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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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