Ventilation/ Perfusion Mismatch Flashcards Preview

Apex 1 - 2 Respiratory II: Physiology (24) > Ventilation/ Perfusion Mismatch > Flashcards

Flashcards in Ventilation/ Perfusion Mismatch Deck (29)
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1

Identify the statements that represent the MOST accurate understanding of V/Q mismatch. (Select 2.)

Study on!!!!

2

True or False

Dead space and shunt always exist in the absolute form

 

False

Dead space and shunt rarely exist in the absolute form

3

True or False

Dead space and shunt rarely exist in the absolute form, but rather ventilation and perfusion exist on a continuum

True

Ventilation and perfusion exist on a continuum

4

What determines the final partial pressures of oxygen and carbon dioxide in the blood?

 

Balance between ventilation and perfusion

(in each unit and throughout the lung - better matching ensures better gas transfer)

5

The image below assumes the patient is in the sitting position. Where are V and Q perfectly matched?

Intersection

(where the lines intersect)

6

The image below assumes the patient is in the sitting position.

What's the relationship between V & Q towards the apex?

A. V  > Q

B. V 

V  > Q

7

The image below assumes the patient is in the sitting position.

What's the relationship between V & Q towards the base?

 

A. V  > Q

B. V 

V < Q

8

In V/Q mismatch, Q can be replaced with which hemodynamic variables?

 

Pulmonary blood flow

or

Cardiac output

9

The patient's position affects the V/Q relationship. Therefore, the base on the graph could be replaced with the -------- , and the apex on the graph could be replaced with the ---------.

A. most dependent region

B. least dependent region

The patient's position affects the V/Q relationship. Therefore, the base on the graph could be replaced with the most dependent region, and the apex on the graph could be replaced with the least dependent region.

10

What's the most common cause of hypoxemia in the PACU?

V/ Q mismatch

(specifically atelectasis)

11

As FRC becomes smaller (the result of anesthesia and surgery), there is less radial traction to hold the airways open. The result is

Atelectasis

Right-to-left shunt

V/Q mismatch

Hypoxemia

12

As FRC becomes smaller (the result of anesthesia and surgery), there is less radial traction to hold the airways open. The result is atelectasis, right-to-left shunt, V/Q mismatch, and hypoxemia.

Treatment includes:

Humidified O2

and

Maneuvers designed to  reopen the airways 

(mobility, coughing, deep breathing, and incentive spirometry)

13

As a Consequence of V/Q Mismatch Blood passing through under-ventilated alveoli tends to retain

A. O2

B. CO2

CO2 ​

14

As a Consequence of V/Q Mismatch Blood passing through under-ventilated alveoli tends to retain CO2 and is unable to take in enough

A. Hydrogen

B. Oxygen

Oxygen

15

As a Consequence of V/Q Mismatch Blood passing through overventilated alveoli tends to give off an excessive amount of

A. O2

B. CO2

CO2

16

CO2 diffuses -----   times faster than oxygen.

20 times

17

As a Consequence of V/Q Mismatch Blood passing through overventilated alveoli tends to give off an excessive amount of CO2. Even though this blood can eliminate a large amount of CO2, it cannot take up a proportionate amount of

O2

18

Blood passing through overventilated alveoli tends to give off an excessive amount of CO2. Remember that CO2 diffuses 20 times faster than oxygen. Even though this blood can eliminate a large amount of CO2, it cannot take up a proportionate amount of O2. This is explained by the -----  of the oxyhemoglobin dissociation curve.

Flatness

19

Once the PaO2 reaches 100 mmHg, hemoglobin is fully

saturated

20

Once the PaO2 reaches 100 mmHg, hemoglobin is fully saturated, and any additional oxygen that enters the blood must be

Dissolved in the blood

(this is a very small amount).

21

An alveolus can transfer much more:

A.  CO2 than it can O2

B. O2 than it can CO2

An alveolus can transfer much more CO2 than it can O2

22

What does a lung V/Q mismatch does to compensates for underventilated alveoli?

 

 

It eliminates CO2 from overventilated alveoli
 

23

Why does the PACO2-PaCO2 gradient usually remain small in a lung with V/ Q mismatch?

A lung with V/Q mismatch eliminates CO2 from overventilated alveoli to compensate for the under-ventilated alveoli

 

24

A lung with V/Q mismatch eliminates CO2 from overventilated alveoli to compensate for the under-ventilated alveoli. Which indicates failure of this compensation mechanism fails?

CO2 retention

25

Why is the PA02-Pa02 gradient usually large with V/Q mismatch?

A lung with V/ Q mismatch cannot absorb more oxygen from overventilated alveoli to compensate for under-ventilated alveoli

26

To compensate for V/Q mismatch, the body responds to the imbalances by attempting to match

Ventilation to Perfusion

(V=Q)

27

How does the body combat dead space (zone 1)?

Bronchioles constrict to minimize dead space

28

How does the body combat shunt (zone 3)?

Hypoxic pulmonary vasoconstriction

reduces pulmonary blood flow to minimize shunt

29

References:

 

Flood. Stoelting's Pharmacology & Physiology in Anesthetic Practice. 5th ed. 2016. p. 573-574.

Hagberg. Benumof and Hagberg 's Airway Management. 3rd ed. 2013 . p. 122.

Nagelhout. Nurse Anesthesia. 6th ed. 2018. p. 574 & 1150.