Podcast
Questions and Answers
What is the typical pressure in the pulmonary artery?
What is the typical pressure in the pulmonary artery?
How does the structure of pulmonary arteries differ from systemic arteries?
How does the structure of pulmonary arteries differ from systemic arteries?
What physiological response occurs in the pulmonary circulation when oxygen levels are low?
What physiological response occurs in the pulmonary circulation when oxygen levels are low?
During fetal development, why is there vasoconstriction in pulmonary arteries?
During fetal development, why is there vasoconstriction in pulmonary arteries?
Signup and view all the answers
What happens to the pulmonary arteries immediately after birth?
What happens to the pulmonary arteries immediately after birth?
Signup and view all the answers
What does the graph of oxygen content versus blood flow in the lungs illustrate?
What does the graph of oxygen content versus blood flow in the lungs illustrate?
Signup and view all the answers
What is the primary role of the right ventricle in relation to the pulmonary circulation?
What is the primary role of the right ventricle in relation to the pulmonary circulation?
Signup and view all the answers
What adaptive function does hypoxic vasoconstriction serve in the lungs?
What adaptive function does hypoxic vasoconstriction serve in the lungs?
Signup and view all the answers
What is the effect of a mutation in the BMPR2 gene on smooth muscle proliferation?
What is the effect of a mutation in the BMPR2 gene on smooth muscle proliferation?
Signup and view all the answers
Which drug is known as a potent vasodilator used in the treatment of PAH?
Which drug is known as a potent vasodilator used in the treatment of PAH?
Signup and view all the answers
How does bosentan help in the management of pulmonary arterial hypertension (PAH)?
How does bosentan help in the management of pulmonary arterial hypertension (PAH)?
Signup and view all the answers
What is a classic finding in a lung biopsy for a patient with idiopathic PAH?
What is a classic finding in a lung biopsy for a patient with idiopathic PAH?
Signup and view all the answers
What percentage of familial cases of idiopathic pulmonary arterial hypertension is associated with mutations in the BMPR2 gene?
What percentage of familial cases of idiopathic pulmonary arterial hypertension is associated with mutations in the BMPR2 gene?
Signup and view all the answers
What is a characteristic of the administration of epoprostenol?
What is a characteristic of the administration of epoprostenol?
Signup and view all the answers
What condition is sildenafil commonly used to treat besides pulmonary arterial hypertension?
What condition is sildenafil commonly used to treat besides pulmonary arterial hypertension?
Signup and view all the answers
What is the primary goal of treating pulmonary arterial hypertension?
What is the primary goal of treating pulmonary arterial hypertension?
Signup and view all the answers
What is the primary characteristic of oxygen transfer in healthy lungs?
What is the primary characteristic of oxygen transfer in healthy lungs?
Signup and view all the answers
What physiological change occurs in patients with pulmonary fibrosis regarding oxygen transfer?
What physiological change occurs in patients with pulmonary fibrosis regarding oxygen transfer?
Signup and view all the answers
What happens to the partial pressure of oxygen during ascents to high altitude?
What happens to the partial pressure of oxygen during ascents to high altitude?
Signup and view all the answers
How is the diffusing capacity of the lungs assessed clinically?
How is the diffusing capacity of the lungs assessed clinically?
Signup and view all the answers
In which condition would the DLCO value be expected to significantly drop below normal?
In which condition would the DLCO value be expected to significantly drop below normal?
Signup and view all the answers
What is the effect of increased lung volumes on alveolar vessels?
What is the effect of increased lung volumes on alveolar vessels?
Signup and view all the answers
What is true about the CO2 levels in venous blood entering the pulmonary capillaries?
What is true about the CO2 levels in venous blood entering the pulmonary capillaries?
Signup and view all the answers
What happens to extra alveolar vessels as lung volumes increase?
What happens to extra alveolar vessels as lung volumes increase?
Signup and view all the answers
What characterizes diffusion limitation in gas exchange?
What characterizes diffusion limitation in gas exchange?
Signup and view all the answers
What is a significant factor affecting the volume of gas taken out by the blood?
What is a significant factor affecting the volume of gas taken out by the blood?
Signup and view all the answers
Which statement about carbon monoxide uptake in lungs is correct?
Which statement about carbon monoxide uptake in lungs is correct?
Signup and view all the answers
In patients with severe lung disease, what is the DLCO typically observed?
In patients with severe lung disease, what is the DLCO typically observed?
Signup and view all the answers
What physiological phenomenon leads to hypoxemia during high altitude ascents?
What physiological phenomenon leads to hypoxemia during high altitude ascents?
Signup and view all the answers
What occurs to blood flow in systemic circulation as PaO2 increases?
What occurs to blood flow in systemic circulation as PaO2 increases?
Signup and view all the answers
What is the approximate normal partial pressure of oxygen in arterial blood after gas exchange in the pulmonary capillaries?
What is the approximate normal partial pressure of oxygen in arterial blood after gas exchange in the pulmonary capillaries?
Signup and view all the answers
What gas is considered perfusion limited during gas exchange in the pulmonary capillaries?
What gas is considered perfusion limited during gas exchange in the pulmonary capillaries?
Signup and view all the answers
Which gas exhibits diffusion limitation in pulmonary gas exchange?
Which gas exhibits diffusion limitation in pulmonary gas exchange?
Signup and view all the answers
What is the typical carbon dioxide partial pressure in venous blood?
What is the typical carbon dioxide partial pressure in venous blood?
Signup and view all the answers
What happens to gas concentrations as blood moves through the pulmonary capillaries?
What happens to gas concentrations as blood moves through the pulmonary capillaries?
Signup and view all the answers
In what scenario is gas exchange considered perfusion limited?
In what scenario is gas exchange considered perfusion limited?
Signup and view all the answers
What phenomenon describes the difference in partial pressures of gases between the lung alveoli and arterial blood?
What phenomenon describes the difference in partial pressures of gases between the lung alveoli and arterial blood?
Signup and view all the answers
What is the average alveolar concentration of oxygen when breathing ambient air at sea level?
What is the average alveolar concentration of oxygen when breathing ambient air at sea level?
Signup and view all the answers
Which component of blood is responsible for delivering carbon dioxide to the lungs?
Which component of blood is responsible for delivering carbon dioxide to the lungs?
Signup and view all the answers
What happens to the concentration of nitrous oxide as blood flows through the pulmonary capillary?
What happens to the concentration of nitrous oxide as blood flows through the pulmonary capillary?
Signup and view all the answers
Which parameter primarily limits gas uptake when a gas is diffusion limited?
Which parameter primarily limits gas uptake when a gas is diffusion limited?
Signup and view all the answers
What is the primary limiting factor for gas transfer in cases where blood flow to the lungs is inadequate?
What is the primary limiting factor for gas transfer in cases where blood flow to the lungs is inadequate?
Signup and view all the answers
What is the primary role of carbon dioxide in blood as it returns to the lungs?
What is the primary role of carbon dioxide in blood as it returns to the lungs?
Signup and view all the answers
At what point during the respiratory cycle is pulmonary vascular resistance minimized?
At what point during the respiratory cycle is pulmonary vascular resistance minimized?
Signup and view all the answers
What is the normal range for mean pulmonary artery pressure?
What is the normal range for mean pulmonary artery pressure?
Signup and view all the answers
What physical exam finding is most classic for pulmonary hypertension?
What physical exam finding is most classic for pulmonary hypertension?
Signup and view all the answers
What is a common symptom that patients with pulmonary hypertension experience?
What is a common symptom that patients with pulmonary hypertension experience?
Signup and view all the answers
What condition can occur as a result of untreated pulmonary hypertension?
What condition can occur as a result of untreated pulmonary hypertension?
Signup and view all the answers
What invasive procedure is considered the gold standard for diagnosing pulmonary hypertension?
What invasive procedure is considered the gold standard for diagnosing pulmonary hypertension?
Signup and view all the answers
How can pulmonary artery pressure be estimated non-invasively?
How can pulmonary artery pressure be estimated non-invasively?
Signup and view all the answers
What is a consequence of chronic high pressure in the pulmonary arteries?
What is a consequence of chronic high pressure in the pulmonary arteries?
Signup and view all the answers
What contributes to the development of pulmonary hypertension according to the flow equation?
What contributes to the development of pulmonary hypertension according to the flow equation?
Signup and view all the answers
What condition arises from elevated left atrial pressure leading to pulmonary hypertension?
What condition arises from elevated left atrial pressure leading to pulmonary hypertension?
Signup and view all the answers
What might occur in the right ventricle as a result of pulmonary hypertension?
What might occur in the right ventricle as a result of pulmonary hypertension?
Signup and view all the answers
What is a physical exam sign associated with right heart failure due to pulmonary hypertension?
What is a physical exam sign associated with right heart failure due to pulmonary hypertension?
Signup and view all the answers
What can prolonged untreated pulmonary hypertension ultimately lead to?
What can prolonged untreated pulmonary hypertension ultimately lead to?
Signup and view all the answers
What is one of the main reasons pulmonary hypertension is considered dangerous?
What is one of the main reasons pulmonary hypertension is considered dangerous?
Signup and view all the answers
What is the primary mechanism leading to pulmonary venous hypertension?
What is the primary mechanism leading to pulmonary venous hypertension?
Signup and view all the answers
Which of the following conditions is NOT associated with pulmonary arterial hypertension?
Which of the following conditions is NOT associated with pulmonary arterial hypertension?
Signup and view all the answers
What is a common physiological response to chronic hypoxemia in the lungs?
What is a common physiological response to chronic hypoxemia in the lungs?
Signup and view all the answers
What is the main distinction between pulmonary venous hypertension and pulmonary arterial hypertension?
What is the main distinction between pulmonary venous hypertension and pulmonary arterial hypertension?
Signup and view all the answers
Which type of lesion is characteristic of idiopathic pulmonary arterial hypertension?
Which type of lesion is characteristic of idiopathic pulmonary arterial hypertension?
Signup and view all the answers
How does pulmonary embolism contribute to increased pulmonary vascular resistance?
How does pulmonary embolism contribute to increased pulmonary vascular resistance?
Signup and view all the answers
Idiopathic pulmonary arterial hypertension primarily affects which demographic?
Idiopathic pulmonary arterial hypertension primarily affects which demographic?
Signup and view all the answers
Chronic hypoxemia can arise from which of the following conditions?
Chronic hypoxemia can arise from which of the following conditions?
Signup and view all the answers
Which of the following conditions is least likely to cause an increase in pulmonary vascular resistance?
Which of the following conditions is least likely to cause an increase in pulmonary vascular resistance?
Signup and view all the answers
In the context of pulmonary hypertension, what does the term 'Eisenmenger syndrome' refer to?
In the context of pulmonary hypertension, what does the term 'Eisenmenger syndrome' refer to?
Signup and view all the answers
What is the approximate normal pressure in the pulmonary veins and the left atrium?
What is the approximate normal pressure in the pulmonary veins and the left atrium?
Signup and view all the answers
Which of the following is a vasoconstrictor that may contribute to idiopathic pulmonary arterial hypertension?
Which of the following is a vasoconstrictor that may contribute to idiopathic pulmonary arterial hypertension?
Signup and view all the answers
What distinguishes pulmonary arterial hypertension from other forms of pulmonary hypertension?
What distinguishes pulmonary arterial hypertension from other forms of pulmonary hypertension?
Signup and view all the answers
What is a common cause of pulmonary arterial hypertension related to high pulmonary vascular resistance?
What is a common cause of pulmonary arterial hypertension related to high pulmonary vascular resistance?
Signup and view all the answers
The pulmonary circulation is a low pressure system, much lower than what you find in the ______.
The pulmonary circulation is a low pressure system, much lower than what you find in the ______.
Signup and view all the answers
When there's a low oxygen level in the lungs, this leads to ______ of blood vessels.
When there's a low oxygen level in the lungs, this leads to ______ of blood vessels.
Signup and view all the answers
In the systemic circulation, low oxygen levels cause ______ of blood vessels.
In the systemic circulation, low oxygen levels cause ______ of blood vessels.
Signup and view all the answers
The right ventricle needs to generate pressures like ______ in the pulmonary circulation.
The right ventricle needs to generate pressures like ______ in the pulmonary circulation.
Signup and view all the answers
During fetal development, the pulmonary arteries constrict due to relatively low ______ content.
During fetal development, the pulmonary arteries constrict due to relatively low ______ content.
Signup and view all the answers
After the baby is born, pulmonary arteries begin to receive more oxygen and then ______.
After the baby is born, pulmonary arteries begin to receive more oxygen and then ______.
Signup and view all the answers
The walls of the pulmonary arteries are very thin relative to systemic ______.
The walls of the pulmonary arteries are very thin relative to systemic ______.
Signup and view all the answers
Hypoxic vasoconstriction allows more blood flow to well ______ areas.
Hypoxic vasoconstriction allows more blood flow to well ______ areas.
Signup and view all the answers
The endothelial cells create multiple ______ within a blood vessel.
The endothelial cells create multiple ______ within a blood vessel.
Signup and view all the answers
Mutations in the ______ gene are associated with idiopathic pulmonary arterial hypertension.
Mutations in the ______ gene are associated with idiopathic pulmonary arterial hypertension.
Signup and view all the answers
Epoprostenol, also known as ______, is a vasodilator used to treat PAH.
Epoprostenol, also known as ______, is a vasodilator used to treat PAH.
Signup and view all the answers
Bosentan is an antagonist of ______ receptors that leads to vasodilation.
Bosentan is an antagonist of ______ receptors that leads to vasodilation.
Signup and view all the answers
Sildenafil is commonly used for both erectile dysfunction and ______ hypertension.
Sildenafil is commonly used for both erectile dysfunction and ______ hypertension.
Signup and view all the answers
Pulmonary venous hypertension is always due to diseases involving the left ______.
Pulmonary venous hypertension is always due to diseases involving the left ______.
Signup and view all the answers
Mutations in the BMPR2 gene are seen in up to a ______ of idiopathic cases of PAH.
Mutations in the BMPR2 gene are seen in up to a ______ of idiopathic cases of PAH.
Signup and view all the answers
When pressure in the pulmonary arteries is high, it is called ______ arterial hypertension.
When pressure in the pulmonary arteries is high, it is called ______ arterial hypertension.
Signup and view all the answers
Treatment for PAH aims to lower ______ to protect the right ventricle.
Treatment for PAH aims to lower ______ to protect the right ventricle.
Signup and view all the answers
The growth of smooth muscle can start to narrow the ______ in blood vessels.
The growth of smooth muscle can start to narrow the ______ in blood vessels.
Signup and view all the answers
A normal pressure in the pulmonary veins and left atrium is about ______.
A normal pressure in the pulmonary veins and left atrium is about ______.
Signup and view all the answers
Mitral stenosis can lead to increased left atrial pressure, contributing to ______ hypertension.
Mitral stenosis can lead to increased left atrial pressure, contributing to ______ hypertension.
Signup and view all the answers
As the PaO2 goes up, there's ______ blood flow in the systemic circulation.
As the PaO2 goes up, there's ______ blood flow in the systemic circulation.
Signup and view all the answers
Chronic hypoxemia can lead to vasoconstriction in the lungs, causing high pulmonary ______ resistance.
Chronic hypoxemia can lead to vasoconstriction in the lungs, causing high pulmonary ______ resistance.
Signup and view all the answers
The concentration of oxygen in venous blood is about ______ millimeters of mercury.
The concentration of oxygen in venous blood is about ______ millimeters of mercury.
Signup and view all the answers
Sleep apnea can cause episodes of hypoxemia, contributing to ______ hypertension.
Sleep apnea can cause episodes of hypoxemia, contributing to ______ hypertension.
Signup and view all the answers
The normal partial pressure of oxygen in arterial blood after gas exchange is about ______ millimeters of mercury.
The normal partial pressure of oxygen in arterial blood after gas exchange is about ______ millimeters of mercury.
Signup and view all the answers
One of the conditions associated with high pulmonary vascular resistance is ______ tissue disease.
One of the conditions associated with high pulmonary vascular resistance is ______ tissue disease.
Signup and view all the answers
Gases that behave as ______ limited can never reach equilibrium with the alveoli.
Gases that behave as ______ limited can never reach equilibrium with the alveoli.
Signup and view all the answers
Once air gets to the alveolus, the partial pressure of carbon dioxide rises to about ______ millimeters of mercury.
Once air gets to the alveolus, the partial pressure of carbon dioxide rises to about ______ millimeters of mercury.
Signup and view all the answers
Eisenmenger Syndrome can occur when a shunt reverses due to high ______ resistance.
Eisenmenger Syndrome can occur when a shunt reverses due to high ______ resistance.
Signup and view all the answers
Carbon monoxide is considered a classic example of a ______ limited gas.
Carbon monoxide is considered a classic example of a ______ limited gas.
Signup and view all the answers
Idiopathic pulmonary arterial hypertension is a rare condition affecting mostly ______ women.
Idiopathic pulmonary arterial hypertension is a rare condition affecting mostly ______ women.
Signup and view all the answers
When the partial pressure of oxygen in venous blood is low, it can stimulate ______ of blood vessels.
When the partial pressure of oxygen in venous blood is low, it can stimulate ______ of blood vessels.
Signup and view all the answers
Plexiform lesions are a unique path finding in patients with idiopathic ______ hypertension.
Plexiform lesions are a unique path finding in patients with idiopathic ______ hypertension.
Signup and view all the answers
Patients with chronic pulmonary emboli may develop ______ vascular resistance.
Patients with chronic pulmonary emboli may develop ______ vascular resistance.
Signup and view all the answers
In the lungs, nitrous oxide behaves as a ______ limited gas.
In the lungs, nitrous oxide behaves as a ______ limited gas.
Signup and view all the answers
Hydroxyurea is associated with pulmonary arterial hypertension in patients using ______ like amphetamines.
Hydroxyurea is associated with pulmonary arterial hypertension in patients using ______ like amphetamines.
Signup and view all the answers
The difference in partial pressures of gases between alveoli and arterial blood is known as the ______ gradient.
The difference in partial pressures of gases between alveoli and arterial blood is known as the ______ gradient.
Signup and view all the answers
Blood flowing from the venous system has a ______ concentration of oxygen.
Blood flowing from the venous system has a ______ concentration of oxygen.
Signup and view all the answers
High pressure in the left atrium can lead to ______ hypertension.
High pressure in the left atrium can lead to ______ hypertension.
Signup and view all the answers
Chronic ______ is a condition that can lead to pulmonary hypertension.
Chronic ______ is a condition that can lead to pulmonary hypertension.
Signup and view all the answers
The primary factor affecting gas transfer is the rate of ______ to the lungs.
The primary factor affecting gas transfer is the rate of ______ to the lungs.
Signup and view all the answers
The ______ pressure of oxygen in inspired air at sea level is about 150 millimeters.
The ______ pressure of oxygen in inspired air at sea level is about 150 millimeters.
Signup and view all the answers
As blood moves through the pulmonary capillaries, it exchanges gases with the ______.
As blood moves through the pulmonary capillaries, it exchanges gases with the ______.
Signup and view all the answers
When discussing gas transport in case of diffusion limitation, the rate of ______ is the limiting factor.
When discussing gas transport in case of diffusion limitation, the rate of ______ is the limiting factor.
Signup and view all the answers
In healthy lungs, oxygen is ______ limited.
In healthy lungs, oxygen is ______ limited.
Signup and view all the answers
Patients with pulmonary fibrosis can develop ______.
Patients with pulmonary fibrosis can develop ______.
Signup and view all the answers
At high altitudes, the partial pressure of oxygen in the alveoli can get as low as ______.
At high altitudes, the partial pressure of oxygen in the alveoli can get as low as ______.
Signup and view all the answers
The diffusing capacity of carbon monoxide, known as DLCO, measures the lungs' ability to ______ gas.
The diffusing capacity of carbon monoxide, known as DLCO, measures the lungs' ability to ______ gas.
Signup and view all the answers
In emphysema, patients lose surface area due to the destruction of their ______.
In emphysema, patients lose surface area due to the destruction of their ______.
Signup and view all the answers
As blood moves along the pulmonary capillary, carbon dioxide levels ______.
As blood moves along the pulmonary capillary, carbon dioxide levels ______.
Signup and view all the answers
Higher lung volumes tend to crush the ______ vessels, causing high resistance.
Higher lung volumes tend to crush the ______ vessels, causing high resistance.
Signup and view all the answers
In conditions like pulmonary edema, the walls of the alveoli become ______.
In conditions like pulmonary edema, the walls of the alveoli become ______.
Signup and view all the answers
Healthy lungs have a normal DLCO value of about ______ to 140% of the predicted value.
Healthy lungs have a normal DLCO value of about ______ to 140% of the predicted value.
Signup and view all the answers
In patients with severe lung disease, the DLCO can drop to less than ______ predicted.
In patients with severe lung disease, the DLCO can drop to less than ______ predicted.
Signup and view all the answers
When a person inhales carbon monoxide, the amount taken up reflects the lungs' ______ capacity.
When a person inhales carbon monoxide, the amount taken up reflects the lungs' ______ capacity.
Signup and view all the answers
The difference in gas pressures across the alveoli and blood is crucial for ______.
The difference in gas pressures across the alveoli and blood is crucial for ______.
Signup and view all the answers
Patients with pulmonary hypertension often experience ______ as a common symptom.
Patients with pulmonary hypertension often experience ______ as a common symptom.
Signup and view all the answers
In the respiratory cycle, pulmonary vascular resistance is ______ minimized.
In the respiratory cycle, pulmonary vascular resistance is ______ minimized.
Signup and view all the answers
Pulmonary vascular resistance is at its minimum at the ______.
Pulmonary vascular resistance is at its minimum at the ______.
Signup and view all the answers
The classic physical exam finding of a patient with pulmonary hypertension is a loud ______.
The classic physical exam finding of a patient with pulmonary hypertension is a loud ______.
Signup and view all the answers
The main symptom of pulmonary hypertension is ______.
The main symptom of pulmonary hypertension is ______.
Signup and view all the answers
If left untreated, pulmonary hypertension can lead to ______ of the right ventricle.
If left untreated, pulmonary hypertension can lead to ______ of the right ventricle.
Signup and view all the answers
The consequence of untreated pulmonary hypertension may lead to cor ______.
The consequence of untreated pulmonary hypertension may lead to cor ______.
Signup and view all the answers
Right heart catheterization is considered the gold standard for diagnosing ______.
Right heart catheterization is considered the gold standard for diagnosing ______.
Signup and view all the answers
Patients with pulmonary hypertension might show signs of ______ venous distension.
Patients with pulmonary hypertension might show signs of ______ venous distension.
Signup and view all the answers
An increase in left atrial pressure leading to pulmonary hypertension is known as ______ venous hypertension.
An increase in left atrial pressure leading to pulmonary hypertension is known as ______ venous hypertension.
Signup and view all the answers
Echocardiography can be used to estimate pulmonary artery ______.
Echocardiography can be used to estimate pulmonary artery ______.
Signup and view all the answers
Pulmonary hypertension often leads to ______ of the walls of the pulmonary arteries.
Pulmonary hypertension often leads to ______ of the walls of the pulmonary arteries.
Signup and view all the answers
The equation for pulmonary artery pressure includes cardiac output, vascular resistance, and pressure in the left ______.
The equation for pulmonary artery pressure includes cardiac output, vascular resistance, and pressure in the left ______.
Signup and view all the answers
The risk of dying from heart disease related to untreated pulmonary hypertension includes the possibility of ______.
The risk of dying from heart disease related to untreated pulmonary hypertension includes the possibility of ______.
Signup and view all the answers
Medial layer thickening in pulmonary arteries due to elevated pressures results in a narrowed ______.
Medial layer thickening in pulmonary arteries due to elevated pressures results in a narrowed ______.
Signup and view all the answers
Patients with pulmonary hypertension may develop ______ extremity edema.
Patients with pulmonary hypertension may develop ______ extremity edema.
Signup and view all the answers
Study Notes
Pulmonary Circulation
- Pulmonary circulation is a low-pressure system (24/12 mmHg) compared to systemic circulation (120/80 mmHg).
- Pulmonary arteries have thinner walls, less smooth muscle, and are more distensible (compliant) than systemic arteries.
- The right ventricle is thinner than the left ventricle because it only needs to generate lower pressures.
Hypoxic Vasoconstriction
- Systemic circulation: Low PaO2 causes vasodilation to increase blood flow to tissues.
- Pulmonary circulation: Low PaO2 causes vasoconstriction, shunting blood flow from poorly ventilated areas to well-ventilated areas.
- This is crucial during fetal development to route blood away from non-functional lungs.
Gas Exchange
- Alveolar gas exchange: Oxygen enters the blood, and carbon dioxide leaves the blood, maintaining equilibrium.
- Inspired air (sea level): ~150 mmHg partial pressure of oxygen (PaO2) and essentially zero carbon dioxide.
- Alveolar air: ~100 mmHg PaO2 and ~40 mmHg partial pressure of carbon dioxide (PaCO2)
- Venous blood entering lungs: ~40 mmHg PaO2, ~46 mmHg PaCO2.
- Arterial blood leaving lungs: ~90 mmHg PaO2, ~40 mmHg PaCO2.
Gas Transfer Limits: Perfusion vs. Diffusion
- Perfusion-limited gas exchange: Blood flow (perfusion) limits the gas transfer rate.
- Example: Nitrous Oxide (quickly reaches equilibrium with alveolar concentration)
- Diffusion-limited gas exchange: Diffusion of gas across the alveolar-capillary membrane limits the gas transfer rate.
- Example: Carbon Monoxide (does not reach equilibrium with alveolar concentration)
- Oxygen uptake: Normally perfusion-limited in healthy lungs, allowing equilibrium.
- Pathologic example: Pulmonary fibrosis shifts oxygen exchange from perfusion-limited to diffusion-limited (lowering blood oxygen).
DLCO Testing
- DLCO (diffusing capacity of carbon monoxide): Measures the lungs' ability to transfer gas.
- Low DLCO suggests diffusion impairment, like in emphysema, fibrosis, and pulmonary edema.
- Healthy lungs show values between 75-140% of predicted.
Pulmonary Vascular Resistance
- Pulmonary vascular resistance (PVR) varies with lung volume.
- Alveolar vessels (capillaries): Resistance higher at higher lung volumes (squeezing effect).
- Extra-alveolar vessels (arteries and veins): Resistance lower at higher lung volumes.
- Minimum PVR occurs at functional residual capacity (FRC).
Pulmonary Hypertension
- Normal pulmonary artery mean pressure: ~10-14 mmHg.
- Pulmonary hypertension: Mean pulmonary artery pressure >25 mmHg.
- Key physical exam finding: Loud P2 (pulmonary component of the second heart sound), best heard at left upper sternal border.
- Main symptom: Dyspnea (especially with exertion).
- Untreated: Leads to right ventricular hypertrophy, dilation, and failure (cor pulmonale), potentially fatal.
Causes of Pulmonary Hypertension
- Pulmonary venous hypertension: Increased left atrial pressure due to left heart disease (e.g., heart failure, valve disease).
- Pulmonary arterial hypertension: Increased pulmonary vascular resistance (PVR).
- Causes: Chronic hypoxemia (COPD, sleep apnea, high altitude), chronic thromboembolism, connective tissue diseases (scleroderma), late-stage HIV infection, congenital heart disease (Eisenmenger syndrome), certain drugs (e.g., amphetamines, cocaine).
- Idiopathic PAH: Unknown cause, often affects young women, involves endothelial proliferation.
Diagnosis and Treatment
- Diagnosis: Right heart catheterization (gold standard), echocardiography.
- Treatment: Aim to reduce PVR and pulmonary artery pressure to prevent right heart failure.
- Epoprostenol (Prostacyclin): potent intravenous vasodilator.
- Oral drugs: Bosentan (endothelin-1 receptor antagonist), Sildenafil (PDE-5 inhibitor).
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
This quiz delves into the fundamentals of pulmonary circulation, highlighting its characteristics compared to systemic circulation. It also covers the unique aspects of hypoxic vasoconstriction and the process of gas exchange in the alveoli, essential for maintaining oxygen levels in the blood.
