Dasgupta - V/Q Matching

Question 1

Normal V/Q ratio in a normal adult whole lung

Answer 1

O.8

3600/4500

Question 2

What are the two pumps involved in the pulmonary system?

Answer 2

The heart pumps blood into the lung

The chest wall pumps air into the lung

Question 3

Areas with blood flow but no ventilation. Pure mixed systemic venous blood

Answer 3

Shunt

Question 4

Areas with ventilation but no blood flow

Answer 4

Dead space

Question 5

The more extreme the V/Q mismatch is, the _____ the gas exchange is

Answer 5

Worse

Question 6

The efficiency in gas exchange is dependent on which 3 things?

Answer 6

High gradient in partial pressure

Low thickness of membrane (~0.5 micron)

High surface area of alveolus

Question 7

PAO2 =

Answer 7

PO2 in alveolar gas

Question 8

PaO2 = PO2 in _____

Answer 8

Systemic arterial blood

Question 9

The bigger the A-a difference is, the _________ the exchange

Answer 9

Poorer

Question 10

A measure of whether optimal V/Q matching is occurring in the lung

Answer 10

A-a gradient

Question 11

What causes the normal low V/Q ratio in the bottom of the lung and high V/Q ratio in the top of the lung?

Answer 11

The gradient of Q from gravity is much greater than that of V.

Question 12

The greater Q is in relation to V, the _____ the PCO2 will be

Answer 12

Higher

Question 13

V/Q is _______ to PaO2

Answer 13

Directly proportional

Question 14

The higher the V/Q, the _____ the PaO2

Answer 14

Higher

Question 15

PCO2 of venous blood = ??

This is what PACO2 of alveoli reaches when it is perfused but not ventilated

Answer 15

46mm Hg

Question 16

A ____ of the V/Q ration will increase the PO2

Answer 16

Increase

Question 17

The lung unit with low V/Q will have ____ PO2 and ____ PCO2

Answer 17

Low

High

Question 18

The lung unit with high V/Q will have ____ PO2 and _____ PCO2

Answer 18

High

Low

Question 19

Nitric oxide ______ hypoxic pulmonary vasoconstriction

Answer 19

Reverses

Question 20

Why is inhaled NO more effective at reducing hypoxic pulmonary vasoconstriction than ingested NTG and NTP?

Answer 20

The inhaled NO only goes to the alveoli that are ventilated and dilating the blood vessels there. Instead of going to all lung segments like NTG and NTP would do.

Question 21

Required concentration of NO for therapy?

Answer 21

20ppm

*NO is very toxic at high concentrations

Question 22

Shunt-like states are said to be ____ V/Q mismatch

Answer 22

Low

Question 23

______ are the most dangerous V/Q mismatch

Answer 23

Low V/Q mismatches

Because these units are shunt-like

Question 24

Low V/Q mismatch results in ______ _

Answer 24

Hypoxemia

High A-a gradient

High PCO2 in arterial blood

Question 25

Low pCO2 in airways causes the airways to ________

Answer 25

Constrict locally

Question 26

Paradox of compensation in low V/Q patients

Answer 26

PaCO2 is normal PaO2 is low

Question 27

Things that limit ventilation:

Answer 27

Obstructive lung disease (emphysema, bronchitis, asthma) Shunt (alveoli filled with fluid or foreign material) Restrictive lung disease (fibrosis)

Question 28

Pneumonia of the lungs is a classic example of a ______

Answer 28

Shunt

Question 29

Normal A-a gradients

Answer 29

5-15mmHg | This one is according to dasgupta, BRS has a different number

Question 30

The fact that there is a normal A-a gradient that is more that 0 is because of ?

Answer 30

V/Q mismatching [due to gravity in normal lungs] Shunts [all lungs have shunts in the form of venous drainage of parts of the heart and large airways]

Question 31

The older you are, the _____ your A-a gradient will be.

Answer 31

Larger

Question 32

Normal range per A-a gradient increases _______ per decade after age 30

Answer 32

3mmHg

Question 33

Five causes for hypoxemia

Answer 33

Breathing air w/ low pO2 Hypoventilation Shunts Low V/Q mismatch Diffusion problem

Question 34

Hypoventilation always results in _____ and ______

Answer 34

Hypoxemia Hypercapnia (A-a gradient normal)

Question 35

Patient presents with hypoxemia. Shows only small increase in PaO2 when 100% O2 is administered. A-a gradient is large. Likely diagnosis is?

Answer 35

Shunts

Question 36

Cause of hypoxemia. Also associated with hypercapnia. A-a gradient is normal

Answer 36

Hypoventilation

Question 37

Pt presents w/ hypoxemia. Shows marked increase in PaO2 when 100% O2 administered. A-a gradient is large

Answer 37

Low V/Q mismatches

Question 38

Cause of hypoxemia. Shows marked increase in PaO2 when 100% O2 administered. A-a gradient large. This type is very uncommon and must be differentiated with more diagnostic methods

Answer 38

Diffusion defects

Question 39

Problems of a pulmonary embolus are initially ______

Answer 39

Cardiovascular. | Right heart has to work harder to move CO thru remaining sections of lungs.

Question 40

V but no Q

Answer 40

Dead space

Question 41

Q but no V

Answer 41

Shunt