9. CP Pulmonary Blood Flow Flashcards
What are the systolic and diastolic pressures for the atria?
15/4 (right and left)
What are the systolic and diastolic pressures for the right ventricle?
25/0
What are the systolic and diastolic pressures for the left ventricle?
120/0
What are the systolic and diastolic pressures for the lungs?
25/15
What are the systolic and diastolic pressures for the aorta?
120/80
What is the function of the extra-alveolar capillaries?
They take oxygenated blood from the left ventricle and supply the tissue of the lungs and respiratory tract itself.
What is meant by the term “venous admixture” in reference to the extra-alveolar capillaries?
Blood that is used by the respiratory tissues is returned via the pulmonary veins, which is carrying freshly oxygenated blood. As such the pulmonary veins return blood that is both freshly oxygenated, and slightly used.
Why might low or very high lung volumes increase pulmonary vascular resistance?
The stretch of the tissue compresses the capillaries.
What is a normal blood flow per minute?
5L / min
What four molecules are chemical modulators of pulmonary blood flow?
NO
Thromboxane A2
Endothelin 1
Oxygen
What is the main player in chemical modulation of pulmonary blood flow?
What is it produced by?
NO (Nitric Oxide)
Produced by the endothelium
What is the role of oxygen in regulating pulmonary blood flow?
Oxygen relaxes (opens) blood vessels.
Therefore areas of low O2 in the lungs have a higher vascular resistance in order to shunt blood away from that area.
Under what conditions do thromboxane A2 and endothelin 1 play a role in pulmonary blood flow?
Pathological conditions
They are both vasoconstrictors
What are the “starling forces?”
Hydrostatic pressure (negative in this case)
Oncotic pressure
What chemicals are produced by immune activation in the lungs?
Leukotrienes
Prostaglandins / Thromboxane A2
What two chemicals are removed from the circulation in the lungs?
Leukotrienes
Prostaglandin E2 and F2α
Which chamber of teh heart has the highest pressure during Diastole?
left and right atrium
Which chamber of the heart has the highest pressure during systole?
left ventricle
Alveolar capillaries receive blood from where?
What is the O2/CO2 levels in blood in the alveolar capillaries?
What does this ‘sheet of capillaries’ over the alveoli participate in?
Right Ventricle
low O2, high CO2 (mixed venous blood)
exchange of O2 and CO2 between blood and air
Extra-alveolar (bronchiole) capillaries receive blood from where?
What is the O2/CO2 levels in the extra-alveolar capillaries
What is the function of the extra-alveolar capillaries?
left ventricle
high O2/Low CO2
deliver O2 to tissues of the lungs (like coronary A. for the heart)
How do the extra-alveolar capillaries return blood to the heart?
Via pulmonary veins (venous admixture)
this reduces the PaO2 of the arterial blood by a few mmHg
Increases the PaCO2 to a small degree
Alveolar Capillary
Source of blood:
PaO2 in artery:
PaCO2 in artery:
Function:
Return to heart via:
Blood gas in vein:
Source of blood: RV via Pulm. Art.
PaO2 in artery: Low
PaCO2 in artery: High
Function: Gas exchange in alveoli
Returns: Pulm. V. to LV
Blood gas in vein: high PaO2/Low PaCO2
Extra-Alveolar Capillary
Source:
PaO2:
PaCO2:
Function:
Return to heart:
Blood gas in vein:
AKA:
Source: LV via Aorta
PaO2: high
PaCO2: low
Function: Provide nutrients/remove waste from airways
Returns: Pulm. V. to LB
Blood gas: Low PaO2/high PaCO2
AKA: venous admixture
How to calculate pulmonary vascular resistance?
PBP=CO x PVR
PBP: pulmonary blood pressure (25/15mmhg)
CO=cardiac output, 5l/min
PVR: resistance to blood flow thru lungs (how hard it is to pump blood through the lungs (18mmhg)
PVR is much lower than we see in the rest of the body due to tons of alveolar capillaries
What are the main factors that contribute to your pulmonary vascular resistance at rest?
high number of capillaries
how many are open at any given time
sympathetic/vasoconstriction (to a much less degree)
How does PVR change during exercise?
PVR drops as more pulmonary capillaries open up to accommodate the increased cardiac output
At very high or very low lung volumes, what can happen to the PVR and why?
the resistance increases a little because the stretch of the tissues compresses the capillaries
Is PVR high or low in lung disease/hypoxemia?
in increases in PVR
(COPD, interstitial lung dz, sleep apnea)
At normal resting state, PVR is ___ and systemic resistance is ____
Blood pressure within the pulmonary system is ____
Blood pressure within the systemic system is ____
Blood volume is __ in both systems
PVR-low, SVR-moderate
Pulmonary: low
Systemic: higher
5L/min
Why do you pass out if you lock your knees?
gravity pulls blood away from the brain towards the feet, so you pass out. Not locking the knees allows muscle pump in legs to bring blood back to heart and brain
this is the same in the lungs essentially
What is going on in the alveoli at the apex of the lung?
blood pressure is reduced since it is above the level of the heart
alveoli pressure is high
alveoli are somewhat expanded
less blood flow
What is going on in the alveoli of the middle regions of the lung?
blood pressure is a little higher since we’re at heart level
essentially normal pressure in blood and alveoli
alveoli are average size
blood flow is “normal”
What is going on in the base of the lung alveoli?
blood pressure is high since we’re lower than the heart
alveolar pressure is low
the alveoli are smaller
blood flow is greater
What is the role of Nitric Oxide in pulmonary blood flow?
made by endothelium
causes smooth muscle relaxation and vasodilation
sign. in normal pulmonary blood flow
(either present and dilating, or absent and no dilating)
It is active under normal conditions
What is the role of endothelin 1 and thromboxane A2 in pulmonary blood flow?
These are strong vasoconstrictors that work under pathological conditions
made in lungs
May be seen in pulmonary arterial hypertension and left sided heart dysfunction (can tx with NO sometimes)
how do the alveoli stay “dry”
Starling forces control how much fluid moves from the capillary to the lung
(lung needs to be “dry” because O2 is not very water soluble)
What is hydrostatic pressure
fluid pushing against the walls of the capillary
capillary hydrostatic pressure: Pc is the blood pressure in the capillary trying to push fluid into the alveoli
tissue hydrostatic pressure: Pt is the rest of the body trying to push fluid into the capillary however due to negative hydrostatic pressure in the tissue, Pt favors filtration of fluid from the capillary into the tissue
What is oncotic pressure?
osmotic pressure of the fluids involved
plasma oncotic pressure: Pic that tries to pull water into the capillary
tissue oncotic pressure: Pit tries to pull water into the alveolus (really small)
What are the forces trying to move water from the capllary to the alveolus?
What are the forces moving water from the alveolus to the capillary?
Pc, Pit, Pt (add these up) and subtract Pic
Pic
net result favors a net filtration of fluid into the alveoli…which is bad…
*Pc is the greatest single force in the lung
Since the net reaction of the starling forces is a wet lung (fluid moving into the alveoli) how do we keep the lung dry?
Lymphatics
Summary Slide of the Dry Lung
interstitial hydrostatic pressure is believed to be negative and favors filtration of fluid from the capillary to the alveolus
the net starling forces favor filtration along the length of the pulmonary capillary
the lymphatics are crucial in removing the filtered fluid from the alveolus
What conidition can occur if your lungs are too wet?
Pulmonary edema (assx with CHF)
Describe the metabolic function of the lung in terms of RAAS
renin converts angiotensinogen (from liver) to angiotensin 1
Ang. 1 is converted to Ang. 2 by ACE in the lungs
ACE can inactivate bradykinin and cause a cough to develop (take off ACE inhibitors in this case) because fluid (from bradykinin accumulation) has started to build up
How does the lung function in the metabolism of arachidonic acid?
both leukotrienes and prostaglandins/Thromboxane A2 are produced by immune system actvation in the lungs
Leukotrienes, Prostaglandins E2 and F2a are almost completely removed from the circulation in the lungs
