Gas Exchange (Sinclair) Flashcards Preview

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Flashcards in Gas Exchange (Sinclair) Deck (30):
1

What are the 2 causes of hypoxemia present with a normal A-a difference?

1. Decreased PIO2 (altitude change)
2. Hypoventilation

2

What are the 3 causes of hypoxemia present with a widened A-a difference?

1. Diffusion limitation
2. R-to-L shunt
3. Ventilation/Perfusion (V/Q) mismatch

3

What does a normal A-s DO2 determine?

*

4

What does an increased A-s DO2 determine?

*

5

Lungs Functionally Divided into 2 ZONES:

conducting and respiratory

6

Respiratory unit served by single terminal bronchiole

Acinus

7

Several adjacent acini with incomplete septa

Lobule

8

What is the calculation of partial pressure for inspired gas?

= (PB - PH2O) x FIGas

9

VE (total ventilation) =

tidal vol x resp rate

10

What air does not participate in gas exchange?

Air which remains in the Conducting airways at end inspiration (anatomic dead space)

11

If a 500mL breath is taken, the amount of fresh gas delivered to alveoli will be:

500 - anat dead space

12

Alveolar Ventilation =

Minute Ventilation - Dead space

13

Alv Gas Equation =
(CO2 Excretion)

PACO2 = VCO2/VA (PB-47)

14

Alv Gas Equation =
(O2)

PIO2-PAO2 = VO2/VA (PB-47)

15

Alv gas equation =
(complete)

PAO2 = PIO2-(PaCO2/R)

16

A-a difference (A-aDO2) is calculated by

subtracting PaO2 from PAO2

17

Widened A-a difference signifies

presence of lung disease

18

Normal A-a gradient signifies

no lung disease

19

_____ oxygen tension is readily measured by ABG

arterial

20

How does age affect arterial oxygen?

1. decreased oxygen transfer to blood due to declingin lung function
2. Arterial oxygen tension decreases with age

21

Formula for normal A-a gradient

(age + 4)/4

22

A-a difference (increases/decreases) with age because:

increases

alveolar oxygen tension remains the same which arterial oxygen tension declines

23

Decreased oxygen tension in the circulating blood compared to normal

hypoxemia

24

PaCO2 is a good measure of:

alveolar ventilation

25

In terms of diffusion, hypoxemia only occurs if:

diffusion capacity severely decreased
transit time decreased

26

Hypoxemia caused by _____ does NOT correct with increased FIO2

R to L shunt

27

Ventilation and Perfusion are higher at the (apices/bases)

bases

28

1. V/Q > 1 are called
2. V/Q < 1 are called

1. dead space-like units
2. shunt-like units

29

T/F: Most lung diseases cause VQ mismatch

T

30

Which causes of hypoxemia correct with O2

1. V/Q mismatch
2. diffusion limitation
3. decreased FIO2
4. hypoxemia?