Ch. 10: Arterial Blood Gas Interpretation

Question 1

Blood gas analysis monitors the following physiologic variables:

Answer 1

1. Arterial oxygenation: PaO2
2. Alveolar ventilation: PaCO2
3. Acid-base status: pH
4. Tissue oxygenation: PvO2

Question 2

Mixed venous blood, obtained from the pulmonary artery via a pulmonary artery catheter, is used to determine what?

Answer 2

Tissue oxygenation

Question 3

Why is the radial artery is the most common site for blood gas sampling?

Answer 3

Presence of good collateral circulation and
easy access.

Question 4

A modified Allen test

The hand should “pink up” within ________. This is considered a positive Allen test, and the radial artery may be punctured to ob- tain arterial blood.

Answer 4

10 to 15 seconds

Question 5

What should happen if you get a NEGATIVE modified Allens test?

Answer 5

Perform an Allen test on the opposite hand to assess collateral circulation.

Question 6

Sometimes the needle passes through the artery and only a small amount of blood enters the syringe. If this happens, what should you do?

Answer 6

The needle should be slowly withdrawn until it is in the artery.

If the needle needs to be redirected, it should first be withdrawn to the subcutaneous tissue.

Question 7

After obtaining 1 mL of blood, apply a sterile gauze pad with pressure over the puncture site for____ or until the bleeding has stopped.

Answer 7

3 to 5 minutes

Question 8

What does air in the sample do to blood gas values?

Answer 8

Air in the blood causes increased PaO2 levels (as high as the
150s torr range) and decreased PaCO2 levels.

Question 9

If the sample can’t be tested in at least 30 minutes, it should be ________ to slow metabolism and keep ABG levels accurate.

Answer 9

Placed in ice

If tested within 30 minutes, the sample should be maintained at room temperature.

Question 10

List the information you must record after obtaining your ABG sample (6)

Answer 10

(1) FiO2
(2) VT
(3) Respiratory rate
(4) Mode of ventilation
(5) Positive end-expiratory pressure (PEEP) level
(6) Mechanical dead space

Question 11

A fever shifts the HbO2 curve to the (left/right), indicating that hemoglobin (Hb) more readily releases O2 to the tissues but does not pick up the O2 as easily.

Answer 11

Right

Question 12

The majority of O carried in the blood is _____.

Answer 12

bound to Hb

Question 13

HbO2 Dissasociaton Curve

If the curve is shifted to the ________, it indicates that the affinity of Hb for O2 has decreased, or Hb will increase O2 to the tissues more readily.

Answer 13

Right

Question 14

HbO2 Dissasociaton Curve

Factors that shift the curve to the right

Answer 14

• Hypercapnia
• Acidosis
• Hyperthermia
• Increased levels of DPG

Question 15

HbO2 Dissasociaton Curve

Factord that shift the curve to the left

Answer 15

• Hypocapnia
• Alkalosis
• Hypothermia
• Decreased levels of DPG
• HbCO

Question 16

If the curve is shifted to the left, what does it indicate?

Answer 16

It indicates that the affinity of Hb for O2 has increased, or Hb will not release O2 to the tissues as readily.

Question 17

As the RBC travels to the tissue, it releases the O2 because elevated CO2 levels, which are present around tissues, decrease the affinity of Hb for O2. This is known as the ____.

Answer 17

Bohr effect

Question 18

Levels of hypoxemia

60-79 mm Hg

Answer 18

Mild

Question 19

Levels of hypoxemia

40-59 mm Hg

Answer 19

Moderate

Question 20

Levels of hypoxemia

<40 mm Hg

Answer 20

Severe

Question 21

The O2 tension at which 50% of the Hb is saturated when the blood is at 37° C, has a PCO2 level of 40 mm Hg, and a pH level of 7.40.

Answer 21

P-50

Question 22

Increased P-50 indicates _____________ affinity.

Answer 22

decreased

Question 23

Decreased P-50 indicates _____________ affinity.

Answer 23

increased

Question 24

What refers to the quantity of O2 being carried by the Hb compared with the maximum that may be carried ?

Answer 24

SaO2

Question 25

Normal SaO2 level is what?

Answer 25

> 97%

Question 26

The adequacy of ventilation is determined by the ____ level.

Answer 26

PaCO2

Question 27

CO2 makes up approximately ________% of inspired air.

Answer 27

0.03

Question 28

CO2 is carried in the blood three ways:

Answer 28

(1) Dissolved in the plasma
(2) Bound to Hb
(3) As HCO32

Question 29

Portable blood gas analyzerst hat allow blood gas testing to be done at or near the patient bedside.

Answer 29

POC analyzers

Question 30

Quality Control Procedures ABG

Blood gas analyzers should undergo one- and two-point calibrations on a routine basis.

Wheh should one-point calibration should be performed?

Answer 30

Before a blood gas sample is run unless the analyzer automatically performs the calibration at programmed intervals

Question 31

Blood gas analyzers should undergo one- and two-point calibrations on a routine basis.

Wheh should two-point calibration should be performed?

Answer 31

Every 8 hours

Question 32

The criteria for acceptable results are below: ABGs

pH must be within ____ of the target value.

Answer 32

0.04

Question 33

PCO2 must be within ____ mm Hg of the target value.

Answer 33

3

Question 34

PO2 must be within ____ mm Hg of standard deviations.

Answer 34

3

Question 35

What are we assessing when we perform the modified Allens test?

Answer 35

Collateral circulation