ABG Blood Interpretation Notes with Latest Structured
Questions and Correct Detailed Answers Already Rated
and A Graded
List 3 common arterial blood sampling sites. - CORRECT ANSWER >>>The arterial blood
sample may be obtained from the radial, dorsalis pedis, brachial, or femoral arteries in the
adult.
Describe the procedure for doing the modified Allen's Test. - CORRECT ANSWER >>>To
perform this test, the clinician instructs the patient to make a tight fist. Then compress both the
radial and ulnar arteries. Now instruct the patient to open and relax his fist, revealing a
blanched palm and fingers. Then release the pressure over the ulnar artery while observing the
patient's palm for changes in color. If collateral flow is adequate, the patient's hand will "pink
up" within 10 to 15 seconds; this constitutes a positive Allen's test. A positive result documents
that collateral blood flow is adequate and that the radial artery is an acceptable puncture site. If
the test is negative (the palm does not pink up rapidly), the radial artery is not an acceptable
site for puncture. In such cases, the other wrist is evaluated or the brachial artery is used for the
puncture site.
Why is it important to remove air bubbles from the sample? - CORRECT ANSWER >>>The
oxygen and CO2 gas tensions of the bubbles may equilibrate with the blood and result in
erroneous measurements.
How long should pressure be applied to the puncture site? - CORRECT ANSWER >>>After
the needle is withdrawn, the wound should be pressurized for a period of at least 3 to 5 minutes
or longer, if clotting problems exist.
1|Page
,List the measurements that are used to assess
oxygen status acid-base
balance
adequacy of ventilation - CORRECT ANSWER >>>The measurements obtained from
analysis of arterial and mixed venous blood samples are useful in evaluating the following:
• Acid-base balance (pH, Paco2, HCO3−, base excess)
• Oxygenation status (Pao2, Sao2, Cao2, Pv¯o2)
• Adequacy of ventilation (Paco2)
List the normal values for the following
PaO2
PAO2 - CORRECT ANSWER >>>Partial Pressure of Oxygen in Arterial Blood
NORMAL VALUE: approximately 80 to 100 mm Hg in room air
Partial Alveolar Oxygen Difference
NORMAL VALUE: 100 torr
Calculate the PAO2 given the following information
FiO2=0.40
Pb = 747 mm Hg
PaCO2 = 40 mm Hg - CORRECT ANSWER >>>PAO2 = (PB- PH2O)FIO2- PaCO2(1.25)
= (747 mm Hg - 47 mm Hg)0.40 - 40 mm Hg(1.25)
2|Page
,= (700 mm Hg)0.40 - 40 mm Hg(1.25)
= (280 mm Hg - 50 mm Hg)
= 230 mm Hg
Define hypoxemia - CORRECT ANSWER >>>When the measured Pao2 is below the
predicted range for a patient breathing room air, regardless of the actual FIO2, it is called
hypoxemia. As long as the Pao2 remains above the minimally acceptable limit, hypoxemia does
not exist, regardless of the actual FIO2.
At any age, a Pao2 of less than 65 mm Hg is considered hypoxemia and a Pao2 of less than 40
mm Hg is considered severe hypoxemia.
List the values for mild, moderate and severe hypoxemia - CORRECT ANSWER >>>60 - 79
(Mild hypoxemia) 40-59 (Moderate hypoxemia) 30- less (Severe hypoxemia)
Give an example of a cause of hypoxemia from V/Q mismatching. - CORRECT ANSWER
>>>Hypoxemia occurs when inhaled gas does not match with lung perfusion. Gas exchange
requires intimate contact between inhaled gas and blood. V/Q mismatching is the most
common cause of hypoxemia in cases of respiratory disease.
-Mucus plug blocks or bronchospasm reduces ventilation, perfusion still enters this part of lung
Perfusion in excess of ventilation
V= 3 L/min, Q = 6 L/min = 0.5. Cause is from atelectasis.
What is dead space ventilation? - CORRECT ANSWER >>>Dead space ventilation
Ventilation in excess of perfusion
3|Page
, Dead space ventilation-ventilation in excess of
Perfusion. V= 10 L/m/ Q = 5 L/min = 2.0. Cause is
pulmonary emboli.
Deadspace is V/Q > 0.8, Shunting is V/Q < 0.8, Normal + 0.8
What.is.a.shunt?.-.CORRECT.ANSWER.>>>Shunt-
Perfusion.without.ventilation.or.in.excess.of.ventilation
Pulmonary.capillary.blood,.which.flows.by.alveoli.that.are.not.ventilated,.does.not.pick.up.any.oxy
gen.and.thus.returns.to.the.systemic.circulation.unchanged..Lack.of.ventilation.occurs.in
alveoli.affected.by.atelectasis,.pneumonia,.and.pulmonary.edema..Hypoxemia.resulting.from.shu
nt.is.classically.nonresponsive.or.refractory.to.oxygen.therapy.
Give.4.examples.of.diffusion.defects..-.CORRECT.ANSWER.>>>Aveolar.collapse
(Atelectasis),.Thickening.of.aveolar.walls.(Aveolar.Fibrosis),.Aveolar-
capillary.destruction.(Emphysema),.Aveolar.consolidation.(Pneumonia),.Frothy.secretions.(Pulmo
nary.Edema),.Interstitial.Edema
Why.does.diffusion.defects.respond.to.increase.FiO2?.-.CORRECT.ANSWER
>>>•Abnormalities.in.lung.structure.that.slow.diffusion.of.oxygen.through.ACM,.resulting.in.hypox
emia.
•Good.response.to.oxygen.therapy.
Hypoventilation.causes. and. ..-
CORRECT.ANSWER.>>>Hypercarbia.and.hypoxemia
.
A.patient.with.hypoventilation.with.lung.disease.will.develop.hypoxemia.from.
and.have.an.increase. ..-.CORRECT.ANSWER
>>>V/Q.mismatch
4.|.P.a.g.e
Questions and Correct Detailed Answers Already Rated
and A Graded
List 3 common arterial blood sampling sites. - CORRECT ANSWER >>>The arterial blood
sample may be obtained from the radial, dorsalis pedis, brachial, or femoral arteries in the
adult.
Describe the procedure for doing the modified Allen's Test. - CORRECT ANSWER >>>To
perform this test, the clinician instructs the patient to make a tight fist. Then compress both the
radial and ulnar arteries. Now instruct the patient to open and relax his fist, revealing a
blanched palm and fingers. Then release the pressure over the ulnar artery while observing the
patient's palm for changes in color. If collateral flow is adequate, the patient's hand will "pink
up" within 10 to 15 seconds; this constitutes a positive Allen's test. A positive result documents
that collateral blood flow is adequate and that the radial artery is an acceptable puncture site. If
the test is negative (the palm does not pink up rapidly), the radial artery is not an acceptable
site for puncture. In such cases, the other wrist is evaluated or the brachial artery is used for the
puncture site.
Why is it important to remove air bubbles from the sample? - CORRECT ANSWER >>>The
oxygen and CO2 gas tensions of the bubbles may equilibrate with the blood and result in
erroneous measurements.
How long should pressure be applied to the puncture site? - CORRECT ANSWER >>>After
the needle is withdrawn, the wound should be pressurized for a period of at least 3 to 5 minutes
or longer, if clotting problems exist.
1|Page
,List the measurements that are used to assess
oxygen status acid-base
balance
adequacy of ventilation - CORRECT ANSWER >>>The measurements obtained from
analysis of arterial and mixed venous blood samples are useful in evaluating the following:
• Acid-base balance (pH, Paco2, HCO3−, base excess)
• Oxygenation status (Pao2, Sao2, Cao2, Pv¯o2)
• Adequacy of ventilation (Paco2)
List the normal values for the following
PaO2
PAO2 - CORRECT ANSWER >>>Partial Pressure of Oxygen in Arterial Blood
NORMAL VALUE: approximately 80 to 100 mm Hg in room air
Partial Alveolar Oxygen Difference
NORMAL VALUE: 100 torr
Calculate the PAO2 given the following information
FiO2=0.40
Pb = 747 mm Hg
PaCO2 = 40 mm Hg - CORRECT ANSWER >>>PAO2 = (PB- PH2O)FIO2- PaCO2(1.25)
= (747 mm Hg - 47 mm Hg)0.40 - 40 mm Hg(1.25)
2|Page
,= (700 mm Hg)0.40 - 40 mm Hg(1.25)
= (280 mm Hg - 50 mm Hg)
= 230 mm Hg
Define hypoxemia - CORRECT ANSWER >>>When the measured Pao2 is below the
predicted range for a patient breathing room air, regardless of the actual FIO2, it is called
hypoxemia. As long as the Pao2 remains above the minimally acceptable limit, hypoxemia does
not exist, regardless of the actual FIO2.
At any age, a Pao2 of less than 65 mm Hg is considered hypoxemia and a Pao2 of less than 40
mm Hg is considered severe hypoxemia.
List the values for mild, moderate and severe hypoxemia - CORRECT ANSWER >>>60 - 79
(Mild hypoxemia) 40-59 (Moderate hypoxemia) 30- less (Severe hypoxemia)
Give an example of a cause of hypoxemia from V/Q mismatching. - CORRECT ANSWER
>>>Hypoxemia occurs when inhaled gas does not match with lung perfusion. Gas exchange
requires intimate contact between inhaled gas and blood. V/Q mismatching is the most
common cause of hypoxemia in cases of respiratory disease.
-Mucus plug blocks or bronchospasm reduces ventilation, perfusion still enters this part of lung
Perfusion in excess of ventilation
V= 3 L/min, Q = 6 L/min = 0.5. Cause is from atelectasis.
What is dead space ventilation? - CORRECT ANSWER >>>Dead space ventilation
Ventilation in excess of perfusion
3|Page
, Dead space ventilation-ventilation in excess of
Perfusion. V= 10 L/m/ Q = 5 L/min = 2.0. Cause is
pulmonary emboli.
Deadspace is V/Q > 0.8, Shunting is V/Q < 0.8, Normal + 0.8
What.is.a.shunt?.-.CORRECT.ANSWER.>>>Shunt-
Perfusion.without.ventilation.or.in.excess.of.ventilation
Pulmonary.capillary.blood,.which.flows.by.alveoli.that.are.not.ventilated,.does.not.pick.up.any.oxy
gen.and.thus.returns.to.the.systemic.circulation.unchanged..Lack.of.ventilation.occurs.in
alveoli.affected.by.atelectasis,.pneumonia,.and.pulmonary.edema..Hypoxemia.resulting.from.shu
nt.is.classically.nonresponsive.or.refractory.to.oxygen.therapy.
Give.4.examples.of.diffusion.defects..-.CORRECT.ANSWER.>>>Aveolar.collapse
(Atelectasis),.Thickening.of.aveolar.walls.(Aveolar.Fibrosis),.Aveolar-
capillary.destruction.(Emphysema),.Aveolar.consolidation.(Pneumonia),.Frothy.secretions.(Pulmo
nary.Edema),.Interstitial.Edema
Why.does.diffusion.defects.respond.to.increase.FiO2?.-.CORRECT.ANSWER
>>>•Abnormalities.in.lung.structure.that.slow.diffusion.of.oxygen.through.ACM,.resulting.in.hypox
emia.
•Good.response.to.oxygen.therapy.
Hypoventilation.causes. and. ..-
CORRECT.ANSWER.>>>Hypercarbia.and.hypoxemia
.
A.patient.with.hypoventilation.with.lung.disease.will.develop.hypoxemia.from.
and.have.an.increase. ..-.CORRECT.ANSWER
>>>V/Q.mismatch
4.|.P.a.g.e
