Pulmonary Circulation
An RBC spends only _______ of a second in the pulmonary capillaries in transit from right to left heart.
0.75 of a second
What will be the effect of moderate hypoxia on perfusion and explains why? A. Decreases of zone 1 B. Increases of zone 1 C. Zone 1 remains the same
A. Decrease of zone 1 (decreases of area of the lung that is not perfused) Let us assume that the lung is exposed to mild or moderate hypoxic conditions. In that case, there will be some vasoconstriction due to hypoxia, which will make the mean pulmonary pressure rise. Let us assume it rises by 10 units, so it becomes pulmonary arterial pressure becomes 29 cmH2O and venous pressure goes up and becomes 16 cm H2O. So with such increased pressures more blood will reach the top of the lung (against a column of water about 16 cm high). This leads to lower zone 1 in the lung. However, this occurs only Incase of mild or moderate hypoxia.
_________ is a severe form of lung injury marked by persistant lung inflammation and increased capillary permeability
ARDS
What are two reasons we see high arterial pressures in systemic circulation? (Functionally speaking why does this need high arterial pressure)
1. Blood has to be pumped uphill to the brain. Also, pumps blood to body extremities through solid organs 2. The high pressure head in permits redistribution of blood flow when required, say during exercise
What are the two circulatory systems associated with the lung?
1. Bronchial circulation 2. Pulmonary circulation
What are the major types of pulmonary edema?
1. Hydrostatic edema/cardiogenic edema 2. Permeability edema
What are methods for measuring blood flow distribution in the lungs?
1. Pulmonary angiography 2. 133Xe technique 3. Microaggregates of albumin (She said randomly at the end of some other notes, that lung perfusion can also be imaged by multislice CT scans) note: 133 is supposed to be superscripted
During exercise, cardiac output rises, however there is only a modest rise of pulmonary arterial pressure. This is because PVR decreases from what mechanisms?
1. Recruitment of. Unperfused capillaries 2. Distinction of existing pulmonary capillaries
Keep in mind that when she refers to the top and bottom of the lungs, they are not anatomical locations. They depend on body position. The following list gives the regions of the lung which receive maximal blood flow in various body positions. Body position and maximal gravity dependent blood flow 1. Supine (lying on back): ________ portion of the lung 2. Prone position (lying on stomach): _______ portion of the lung 3. Lying on the side: ________ half of lung _______ to the ground. 4. Suspended upside down: lung ________
1. supine (lying on back): posterior portion of lung 2. Prone (lying on stomach): anterior portion of lung 3. Lying on the side: lateral half of lung nearest to the ground 4. Suspended upside down: lung apices
Thus, mean intravascular pressure at the lung apex is ______ cm H2O lower than arterial pressure at the hilum
16 cm H2O (For a mean arterial pressure of 19 cm H2O entering at the hilum the arterial pressure at the apex of the lung would be 3 cm H2O)
Similarly, mean intravascular pressure at the base of the lung is about ______ cm H2O ______ than pulmonary arterial pressure at the hilum
16 cm H2O higher than pulmonary arterial pressure at the hilum (For a mean arterial pressure of 19 cm H2O the mean intravascular pressure at the base of the lungs would be 35 cm H2O)
The mean arterial pressure in pulmonary circulation is ______*cm H2O* The mean venous pressure = ________ *cm H2O*
19 cm H2O - arterial pressure 6 cm H20 - venous pressure
The bronchial circulation comprises ____% of the cardiac output from the LEFT heart (cause part of systemic circulation)
2%
Which of the following diagnostic test will be the most useful in determining the cause of the patients case in previous notecard's pulmonary edema? 1. Measurement of plasma oncotic pressure 2. Echocardiogram 3. Arterial blood gas 4. Ventilation-perfusion scan Give the answer and explain why each is right or wrong.
2. Echocardiogram A low oncotic pressure is rarely the principal cause of pulmonary edema. Arterial blood gas may give important indicates but it will not tell the cause of the pulmonary edema. Similarly ventilation-perfusion scan is best for diagnosing pulmonary emboli, but emboli rarely cause edema. An echocardiogram would easily identify the suspected mitral stenosis in the patient. So if you suspect that the edema is due to left heart failure then the test of choice is the echocardiogram
The upright human lung measures about _______ from the apex to the base.
32 cm
Right heart failure is also known as what?
"Cor pulmonale"
Therefore, as lung volume increases, the resistance to blood flow offered by the extralveolar vessels _________
*DECREASES*
Stimuli that evoke contraction or relaxation of vascular smooth muscle are considered to be _______ influences upon PVR.
Active influences
Permeability edema, also called non-cardiogenic edema, is the principal disorder in ___________________________.
Adult respiratory distress syndrome (ARDS)
What is an example of an active control of pulmonary vascular resistance?
Alveolar hypoxia
It is the mechanism fo ________ ________ that is also problematic for mountain climbers who expose themselves to low PO2 for long periods which can lead to the high altitude pulmonary edema.
Alveolar hypoxia (Low PO2 results in widespread vasoconstriction)
280 billion pulmonary capillaries supply blood to ______ for gas exchange.
Alveoli
_______ are connections between bronchial and pulmonary capillary
Anastomoses
At high lung volumes, then, the resistance to blood offered by the alveolar vessels _________ greatly; at low lung volumes, the resistance to blood flow offered by the alveolar vessels __________.
At high lung volumes, then, the resistance to blood offered by the alveolar vessels increases greatly; at low lung volumes, the resistance to blood flow offered by the alveolar vessels DECREASES
So what is the bad news for those on mechanical positive-pressure ventilation?
BAD NEWS: PVR is elevated in both alveolar and extra-alveolar vessels throughout the respiratory cycle. Because intrapleural pressure is always positive, a large number of blood vessels throughout the lung are compressed and provide a high amount of resistance. This greatly increases the workload of the right ventricle to pump blood to the heart. Danger: high PVR and a fall in cardiac output may cause right heart failure
In the ______ circulation of the lung, the arterial blood perfuses bronchi.
Bronchial
Hydrostatic edema is principally related to an increase in ________.
Capillary pressure (Pc)
Hydrostatic edema is also sometiems referred to as ________ edema.
Cardiogenic edema
Alveolar hypoxia Pulmonary vascular smooth muscle _____ in low PO2
Contracts *this is opposite to the effect of low PO2 in systemic circulation
Thus, at high lung volumes (attained by normal negative-pressure breathing), the resistance to blood flow offered by teh extra-alveolar vessels _________
Decreases (Recall that at high lung volumes, the resistance to blood flow of the alveolar vessels increases)
During exercise, the cardiac output increases several fold. However, there is only marginal increase of pulmonary arterial pressure. This is due to a decrease in ________ which causes an _______ in blood flow. Two processes account for this, what are they?
Decreases in PVR results in increase in blood flow. 1. Recruitment: opening of previously closed (collapsed) arteries 2. Distinction: increase in the radius of the existing blood vessels to allow blood flow. By Poiseuille's equation, this causes fall of PVR Both of these phenomena happen concurrently so there is effective fall of PVR
What is the significance of mechanical positive-pressure ventilation in reference to resistance of both alveolar and extra-alveolar vessels?
During mechanical positive-pressure ventilation, alveolar pressure (PA) and intrapleural pressure are positive during inspiration. So, both the alveolar and extra-alveolar vessels are compressed as lung volume increases, and the resistance to blood flow offered by both alveolar and extra-alveolar vessels increases during lung inflation.
During regular inspiration Ppl is ________, during mechanical respiration Ppl is ________ and PA is _______.
During regular inspiration Ppl is negative, during mechanical respiration Ppl is positive and PA is positive (this leads to a high PVR)
The pulmonary capillaries are very thin walled and have low vascular resistance, they are soft and easily ________ (diameter = 6 microns).
Easily distended
LOOK at the perfusion scan on slide 21, the dark regions represent area in both lungs that are not being perfused as a result of a pulmonary _________
Embolus Should be able to look at perfusion scan a recognize when a pulmonary embolus might be present
Other causes of permeability edema include exposure to _________ and ________
Exposure to bacterial toxins and oxygen toxicity (Or in response to major injury was listed in the slides)
What is pulmonary edema?
Extravascular accumulation of fluid in the lung
T or F: you can see the normal gradient of perfusion associate with gravity in the microaggregates of albumin technique of measuring blood flow
FALSE: it is typically injected into the venous blood while the subject is supine so that the normal gradient associated with gravity is not seen.
T or F: pulmonary and systemic circulations have similar blood flow rates and vascular pressures
False: despite similar blood flow rates, vascular pressures are considerable lower in the pulmonary than in the systemic circulation
T or F: the bronchial circulation is part of the pulmonary circulation
False: the bronchial circulation is part of the systemic circulation
T or F: the microaggregates of albumin technique for measuring blood flow is a health threat due to blockage of capillaries by the aggregates
False: the microaggregate is administered in sufficiently quantities that is occluded roughly 1 in 50,000 capillaries. This is not a high health threat
Measuring blood flow distribution: Microaggregates of albumin: Places where there are 1. Few capillaries working = ________ 2. Many capillaries working = _______ *see image on slide 20
Few capillaries working = dark Many capillaries working = light (Because the aggregates of albumin send out gamma rays which appear as white from the areas where they got stuck which would be in capillaries that are working)
As the edema fluid builds up, first in the _______ and later in the ______, diffusion of gases — particularly _______—decreases
First in the interstitium and later in alveoli Oxygen
The difference between PC and Pis in the starling law represents the net force favoring fluid __________. (Reabsorption or filtration)
Fluid filtration from the vascular space to the interstitial space
Microaggregates of albumin: Once administered, the patient stands in front of a _______ detector, and an image is rendered. The region that is emitting the _______ rays appears as white.
Gamma detector Gamma rays
The lower you go in the lung, the ______ the perfusion
Greater
Under hemorrhage or general anesthesia = high amounts of which. Zone and why?
High amounts of zone 1 because of low pulmonary systolic pressure.
How do the zones change during exercise?
High cardiac output... increase in zones 2 and 3. Blood in top of lungs will increase 700-800%. Blood in bottom of the lungs will increase 200-300% 1. Zone 1 will be recruited to zone 2 2. zone 2 will be recruited to zone 3
Another factor tending to decrease the resistance to blood flow offered by extra-alveolar vessels at ______ lung volumes is _____ _____ by the connective tissue and alveolar septa holding the larger vessels in place in the lung.
Higher lung volumes is radial traction
The pulmonary artery enters the lung at the level of the _______, located approximately ______ between apex and base of the lung.
Hilum located approximately midway between apex and base of the lung
Give the change in each of these values for hydrostatic and permeability types of pulmonary edema 1. Qf 2. Kf 3. Pc 4. Sigma
Hydrostatic 1. Qf - increases 2. Kf - no change 3. Pc - increases 4. Sigma - no change Permeability 1. Qf = increased 2. Kf = increased 3. Pc - no change 4. Sigma = decreased
Hydrostatic edema is caused by changes in what factors of starling's law?
Hydrostatic edema/cardiogenic edema is caused by increases in capillary pressure.
What is another name for alveolar hypoxia?
Hypoxia-induced vasoconstriction
This pathological condition of pulmonary edema may be caused by one or more physiological abnormalities, but the result is inevitably impaired _____ ______.
Impaired gas transfer (Recall that it results in a decreased DLCO)
What is the functional significance of alveolar hypoxia?
In lung regions that are poorly ventilated, PO2 will be low. This mechanism increases local vascular resistance, and thus diverts blood away from the area of low PO2. Therefore, the mixed venous blood is redistributed to other well-aerated areas of the lung. It is a mechanism that has excellent use in normal lungs: redistributing blood away from any area that might be under ventilated.
What would be the effect on PVR with removal of one lung? and explain why (longer answer)
In the remaining lung... the vascular resistant of the remaining lung will decrease. The whole cardiac output has to be pumped through the remaining lung. This will cause recruitment of additional capillaries especially in the uppermost part of the lung where capillaries may normally be perfused intermittently. The increase in pressure causes distention and increases the diameter capillaries of the entire vascular tree in that lung. Increases in diameter strongly influence resistance because the 4th power relationship in the Poiseuille equation. The phenomenon of recruitment and distention will keep pulmonary arterial pressure to a normal value. The total net pulmonary vascular resistance of the lung Blood formerly was pumped through two lungs that are in parallel with each other. Take away one of them and the net resistance increases. (This is similar to the removal of a capillary in parallel cusing an increase in the resistance from last test. **be aware of difference in net pulmonary vascular resistance and the resistance in the remaining lung
What would be the effect of mechanically ventilating the lung with positive pressure?
Increase in PVR
Hydrostatic edema An increased Pc (filtration pressure) causes an ________ in fluid flux (Of), often without any change in the _____ or ______.
Increase in fluid flux (Qf) Often without any change in the Kf or sigma
Extralveolar Vessels Some extra-alveolar vessels, for example, the larger arteries and veins, are exposed to the _______ pressure.
Intrapleural
What is the drainage pattern of the bronchial circulation?
It is unusual. About two-thirds of the bronchial capillary venous blood from this circulation drains into the pulmonary veins!!! You are adding desaturated, venous blood to the arterial blood (the pulmonary veins carry oxygenated blood) thus in the parlance of lung perfusion, this counts as a shunt (She referred to it as a physiological right to left shunt and said that this is what accounts for that range of normal PaO2 from 80 to 100)
During mechanical positive pressure ventilation with PEEP (positive end-expiratory pressure) 1. PA is positive during mechanical ventilation. Let's assume that a positive pressure of 20 chem H2O is being maintained. 2. At point B (on slide 11), now the arterial column arterial pressure = 7 cm. H2O and venous pressure = -4 cm H2O. Means intravascular pressure = 1.5 cm H2O. So this region which was intermittently perfused earlier (zone ______) will have what perfusion now?
It was intermittent perfusion earlier (zone 2) but with the mechanical ventilation, the alveolar pressure is held at a value of +20cm H2O so it is not perfused at all. (Her slide says also alveolar pressure will no longer be zero but will be 20 cm H2O, I think this is making the point that before at the end of exhalation at FRC, the alveolar pressure is 0 but in the cases of PEEP the positive pressure is maintained at the end of exhalation to prevent the alveoli from collapsing because it would be hard to open them back up again)
Due to gravitational forces, both intravascular pressure and blood flow are considerably less at the ________ than at the ______ or the lung
Less at the apex than at the base of the lung (Think of the cartoon with the people stacked on top of each other, the person at the top feels little weight the person at the bottom feels more weight) Note that it is both intravascular pressure and blood flow
ARDS is usually observed after some form of insult to the lung like what?
Like inhalation of toxins of infection
In lung regions that are poorly ventilated, PO2 will be ______.
Low
****she said that we do need to know all of the clinical problems and how they can lead to edema that are given in the last table on slide 30
Make sure that you look over this because there were no notecards made on it
What is the therapy for ARDS?
Mechanical ventilation (Treat the underlying symptoms of the ARDS)
During mitral ________, the mitral valve does not open fully
Mitral stenosis
How is it that mitral stenosis can lead to pulmonary edema?
Mitral stenosis is where the mitral valve does not open fully. So, when the blood does not go to the aorta instead it goes back to left atrium and then is dumped into pulmonary capillaries. This leads to a great increase in pulmonary vascular pressure leading to flooding of interstitial spaces and alveoli, leading to hydrostatic edema Note: this is the same mechanism by which left ventricular infarction leads to hydrostatic edema
The ______ valve separates the left atrium from the left ventricle.
Mitral valve
Extralveolar vessels As lung volume is increased by making the intrapleural pressure more ______, the transmural pressure gradient of the large arteries and veins ____________.
More negative Transmural pressure increases and they distend.
Permeability edema is also called what?
Non-cardiogenic edema
Alveolar vessels As lung volume increases during a normal _____-pressure inspiration, the alveoli increase in volume. Whites the alveoli expand, the vessels found between them, mainly pulmonary capillaries are _________. What happens to their diameters and thus what happens to resistance?
Normal negative-pressure Pulmonary capillaries are elongate. As these vessels are stretched, their diameters decrease, just as stretching a rubber tube causes its diameter to narrow. Resistance to blood flow through the alveolar vessels increases as the alveoli expand because the alveolar vessels are longer (resistance is directly proportional to length) and becasue their radii are smaller (resistance is inversely proportional to radius to the FOURTH power - Poiseuille's equation)
During mechanical positive pressure ventilation with PEEP (positive end-expiratory pressure) 1. PA is ________ during mechanical ventilation
PA (alveolar pressure) is positive during mechanical ventilation Let's assume that a positive pressure of 20 cm H2O is being maintained
The figure in slide 8 depicts the distribution of pressure in the arterial and venous columns in an upright lung. At this instant, Pa = 19 cm H2O and Pv = 6 cm H2O. If we assume the lung to be at FRC and PA = ______(the alveolar pressure) then the average pressure inside the capillary located at the top of the lungs is ______ than PA. (Greater or less than?)
PA = 0 Average pressure in the capillary located at the top (not anatomical top) of the lungs is less than PA (in the example arterial is 3 and venous is -10 cm H2O pressure so the average is 3-10/2 = -3.5 this value is lower than the alveolar pressure)
A patient on positive pressure ventilator with PEEP will have what changes in their zones?
PEEP stands for positive end-expiratory pressure = high amounts of zone 1
During mechanical positive-pressure ventilation, alveolar pressure (PA) and intrapleural pressure are _______ during inspiration.
POSITIVE *notice that it is both alveolar and intrapleural pressure
All fluids flowing steadily through a non-distensible tube in laminar flow encounter resistance to flow in the pulmonary circulatory system this is termed as _______.
PVR (pulmonary vascuarl resistance)
What would be the effect of breathing at high altitude on PVR?
PVR increases due to alveolar hypoxia
_______ influences on pulmonary vascular resistance are independent of contraction and relaxation of vascular smooth muscle tone.
Passive
The decreases in vascular resistance in the remaining lung when one lung is removed in a procedure called _____________, allows for the pulmonary arterial pressure to be within normal range at REST despite the. Whole of the cardiac output passing through this one lung. HOwever, the pulmonary arterial pressure will rise in these patients during what?
Penumonectomy Will rise during effort or exercise
Look at the figure on slide 8 and answer whether or not the perfusion will be greater at point C or the unlabeled point D which is the lowest set of values on the figure and why?
Perfusion will be greater at point D, not just because there is an increase in pressure but also because when the pressure inside the capillaries gets high they are soft and thin and surrounding by air so there is nothing stopping them from expanding. Expansion means an increase in their radius. Remember that resistance to fluid flow is given by Poiseuille: R = 1/radius to the fourth) so with distinction you get decreased resistance and a greater perfusion of these capillaries at the bottom
ARDS is a severe form of lung injury marked by persistent lung __________ and ________ capillary permeability
Peristant lung inflammation and increased capillary permeability
Kf and sigma in the starling law reflect _________ characteristics of the membrane (i.e. barriers) that separate blood from the interstitial space
Permeability
What does permeability edema of the lung result from? (From the standpoint of the starling law forces that change)
Permeability edema of the lung results from an increase in the permeability of the barrier (vessel wall) that separates the blood from the tissue. Vascular fluid (plasma) exits the vascular space (capillary) simply because the barrier funciton of the membrane is compromised or incompetent with permeability edema, the barrier (capillary wall) is more porous ("leaky") and/or permeable to fluid (increased Kf) or protein (decreased sigma)
What is the equation that describes the resistance to blood flow?
Poiseuille's equation R = (8 x viscosity x length) / (pi r to the fourth power)
Which has a higher pressure drop across circulation, the systemic or the pulmonary?
Pressure drop across systemic circulation is higher Delta P (systemic) = 98 mmHg Delta P (pulmonary) = 10 mmHg I think this is something she asked a question about in a previous year, something about the 10 fold higher pressure drop across systemic circulation is due to a 10 fold higher resistance in systemic compared to pulmonary or something like this (she was asking for the ratio of resistance between them) **had this section highlited
In ______ _________ a radiopaque substance is injected into pulmonary artery and its movement is monitored by X-rays.
Pulmonary angiography
Pulmonary Arteries = carry _________ blood Pulmonary veins = Carry _______ blood
Pulmonary arteries = carry deoxygenated blood Pulmonary veins = carry oxygenated blood
The sketch shows pulmonary capillaries bulging in the bottom of the lung. This is because pulmonary blood vessels are very _____ and ______. They are located in alveolar walls, and they have air on both side. There is little to stop them from expanding when the __________ inside them is high.
Pulmonary blood vessels are very thin and soft. Pressure inside them is high (like it is at the bottom of the lungs due to the effect of gravity)
Pulmonary capillaries have very ______ walls and ______ vascular resistance
Pulmonary capillaries have very thin walls and low vascular resistance
The whole cardiac output of the right ventricle is delivered to the ________ circulation via the lung
Pulmonary circulation
______ _______ is the extravascular accumulation of fluid in the lung.
Pulmonary edema
What does PVR stand for?
Pulmonary vascular resistance
Pulmonary veins = _______ arterial blood whereas pulmonary arteries carry ______ blood
Pulmonary veins = oxygenated arterial blood whereas. Pulmonary arteries carry deoxygenated blood
The difference between plasma and interstitial oncotic pressure represents the net force determining ___________ of fluid.
Reabsorption of fluid from the interstitial space into the vascular space
In order for the ______ heart to pump blood to the apex of the lung, it must pump against a column of water about ______ cm high, or against a pressure head of ________ cm H2O resulting from gravity.
Right heart Column of water 16 cm high Or against a pressure head of 16 cm H2O
The pulmonary circulation is driven by the _______ ventricle
Right ventricle
Note that the decrease in zone 1 only occurs in case of mild or moderate hypoxia. Exposure to high altitude is considered ______ hypoxia and so is "cor pulmonale"
Severe
What would be the effect of moderate hypoxia on PVR?
She doesn't given an answer but I think it would increase, ask her
** make sure to look at the images of both permeability and cardiogenic edema and know the differences between them
Slides 29 and 26
What is starling law? *note, she said not to memorize this but it would be good to be familiar with it
Starling Law Qf = Kf [[PC-Pis] - sigma (oncotic pressure of capillary - oncotic pressure of interstitial)] Qf = also referred to as Jv Kf = capillary filtration coefficient (describes permeability characteristics of the membrane to fluids) Pc = capillary hydrostatic pressure Pi's = hydrostatic pressure of interstitial fluid sigma = reflection coefficient Pic = colloid osmoatic (oncotic) pressure of capillary Pis = colloid osmotic (oncotic) pressure of interstital fluid
What are the means systolic and diastolic pressures of the systemic circulation?
Systolic aortic pressure = 120 mmHg Diastolic = 80 mmHg
What are the mean systolic and diastolic pressures in pulmonary circulation?
Systolic mean pulmonary arterial pressure = 25 mmHg (it ranges between 20-25 mmHg) Mean diastolic = 8 mmHg
Thus, even at normal hydrostatic pressure, in permeability edema, more fluid is filtered from the vascular to interstital space than can be reabsobed by ___________ forces or _________.
Than can be reabsorbed by plasma oncotic forces of the lymphatic system
What is the function of these anastomoses?
The anastomoses are connection between bronchial and pulmonary capillaries. They have little function in healthy adults but may open in pathological conditions, such as when either bronchial or pulmonary blood flow to a portion of lung is occluded.
The figure in 9 shows the bottom line for how perfusion is distributed in a normal, upright person. The bottom of the lung is perfused much ______ than the top is.
The bottom of the lung is perfused much more than the top is Depending on the size of the person, almost 8 times more
The capillaries at the very ______ of the lung are not perfused. As the arterial pressure increases the extent of perfusion also ________.
The capillaries at the very top of the lung are not perfused. As the arterial pressure increases the extent of perfusion also increases (I think that this means as the arterial pressure increases as you go down the arterial column, the extent of perfusion increases in the capillaries)
What is the etiology of high altitude pulmonary edema?
The chart on her slide 30 shows the etiology is unknown Loook over the chat of clinical problems that can lead to changes in each of the values of starlings law
What do the dark areas in the perfusion scan indicate?
The dark areas in the perfusion scan represent lung regions that are not perfused.
What is the functional consequence of the average pressure inside the capillary at the top of the lungs being less than PA (alveolar pressure)?
The higher alveolar pressure tends to crush the capillary and prevents blood flow. The capillaries at the very top of the lung are not perfused.
When looking at a perfusion scan, what do the light areas represent?
The light areas in the perfusion scan represent areas that are perfuse (or, that were being perfused when the microaggregate was administered)
What do the light areas in a ventilation scan indicate?
The light areas in the ventilation scan represent areas that are ventilated.
Where would be the maximum amounts of xenon be found in the lungs?
The maximum amount of xenon would be found in the bottom of the lungs which are both better perfused and better ventilated (see previous lecture on ventilation) *on slide it shows graph with the lower as having peak blood flow and the upper as having the lowest blood flow, look at this slide 19 to see this graph and the pulmonary angiography
The pulmonary arterial pressure averages _______ compared to _______ in systemic arteries. Similar pressure differences exist in other comparable vessels segments, what accounts for the different.
The pulmonary arterial pressure averages 15 mmHg (25 + 8 /2) compared to the 100 mmHg in systemic arterial (120 + 80 /2). This lower pulmonary vascular pressure is largely accounted for by the lack of high resistance arterioles that are characteristic of systemic arteries.
What is the physiological significance of the thin walls and small amount of smooth muscle found in the pulmonary arteries?
The pulmonary vessels offer much less resistance to blood flow than do the systemic arterial vessels. They are also much more distensible and compressible than systemic arterial vessels. These factors lead to much lower intravascular pressure than those found in the systemic arteries
The ventilation scan that corresponds to the perfusion scan which showed large areas of both lungs that are unperfused due to an embolus indicated that ventilation is quite uniform, and that therefore the un-perfused areas are still __________. Thus from the standpoint of gas exchange, those (under-perfused) regions constituted _________
The un-perfused areas are still ventilated. These regions constitute dead space
What are common features seen on x-ray of cardiogenic edema (hydrostatic edema)?
The x-rays usually show perihilar patchy infiltrates. Another symptom is cardiomegaly. The cardiac silhouette is usually enlarged in the chest radiograph. On close examination, the X-rays show thickened septal lines called as Kerley B lines **look at the radiograph images on slide 26 (Kerley B line is pointed out by black arrows**
Measuring blood flow distribution 133Xe technique: 133Xe is injected intravenously. The amount of soluble 133Xe in the pulmonary artery blood gives regional blood flow. Xenon is not very soluble in blood so what happens to it?
The xenon comes out of solution in the lungs and enters alveoli and is expelled out
Measuring blood flow distribution Microaggregates of albumin: albumin microaggregates labeled with 131I or 99mTc (10-50 mm) are injected in peripheral vein. Then what happens to these microaggregates of albumin?
They get trapped in small pulmonary vessels as they enter the lung.
What do the bronchial arteries of the bronchial circulation supply?
They supply the tracheobronchial tree with both nutrients and O2
Vessel walls of the pulmonary vasculature are much ________ and contain ______ smooth muscle than corresponding segments in the systemic circulation.
Thinner and contain less smooth muscle than corresponding segments in the systemic circulation
The hydrostatic type of edema is common with what types of pathology?
This hydrostatic edema/cardiogenic edema is common with left heart failure due to left ventricular infarction or mitral stenosis
While the alveolar hypoxia (hypoxia-indeed vasoconstriction) an active control mechansims for PVR is a mechanism that has excellent use in normal lungs: redistributing the blood flow away from any area that might be under ventilated. But, smoke for long enough and develop COPD, and what occurs in this mechanism?
This mechanism becomes maladaptive in that it will kill you. The heart has to pump the whole cardiac output through the lung. Ordinarily the lung has very low vascular resistance, and very low pressures are required. *in people with obstructive or restrictive diseases lung disease, the alveolar PO2 is low so if the overall PO2 is low, it causes pulmonary vasoconstriction throughout the lung* when pulmonary vascular smooth muscle contracts throughout the lung, the resistance is increased and the workload on the right heart is increased along with it. It can lead to right heart failure. Right heart failure is also known as "cor pulmonale"
*Thus resistance to blood flow _________ as you go to the bottom of the lung. Therefore, perfusion is smallest in the _______ and greatest in the ______ part of the lung.*
Thus, resistance to blood flow decreases as you got to the bottom of the lung. Therefore, perfusion is smallest in the top and greatest in the lowest part of the lung
Hence, pulmonary blood flow represents total ____ _____ and is usually the blood flow measured to determine this value
Total cardiac output
T or F: pulmonary blood flow is equal to the total blood flow of the systemic circulation
True: Since cardiac output of the left and right heart are essentially the same, pulmonary blood flow is equal to the total blood flow of the systemic circulation
T or F: the amounts of zones 1, 2, and 3 can change under physiological conditions
True: see below examples
When the lung is ventilated but not perfused, this is wasted ventilation = _____ _____ When it is not ventilated but perfused = _______
When the lung is ventilated but not perfused = dead space When it is not venitatled but perfused = shunt
ARDS is a severe form of lung injury marked by persistence lung inflammation and increased capillary permeability. It is usually observed after some insult to the lung like inhalation of toxins or infections. Which results in diffuse ________ damage and ___________. What are the symptoms and typical x-ray findings?
Which results in diffuse alveolar damage and pulmonary edema Symptoms include breathlessness, rapid, shallow, breathing, dry cough, chest pain The X-ray shows diffuse airspaces and bilateral alveolar infiltrates The patients also show typical edema symptoms like inability to lie flat. The infiltrates in the X-ray sometimes look similar to cardiogenic edema but the cardiac silhouette is normal. Kerley B lines are uncommon in permeability edema and high altitude pulmonary edema, although they are sometimes observed. (She said that there would be diffuse whiteness all over the lungs)
During mechanical positive pressure ventilation with PEEP (positive end expiratory pressure) 3. High alveolar pressure causes collapse of pulmonary capillaries increasing zone _______.
Zone 1 (I think the past few notecards were just explaining why under these circumstances the patient would have a high amount of zone 1)
What is the characteristic features of zone 1 of the lung?
Zone 1 is defined as the region that is NOT perfused PA> Pa> Pv
What is the characteristic feature of zone 3 of the lung?
Zone 3 is the region in which always perfused Pa > Pv > PA
A 60 year old woman is brought to the ER by her husband. She got up in the morning with shortness of breath and then experienced severe shortness of breath while walking from the first floor to the second floor of her home and was brought to the ER. She is mildly obese, pale, and diaphoretic (sweating) and has a faint cyanosis color to her face. She complains of fatigue and breathlessness. You notice that the patient is sitting on a chair in the tripod position. Over the past few days she has noticed that she cannot breathe properly when she is in supine position and she is sleeping on a recliner at night. She complains of cough and coughs up pink frothy sputum. Other symptoms include 1. Diffuse crackles on auscultation (listening to the internal sounds of the body, usually using a stethoscope) of lungs 2. Murmur is left heart. This person has pulmonary edema, what are some signs/symptoms of pulmonary edema in this vignette that can help to clue you in to her condition
symptoms of pulmonary edema. The acuteness of the patient's symptoms upon climbing the stairs is highly suggestive of heart disease. Notice that the person is short of breath and experiences shortness of breath in the supine position. By sleeping on a recliner she is trying to minimize the magnitude of wet alveoli in the lung. So often older people with history of congestive heart failure sleep on a recliner or remain constantly in a higher position (where the patients head is raised 80-90 degrees) the murmur in the left heart agains suggest left ventricular dysfunction or mitral stenosis
What is the characteristic feature of zone 2 of the lung?
zone 2 is the region that is perfused intermittently only at systolic pressure Pa > PA > Pv
