54 Questions
What is the most common cause of hypoxemia in the clinical setting?
V ̇/Q ̇mismatching
What areas in the lung are associated with low end-capillary PO2?
Areas with low V/Q ratio
Which factor limits the ability of normal and high V/Q regions to increase O2 content and compensate for low V/Q regions?
O2Hb dissociation curve plateau
What occurs in a right-to-left shunt?
Extreme case of V/Q mismatch
In healthy awake spontaneously breathing subjects, what is the status of intrapulmonary shunt?
<1% of cardiac output
Why does V/Q mismatch result in hypoxemia?
Limited O2 compensation due to the O2Hb dissociation curve
What is the normal range for PaO2 in healthy adults breathing room air at sea level?
80-100 mm Hg
Which of the following is NOT a physiologic cause of hypoxemia?
Left-to-right shunt
How does hypoventilation contribute to hypoxemia?
By reducing the PAO2
Which factor can produce hypoxemia by affecting the different steps of O2 transport from the environment to arterial blood?
hypoventilation
In which conditions does diffusion limitation play a role in causing hypoxemia?
In interstitial lung diseases
Which step of O2 transport to arterial blood is affected by V ̇/Q ̇ mismatch and right-to-left shunt?
Efficiency of O2 exchange
which of the following causes explain the majority of hypoxemia in the perioperative setting
all of the above
The normal value of PaO2 decreases with ?
increasing age
How does an increase in FIO2 affect PaO2 in the presence of a large true right-to-left shunt?
It has a small effect on PaO2
What is a possible cause of right-to-left shunt during general anesthesia as mentioned in the text?
Atelectasis
In addition to atelectasis, which other pathologic condition can lead to a right-to-left shunt?
Pneumonia
What factors determine the effect of a right-to-left shunt on PaO2?
Magnitude of the shunt, FIO2, and the cardiac output
What does the shunt fraction equation use to calculate the shunted blood flow in the three-compartment lung model?
End-capillary O2 content
In the ideal alveolar gas equation, the ratio of pulmonary CO2 elimination to O2 uptake is represented by which parameter?
Respiratory quotient (R)
Under normal diet and metabolic conditions, what value does the respiratory quotient (R) typically have?
0.8
Which lung compartment represents regions with ventilation but no perfusion in the three-compartment lung model?
Dead space compartment
What does Q ̇S/Q ̇T represent under conditions of FIO2 less than 100%?
Combination of factors producing hypoxemia
What is the term used when Q ̇S/Q ̇T is referred to as the calculated estimate of how much hypoxic blood is required to produce the measured arterial oxygen results?
Venous admixture
What condition can be caused by the administration of 100% oxygen (FIO2 of 1.0), particularly in compartments with very low V ̇/Q ̇?
Absorption atelectasis
In the simplified form of the shunt fraction equation, what does Q s/Q T= (1−SaO2)/ (1 − SvO2) represent?
Relationship between arterial and mixed venous saturation levels
What is the purpose of the shunt fraction equation assuming end-capillary blood has an O2 saturation of 100%?
To calculate the shunt fraction accurately
Which factor is eliminated when FIO2 is at 100% according to the text?
Effects of V ̇/Q ̇ heterogeneity
Why is proper handling of arterial blood gas samples important?
is important to prevent errors.
In adult patients during procedures involving deep hypothermic circulatory arrest (DHCA), which management strategy is suggested for increasing the rate and uniformity of cooling?
pH-stat management
What is the potential consequence of a delay in analyzing an arterial blood gas sample for 20 minutes at room temperature or 4°C?
Decline in PaO2
What issue can arise if an air bubble is present in the sampling syringe during arterial blood gas sample collection?
decline in PaCO2
Which strategy is supported for hypothermic circulatory pulmonary bypass (HCPB) in adult patients?
Alpha-stat management
What is a limitation of indices of oxygenation based on PaO2?
They vary with changes in FIO2, PaCO2, Hb, and V ̇O2
What is an ideal characteristic of an index of oxygenation?
It should change with changes in lung function
What is a disadvantage of using indices of oxygenation based on PaO2?
They are limited in providing a measure of the magnitude of the O2 exchange deficiency
Why do indices of oxygenation based on PaO2 vary with changes in FIO2?
Because they are dependent on FIO2
What is the main purpose of developing less invasive indices of oxygenation?
To reflect the efficiency of oxygenation using non-invasive measures
What should an ideal index of oxygenation do when there are changes in extrapulmonary conditions like FIO2?
Remain constant
Why is a pulmonary artery catheter needed for measuring SvO2?
To calculate shunt fraction directly
What is a main limitation of indices of oxygenation based on PaO2?
They vary with FIO2, PaCO2, Hb, and O2 consumption
What does the (A-a)PO2 help to differentiate?
Hypoventilation and low FIO2 from V ̇/Q ̇ mismatch, shunt, and diffusion limitation
What is the normal value of the (A-a)PO2 in young adults breathing room air?
Less than 10 mm Hg
What happens to the (A-a)PO2 under conditions of decreased FIO2 and hypoventilation?
It remains unchanged
What effect does lower temperature have on the solubility of CO2 and O2 in blood?
Increases solubility
In blood gas analyzers, As blood from a hypothermic patient is warmed to 37°C by the analyzer lead to
PaCO2 and PaO2 higher
What potential benefit does alpha-stat management offer in the management of hypothermic patients?
Preservation of cerebral autoregulation
In pH-stat management, why are measurements corrected to the patient’s actual temperature before being used for analysis?
Because patients are hypothermic, the PaO2 and PaCO2 at the patient’s temperature are lower and the pH higher
What stands out as a key difference between alpha-stat and pH-stat management during blood gas analysis?
Temperature corrections
What is a limitation of the PaO2/FIO2 ratio for characterizing respiratory failure severity?
Dependence on lung recruitment
In which condition is the SpO2/FIO2 ratio, also referred to as SF, considered useful?
respiratory failure
What does the PaO2/FIO2 ratio not depend on according to the text?
PAO2
What values are used as part of the diagnostic criteria for ARDS?
PaO2/FIO2
Which ratios show good correlation when SpO2 values are in the range of 80% to 97%?
PaO2/FIO2 and SF
This quiz covers the basics of arterial blood gas analysis, focusing on assessing oxygenation, ventilation, and acid-base status. It includes information on PaO2 values in healthy adults, the impact of age and altitude on PaO2, and the definition of hypoxemia.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
