Pulmonary Physiology: Perfusion Flashcards
What are the two functional zones of the lungs and what do each do?
Conducting zone: Gets air into the distal structures, no gas exchange.
Respiratory zone: Gas exchange.
Is the pulmonary vasculature low, or high pressure?
Low
Name three characteristics of pulmonary vessels.
- Larger diameters
- Shorter, more branches
- Large number of arterioles that have low resistance
Describe the smooth muscle of pulmonary arterioles.
There is not as much –> high compliance, low resistance, allows for distension.
As pulmonary arterial pressure increases, pulmonary resistance _________.
decreases
In which part of the lungs is flow the highest?
Lower lungs (zone 3)
What are the two ways the pulmonary vasculature accomodates increased flow?
- Recruitment (upper lungs will get used)
2. Distension of the arterioles and capillaries
How is alveolar vessel resistance affected by high intravascular pressure and low alveolar pressure?
Vessel resistance is decreased in this case
How is alveolar vessel resistance affected by low intravascular pressure and high alveolar pressure?
Vessel resistance is increased in this case
What happens to the extra-alveolar vessels in the lung parenchyma during inspiration?
They expand because they are pulled open by expansion of the surrounding tissue.
Can expansion of alveoli compress alveolar capillaries?
Yeah
When PO2 is less than 60mmHg, what happens to pulmonary vessels? How does this differ from systemic vessels?
Pulmonary vessels constrict. Systemic vessels dilate in response to hypoxia.
What is the advantage to having pulmonary vessels constrict in response to hypoxia? Is this a neural, or metabolic function?
It shunts blood to alveoli that are actually being ventilated and that is good. It is a metabolic function.
In which lung zone (1, 2, or 3) is pulmonary blood flow intermittent?
Zone 2
What is pulmonary wedge pressure used to measure?
Left atrial pressure
Pulmonary capillary fluid flow is determined by the balance between _________ and ________ pressures.
hydrostatic and osmotic
What are the three ways in which interstitial fluid in the lungs is removed?
- Alveolar vaporization
- Venule resorption
- Lymphatic drainage
Pulmonary hypertension is defined as greater than _____mmHg of mean ARTERIAL pressure.
25
Name one heart condition that can cause pulmonary hypertension.
ventricular septal defect
Which three mechanisms cause pulmonary hypertension?
- Increased pulmonary flow relative to systemic flow (like with a VSD).
- Increased pulmonary resistance from vasoconstriction.
- Increased left atrial pressure causes a back-up into the pulmonary circulation (left heart disease).
Pulmonary pressure will increase to greater than 25mmHg when pulmonary flow:systemic flow exceeds __:1
1.5:1
Pulmonary edema occurs when CAPILLARY pressure exceeds _____mmHg.
25mmHg
What are the three steps in the progression of pulmonary edema?
- Flooding of peri-capillary interstitial spaces.
- Crescentic filling of the alveoli.
- Flooding of individual alveoli with loss of gas exchange.
How does ARDS cause pulmonary edema even at normal capillary pressures?
Increased vascular permeability.
