Ventilation perfusion relationship

Question 1

How does the systemic circulation play into the nutrtition of the lungs?

what preventts pulmonary edema?

Answer 1

Bronchial circulation (systemic vessels)= carry oxygenated blood to supporting tissues of the lung: bronchi, connective tissue

Lymphatics: present in all supportive tissue, helps prevent pulmonary edema

Question 2

what is the flow in the pulmonary and systemic blood flow?

Answer 2

pulmonary and systemic blood flow both = 5L/min

the difference is in the pressure. The blood pressure in the pulmary system experiences low pressure

low pressure and resistnace minimize cardiac work and prevent damage

Question 3

regulation of pulmonary blood flow:

increase/decrease in PACO2 is met with what type of response?

Answer 3

increase PACO2 =bronchiole dilation

decrease in PA CO2 = bronchiole constriction

Question 5

ana increase/ decrease in pAO2 is met by what type of reaction?

Answer 5

PaO2

1. increase= systemic constriction. but really not much of a problem
2. decrease = pulmonary contriction, systemic dilation. this is the big effector

Question 6

an increase in PaCO2 = a decrease in PaO2. What affect does this have on the lungs?

Answer 6

1. bronchioles-CO2 increasing
   
   1. decrease contractile activity =broncihodilation
      
      1. respiritory tract
         
         1. decrease resistance
         2. increase ventilation
   2. explaination
      
      1. increasing the diameter of the air way will allow for more air to get to the alveoli
2. pulmonary arterioles- O2 decreasing
   
   1. increase contractile activity of smooth muscle= vasoconstriction
      
      1. pulmonary circuit
         
         1. increase resistance
         2. decrease perfusion
   2. decreasing circulation to the areas of the lungs that are not receiving O2 will ensure perfusion to the areas that are receiving oxygen

Question 7

of the changes in blood gas, which has a greater affect on pulmonary blood flow? why? what happens in systemic?

Answer 7

Changes in PaO2 (low alveolar oxygen levels, lead to pulmonary vasoconstriction hypoxic vasocontriction) LOCAL EFFECTS

Local hypoxia in the lungs

1. vasoconstiriction of blood to the area = decrease blood flow

systemic capillaries experience the opposite

1. vasodilation of blood to the area = increase blood flow

Question 8

what is the mechanism that causes blood to flow only to areas of the lungs that receive oxygen?

Answer 8

HYPOXIC PULMONARY VASOCONSTRICTION- local hypoxia inhibits perfusion of blood to the area by causing vasoconstriction of blood vessels to areas of low ventilation.

Question 9

exalain the three factors that affect pulmonary resistance

Answer 9

1. [assive
   
   1. lung volumes and pressure
      
      1. this is the ability to draw in and the pressure generated by the atmospheric pressure and like wise the heart
2. active
   
   1. neurohumoral
      
      1. local hypoxia causes blood flow to decrease in areas receiving less oxygen. this then allows more perfusion to areas of greater ventilation
      2. Hypoxic pulmonary ventilation
3. gravity
   
   1. being right side up the blood pools to the bottom of the lungs, generating very little V/Q in zone 1 of the llungs and very high V/Q to zone 3(bottom) of the lungs
   2. laying down dimishes this effect

Question 10

what happens to the zones during exercise and blood loss?

Answer 10

exercies converts zone 1 into zone 2, due to high cardiac output.

blood loss converts zone 2 into zone 1

Question 11

explain the pressures with regard to the zones of the lungs

Answer 11

1. zone1
   
   1. lowest blood flow
   2. PA>Pa>Pv
   3. most of the capillaries are non-perfusing
   4. alveoli are large and lowest compliance
2. zone 2
   
   1. medium
   2. Pa>PA>Pv
3. zone 3
   
   1. highest
   2. Pa>Pv>PA
   3. highest perfusion in capillaries
   4. alveoli are smallest and have the highest compliance

Question 12

there is a regional distribution in prefusion and ventilation of the lung. exaplainthe differenc between the apex and the base

Answer 12

1. apex
   
   1. ventilation
      
      1. intrapleural pressure more negative = greater transmural pressure = larger alveoli
      2. less compliant = less ventilation
   2. perfusion
      
      1. lower intravascular perssures = less recruitment
      2. distention higher resistance = less blood flow
2. base
   
   1. ventilation
      
      1. intrapleural pressure more positive (les negative) = smaller transmural pressure gradient
      2. alveoli smaller = more compliant = more ventilation
   2. perfusion
      
      1. greater vascular pressures = more recruitment
      2. distension lower resistance greater blood flow

Question 13

what is the normal intrapleural pressure of the lungs? what happens when a person sits/stand up? (pleur

Answer 13

the base

1. transpulmonary pressure
   
   1. pressure is lower is lower
2. alveoli are smaller
   
   1. greater compliance
3. alveolar ventilation is greater, alveoli receive more of each tidal volume
   
   1. ventilation is greater at the base

Question 14

which zone has the highest blood flow?

Answer 14

zone 3 has the highest blood flow

Question 15

which zone has the lowest blood flow?

Answer 15

zone 1 has the lowest blood flow

Question 16

which zone has the higest ventilation?

Answer 16

zone 3 has the highest ventilation

Question 17

which zone has the lowest ventilation?

Answer 17

zone 1 has the lowest ventilation

Question 18

which zone has the highest V/Q?

Answer 18

zone 1 has the highest V/Q, because very little blood is flowing there, due to hypoxic pulmonary vasoconstriction. The alveoli are largest there due to transpulmonary pressure being the largest at the apex ( when intrapleural pressure gets smaller, the alveoli gets larger)

Question 19

what zone has the smallest V/Q?

Answer 19

zone 3 has the smallest V/Q, blood perfusion and ventilation are the largest in these arease.

blood perfusion (HPV doesnt act here. The PaO2 is lowest in zone 3. BUT PaCO2 is highest in Zone 3. CO2 causes a bonchiole dilation, compared to zone 1 where a lower CO2 causes bronchiole constriction ( this then shunts the blood)

Question 20

What zone has the highest PaO2

Answer 20

the highest PaO2 is in zone 1, this is due to a lower compliance (the alveoli are maxed to size b/c of the intrapleural pressure decreasing to -10) with the larger alveoli and little blood perfusion.

Question 21

what happens when there is a mismatch of ventialtion and perfusion?

Answer 21

abnormal gas exchange: defects caused by 1)ventilation of regions that are not perfused (dead space) 2)perfusion of regions that are not ventilated (shunts)

1. atreial hypoxemia = PaO2 < 80mmHg
2. hypercapnia= PaCO2 > 45mmHg
3. hypocapnia=PaCO2<35mmHg

Question 22

what are the two reasons for abnormal gas exchange?

Answer 22

1. ventilation to areas that are not perfused = zone 1 and dead space
2. perfusino of regions that are not ventilated -shunts (left to right -lungs and coronary shunts in the heart)

Question 23

represents about 2% of the cardiac output, explain the two important locations/actions and contributions

Answer 23

shunts refer to portions of venous blood flow that has not been oxygenated (or not fully oxygenated ) and diverted/rerouted and into the arterial blood

1. physiological shunts
   
   1. bronchial blood flow** **​
      
      1. supports metabolis activity of the bronchi
   2. coronary blood flow
      
      1. ​drains directly into the left ventricle
2. bothe of these contribute to the concept that PaO2 will always be slightly less than PAO2