Pulmonary circulation

Question 1

bronchial circulation characteristics

Answer 1

1. )high pressure, low flow
2. )supplies arterial blood to the tissues of the respiratory system (1-2% of CO)
3. )branches off the thoracic aorta and delivers oxygenated blood to lungs
4. )returns venous blood to pulmonary veins

Question 2

pulmonary circulation characteristics

Answer 2

1. )low-pressure, high flow
2. )supplies deoxygenated venous blood to pulmonary capillaries for gas exchange
3. ) returns oxygenated arterial blood to LA
4. )Pulmonary arteries have large compliance (7ml/mmhg) because of shorter, thinner, larger diameter (less branching)

Question 3

Pulmonary blood pressures

Answer 3

right ventricular diastolic / RA: 0-1 mmHg
right ventricular systolic / PA Systolic: 25mmHg
mean- 15mm Hg
PA diastolic: 8 mmHg
pulmonary caps: 7 mmHg
PWCP:5 mmHg
LA: 2mmHg

Question 4

total blood volume of lungs

Answer 4

9% of total blood volume. 450mls. 70 mls in the pulmonary caps.

Question 5

changes in blood volume of lungs

Answer 5

can change from 1/2 normal - 2 times normal.
Left heart failure or mitral valve problems can create increased resistance to flow leaving pulmonary caps. This is very bad and can cause 100% increase in volume and increases in pressure. ( not a good kid)

Question 6

Alveolar pressure that causes constriction of surrounding arterioles to poorly oxygenated alveoli (opposite of what happens at a systemic level) why is this an advantage?

Answer 6

73 mmHg. Increases ventilation perfusion ratio which makes lungs more efficient because they are not supplying blood to alveoli that are not receiving ventilation.

Question 7

pascal’s hydrostatic law

Answer 7

pressure at surface is equal to atmosphere. Pressure in bucket will increase 1 mmHg for every 13.6 mm (weight of water) due to gravity.

Question 8

total pressure diference of lungs

Answer 8

about 23mm Hg

Question 9

pressure difference at top of lungs compared to heart

Answer 9

about 15 mmHg lower

Question 10

pressure difference at bottom of lungs compared to heart

Answer 10

about 8 mmHg higher

Question 11

why is flow different at top of lungs than bottom

Answer 11

because there is a higher driving pressure (23 mmHg higher) Q= delta P/ R

Question 12

zone 1 blood flow

Answer 12

no blood flow at any time. alveolar pressure is greater than pulmonary cap. pressure. This causes collapsing of lungs. Zone 1 does not occur in healthy lungs!!!

Question 13

zone 2 blood flow

Answer 13

intermittent blood flow due to fluctuating pressure. systolic pulmonary cap. pressure will be higher than alveolar pressure. little or no flow during diastole

Question 14

zone 3

Answer 14

continuous blood flow. pulmonary cap pressure is always higher than alveolar pressure. as blood pressure increases due to increases in CO zone 2 can convert to zone 3

Question 15

perfusion no ventilation

Answer 15

only venous blood so PO2 and PCO2 equilibrate at venous blood pressures. PO2=40 PC02=45 V/Q=0

Question 16

normal alveolar pressure

Answer 16

V/Q=normal PO2=104 PCO2=40

Question 17

ventilation no perfusion

Answer 17

alveoli continually refreshed. both reach max O2 and min. CO2 possible in alveoli V/Q equals infiniti. Po2=149 PCO2=0

Question 18

cardiac output increases …. times during heavy exercise

Answer 18

4-7

Question 19

lungs handle increased flow during exercise by…

Answer 19

tripling number of open capillaries. doubling distension of open caps. allowing increased flow by decreased resistance. increasing pulmonary arterial pressure

Question 20

affect of increased CO on pulmonary arterial pressure

Answer 20

increases in pressure small compared to increases in blood flow. This reduces work on RV and pulmonary edema

Question 21

pulmonary response high LA pressure

Answer 21

slight increase in LA pressure cause dilation of pulmonary veins which reduces overall resistance to flow

Question 22

left side heart failure LA pressure can go as high as

Answer 22

40 - 50 mmHg

Question 23

pulmonary circ. can accommodate LA pressure up to

Answer 23

7 mmHG. Above this there will be in increase in pulmonary pressure all the way back to RV. LA pressure above 30 mmHg will result in formation of pulmonary edema

Question 24

flow in capillaries of alveoli is also known as

Answer 24

sheet flow

Question 25

Time it takes blood to travel through pulmonary caps during normal CO

Answer 25

.8 sec. can go as low as .3 sec with high CO

Question 26

DIFFERENCES BETWEEN SYSTEMIC AND PULMONARY CAPILLARIES

Answer 26

1. )pulmonary caps lower (7 vs. 17)
2. )pulmonary caps interstitial fluid more neg (-5 to -8 vs.-3)
3. )pulmonary caps are more leaky allowing protein to escape interstitial fluid which makes interstitial oncotic pressure higher (14 vs. 8)
4. ) alveolar wall are thin are friable- can be broken if interstitial pressure is greater than alveolar pressure (i.e. if interstitial pressure is greater than 0) makes it relatively easy to move interstitial fluid into the alveoli

Question 27

forces moving in and out in pulmonary caps

Answer 27

forces moving in :plasma colloid osmotic pressure (28)
forces moving out: cap pressure (7)
neg. interstitial pressure (8)
interstitial fluid oncotic pressure (14)
balance: net force outward (1)

Question 28

causes of pulmonary edema

Answer 28

anything that increases rate of capillary filtration or decreases lymphatic removal.
most common causes: left side heart failure or mitral valve disease. damage to pulmonary cap membranes (pneumonia, toxic gases)

Question 29

lethal pulmonary edema

Answer 29

25 -30 mmHg higher than safety level of 28 mmHg. Patient dead in less than 30

Question 30

lungs can compensate for increases in pulmonary capillary pressure if it remains elevated for more than 2 weeks by…

Answer 30

large expansion in lymphatic blood vessels which increase capacity by 10 fold. allows patients with chronic cap. pressure greater than 40mmHg to live without developing pulmonary edema. Has to occur slowly over time!!!

Question 31

pleural cavity fluid

Answer 31

lubricates, kept at a minimum by lymphatics, provides negative pressure (-4) to keep lungs expanded to normal resting size

Question 32

pleural effusion caused by

Answer 32

blockage of lymphs, cardiac failure with high pulmonary pressures, greatly reduced plasma colloid pressure, infection/inflammation which changes permeability

Question 33

Alveolar surface area

Answer 33

770-1076 ft ^2

Question 34

Shunt unit

Answer 34

No ventilation so alveolar unit collapses. Perfusion continues. Examples include atelectasis and pneumonia .

Question 35

Dead space unit.

Answer 35

Ventilation without perfusion. Example pulmonary embolus preventing blood flow through capillaries.