39 Questions
Which equation is used to determine the physiologic dead space?
Bohr equation
What does an increased arterial-alveolar CO2 difference suggest?
Increased ventilation-perfusion mismatch
Intrapulmonary shunting refers to:
Blood perfusion without ventilation in alveoli
Which of the following contributes to anatomic shunts?
Systemic venous blood entering the left ventricle directly
What does the shunt equation divide all alveolar-capillary units into?
Well-matched and poorly-matched V/Q units
How does a shunt-like state differ from anatomic shunts?
A shunt-like state involves impaired ventilation with excess perfusion
What contributes to normal physiologic shunts?
Venous blood that bypasses pulmonary capillaries
What does an absolute intrapulmonary shunt refer to?
'True shunts' where venous blood perfuses unventilated alveoli
What is the primary purpose of the shunt equation in the context of ventilation-perfusion ratios?
To quantify the extent of venous admixture
Which of the following statements best describes the concept of physiologic dead space?
It represents alveoli that are well-ventilated but not perfused
How is the Bohr equation relevant to the understanding of ventilation-perfusion ratios?
It describes the relationship between CO2 elimination and alveolar ventilation
Why is venous admixture a concern when analyzing ventilation-perfusion ratios?
It results in a decrease in arterial oxygen content
Which scenario best describes a ventilation-perfusion mismatch?
Alveoli with high ventilation and low perfusion
When considering regional differences in ventilation-perfusion ratios, what effect does gravity have on V/Q matching?
Gravity causes higher V/Q ratios at the lung bases
Which statement accurately reflects the consequence of a significant shunt in the lungs?
'Left-to-right' intrapulmonary shunting of blood
In the context of venous admixture, what accurately describes 'Bohr effect'?
'Bohr effect' causes a right shift in the oxyhemoglobin dissociation curve
Which factor plays a key role in maintaining gas exchange by bringing O2 into the lungs and removing CO2?
Alveolar ventilation
What is a common influence on mixed venous blood that brings CO2 into the lungs and takes up alveolar O2?
Histamine
Which neural regulation factor may lead to an increase in pulmonary vascular resistance and a decrease in distensibility?
Sympathetic innervation
What effect do pulmonary vasoconstrictors have on pulmonary vascular resistance (PVR)?
Increase PVR
Intrinsic autoregulation leading to vasoconstriction is mainly attributed to which phenomenon?
HPV
Which of the following substances contributes to decreased PVR and increased blood volume?
$\text{PGE1}$ and $\text{PGI2}$
'Bohr equation' is related to which concept in gas exchange physiology?
Venous admixture
'Physiologic dead space' is primarily associated with which aspect of gas exchange?
$\text{Ventilation-perfusion mismatch}$
What condition results in a V/Q ratio approaching infinity?
Pulmonary embolism
In which scenario would you observe alveolar dead space?
Intrapulmonary shunts causing underventilation
Which condition allows fresh gas to reach alveoli lacking perfusion?
Physiologic dead space
What happens when the ventilation-perfusion ratio (VA/Q) is higher than normal?
PAO2 increases and PACO2 decreases
What is the consequence of a ventilation-perfusion ratio (VA/Q) less than normal?
PAO2 decreases and PACO2 increases
What is a major cause of hypoxemia related to ventilation-perfusion mismatch?
Intrapulmonary shunts causing underventilation
In the context of ventilation-perfusion ratios, what do alveolar dead space and intrapulmonary shunt represent?
Low VA/Q
How do small shunts manifest when measuring PaO2 during FiO2 1.0 (100%)?
Unchanged PaO2 values
What are the consequences of ventilation-perfusion ratios close to 1.0?
Alveolar PO2s around 100 mmHg and PCO2s close to 40 mmHg
Which scenario increases the required minute ventilation for gas exchange according to the text?
Extrapulmonary shunts like CHD/VSD
What occurs when the VA/Q ratio is higher than normal in terms of oxygen and carbon dioxide levels?
Increase in O2 delivery relative to its removal
When does the Bohr equation not respond to an increase in FiO2?
In case of increased A-a O2 difference
Why does intrapulmonary shunt cause hypoxemia?
Alveoli are underventilated
How does a ventilation-perfusion ratio less than normal affect alveolar gases?
Alveolar gases resembling mixed venous blood
In terms of ventilation-perfusion ratios, what happens when the PO2 increases and PCO2 decreases?
A higher than normal VA/Q ratio
Explore the effects of high and low ventilation (V) and perfusion (Q) on alveolar ventilation and capillary perfusion. Learn how alterations in the VA/Qc ratio can impact PAO2 and PACO2 levels. Understand how VA/Qc affects the entire lung.
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