Physiology-Pulmonary Circulation Flashcards
In essence, what are capillaries in the lungs?
Walls filled with blood right next to the alveolar sacs.
How do you clinically measure left atrial pressure?
Put the catheter far out into the pulmonary arteriole and inflate the balloon to close it off. Downstream from the balloon you will have a column of blood heading to the left atrium and that pressure will transmit back to your catheter.
How do you calculate pulmonary vascular resistance?
change in pressure across the lungs (The mean pulmonary arterial pressure - the left atrial pressure) / pulmonary blood flow (cardiac output).
How do you measure cardiac output to the lungs in a normal heart?
Thermodilution catheter. Systemic cardiac output = pulmonary cardiac output in a normal heart.
Why accounts for flow differences in the three hydrostatic zones of the lung?
Gravity makes blood flow inferiorly, creating greater arterial pressure in the more inferior zones. In the superior zones, arterial pressure is lower and cannot overcome alveolar pressure and either remain closed or only open during systole.
What assumptions go into the differences in flow in the hydrostatic zones of the lung?
The patient is standing and resting.
How do the lungs accommodate for increased cardiac output during exercise?
Increased cardiac output causes the pulmonary arterial pressure to increase. This results in opening of more capillaries and widening of the capillaries.
Why would a patient on a ventilator be at risk for right heart failure if his lung volume is not monitored closely?
Under inflation of the lung crinkles the capillaries, making it harder to push blood through them. Over inflation of the lung stretches the capillaries, making it harder to push blood through them. The sweet spot is around 100mL O2.
How do pulmonary arterioles act in response to hypoxia in comparison with systemic arterioles?
Pulmonary arterioles will constrict and even collapse in areas with low [O2], giving more attention to areas of the lung with higher [O2]. This is the opposite of the systemic arterioles.
A 66 year old patient comes to see you with pitting edema and jugular venous distention. He has a 30 pack year history of smoking. How might his history of smoking contribute to right-sided heart failure?
Damaging alveoli increases resistance to blood flow in the lungs. This makes the right side of the heart pump harder and can cause heart failure.
