Quiz 3 Pulmonary & Bronchial Circulations Flashcards
How does pulmonary blood pressure and flow compare to the systemic system?
Pulmonary circulation= low pressure, high flow (because resistance is 1/10th of systemic circulation)
Systemic circulation= high pressure, low flow
What is different about the Pulmonary Artery compared to the Aorta?
Pulmonary artery is 1/3 thickness of aorta and is very compliant
What is the pressure in the Right Atrium?
1 to 10
Mean 5
What is the pressure in the Right Ventricle?
15-30/0-8
Mean 25/5
What is the pressure in the Pulmonary Artery?
15-30/ 5-15
Mean = 15
What is the pressure in the Pulmonary Capillaries (PAWP)?
5-15
Mean 10
What is the pressure in the Left Atrium?
4-12
Mean 8
What is the pressure in the Left Ventricle?
90-140/ 4-12
Mean 130/8
What is the pressure in the Aorta?
120/80
Mean 90
Will high positive pressure during lung expansion collapse the alveolar vessels? What about extra-alveolar vessels?
Yes, but not the extra-alveolar vessels
What is the difference between alveolar vessels and extra-alveolar vessels?
Alveolar vessels= small vessels on the acini involved in gas exchange (alveolarcapillary unit)
Extra-alveolar vessels= larger vessels that deliver blood to-and-from the respiratory units
-also contain Bronchial Vessels
What are Bronchial Vessels and and much of CO goes into them?
Vessels that supply systemic oxygenated blood to respiratory structures themselves.
1-2% of the cardiac output
Empties into the left atrium (natural physiologic shunt)
How much do the alveolar capillary walls contribute to resistance in the pulmonary system?
40 %
How much do the alveolar arterioles contribute to the resistence in the pulmonary system?
50 %
How much of the alveolar surface area is covered by capillary bed?
70 - 80 %
What is the normal capillary volume at rest in the pulmonary system?
What is the max volume?
70 mL (1 mL/kg)
Max 200mL during exercise
What is the total capillary network blood volume equal to?
answer not numeric
RV stroke volume
How long do RBCs remain in network and how long does it take for gas exchange equilibrium?
Remain in network for .75 sec (1 cardiac cycle), but only takes 0.25 seconds to exchange!
How much weight is blood in the lung?
40 - 50 % blood by weight, more than any other organ!
How much can the pulmonary vasculature alter its volume and what does it act as for the LA?
Acts as a capacitance reservoir for the LA.
Can alter from 50% to 200% of resting volume
Total blood volume in pulmonary circulation (PA to LA)?
500 mL
What is recruitment and distention in the pulmonary system?
2 mechanisms to passively regulate increases in BF due to increased CO
Recruitment- the opening of previously closed vessels to increase the capillary volume
Distention- widening of capillary beds to accommodate increased blood/pressure. Seen in disease states LV failure/Mitral regurg
When CO is increased and raises pulmonary vascular pressures, what happens to pulmonary vascular resistance?
It decreases the pulmonary vascular resistance because of recruitment (expands to make a larger surface area)
*Recruitment is a Chief mechanism for reduction in PVR
How happens to pulmonary blood flow on inspiration in terms of pleural/thorax pressure and ventricular ejection?
Pleural pressure is more negative= higher thoracic pressure
- venous return is increased, so RV SV increased
- LV SV decreased d/t increased pressure gradient
How happens to pulmonary blood flow on expiration in terms of pleural/ thoracic pressure and ventricular ejection?
Pleural pressure is less negative= lower/more positive thoracic pressure
- venous blood return decreased, so RV SV decreased
- LV SV increased r/t reduction in the pressure gradient
True or False: Pulmonary vascular resistance increases with both higher and lower lung volumes
True
Bronchial blood circulation returns to right atrium via WHAT?
Azygos vein
True or False: Approximately 50 % of the bronchial blood exits lung by small anastomoses with pulmonary veins contributing to normal venous admixture?
True
How fast does the pulmonary lymphatic system drain fluid out?
20 mL /hr
Is the interstitium kept at a negative or positive pressure?
Slightly negative (-5) for lymphatics to drain
What are the measurement techniques of Fick’s Principle?
not super important..
- way to determine CO by using bloodflow through lungs/min
- oxygen consumption/min=oxygen uptake by blood in lungs/min
- Measurement of arterial and mixed venous blood and determination of O2 consumption.
- CO = O2 consumption (VO2)/ arteriovenous (O2) difference.
What is the minimum VO2 at rest?
300 ml/min
What effect does exercising have on blood flow to the lungs?
increases flow 4 to 7 fold and turns entire lung into zone 3.
What is hydrostatic pressure and what are the Zero Reference Points?
Hydrostatic pressure is the pressure effect gravity has on a column of fluid.
Zero Reference Points:
Right Atrium level and middle of the lung
How does gravity affect the differenct zones in the lung?
- Lung bases receive more of the RV ejection fraction than do the apex.
- Hydrostatic pressure causes distention and recruitment of pulmonary capillaries in base of lung (when standing)
- Gravity pulls down on the lung causing alveoli at apex to be more open compared to the bases
- Ventilation and perfusion are affected by gravity
Which lung zone is optimum for gas exchange and why?
Zone 3 because that area has the best blood flow d/t gravity.
P artery> P vein> P alveoli
Is a low or high V/Q mismatch better for gas exchange?
A low V/Q mismatch means that ventilation and perfusion are nearly equal
which zone of the lungs has intermittent gas exchange?
Zone 2
P artery> P alveoli> P vein
Which zone has no gas exchange and why?
Zone 1 because PA>Pa>Pv
Higher alveolar pressure will collapse the pulmonary capillaries
What are some factors that create more zone 1 conditions?
- Decreased Pulm Artery pressure (shock, sepsis)
- Increased alveolar pressure (PEEP)
- Occlusion of vessels (PE)
What are some factors that decrease zone 1 conditions?
- Increased Pulm Artery pressure (infusion of blood or fluid)
- Reduced hydrostatic effect (change pt position, standing to supine)
What can increase and decrease PVR?
Increase PVR - Hypoxia
Decrease PVR - Increased Cardiac Output
How does active regulation of blood flow throughout the pulmonary system occur?
- by altering vascular smooth muscle tone in arterioles and capillaries.
- sympathetic outflow causes vasoconstriction
- most active regulation of pulm vessels is mediated by local metabolic influences*
What are 4 of the many vasoconstrictors?
- Reduced PAO2
- Increased PCO2
- Histamine
- Thromboxane A2: local vasoconstrictor produced during acute lung tissue damage
What are 3 of the many vasodilators?
- Increased PAO2
- Nitric Oxide: epithelial vasodilator
- Prostacyclin: potent vasodilator
What is unique about Nitric Oxide?
- Produced right in area where it works (strictly localized)
- smooth muscle relaxation through synthesis of cyclic GMP
- is very toxic in high concentrations
- binds to heme 200,000 times > oxygen
What happens if there is a global reduction in alveolar oxygen tension?
Total PVR increase by constriction of arterioles and small arteries
How is the pulmonary vasculature opposite of the systemic vasulature when it becomes hypoxic?
Hypoxia in alveoli produces hypoxic pulmonary vasoconstriction (HPV), so blood is shifted to better oxygenated alveoli
Opposite reaction of hypoxia in the systemic vasculature which causes vasodilation
Why is hypoxic pulmonary vasoconstriction (HPV) important for balancing the V/Q ratio?
It will help shunt blood to better ventilated areas of the lungs. (does not affect overall PVR if <20% involved)
What is pulmonary Hypertension?
Increased resistance to blood flow in the lung
High PVR/ elevated PA pressures
What causes high PVR and elevated pulmonary artery pressures (Pulmonary Hypertension)?
- generalized alveolar hypoxia
- Low PO2, High PCO2
- Hypoventilation
- Pain
- Histamine release
Which side of the heart does pulmonary HTN cause increased work and why?
Right Ventricle
- RV hypertrophy
- Tricuspid regurg
- R heart failure (cor pulmonale)
What is the only effective treatment for pulmonary htn?
lung transplant
Which portion of the lung tends to be better ventilated?
the lower portion of the lung. (upper lung is open 60% vs lower lung open 40% at FRC. With inspiration, both will open to 100% but the lower portion actually opens more than the upper lung can.
What is a normal A-a gradient? What does an elevated A-a gradient indicate?
Normal: 10-15mm Hg
if larger Alveolar to arterial gradient, there is some degree of shunting (disease process)
What is a R–>L heart shunt?
Shunt = Perfused but not ventilated
- some blood not being oxygenated/ participating in gas exchange
- venous admixture = BF equivalent of wasted ventilation
What is a L–>R heart shunt?
Portion of CO return to right heart without flowing to body (does not affect systemic arterial O2 tension)
What is the pressure gradient on the systemic system due to gravity?
0.74 mm Hg/cm
Is the blood pressure higher or lower in the feet when a person is in the supine position?
Higher pressures in the feet.
What does the right ventricle EF of blood equal?
LV Cardiac Output
When is total pulmonary vascular resistance highest?
What happens to alveolar and extra-alveolar vessels?
At either volume extreme (high lung volumes and low lung volumes):
Max inspiration: alveolar resistance= high because alveoli pressure increases and increases pressure on alveolar blood vessels + they constrict (and extra-alveolar dilate)
Max expiration: extra-alveolar resistance = high because pleural pressure is less negative and extra-alveolar blood vessels are compressed (alveolar?)
When is total pulmonary vascular resistance lowest?
When lung volume close to FRC (at passive expiration)
FYI Total vessel resistance= alveolar+extra alveolar resistance, but the alveolar capillaries contribute more
How does mechanical ventilation affect alveoli and pulmonary vascular resistance?
- Positive pressure increases alveolar pressure= increase in resistance to blood flow
- Increases amount of Zone 2 lung volume: those alveoli will distend greater and not allow flow through
- can decrease CO (by decreasing venous return) or increase V/Q imbalance
