Respiratory Physiology II PDF 2022

5 Ola Qutaiba & Naseem Al-Ta'mari Dental student Dr. Yanal Shafagoj Before talking about our main topic, we have to Make a quick revision between the pulmonary and the systemic circulations: Comparison (arterial pressure if it was) Systolic Diastolic Mean (1/3 systolic + 2/3 diastolic) capillary ‫ال...

5 Ola Qutaiba & Naseem Al-Ta'mari Dental student Dr. Yanal Shafagoj Before talking about our main topic, we have to Make a quick revision between the pulmonary and the systemic circulations: Comparison (arterial pressure if it was) Systolic Diastolic Mean (1/3 systolic + 2/3 diastolic) capillary ‫المحاضرة شوي صعبة‬ ‫ياريت تكونوا مركزين منيح بدراستها‬ Good Luck!!! Pulmonary circulation Systemic circulation 25mmHg 8mmHg 14-15mmHg 100mmHg 80mmHg 95mmHg 7-10mmHg 30mmHg (if it was surrounding a muscle knowing that the starting point is 40 and the ending point is 20, we measure the pressure in the center to get 30mmHg). Notice, there’s a tiny amount of blood pressure going to the pulmonary capillary, that’s because we do not want to make Filtration, it’s not the main function here! Lungs can get some nutrients and filtration from another sites, and just by imagining if the amount of blood going to the pulmonary capillary was huge, we would suffer from a Pulmonary Edema, and the problem never stops here, the case will get worse to have an interstitial edema, ending with an alveolar edema, why so? Well, as we know the diffusion is inversely related to the thickness, in Edema we have a great increase in the thickness, resulting in a very poor diffusion, and that could rupture the alveoli, so the gas exchange won’t happen properly (Hypoxia later), that’s why we have the Lymphatic System to correct such actions (we will talk about it later). Ok, going inside a pulmonary capillary, we will see 2 main forces, the capillary hydrostatic pressure (Pc) (10mmHg), and the πcap (from proteins) (28mmHg, dividing into 20 from the Albumin, and 8 from the Globulin), while outside the capillary there’ll be the interstitial pressure (Pi) (-5mmHg) and πinterstitial (14mmHg) the last one is kind of big due to the presence of proteins in interstitial. The previous forces are involved in one law, that helps to know Whether there’s an absorption or filtration, which is the Starling Forces Law (Forces going outside – the ones going inside) (πinterstitial + interstitial pressure + oncotic pressure =29mmHg) – (πcap =28mmHg) = +1 mmHg {FILTRATION, but so little and we discussed why above}. - Qleft heart area = Pa /TPR = 100/100 = 1 and that means the blood output is 5L per min. - QRight heart area = Pa / PVR = 14/14 = 1 and that means the blood output is 5L per min. From the two statements above, you clearly can see that the Total Peripheral Resistance (TPR) is higher than Pulmonary Vascular Resistance (PVR), nearly by 7 times more and that’s why the thickness of the left area is bigger than the right one (High R = High P = more the thickness). The lung has an apex and a base, by looking at the figure You can sense where the blood prefers to stay, which is at BASE , due to Gravity. Apex So, Q base > Q apex (By 20 times). In a standing person, the plural pressure is differing in different. sites (Regional Difference), in apex it might reach -8mmHg, while in base it reaches -2 mmHg, with that amount of pressure. The apical alveoli are already inflated, and the ones in the base are partially inflated (very compliance), so in any action of taking a breath, most air will just go directly to the base, making the ventilation higher than the one at the apex. Base Remember! It’s not wise to inflate a totally inflated lung. So, V base > V apex. Now, if you remembered the Alveolar Ventilation was equal to 4.2 L per min ( we reached it by multiplying 350 with 12), dividing the result with 5 (cardiac output), we will get 0.84 (we also refer to it as 1) and that’s the Average V/Q. Here, the V/Q apex > V/Q base. V/Q in the apex = 3.4 which means we have air more than blood so this region helps to have alveolar wasted volume (so PDS>ADS) Don’t memorize the numbers. But you have to know that V and Q are more in the base but V/Q RATIO more in apex A question to ask!!! If we have an alveolus surrounded with a Closed blood vessel (No blood perfusion), that case is called a Pulmonary Embolism, can you tell the V/Q value and the value of the O2 pressure inside the respiratory zone ? Answer: We have an air Ventilation (V) but no Perfusion (Q), so the Ratio will become ∞ (Any number / 0 = infinity), in addition to that the O2 pressure will be equal to that in the ADS (150mmHg), due to the poor diffusion, same thing applies to the Pco2 (0mmHg). Same case but replacing the closed BV with a poorly ventilated lung (due to a closure in the airways), the ratio will be equal to ZERO & the Po2 will equal the one in the capillary venous side (40mmHg) (O2 will diffuse from the capillary to the alveoli until PO2 in alveoli become as much as PO2 in capillary ). The V/Q in the Apex >1, according to that the PAO2 in an apical alveolus will be MORE than a 100, could be 130mmHg, while in a basal alveolus the PAO2 will be Less than a 100 (90mmHg). The blood drained from the Apical region as PAO2= 130mmHg (in a standing person), same thing applies to the basal region, the drainage of PAO2=90mmHg, but if we are asking about the Quantity, the base is higher by 20 times than the Apex (Q of the base > Q of the apex) PAO2 =130 PAO2 =90 So when we calculate PO2 for blood that goes from lungs to the heart it will be 100 mmHg (actually it`s 95 and we will know why in the next lec). Talking about the aerobic bacteria, which prefers to live in the apical alveolar regions, where the higher oxygen pressure Do you still remember the Respirator??? Yes, that one machine we’ve talked about in sheet2! Well, we said that using it with an inserted tracheal tube (intubation) helps in the breathing mechanism (artificially), if that machine was calibrated to give pressure (positive pressure breathing), the alveoli might inflate way too much (because of high pressure) and it could affect the surrounding capillaries, and that might lead to a capillary closure, resulting in V/Q = infinity. CARDIAC SYSTEM ☺ As you can see, the blood flow is fluctuating between The Systolic and the Diastolic (Systolic is higher by 35%). In that case, we call the blood flow Pulsatile (Fluctuate more in systole, less in diastole), with the only exception is the Coronaries (in the heart), they receive more blood during Diastole than the systole because in contraction the arteries close, so no blood entry. →Zones of pulmonary blood flow: ▪ Zone 1 Blood flow in pulmonary capillaries is pulsatile but in systemic capillaries is not pulsatile, while the blood flow is no more continuous with respect to time but it's intermittent situation, because 1/3 capillaries are opened at any time while the other 2/3 are closed, (don’t forget that they have pre capillary sphincter). → No flow at cardiac cycle because alveolar pressure> systolic pressure> diastolic pressure (PA >Pa>Pv ) - This zone doesn’t exist in normal human lungs. - Occur in some cases like bleeding or when we set the ventilator at very high pressure. ▪ Zone 2 Systolic pressure> alveolar pressure>diastolic pressure (Pa>PA>Pv) → Flow during systole only - Intermittent or pulsatile flow - Occur in small area in apex of the lung. ▪ Zone 3 Systolic pressure > diastolic pressure> alveolar pressure (Pa>PV>PA) - It flows through the entire cardiac cycle. - Occur in our normal lungs. NOTE: During exercise there is only zone 3 :(lymphatic system) ‫اوك هسا الزم تركيز حاد ألنه تكملة للجزء اللي بأول صفحة‬ Normally, we have filtration and reabsorption happened at the wall of capillaries, and these events are controlled by what we called starling forces. - Starling forces are 4 forces, and they are: 1- Pc; Capillary Hydrostatic pressure - a filtration force (pushes fluid outside the capillary) it equals (10 mmHg) in pulmonary capillaries. 2-πc; osmotic (oncotic) force, due to plasma protein concentration – a reabsorption force, *It equals (28mmHg) in all capillaries of the body 3-Pi; interstitial fluid Hydrostatic pressure – it’s variable but ranges from zero to slightly negative. *It equals (-5mmHg) in the lungs >>represent the intra-pleural pressure 4-πi; osmotic force due to interstitial fluid protein concentration - a filtration force. *It equals (14 mmHg). - The summation of these forces: 10+14+5= 29 (filtration forces outward) “due to proteins”. -28 inside (reabsorption force). So, there is a difference of +1 between filtration and reabsorption, there is a little filtration which is taken up by lymphatic system (scavengers of our bodies) it removes everything (proteins, dead cells, access fluids….etc). →The lung should always be dry, we cannot tolerate pulmonary Edema, top medical emergency (threatening situation). - If the capillary Hydrostatic pressure becomes 28 mmHg instead of 10 mmHg the extra filtration will become +19 so more fluid filtration which causes edema. → In acute MI (Myocardial infarction), patient will have pump failure (left ventricle can't pump the blood) so he will have accumulation of blood in left ventricle and pulmonary veins and capillaries so Pc will increase to 28 mmHg, even if Pc increases and reaches up to 25 mmHg, (This is called pulmonary edema safety factor), lymphatics can still take care of the extra filtered fluid →In chronic conditions -like chronic left heart failure: even if Pc reaches 45 mmHg, lymphatics can still take care of the extra filtered fluid. This means that if a person developed pulmonary edema, his situation must have been severe (and his body has undergone severe damage). - However, the lung is full of lymphatics and can take care of the excess filtrated fluids and edema does not occur. Bronchial Circulation: That circulation arises from the Aorta, it also considers as a part of the systemic circulation (oxygenated), it receives about 1-2% of the left ventricular output (polluted and mixed circulation). Look at the figure, there are 2 alveoli, and between them there’s an alveolar capillary, on the outside we can see an Extra capillary, when we inhale these 2 alveolus will get bigger compressing on the capillary between, while the intraplural pressure becomes -6 mmHg, which leads the extra capillary to dilate, now there are 2 different R, the first one is high and the other is low, in that case we take the Total R by saying: TR= R1 + R2 Notice→the graph shows the least point of TR, which is at the FRC. In emphysema (FRC is higher than normal) and fibrosis (FRC is lower than normal), the pulmonary vascular resistance (PVR) will be high enough to reach the AFTER LOAD which lead to (Right Heart Failure). After load: the amount of blood that remains in heart in right ventricle after contraction. - The load imposed on the ventricle after contraction: it is the systolic ABP End of sheet #5