Ch. 10: Arterial Blood Gas Interpretation Flashcards
Blood gas analysis monitors the following physiologic variables:
- Arterial oxygenation: PaO2
- Alveolar ventilation: PaCO2
- Acid-base status: pH
- Tissue oxygenation: PvO2
Mixed venous blood, obtained from the pulmonary artery via a pulmonary artery catheter, is used to determine what?
Tissue oxygenation
Why is the radial artery is the most common site for blood gas sampling?
Presence of good collateral circulation and
easy access.
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.
10 to 15 seconds
What should happen if you get a NEGATIVE modified Allens test?
Perform an Allen test on the opposite hand to assess collateral circulation.
Sometimes the needle passes through the artery and only a small amount of blood enters the syringe. If this happens, what should you do?
The needle should be slowly withdrawn until it is in the artery.
If the needle needs to be redirected, it should first be withdrawn to the subcutaneous tissue.
After obtaining 1 mL of blood, apply a sterile gauze pad with pressure over the puncture site for____ or until the bleeding has stopped.
3 to 5 minutes
What does air in the sample do to blood gas values?
Air in the blood causes increased PaO2 levels (as high as the
150s torr range) and decreased PaCO2 levels.
If the sample can’t be tested in at least 30 minutes, it should be ________ to slow metabolism and keep ABG levels accurate.
Placed in ice
If tested within 30 minutes, the sample should be maintained at room temperature.
List the information you must record after obtaining your ABG sample (6)
(1) FiO2
(2) VT
(3) Respiratory rate
(4) Mode of ventilation
(5) Positive end-expiratory pressure (PEEP) level
(6) Mechanical dead space
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.
Right
The majority of O carried in the blood is _____.
bound to Hb
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.
Right
HbO2 Dissasociaton Curve
Factors that shift the curve to the right
- Hypercapnia
- Acidosis
- Hyperthermia
- Increased levels of DPG
HbO2 Dissasociaton Curve
Factord that shift the curve to the left
- Hypocapnia
- Alkalosis
- Hypothermia
- Decreased levels of DPG
- HbCO
If the curve is shifted to the left, what does it indicate?
It indicates that the affinity of Hb for O2 has increased, or Hb will not release O2 to the tissues as readily.
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 ____.
Bohr effect
Levels of hypoxemia
60-79 mm Hg
Mild
Levels of hypoxemia
40-59 mm Hg
Moderate
Levels of hypoxemia
<40 mm Hg
Severe
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.
P-50
Increased P-50 indicates _____________ affinity.
decreased
Decreased P-50 indicates _____________ affinity.
increased
What refers to the quantity of O2 being carried by the Hb compared with the maximum that may be carried ?
SaO2
Normal SaO2 level is what?
> 97%
The adequacy of ventilation is determined by the ____ level.
PaCO2
CO2 makes up approximately ________% of inspired air.
0.03
CO2 is carried in the blood three ways:
(1) Dissolved in the plasma
(2) Bound to Hb
(3) As HCO32
Portable blood gas analyzerst hat allow blood gas testing to be done at or near the patient bedside.
POC analyzers
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?
Before a blood gas sample is run unless the analyzer automatically performs the calibration at programmed intervals
Blood gas analyzers should undergo one- and two-point calibrations on a routine basis.
Wheh should two-point calibration should be performed?
Every 8 hours
The criteria for acceptable results are below: ABGs
pH must be within ____ of the target value.
0.04
PCO2 must be within ____ mm Hg of the target value.
3
PO2 must be within ____ mm Hg of standard deviations.
3
What are we assessing when we perform the modified Allens test?
Collateral circulation
