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Questions and Answers
Which of the following factors would lead to a decrease in the affinity of hemoglobin for oxygen, resulting in increased oxygen unloading in the tissues?
Which of the following factors would lead to a decrease in the affinity of hemoglobin for oxygen, resulting in increased oxygen unloading in the tissues?
- Increased tissue pH
- Decreased tissue temperature
- Decreased P_CO2_ in the tissues
- Increased 2,3-DPG production (correct)
A patient with pulmonary fibrosis experiences diffusion limitation. Which of the following gases would be most affected by this condition during gas exchange?
A patient with pulmonary fibrosis experiences diffusion limitation. Which of the following gases would be most affected by this condition during gas exchange?
- Oxygen (O_2_) (correct)
- Nitrous oxide (N_2O_)
- Carbon dioxide (CO_2_)
- All gases are equally affected
During strenuous exercise, several factors cause the oxygen-hemoglobin dissociation curve to shift to the right. Which of the following is NOT a typical cause of this rightward shift during intense physical activity?
During strenuous exercise, several factors cause the oxygen-hemoglobin dissociation curve to shift to the right. Which of the following is NOT a typical cause of this rightward shift during intense physical activity?
- Decreased tissue pH
- Increased body temperature
- Increased tissue P_CO2_
- Decreased 2,3-DPG (correct)
A patient is diagnosed with a condition that decreases their alveolar ventilation. According to the alveolar ventilation equation, how will this change most likely affect their arterial P_CO2_ (P_aCO2_)?
A patient is diagnosed with a condition that decreases their alveolar ventilation. According to the alveolar ventilation equation, how will this change most likely affect their arterial P_CO2_ (P_aCO2_)?
A person standing upright has uneven distribution of pulmonary blood flow. Where is the blood flow the lowest?
A person standing upright has uneven distribution of pulmonary blood flow. Where is the blood flow the lowest?
A researcher is studying the effect of bronchodilators on airway resistance. Stimulation of which type of receptors would lead to dilation of the airways?
A researcher is studying the effect of bronchodilators on airway resistance. Stimulation of which type of receptors would lead to dilation of the airways?
In a healthy individual at Functional Residual Capacity (FRC), what is the relationship between the forces of the chest wall and the lungs?
In a healthy individual at Functional Residual Capacity (FRC), what is the relationship between the forces of the chest wall and the lungs?
Which of the following best describes the physiological dead space?
Which of the following best describes the physiological dead space?
A patient is suffering from hypoxemia due to hypoventilation. Which of the following mechanisms is the primary cause of the low arterial oxygen (P_aO2_) in this scenario?
A patient is suffering from hypoxemia due to hypoventilation. Which of the following mechanisms is the primary cause of the low arterial oxygen (P_aO2_) in this scenario?
Central chemoreceptors play a critical role in regulating breathing. What is the primary stimulus that these receptors respond to?
Central chemoreceptors play a critical role in regulating breathing. What is the primary stimulus that these receptors respond to?
A patient has a condition that increases the resistance of their airways. According to the principles of airflow, what compensatory mechanism is most likely to occur to maintain adequate ventilation?
A patient has a condition that increases the resistance of their airways. According to the principles of airflow, what compensatory mechanism is most likely to occur to maintain adequate ventilation?
A patient is found to have a ventilation/perfusion (V/Q) ratio that is significantly higher than 0.8 in a specific region of the lung. What does this suggest about the relationship between ventilation and perfusion in that area?
A patient is found to have a ventilation/perfusion (V/Q) ratio that is significantly higher than 0.8 in a specific region of the lung. What does this suggest about the relationship between ventilation and perfusion in that area?
During exercise, the body increases ventilation rate and cardiac output. What is the primary reason mean arterial $P_{O_2}$ and $P_{CO_2}$ values remain relatively constant despite the increased metabolic demand?
During exercise, the body increases ventilation rate and cardiac output. What is the primary reason mean arterial $P_{O_2}$ and $P_{CO_2}$ values remain relatively constant despite the increased metabolic demand?
A scientist is investigating the effect of different blood pH levels on the oxygen-hemoglobin dissociation curve. Which of the following conditions would cause a rightward shift in the curve?
A scientist is investigating the effect of different blood pH levels on the oxygen-hemoglobin dissociation curve. Which of the following conditions would cause a rightward shift in the curve?
A patient is diagnosed with severe emphysema. How would this condition typically affect the compliance of the lungs and the functional residual capacity (FRC)?
A patient is diagnosed with severe emphysema. How would this condition typically affect the compliance of the lungs and the functional residual capacity (FRC)?
A patient is suffering from carbon monoxide (CO) poisoning. How does CO affect oxygen transport in the blood?
A patient is suffering from carbon monoxide (CO) poisoning. How does CO affect oxygen transport in the blood?
Which of the following conditions would lead to an increased production of 2,3-diphosphoglycerate (2,3-DPG) in red blood cells and a subsequent rightward shift in the oxygen-hemoglobin dissociation curve?
Which of the following conditions would lead to an increased production of 2,3-diphosphoglycerate (2,3-DPG) in red blood cells and a subsequent rightward shift in the oxygen-hemoglobin dissociation curve?
A person is at rest and then begins to hyperventilate voluntarily. How will their arterial $P_{CO_2}$ ($P_aCO_2$) and cerebrospinal fluid (CSF) pH change, respectively?
A person is at rest and then begins to hyperventilate voluntarily. How will their arterial $P_{CO_2}$ ($P_aCO_2$) and cerebrospinal fluid (CSF) pH change, respectively?
A climber ascends to a high altitude, where the partial pressure of inspired oxygen ($P_{O_2}$) is significantly reduced. Which of the following is an immediate compensatory response mediated by the peripheral chemoreceptors?
A climber ascends to a high altitude, where the partial pressure of inspired oxygen ($P_{O_2}$) is significantly reduced. Which of the following is an immediate compensatory response mediated by the peripheral chemoreceptors?
Which of the following scenarios primarily exemplifies perfusion-limited gas exchange in the lungs?
Which of the following scenarios primarily exemplifies perfusion-limited gas exchange in the lungs?
Flashcards
Dead Space
Dead Space
Volume of airways/lungs not participating in gas exchange. Includes anatomic dead space (conducting airways) and regions in the respiratory zone without gas exchange.
Alveolar Ventilation Equation
Alveolar Ventilation Equation
Inverse relationship: alveolar ventilation increases, PaCO2 decreases. Also predicts PaO2.
Compliance of Lungs
Compliance of Lungs
Lungs/chest wall's ability to stretch under pressure. Decreases in fibrosis or surfactant absence.
Surfactant
Surfactant
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Air Flow Dynamics
Air Flow Dynamics
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Diffusion-limited Gas Exchange
Diffusion-limited Gas Exchange
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Perfusion-limited Gas Exchange
Perfusion-limited Gas Exchange
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Oxygen Transport in Blood
Oxygen Transport in Blood
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Carbon Dioxide Transport
Carbon Dioxide Transport
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Pulmonary Blood Flow
Pulmonary Blood Flow
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Lung Volumes and Capacities
Lung Volumes and Capacities
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Quiet Breathing
Quiet Breathing
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Airway Diameter Control
Airway Diameter Control
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O2-Hemoglobin Curve Shifts
O2-Hemoglobin Curve Shifts
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V/Q Mismatch Effects
V/Q Mismatch Effects
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Chemoreceptor Sensitivity
Chemoreceptor Sensitivity
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Pulmonary Blood Flow Distribution
Pulmonary Blood Flow Distribution
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Exercise: O2-Hb Curve
Exercise: O2-Hb Curve
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High Altitude Hypoxemia
High Altitude Hypoxemia
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What causes Hypoxemia?
What causes Hypoxemia?
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Study Notes
- Lung volumes and capacities are measured with a spirometer, except for those including residual volume.
- Dead space is the volume of airways/lungs not participating in gas exchange.
- Anatomic dead space consists of the volume of conducting airways, while physiologic dead space includes anatomic dead space plus respiratory zone regions not involved in gas exchange.
- The alveolar ventilation equation shows an inverse relationship between arterial partial pressure of CO_2 (P_a CO_2) and alveolar ventilation.
- The alveolar gas equation extends this relationship to predict arterial partial pressure of O_2 (P_a O_2).
- Respiratory muscles (diaphragm) are used only for inspiration during quiet breathing; expiration is passive.
- Lung and chest wall compliance is the slope of the pressure-volume relationship.
- The chest wall tends to expand, and the lungs tend to collapse due to their elastic forces.
- At Functional Residual Capacity (FRC), these forces balance, resulting in negative intrapleural pressure.
- Lung compliance increases in emphysema and with aging, but decreases in fibrosis and when pulmonary surfactant is absent.
- Surfactant, a phospholipid mixture produced by type II alveolar cells, reduces surface tension so that alveoli remain inflated.
- Neonatal respiratory distress syndrome occurs when surfactant is absent.
- Airflow depends on the pressure gradient between the atmosphere and alveoli, and is inversely proportional to airway resistance.
- Stimulation of β_2-adrenergic receptors dilates airways, and stimulation of cholinergic muscarinic receptors constricts them.
- Diffusion of O_2 and CO_2 across the alveolar/pulmonary capillary barrier is governed by Fick's law and the partial pressure difference of the gas.
- Mixed venous blood becomes "arterialized" in pulmonary capillaries as O_2 is added and CO_2 is removed.
- Blood leaving the pulmonary capillaries becomes systemic arterial blood.
- Diffusion-limited gas exchange is illustrated by CO and O_2 in fibrosis or strenuous exercise.
- Perfusion-limited gas exchange is illustrated by N_2O, CO_2, and O_2 under normal conditions.
- O_2 in blood exists in dissolved form and bound to hemoglobin (Hb) in which each Hb molecule binds four O_2 molecules.
- The sigmoidal shape of the O_2-Hb dissociation curve shows the increased affinity for each successive O_2 molecule bound.
- Right shifts of the O_2-Hb dissociation curve indicate decreased affinity, increased O_2 unloading in tissues.
- Left shifts indicate increased affinity, decreased partial pressure of oxygen (P_o_2), and decreased O_2 unloading in tissues.
- Carbon monoxide (CO) decreases the O_2-binding capacity of Hb and causes a leftward shift.
- CO_2 in blood exists dissolved, as carbaminohemoglobin, and as bicarbonate (HCO_3^-).
- HCO_3^- is produced in red blood cells from CO_2 and H_2O via carbonic anhydrase.
- HCO_3^- is transported to the lungs, where reactions occur in reverse to regenerate CO_2, which is then expired.
- Pulmonary blood flow is the right heart's cardiac output and equals the left heart's output.
- Pulmonary blood flow is regulated primarily by arterial partial pressure of carbon dioxide (P_a CO_2), with alveolar hypoxia causing vasoconstriction.
- Pulmonary blood flow is unevenly distributed in the lungs of a standing person: blood flow is lowest at the apex and highest at the base.
- Ventilation distribution is similar, but regional variations in ventilatory rates are not as pronounced as for blood flow.
- The ratio of ventilation (V) to perfusion (Q) is highest at the apex and lowest at the base, averaging 0.8.
- Arterial partial pressure of oxygen (P_a O_2) is highest and arterial partial pressure of carbon dioxide (P_a CO_2) is lowest where V/Q is highest.
- V/Q defects impair gas exchange
- If ventilation decreases relative to perfusion, arterial partial pressure of oxygen (P_a O_2) and arterial partial pressure of carbon dioxide (P_a CO_2) approach mixed venous blood values.
- If perfusion decreases relative to ventilation, arterial partial pressure of oxygen (P_a O_2) and arterial partial pressure of carbon dioxide (P_a CO_2) approach inspired air values.
- Breathing is controlled by the medullary respiratory center, which gets sensory input from central chemoreceptors in the brain stem, peripheral chemoreceptors in the carotid and aortic bodies, and mechanoreceptors in the lungs and joints.
- Central chemoreceptors primarily sense changes in Cerebrospinal fluid (CSF) pH; decreased pH causes hyperventilation.
- Peripheral chemoreceptors primarily sense O_2; hypoxemia causes hyperventilation.
- During exercise, the ventilation rate and cardiac output increase to match the body's O_2 needs so oxygen arterial partial pressure (P_a O_2) and CO_2 arterial partial pressure (P_a CO_2) average values do not change.
- The O_2-hemoglobin dissociation curve shifts right due to increased tissue partial pressure of carbon dioxide (P CO_2), increased temperature, and decreased tissue pH.
- At high altitude, hypoxemia results from decreased inspired air partial pressure of oxygen (P_o_2).
- Adaptive responses to hypoxemia include Hyperventilation, respiratory alkalosis, pulmonary vasoconstriction, polycythemia, increased 2,3-DPG production, and a right shift of the O_2-hemoglobin dissociation curve.
- Hypoxemia, or decreased oxygen arterial partial pressure (P_a O_2), is caused by high altitude, hypoventilation, diffusion defects, V/Q defects, and right-to-left shunts.
- Hypoxia, or decreased O_2 delivery to tissues, is caused by decreased cardiac output or decreased O_2 content of blood.
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