blood flow and VQ Flashcards
Describe the wall thickness and smooth muscle content of pulmonary artery?
- thin walls
- little smooth muscle
Describe the wall thickness and smooth muscle content of aorta?
- thick walls
- lots of smooth muscle
pulmonary blood flow is directly proportional to the pressure gradient between pulmonary artery and ?
left atrium
- systemic circulation: P = 100 mmHg
- pulmonary circulation: P = 15 mmHg
pulmonary blood flow is inversely proportional to
resistance of the pulmonary vasculature
regulation of pulmonary blood flow is via alterations in the of arterioles
resistance
what is the major factor to regulate pulmonary blood flow
PAO2 = PO2 of alveolar gas
what is an adaptive mechanism to reduce BF to poorly ventilated regions
-
hypoxic vasoconstriction
- decrease PAO2
- assists in directing pulmonary blood flow to other regions of the lung where gas exchange can occur
Is O2 lipid soluble?
- yes, meaning it is very permeable
When PAO2 is < 70 mHg, what happens to vascular smooth muscle cells
- vascular SMC sense the hypoxia -> arteriole vasocontricts -> blood flow to that region falls
When PAO2 is 70-100 mHg, what happens to vascular smooth muscle cells
little effect on vascular tone
When PAO2 is normal at 100 mmHg, what happens to vascular smooth muscle cells
- O2 diffuses from alveoli to arteriole
- smooth muscle arterioles are relaxed and dilated
mechanism of hypoxic vasoconstriction
- inhibition of nitric oxide production from endothelial cells of vessel walls
- hypoxia -> depolarized Vascular Smooth Muscle -> opens voltage-gated CA2+ channels -> increase Ca2+ entry -> contraction
mechanism of nitric oxide
- nitric oxide is produced from L-arginine by nitric oxide synthase (NOS)
- NO activates guanylyl cyclase -> produce cGMP
- cGMP directly acts on vascular smooth muscle producing relaxation and vasodilation
describe global hypoxic vasconstriction seen at high altitude
- decreased PAO2 throughout entire lung
- produces a global vasocontriction of pulmonary arterioles and increase in pulmonary vascular resistance
- in response to increased resistance -> increase in pulmonary arterial pressure
- the increase in pulmonary arterial pressure -> hypertrophy of the RV
describe global hypoxic vasconstriction seen with fetal circulation
- fetus does not breath air, thus mom’s PAO2 > fetus PAO2
- this results in vasoconstriction, an increase in vascular resistance and decrease in pulmonary blood flow to the fetal lung
Thromboxane A2 is from AA metabolism by whic pathway
cyclooxygenase
Thromboxane A2 is produced in response to? and results in?
- produced in response to lung injury
- from macrophages, leukocytes, and endothelial cells
- results in vasoconstriction of arterioles and venules
Prostacyclin (PGI2) is from AA metabolism by which pathway
cyclooxygenase
Prostacyclin is produced by ? And results in?
- lung endothelial cells
- local vasodilation
Leukotrienes are from AA metabolism by which pathway
lipoxygenase
Leukotrienes results in
- vasoconstriction of blood vessels and airways
blood flow in the lungs is uneven due to gravity. Which zone has the lowest and highest blood flow?
- zone 1, at apex, has lowest BF
- zone 3, at base, has highest BF
Blood flow to the lung is affected by
- gravity
- exercise
in a patent ductus arteriosis, the PO2 to the Right heart will be increased or decreased and why?
- increased
- getting oxygenated blood from aorta
what type of shunt is patent ductus arteriosis
- left to right
- does not cuase hypoxemia
tetralogy of fallot is what type of shunt
right to left shunt
- Hypoxemia always occurs because a significant portion of CO is not delivered to lungs for oxygenation
shunts in tetralogy of fallot
- ventricular shunt: up to 50% of the CO is routed to the LV directly and is not pumped to the lungs
can the effects of tetralogy of fallot be corrected by breathing high O2
No, shunted blood is NOT going to lungs for oxygenation
what is the ventilation/perfusion ratio
the ratio of alveolar ventilation to pulmonary blood flow
what is the normal value for ventilation/perfusion ratio
- 0.8
- alveolar ventilation = 80% of pulmonary blood flow
ventilation/perfusion ratio is normal when what three factors are normal
- tidal volume
- breathing frequency
- cardiac output
when ventilation/perfusion ratio is normal, what are the values of PaO2 and PaCo2
- PaO2: 100 mmHg
- PaCo2: 40 mmHg
which zone has the highest ventilation/perfusion ratio
zone 1 (apex)
which lung zone has the highest PaO2
zone 1 (apex)
**organisms that thrive in high O2 (TB) flourish in apex
which lung zone has the highest and lowest PaCO2
- zone 1 has lower
- zone 3 has higher
in dead space, what is the value of ventilation/perfusion ratio
- infinity
- ventilation of lung regions not perfused (V/Q)
- no gas exchange
dead space alveolar gas has the same composition as humidified inspired air. What are the values for PAO2 and PACO2
- PAO2 : 150 mmHg
- PACO2: 0 mmHg
what does a high ventilation/perfusion ratio indicate? Give an example
- high ventilation relative to perfusion
- blood flow is low
- pulmonary capillary blood from these regions has
- high PO2 and low PCO2
- ex: zone 1 (apex)
what does a low ventilation/perfusion ratio indicat? Give an example
- low ventilation relative to perfusion
- ventilation is diminished
- pulmonary capillary blood from these regions has
- low PO2 and high PCO2
- Zone 3 (base)
shunt ventilation/perfusion ratio =
- perfusion of lungs that are not ventilated (e.g. airway obstruction)
- V/Q = 0
pulmonary capillary blood from regions without ventilation due to shunt (airway obstruction) has the same composition as what? Name values
- mixed venous blood
- PaO2= 40 mmHg
- PaCO2 = 46 mmHg
- **this is for the shunted blood only
pressure of pulmonary system is ? Pressure of systemic system is ?
- pulmonary: 15 mmHg
- systemic: 100 mmHg
