test 5 part 2

Question 1

Bronchial circulation

Answer 1

 High-pressure, low-flow
 Carries arterial (oxygenated) blood to tissues of respiratory system
-1% to 2% of total cardiac output
-Arises from thoracic aorta
 Returns venous (deoxygenated) blood to pulmonary veins
-Deoxygenated blood merges with oxygenated blood

Question 2

Pulmonary circulation

Answer 2

 Low-pressure, high-flow
 Carries venous (deoxygenated) blood to pulmonary capillaries
-Gas exchange
 Returns arterial (oxygenated) blood to left atrium

Question 3

Pulmonary Artery anatomy

Answer 3

 Divides into Right and Left Main Pulmonary Arteries
-Go to each lung
 PA is thin (1/3 thickness of aorta) and distensible
-Large compliance to accommodate the stroke volume of RV (7 mls/mmHg)
 Short
 Carries deoxygenated blood (25% deoxygenated)

Question 4

Bronchial Vessels anatomy

Answer 4

 Small bronchial arteries
-Part of systemic circulation
 Receive 1% - 2% of total Cardiac Output
 Carry oxygenated blood
 Supplies tissue of lungs
 Empties into the pulmonary veins and enters Left Atrium
-Flow into the LA is 1% to 2% greater than the stroke volume out of the right ventricle (i.e. functions as a shunt)

Question 5

Lymphatics anatomy

Answer 5

 Present in all supportive tissues of the lungs
-Starts in tissue around terminal bronchioles
 Empty into the right thoracic lymphatic duct
 Particulate matter entering the alveoli is partially removed via these lymphatic ducts
 Collect plasma proteins leaked from pulmonary
capillaries
-Prevent pulmonary edema

Question 6

Pulmonary Blood Pressure

Answer 6

 Right ventricular diastolic / RA: 0 to 1 mmHg
 Right ventricular systolic / PA systolic: 25 mmHg
 Mean: ≈15 mmHg
 PA diastolic: 8 mmHg
 Pulmonary Capillary: 7 mmHg
 Pulmonary capillary wedge pressure (PCWP): 5 mmHg
 Left atrial: 2 mmHg

Question 7

Blood Volume of Lungs

Answer 7

 Holds ≈ 9% of total blood volume
 450 mls (arteries + capillaries + veins)
 Pulmonary capillaries hold ≈ 70 mls
 Normal alveolar surface area 770 ft2 to 1076 ft2

Question 8

Changes in pulmonary blood volume

Answer 8

 Can see big changes: from ½ normal to 2 times normal
-Hard expulsion of air from lungs can move 250 mls of blood out of pulmonary circulation
 Left heart failure / mitral valve problems create increased resistance to flow leaving pulmonary capillaries
-Can cause 100% increase in volume and huge increases in pulmonary pressures

Question 9

Blood Flow & Blood Distribution for pulmonary vessels

Answer 9

 Pulmonary vessels act as passive, distensible tubes
-As pressure increases, vessels enlarge allowing more flow with smaller increase in pressure – helps minimize high pressure risk for right ventricle

Question 10

Blood Flow & Blood Distribution for alveoli

Answer 10

 Low oxygen content in alveoli cause changes in vascular resistance
 Alveolar PO2
less than 73 mmHg stimulates surrounding arterials to constrict limiting flow to the alveoli. This is opposite of what happens in the systemic capillaries
-advantageous because it increases blood flow through the alveoli where oxygen transfer is normal

Question 11

Hydrostatic Pressure Gradients in Body

Answer 11

 Pascal’s Hydrostatic Laws [P = pgh]

 Pressure in the bucket will increase 1 mmHg for every 13.6 mm of depth due to force of gravity (i.e. weight of water)

Question 12

Water is 12” deep what is the pressure at the bottom?

Answer 12

 (12 inches x 2.54 cm/inch) = (30.12 cm x 10 mm/cm) = (301.2 mm / 13.6 mm/mmHg) = 22.1 mmHg

Question 13

Gravity affects blood pressure in the body

Answer 13

 Pressure in the right atrium is approximately 0 mmHg as heart will pump any excess blood

Question 14

what is the pressure difference between the top and the bottom of the lung?

Answer 14

23 mmHg

-pressure at the bottom is 23 mmHg higher than the top of the lung

Question 15

Hydrostatic pressure in the lung from the level of the heart

Answer 15

 Pressures at top of lungs will be ≈15 mmHg lower than pressures at the level of the heart
-i.e. Pcap at heart of 7 mmHg would be ≈ -8 mmHg Pcap at top
 Pressures at bottom of lungs will be ≈8 mmHg higher than pressures at the level of the heart
-i.e. Pcap at heart of 7 mmHg would be ≈15 mmHg Pcap at bottom

Question 16

Hydrostatic Gradients in the Lungs affecting flow

Answer 16

 Assume pulmonary resistance the same throughout the lung then flow at the top of the lung would be lower than flow at the bottom of the lung because of the difference in the driving pressure (23 mmHg higher at the bottom)
[Q = P / R]
 Flow at bottom approximately 5 times greater than flow at the top of the lungs

Question 17

If alveolar pressure is greater than hydrostatic pressure, what happens?

Answer 17

• capillaries collapse and no flow

- The pulmonary capillaries surround the alveoli, so the pressure in the alveoli have an impact on those capillaries

Question 18

what happens to the alveolar pressure during inhalation?

Answer 18

• alveolar pressure drops

- flow during inhalation

Question 19

Pressure in capillaries depends on

Answer 19

a) driving pressure from RV
b) effect of hydrostatic pressure
c) pressure in surrounding tissue mainly alveolar pressure

Question 20

Blood Flow Through Different Areas of Lung: zone 1

Answer 20

 No blood flow at any time

 Alveolar pressure always greater than pulmonary capillary pressure

Question 21

Blood Flow Through Different Areas of Lung: zone 2

Answer 21

 Intermittent blood flow
 Flow during systole pulmonary capillary pressure will be higher than alveolar pressure
 Little or no flow during diastole

Question 22

Blood Flow Through Different Areas of Lung: zone 3

Answer 22

 Continuous blood flow

 Pulmonary capillary pressure is always higher than alveolar pressure

Question 23

When does zone 1 flow occur

Answer 23

• abnormal conditions!
  • Low arterial blood pressure
  • High intra-alveolar air pressure

Question 24

part of the lung receive which zone flow

Answer 24

• Apex of lung receives Zone 2 flow, rest of lung receives Zone 3.

Question 25

Blood Flow Through Different Areas of Lung during exercise

Answer 25

 During exercise see overall increase in flow over full length of the lung  As overall blood pressure increases with increased cardiac output, the top areas of the lung convert from Zone 2 to Zone 3 flow

Question 26

Perfusion and No Ventilation

Answer 26

- shunting venous blood to arterial side | - high PCO2 and low PO2

Question 27

Normal ventilation vs perfusion

Answer 27

- normal alveolar air - PO2= 104 - PCO2= 40

Question 28

Ventilation and No Perfusion

Answer 28

- Alveoli continually refreshed both reach max O2 and min CO2 possible in alveoli - zone 1 - PO2= 149 (max in room air) - PCO2= 0

Question 29

Affect of Increased Cardiac Output and how lungs handle the increased blood flow

Answer 29

 Cardiac output can increase 4 to 7 times normal during heavy exercise  Increasing number of open capillaries (x3). All of the available capillaries are not open during normal levels of blood flow  Distending open capillaries. Decreases overall resistance to flow allowing increased flow through each capillary (x2)  Increasing pulmonary arterial pressure

Question 30

Affect of Increased Cardiac Output

Answer 30

 Increase in pressure small compared to increase in blood flow  Reduces exposure of right ventricle to high pressure work  Reduces overall increase in pulmonary capillary pressure thus reducing / preventing formation of pulmonary edema

Question 31

Pulmonary Response to High LA Pressure

Answer 31

 Left atrial pressure almost never goes above 6 mmHg -Slight increase in LA pressure cause dilation of pulmonary veins reducing overall resistance to flow through the pulmonary veins

Question 32

During left side failure, LA pressure can go as high as

Answer 32

40 to 50 mmHg  Pulmonary circulation can accommodate LA pressures up to approximately 7 mmHg  Above 7 mmHg there will be a assosiated increase in pulmonary pressure all the way back to the right ventricle – increased work load for the right heart  LA pressure above 30 mmHg will usually result in the formation of pulmonary edema

Question 33

Pulmonary Capillary Dynamics

Answer 33

 Each alveoli surrounded by capillaries – “sheet of flow”  Normal cardiac output – blood takes 0.8 sec to travel through pulmonary capillaries – can go as low as 0.3 sec with high cardiac outputs  Additional capillaries open as blood flow increases which keeps transit time from dropping lower -increase CO = transit time decreases = time for gas transfer decreases

Question 34

differences between capillary dynamics of the systemic capillaries and pulmonary capillaries

Answer 34

 Pulmonary capillary pressure significantly lower (7 mmHg versus 17 mmHg)  Pulmonary interstitial fluid pressure more negative (-5 to -8 versus -3)  Pulmonary capillaries are “leaky” allowing more protein to escape to interstitial fluid so interstitial oncotic pressure is higher (14 mmHg versus 8 mmHg)  Alveolar walls are thin and friable – can be broken if interstitial pressure is greater than alveolar pressure (i.e. interstitial pressure is greater than 0 mmHg) – makes it relatively easy to move fluid from interstitial fluid INTO the alveoli

Question 35

Pulmonary forces moving fluid in and out of the capillaries

Answer 35

```  FORCES MOVING FLUID IN (ABSORPTION) -Plasma colloid osmotic pressure: 28  FORCES MOVING FLUID OUT -Capillary pressure: 7 -Neg interstitial pressure: 8 -Interstitial fluid colloid oncotic pressure: 14 -total out: 29 -net outflow of 1 mmHg ```

Question 36

Pulmonary Edema – Acute Conditions

Answer 36

 Anything that increases the rate of capillary filtration OR decreases the rate of lymphatic removal can cause pulmonary edema

Question 37

Pulmonary Edema – Acute Conditions most common causes

Answer 37

 Left side heart failure OR mitral valve disease – produce large increases in LA pressure  Damage to pulmonary blood capillary membranes – pneumonia, breathing toxic gases

Question 38

Studies leading up to pulmonary edema: animal, humans, and lethal

Answer 38

 Graph – Animal studies show that pulmonary capillary pressure (LA pressure + 1 to 2 mmHg) must exceed pulmonary plasma oncotic pressure BEFORE edema formation begins  In humans would expect that pulmonary capillary pressure would have to go from 7 mmHg to more than 28 mmHg before edema formation  Lethal pulmonary edema – if pulmonary capillary pressure rises 25 to 30 mmHg higher than safety level of 28 mmHg, patient will be dead in less than 30 minutes (Pcap of 53 to 58 mmHg)

Question 39

Pulmonary Edema – Chronic Conditions

Answer 39

Lungs begin to compensate if pulmonary capillary pressure remains elevated for more than 2 weeks  Large expansion in lymphatic blood vessels which can increase carrying capacity up to 10 times normal  Allows patients with chronic pulmonary capillary pressure greater than 40 mmHg to live without developing lethal pulmonary edema  Overall increase in pressure has to occur gradually over time

Question 40

Fluid in the Pleural Cavity

Answer 40

 Pleural cavity filled with fluid – only a few mls  Membrane porous so interstitial protein will migrate to pleural fluid – helps to provide lubrication factor of fluid  Fluid volume within cavity kept at minimal level by lymphatics  Provide negative pressure (minimum of -4 mmHg) that keeps lungs expanded to normal resting size

Question 41

What happens if the negative pressure is lost??

Answer 41

- lose pleural pressure and lungs collapse

Question 42

Pleural effusion caused by

Answer 42

 Blockage of lymphatic vessels  Cardiac failure with high pulmonary pressures leading increased movement of fluid and protein into pleural space  Greatly reduced plasma colloid pressure  Infection/inflammation of pleural membrane changing permeability