Gas Transport 2 Flashcards
What factors affect overall pulmonary vascular resistance
- Passive factors: Factors that when changes cause secondary changes to vascular resistance by imposing a passive increase or decrease in caliber of individual blood vessels and/or total vascular cross-sectional area
- Active factors: Factors that cause an active increase or decrease in the caliber of blood vessels by altering vasomotor tone
What factor is most important in determining pulmonary vascular resistance due to pulmonary circulation structure/architecture
Passive Factors
What are 3 passive factors to decrease pulmonary vascular resistance
How do passive factors decrease pulmonary vascular resistance
1) Pulmonary vessels are distensible and offer little resistance to stretched so increased arterial and venous pressures and blood volume can increase the cross-sectional area of flow therefore decreasing resistance
2) Recruitment: Occurs with increased arterial perfusion (see image)
3) Distention: Occurs particularly with increased left atrial back pressure (venous) (see image)
What are 3 passive factors to increase pulmonary vascular resistance
How do passive factors increase pulmonary vascular resistance
Describe the 3 blood flow zones of the lungs
Describe the 4 zones of the lungs and the difference in blood flow and pressure
Zone 1 = alveolar pressure is greatest (collapse on vessel by alveoli)
Zone 2 = arterial pressure greatest resulting in waterfall
Zone 3 = arterial and venous pressure are greater than alveolar pressure resulting in distention
Zone 4 = arterial pressure is greatest but also interstitial pressure is present from weight of lung which is greater than venous or alveolar pressure which is causes decrease in blood flow
How does perfusion change when laying in supine
What are 3 types of active factors
Regulation:
1) Neural
2) Cardiac
3) Chemical
Describe neural global regulation
Uses:
1) Nervous system
-sympathetic = vasoconstriction
-parasympathetic = vasodilation
2) Reflexes
-increased blood pressure (baroreceptors) decreases pulmonary vascular resistance
-decreases in oxygen or pH (aortic body chemoreceptors) increases pulmonary vascular resistance
Do active factors have a smaller or bigger role than passive factors
Much smaller
Describe cardiac global regulation (why would hypoxemia cause increased pulmonary vascular resistance
Describe chemical regional regulation (aka regional hypoxemia)
Occurs with local hypoxemia where decreased alveolar PO2 causes vasoconstriction and decreased blood flow
Explain this image
List vasodilators and constrictors
