung it's the transmural pressure that's why it's increased at the end of inspiration and decreased at the end of expiration you're struggling to learn about Legionella mycoplasma Pseudomonas rhino staff and stripped and e-coli check out this amazing website called pic Manik pictured mnemonics for medical students nursing students pharmacy students etc please see the link in the description below and they are not a sponsor of this video but they are awesome thank you for watching please consider supporting this channel on patreon so that I can make more videos in the future just $1 makes a difference with me and I'll send you my notes my cases and my audio nose depending on your tier and please subscribe to my youtube channel and hit the bell to get notified follow me on Facebook I 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