Podcast
Questions and Answers
What volume of atmospheric air is typically inspired during each breath?
What volume of atmospheric air is typically inspired during each breath?
- 800 ml
- 150 ml
- 500 ml (correct)
- 350 ml
What is the partial pressure of carbon dioxide at the level of the alveoli at the end of expiration?
What is the partial pressure of carbon dioxide at the level of the alveoli at the end of expiration?
- 42 mmHg (correct)
- 97 mmHg
- 103 mmHg
- 38 mmHg
How much stale air remains in the conducting zone at the end of expiration?
How much stale air remains in the conducting zone at the end of expiration?
- 500 ml
- 150 ml (correct)
- 200 ml
- 350 ml
What process is responsible for the movement of gases between the alveoli and capillary blood?
What process is responsible for the movement of gases between the alveoli and capillary blood?
What is the partial pressure of oxygen at the level of the alveoli at the end of inspiration?
What is the partial pressure of oxygen at the level of the alveoli at the end of inspiration?
What type of breathing occurs when expired gas contains air from both the atmosphere and the stale air?
What type of breathing occurs when expired gas contains air from both the atmosphere and the stale air?
What factor optimizes gas diffusion in the alveolar capillary bed?
What factor optimizes gas diffusion in the alveolar capillary bed?
During normal breathing, how much of the total inspired air reaches the alveoli?
During normal breathing, how much of the total inspired air reaches the alveoli?
What is the primary significance of an elevated alveolar to arterial PO2 difference, (A-a) DO2?
What is the primary significance of an elevated alveolar to arterial PO2 difference, (A-a) DO2?
Which factor is NOT a determinant of the diffusion of oxygen and carbon dioxide across the alveolar membrane?
Which factor is NOT a determinant of the diffusion of oxygen and carbon dioxide across the alveolar membrane?
In which lung zone does pulmonary blood flow typically exceed alveolar pressure?
In which lung zone does pulmonary blood flow typically exceed alveolar pressure?
What is the effect of vasoconstriction on vascular compliance and pulmonary vascular resistance?
What is the effect of vasoconstriction on vascular compliance and pulmonary vascular resistance?
What characterizes physiological shunting in pulmonary physiology?
What characterizes physiological shunting in pulmonary physiology?
Which factor is least likely to impact net fluid outflow from capillaries?
Which factor is least likely to impact net fluid outflow from capillaries?
How does hyperventilation primarily affect partial pressure of carbon dioxide (PCO2) in the blood?
How does hyperventilation primarily affect partial pressure of carbon dioxide (PCO2) in the blood?
How does hypoventilation affect arterial levels of oxygen and carbon dioxide?
How does hypoventilation affect arterial levels of oxygen and carbon dioxide?
What is the typical pH level of arterial blood under normal conditions?
What is the typical pH level of arterial blood under normal conditions?
Which condition would likely lead to an increase in hydrostatic pressure and subsequently cause pulmonary edema?
Which condition would likely lead to an increase in hydrostatic pressure and subsequently cause pulmonary edema?
Which component would contribute to the outward net pressure in capillary fluid exchange?
Which component would contribute to the outward net pressure in capillary fluid exchange?
What best describes the average ventilation/perfusion (V/Q) ratio in a healthy lung?
What best describes the average ventilation/perfusion (V/Q) ratio in a healthy lung?
What happens to arterial blood pH if carbon dioxide levels increase without ventilation change?
What happens to arterial blood pH if carbon dioxide levels increase without ventilation change?
What effect does altered gravity have on the distribution of ventilation and perfusion in the lung?
What effect does altered gravity have on the distribution of ventilation and perfusion in the lung?
What role does ventilation play in acid-base balance in the bloodstream?
What role does ventilation play in acid-base balance in the bloodstream?
Which condition is associated with increased interstitial fluid hydrostatic pressure affecting fluid exchange?
Which condition is associated with increased interstitial fluid hydrostatic pressure affecting fluid exchange?
What happens to the PCO2 value when the alveoli are inadequately perfused with blood?
What happens to the PCO2 value when the alveoli are inadequately perfused with blood?
How does gravity affect blood flow distribution in the lungs?
How does gravity affect blood flow distribution in the lungs?
What is the primary effect of variations in ventilation and perfusion at different lung levels?
What is the primary effect of variations in ventilation and perfusion at different lung levels?
As one moves from the apex to the base of the lung, how does the V/Q ratio change?
As one moves from the apex to the base of the lung, how does the V/Q ratio change?
What compensatory mechanisms exist in the lungs to correct V/Q mismatches?
What compensatory mechanisms exist in the lungs to correct V/Q mismatches?
What effect does a lower V/Q ratio at the base of the lung have on gas concentration?
What effect does a lower V/Q ratio at the base of the lung have on gas concentration?
When ventilation is greater at the base of the lungs compared to the apex, what can be inferred?
When ventilation is greater at the base of the lungs compared to the apex, what can be inferred?
How does inadequate blood perfusion in the alveoli affect alveolar gas levels?
How does inadequate blood perfusion in the alveoli affect alveolar gas levels?
What happens to the V/Q ratio when one lung is completely obstructed?
What happens to the V/Q ratio when one lung is completely obstructed?
How does the body respond to decreased ventilation in one lung?
How does the body respond to decreased ventilation in one lung?
What is the expected change in the partial pressure of carbon dioxide in an obstructed lung?
What is the expected change in the partial pressure of carbon dioxide in an obstructed lung?
What occurs when one lung is adequately ventilated but not perfused?
What occurs when one lung is adequately ventilated but not perfused?
What effect does an increased V/Q ratio have on the bronchial smooth muscle in an unperfused lung?
What effect does an increased V/Q ratio have on the bronchial smooth muscle in an unperfused lung?
What is the likely arterial blood gas consequence when an individual inhales 100% oxygen with a V/Q mismatch?
What is the likely arterial blood gas consequence when an individual inhales 100% oxygen with a V/Q mismatch?
How does reduced perfusion affect surfactant production in the unperfused lung?
How does reduced perfusion affect surfactant production in the unperfused lung?
What compensation occurs when the body detects a high V/Q ratio in a lung?
What compensation occurs when the body detects a high V/Q ratio in a lung?
Study Notes
Normal Blood Gas Values
- Typical Values:
- Alveolar PO2: 100 mmHg
- Alveolar PCO2: 40 mmHg
- Arterial PO2: 95 mmHg
- Arterial PCO2: 40 mmHg
- Mixed Venous PO2: 40 mmHg
- Mixed Venous PCO2: 46 mmHg
Alveolar to Arterial PO2 Difference (A-a) DO2
- Calculation: Arterial PO2 subtracted from Alveolar PO2
- Normal Value: Less than 10 mmHg
- Elevated (A-a) DO2 Significance: Indicates a problem with gas exchange in the lungs:
- Diffusion impairment
- Shunt
- Ventilation/perfusion mismatch
- Hypoventilation
Factors Affecting Gas Diffusion Between Alveoli and Capillaries
- Solubility: Higher solubility means faster diffusion.
- Gas Molecular Weight: Lighter gases diffuse faster.
- Cross-Sectional Area: Larger surface area means increased diffusion.
- Membrane Thickness: Thinner membrane allows faster diffusion.
Diseases Affecting Gas Diffusion
- Emphysema: Destroys alveoli, reducing surface area for gas exchange.
- Fibrotic Lung Disease: Thickens alveolar walls, slowing diffusion.
- Pulmonary Edema: Fluid in the alveoli interferes with gas exchange.
Pulmonary Edema Development
- Increased Hydrostatic Pressure: Left-sided heart failure increases pressure in pulmonary capillaries, forcing fluid into alveoli.
- Increased Permeability: Inflammation or injury allows fluid to leak from capillaries into alveoli.
- Impaired Lymphatic Drainage: Impaired lymphatic system prevents proper fluid removal from interstitial space.
Shunts
- Right-to-Left Shunts: Blood bypasses the lungs without oxygenation.
- Anatomic Shunts: Blood flow through congenital heart defects avoids pulmonary circulation.
- Physiological Shunts: Blood flow through poorly ventilated lung regions.
- Physiological Dead Space: Alveoli ventilated but not perfused.
Ventilation/Perfusion (V/Q) Ratio
- V/Q Ratio: Ratio of ventilation to perfusion in a specific alveoli-capillary unit.
- Normal Average V/Q: 0.8 (Slightly higher at the apex of the lungs)
- Impact of Gravity on V/Q:
- Base of Lungs: Higher blood flow, slightly lower ventilation, lower V/Q.
- Apex of Lungs: Lower blood flow, slightly higher ventilation, higher V/Q.
Lung Zones (Upright Person)
- Zone 1: Apex of the lung. Alveolar pressure is higher than pulmonary arterial pressure, limiting blood flow.
- Zone 2: Middle of the lung. Pulmonary arterial pressure is higher than alveolar pressure, but lower than venous pressure. Blood flow increases.
- Zone 3: Base of the lung. Pulmonary arterial pressure is higher than both alveolar and venous pressures. Blood flow is highest.
Hypoventilation and Hyperventilation
- Hypoventilation: Lowers arterial PO2 and elevates arterial PCO2.
- Hyperventilation: Elevates arterial PO2 and lowers arterial PCO2.
Ventilation/Perfusion Mismatch
- Non-Uniform V/Q: Variations in ventilation and perfusion can occur even in healthy lung tissue.
- V/Q Mismatch Effects: Can cause hypoxemia (low blood PO2) and hypercapnia (high blood PCO2).
Compensatory Mechanisms for V/Q Mismatch
- Obstructed Lung: Unventilated lung reduces V/Q to zero, leading to shunt. Pulmonary vasoconstriction diverts blood to ventilated lung.
- Non-Perfused Lung: V/Q approaches infinity. Ventilation decreases in the non-perfused lung to compensate, diverting airflow to the perfused lung.
Diagnosing V/Q Mismatch
- 100% Oxygen Inhalation: Helps differentiate between a shunt and a ventilation/perfusion ratio mismatch.
- Shunt: Increased arterial PO2, but not to normal levels.
- V/Q Mismatch: Arterial PO2 will approach normal with 100% oxygen.
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Description
Test your knowledge on normal blood gas values and the factors influencing gas diffusion. This quiz covers essential parameters like alveolar and arterial PO2, PCO2, and the significance of A-a DO2 differences in diagnosing respiratory issues. Additionally, learn about diseases that can affect gas diffusion.
