Arterial Blood Gases

Question 1

Normal blood pH

Answer 1

7.35 to 7.45

Question 2

Normal PaCO2

Answer 2

35 to 45

Question 3

Normal PaO2

Answer 3

80 to 100

Question 4

Normal HCO3-

Answer 4

22-26

Question 5

Normal BE

Answer 5

+/-2

Question 6

Life is not compatible with what pH?

Answer 6

7.7

Question 7

When does CO2 from tissues form carbonic acid?

Answer 7

When PCO2>40mmHg in tissues, CO2 spills over into blood plasma and combines with water

Question 8

PaCO2 is a measure of the adequacy of what?

Answer 8

alveolar ventilation

Question 9

Hypoventilation causes what in terms of CO2? in terms of pH?

Answer 9

hypercapnea. acidosis

Question 10

Hyperventilation causes what in terms of COS? in terms of pH?

Answer 10

hypocapnea. alkalosis

Question 11

What are some reasons for hypercapnea?

Answer 11

defective respiratory control centers (ie with head injury)
defective neuromuscular breathing apparatus (ie with MS)
airway obstruction (ie COPD)

Question 12

What are some reasons for hypocapnea?

Answer 12

anxiety
pregnancy
pulmonary embolus*
pulmonary fibrosis*

*because entire section of lung won’t work –> drop in O2–> hyperventilation –> drop in CO2

Question 13

What is PaO2’s effect on pH?

Answer 13

NONE!

Question 14

What’s the difference between SaO2 and SpO2?Which is more accurate?

Answer 14

SaO2 = (amt of O2 in blood with Hgb)/(amt of O2 that could possibly combine with Hgb)

SpO2= O2 saturation as measured by pulse ox.

SaO2 - more accurate.

Question 15

What regulates Bicarbonate?

Answer 15

kidneys!

Question 16

What is BE? What does it reflect?

Answer 16

Base excess- reflects concentration of ALL buffer anions in arterial blood (ie bicarbonate, hemoglobin, plasma, proteins, phosphates)

Question 17

how long do metabolic components take to respond?

Answer 17

can take (kidneys) 3 to 5 days

Question 18

how long does it take respiratory components to respond?

Answer 18

30 to 60 seconds (lungs, medulla)

Question 19

How can you estimate an expected PaO2 values?

Answer 19

(FiO2)x (500)= PaO2

FiO2= percentage of inspired air that is O2

Remember, % atmospheric O2 = 21%

Question 20

What should SpO2 be during exercise and what PaO2 does it correspond to?

Answer 20

90%, 60mmHg

Question 21

why is it dengerous for COPD pts to be on high concentrations of oxygen?

Answer 21

by they have persistent hypercapnea, the sensitivity in their CO2 receptors in brain diminishes in 1 to 2 days, so they rely on HYPOXIC DRIVE to breath

Question 22

Hypoxic drive relizes on what receptors?

Answer 22

receptors sensitive to PO2 (carotid body, aortic bodies). respond most potently in PO2 range of 30 to 60mmHg