Pulmonary Circulation Flashcards
(37 cards)
Lung receives blood flow from:
- bronchial circulation (oxygenated)
- pulmonary circulation (deoxygenated)
Bronchial blood flow constitutes what percentage of left ventricular output:
2%
The entire output of the right ventricle goes to:
- pulmonary circulation
- supplies the lung with mixed venous blood draining all tissues of the body.
Pressure in pulmonary circulatory system:
- low pressure
- allows for pulmonary capillaires to be very thin walled (for gas exchange).
Alveoli are connected to:
- interstitium, which is connected to a pulmonary capillary bed.
Pressure in pulmonary circulation is what percentage of systemic blood pressure?
1/8th to 1/10th
Why can the pulmonary artery and its branches be much thinner walled than corresponding parts of systemic circulation?
pulmonary circulation is a low pressure system.
Pulmonary vessels have little vascular smooth muscle. What does this allow for?
- less resistance and more distension than the systemic arterial tree.
Why are pulmonary vessels much more compressible than systemic arteries?
- much lower intravascular pressures
Reasons for left ventricular maintaining high arterial pressure:
- overcome hydrostatic forces.
- pump blood “uphill” to brain.
- redistribution of left ventricular output to control blood flow to different tissues.
Why is high pressure output from the right ventricle unnecessary?
- apices of lung short distance from right ventricle.
- redistribution of right ventricular output not necessary.
Why is redistribution of right ventricular output not necessary?
- all alveolar-capillary units are performing the same function.
Right ventricle has thinner walls than the left ventricle because:
- RV pumps blood into a low pressure/resistance system.
- No redistribution of flow.
Higher pulmonary pressures will put the right ventricle under stress, which will cause:
- right ventricle to dilation.
- leads to a flattened interventricular septum.
A dilated right ventricle on echocardiogram/ultrasound is indicative of:
increased pulmonary pressure/resistance.
What type of catheter is used for measuring pulmonary artery pressures?
- balloon tipped Swan Ganz catheter
- measures:
- RA pressure
- pulmonary artery pressure
- pulmonary capillary wedge pressure
- measures:
Pulmonary capillary wedge pressure is:
- the pressure measured by wedging a pulmonary catheter with an inflated balloon into a small pulmonary arterial branch.
- Gives pulmonary pressure and an indirect measurement of left atrium pressure.
Gravity effect on the lungs:
- pressures greater in lower lobes.
- resistance to blood flow is lower in lower lobes.
Why is resistance to blood flow lower in the lower lobes of the lung?
- gravity causes higher pressure, which leads to greater blood flow and more recruitment and distention of vessels.
When does perfusion seize in the lung?
- alveolar pressure = pulmonary arterial pressure.
- alveolar pressure > pulmonary arterial pressure.
Characteristics/pressures of Zone 1 of the lung:
- PA > Pa > Pv
- ventilated, not perfused:alveolar dead space.
Characteristics/pressures of Zone 2 of the lung:
- Pa > PA > Pv
- arterial pressure drives perfusion; perfusion in pulses.
Characteristics/pressures of Zone 3 of the lung:
- Pa > Pv > PA
- ventilated and perfused.
High alveolar pressure can compress the capillaries and reduce blood flow in Zone 1 of the lungs. What can cause this?
- gravity when standing.
- hemorrhage (decreases arterial pressure; Pa).
- PPV (increases alveolar pressure).
