Pulmonary Circulation-Khundmiri

Question 1

systemic high pressure

pulm low pressure travel smaller distance

Answer 1

?????

Question 2

Pulmonary system has very low resistance compared to systemic. Why?

Answer 2

less smooth muscles cells in the arteries and capillaries compared to systemic which is rich in smooth muscle

Question 3

Why is there high compliance in pulmonary system and low compliance in the systemic system?

Answer 3

pulmonary system accommodates for shifts in the blood more quickly than systemic

lung can be divided in to 3 zones;shifting from zone 1-3 you get shifts in blood circulation which needs high compliance

Question 4

How do you measure pulmonary circulation? Do you need to measure?

Answer 4

you do an US driven catheter through RV going through pulmonary artery and pressure exerted on the balloon will give the pressure in the pulmonary arteries and capillaries

Question 5

What is the net driving pressure of systemic and pulmonary system?

Answer 5

93 mmHg for systemic circulation:

• At rest the systemic capillaries are closed: Aorta = ~95 mmHg
• At the opposite end of the circuit at the RA = ~2 mmHg

7 mmHg for pulmonary circulation:

• In the pulmonary artery = ~15 mm Hg
• At the other end of the circuit at the LA

Question 6

The pulmonary artery subdivides into terminal branches with internal wall bigger due to less smooth muscles. The walls are highly distensible compared to vein as they can accommodate cardiac output because of?

Answer 6

because of the tone of the pulmonary smooth muscles the have effect on resistance

transmural pressure difference across the walls will determine pulmonary vascular resistance
can be calculated

Question 7

Pulmonary vascular resistance

can be calculated by?

Answer 7

PVR = (MPAP-MLAP)/PBF

Mean pulmonary artery pressure (MPAP), mean left atrial pressure (MLAP), pulmonary blood flow (PBF)

normal is 1 mmHg/L/min

Question 8

Increase in blood flow causes?

Answer 8

decrease in transmural vascular resistance because:

• pulmonary blood vessels are shorter and wider than those in the systemic circulation
• arterioles are alos present in much higher numbers
• pulmonary arterioles are less muscular than those in the systemic circulation
• therefore, their resting tone is low

During exercise you increase your blood flow causing a decrease in pulmonary circulation vascular resistance to increase your oxygenation of the blood

Question 9

Pulmonary vascular resistance: the extravascular events or the passive factors may have much greater importance in pulmonary vascular circulation resistance compared to the systemic vascular circulation. Why?

Answer 9

Gravity, body position, lung volume,
alveolar and intrapleural pressures, intravascular pressures, and right ventricular output
all can have profound effects on PVR without any alteration in the tone of the pulmonary
vascular smooth muscle.

Question 10

What is the transmural pressure difference?

Answer 10

As transmural pressure increases, the vessel diameter increases and resistance falls;
as the transmural pressure difference decreases, the vessel diameter decreases and
the resistance increases. Negative transmural pressure differences lead to compression
or even collapse of the vessel.

vessel diameter increase resistance decreases

opposite eventually arteries will collapse

Question 11

Intrapleural pressure taken during your inspiration does?

Answer 11

this pulls the extravascular vessels to increase blood

when the alveoli fill up they will cause pressure on the capillaries surrounding the alveoli

negative intrapleural pressure in the interstitium around the capillaries will cause expansion of the extra alveolar BV (capillaries surrounding the alveoli are lengthening) whereas alveoli capillaries will extend

Question 12

What happens to your pulmonary vascular resistance at RV?

Answer 12

the highest due to the extraalveolar BV which have higher pulmonary resistance and alveolar BV would have lower pulmonary resistance

Question 13

What happens to your pulmonary vascular resistance at TLC? would be

Answer 13

alveolar BV would have higher pulmonary resistance compared than extraalveolar pulmonary resistance

Question 14

Total resistance would be lowest at FRC and highest at RV and TLC. Why?

Answer 14

resistance would be biphasic (highest at RV and TLC and lowest at FRC )

As lung volume increase, the alveolar walls become more stretched out.

The AV is stretched along their longitudinal axis but crush when viewed in cross section.

Increasing lung volume from RV to TLC which is biphasic, the alveolar wall would be stretched along the longitudinal axis.

Question 15

Because of their location, the extraAV BV are not going to be influenced directly under alveolar pressure but are controlled by?

Answer 15

intrapleural pressures

Question 16

Pulmonary blood flow in lungs is similar to ventilation as it is?

Answer 16

gravity dependent

lowest at apex and highest at bottom in standing position

Question 17

When lying down down, how is pulmonary blood flow?

Answer 17

the lowest would be highest and the bottom would be lower

BF can shift very easily to one position to another because of the high compliance of the vessels

Question 18

Variation in ventilation in parts of the lung are due to mechanical factors and environmental stress. Why?

Answer 18

the zone are not anatomical but are PHYSIOLOGICAL

Question 19

What causes the uneven distribution of blood flow in the lung in the different zones?

Answer 19

Zone I: alveolar pressure is higher than arterial pressure than venous pressure (the arteries and capillaries would be crush)

Zone II: arterial pressure higher than alveolar

Zone III: arterial pressure is the highest, venous pressure next, and the lowest pressure would be the alveolar lowest

Question 20

How does the changing of zones in lungs occur?

Answer 20

two things:

recruitment and distension

Question 21

During exercise our cardiac output increases several fold without corresponding increase in mean arterial blood pressure however?

Answer 21

drop in pressure will be proportional to decrease in CO–it is passive meaning it is not the result of change in tone of the muscle cells or humoral changes

Question 22

At resting states not all of the capillaries and arteries are conducting blood. some are open and conducting blood or not conducting blood others are crushed and not conducting blood

Answer 22

with the increasing pressure all of your capillaries will start conducting blood

controlling blood flow to the regions

Question 23

What comes first recruitment or distension?

Answer 23

research wise we don’t know what happens first so the answer is the decreased PVR seen with elevated perfusion pressure is probably both (stating that they happen at the same time).

recruitment has higher pressure increasing surface area???
distension is due to low ventricular output or high alveolar pressure

Question 24

Decrease in PACO2, increase in PAO2 will cause what movement of pulmonary arteries?

Answer 24

dilation

Question 25

Increase in PACO2, decrease in PAO2 will cause what movement of pulmonary arteries?

Answer 25

constriction

Question 26

What happens in hypoxic pulmonary vasoconstriction?

Answer 26

decrease flow of blood to keep V/Q ratios normal

Question 27

What occurs when you constrict the alveoli?

Answer 27

decrease the PACO2 and increase in pH????

i’m not getting enough O2 out of the alveoli so stop flowing blood

changing the flow of blood to keep V/Q normal

Question 28

What occurs when you constrict the artery?

Answer 28

happen because of low O2 causing flow to go to the other lung to maintain the V/Q ratio

Question 29

body under best scenario

Answer 29

shift blood flow to the other lung to maintain V/Q

Question 30

What is the difference of the alveolar shunt and capillary shunt ?

Answer 30

alveolar shunt: increased CO2 and decreased O@ as there is no flow of O2 coming from outside (the arteries are still conducting); alveoli?? will shrink because of hypoxia

capillary shunt:

Question 31

will not get filled up with water due to

Answer 31

Starling forces: keeping the lungs dry

Question 32

What do the starling forces do?

Answer 32

they cause the flow of fluid into the lymphatic system which is very important in keeping the lungs dry

Question 33

Which factors in the starling equation will result in acute respiratory distress syndrome oxygen toxicity?

Answer 33

increased capillary permeability

Question 34

tumor–breast cancer

Answer 34

insufficient lymphatic drainage resulting in pulmonary edema

Question 35

What are the features of bronchial blood flow?

Answer 35

supplies blood to trachea and airways up to the level of terminal bronchioles and BVs

they supply new ???? oxygen to lung tissue

A second, separate circulatory system in the lung with oxygenated blood from the systemic circulation.

Bronchial blood flow comprises only 1% to 3% of the output of the left ventricle.

The return of venous blood from the capillaries of the bronchial circulation to the heart occurs either through true bronchial veins or through bronchopulmonary veins.

Question 36

Where do the bronchial veins drain?

Answer 36

azygos and hemiazygos vein