ABG Blood Interpretation Notes 2026
Questions and Answers Graded A+
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.
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,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the needle is withdrawn, the wound should be pressurized for a period of at least 3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.
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)
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,• Adequacy of ventilation (Paco2)
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
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, 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
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 oxygen and thus returns to the systemic circulation unchanged. Lack
of ventilation occurs in alveoli affected by atelectasis, pneumonia, and pulmonary
edema. Hypoxemia resulting from shunt is classically nonresponsive or refractory
to oxygen therapy.
©COPYRIGHT 2026, ALL RIGHTS RESERVED 4
Questions and Answers Graded A+
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.
©COPYRIGHT 2026, ALL RIGHTS RESERVED 1
,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.
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)
©COPYRIGHT 2026, ALL RIGHTS RESERVED 2
,• Adequacy of ventilation (Paco2)
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
©COPYRIGHT 2026, ALL RIGHTS RESERVED 3
, 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
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 oxygen and thus returns to the systemic circulation unchanged. Lack
of ventilation occurs in alveoli affected by atelectasis, pneumonia, and pulmonary
edema. Hypoxemia resulting from shunt is classically nonresponsive or refractory
to oxygen therapy.
©COPYRIGHT 2026, ALL RIGHTS RESERVED 4
