Special Procedures

Question 1

Effect of improper cooling of ABG sample

Answer 1

pH, PO2 & PCO2 decrease

Question 2

Effect of excess heparin in ABG sample

Answer 2

pH moves toward 7.0
PO2 and PCO2 react like air bubble

Question 3

Effect of flush solution in ABG sample

Answer 3

pH decreases
PO2 and PCO2 react like air bubble

Question 4

Effect of air bubble in ABG sample

Answer 4

pH increases
PO2 moves toward 150
PCO2 decreases

Question 5

Effect of high patient temp on ABG results

Answer 5

pH will be higher than actual
PO2 & PCO2 will be lower than actual

Question 6

Effect of low patient temp on ABG results

Answer 6

pH will be lower than actual
PO2 & PCO2 will be higher than actual

Question 7

Capillary sample vs ABG

Answer 7

pH & PCO2 correlate closely with ABG
PO2 does not correlate with ABG

Question 8

Alveolar Air Equation

Answer 8

Calculates the PO2 in alveoli
PAO2 = (PB - PH2O) FIO2 - (PaCO2 / 0.8)
PB = 760
PH2O = 47
Cheat: PAO2 = (FIO2 x 7) - (PaCO2 + 10)

Question 9

A-a Gradient (A-aDO2)

Answer 9

Measures the difference between alveolar and arterial PO2
Most accurate after the patient had breathed 100% O2 for 20 minutes or more
A-aDO2 = PAO2-PaO2

Question 10

A-a gradient values on 100% O2

Answer 10

25 - 65 = normal
66 - 300 = V/Q mismatch
>300 = shunt

Question 11

Normal PAO2 by FiO2

Answer 11

21% = 100
50% = 300
100% = 600

Question 12

Normal A-a gradient

Answer 12

Should be less than FIO2
Up to 300 = increase O2
Over 300 = recruit alveoli with PPV

Question 13

Normal CaO2

Answer 13

17 - 20 vol%
*If all values given are normal, the CaO2 will likely be normal

Question 14

Purpose of Arterial Oxygen Content (CaO2)

Answer 14

Best measurement of oxygen delivered to tissues (oxygen transport)
Estimates the oxygen carried by hemoglobin as well as oxygen dissolved in plasma

Question 15

Purpose of Mixed Venous Oxygen Content (CvO2)

Answer 15

Measures the total amount of oxygen carried in mixed venous blood
Reflects cardiac function

Question 16

Normal CvO2

Answer 16

12 - 16 vol%

Question 17

Purpose of Arterial-Venous Oxygen Difference (C(a-v)O2)

Answer 17

Indicates tissue oxygen consumption

Question 18

Normal C(a-v)O2

Answer 18

4 - 5 vol%

Question 19

Calculation for Cardiac Output (QT)

Answer 19

QT = VO2 / C(a-v)O2 x 10
VO2 = oxygen consumption
The values will be provided

Question 20

Normal QT

Answer 20

4 - 8 L/min

Question 21

Shunt Equation (QS/QT)

Answer 21

QT = cardiac output
QS = shunt
Cheat: QS/QT = (5 for each 100 of A-aDO2) + 5
(e.g. 100 = 10%, 200 = 15%, 300 = 20%, etc… estimated maximum)

Question 22

Normal QS/QT

Answer 22

3 - 5%

Question 23

Estimated SaO2 based on PaO2

Answer 23

SaO2 = PaO2 + 30

Question 24

Estimated Hct based on Hb

Answer 24

Hb x 3

Question 25

Purpose of Dead Space to Tidal Volume Ratio (VD/VT)

Answer 25

The percentage of tidal volume that doesn’t participate in gas exchange An increased VD/VT represents increasing dead space (e.g. PE)

Question 26

Normal VD/VT

Answer 26

20 - 40%

Question 27

O2/Hb dissociation curve shifted left

Answer 27

Increased O2 affinity -Decreased hydrogen ions (Increased pH) -Decreased PCO2 -Decreased temperature -Decreased DPG

Question 28

O2/Hb dissociation curve shifted right

Answer 28

Decreased O2 affinity -Increased hydrogen ions (decreased pH) -Increased PCO2 -Increased temperature -Increased DPG

Question 29

Typical COHb levels

Answer 29

Normal = 0-2% Smokers = 5-10% CO poisoning = >20%

Question 30

The only way CaO2 can be greater than 20 is…

Answer 30

Polycythemia

Question 31

Calculation for CaO2

Answer 31

CaO2 = (Hb x 1.34 x SaO2) + (PaO2 x 0.003) **Cheat: Only need 1st part of the equation, Hb x 1.34 x SaO2

Question 32

Calculation for CvO2

Answer 32

CvO2 = (Hb x 1.34 x SvO2) + (PvO2 x 0.003) If SvO2 or PvO2 decrease, CO is decreased

Question 33

Calculation for arterial-venous oxygen difference

Answer 33

C(a-v)O2 = CaO2 - CvO2 High C(a-v)O2 = decreased CO

Question 34

Calculation for VD/VT

Answer 34

VD/VT = ((PaCO2 - PECO2) / PaCO2) x 100