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Questions and Answers
Which of the following best describes the concept of the oxygen cascade?
Which of the following best describes the concept of the oxygen cascade?
- The solubility of O2 increases as it moves from the atmosphere to the mitochondria in the tissues.
- The partial pressure of O2 decreases as it moves from the atmosphere to the mitochondria in the tissues. (correct)
- The solubility of O2 decreases as it moves from the atmosphere to the mitochondria in the tissues.
- The partial pressure of O2 increases as it moves from the atmosphere to the mitochondria in the tissues.
What happens if there is a disruption to the oxygen cascade?
What happens if there is a disruption to the oxygen cascade?
- Arterial Po2 increases and tissue Po2 remains the same.
- Arterial Po2 decreases and tissue Po2 decreases. (correct)
- Arterial Po2 remains the same and tissue Po2 decreases.
- Arterial Po2 decreases and tissue Po2 remains the same.
How much O2 is dissolved in every 100 mL of blood at 100 mmHg?
How much O2 is dissolved in every 100 mL of blood at 100 mmHg?
- 3 mL
- 0.3 mL (correct)
- 30 mL
- 0.03 mL
What is the approximate O2 consumption at rest?
What is the approximate O2 consumption at rest?
How does the amount of O2 needed by the heart compare to the amount of O2 consumed by the tissues?
How does the amount of O2 needed by the heart compare to the amount of O2 consumed by the tissues?
What is the purpose of haemoglobin (Hb) in oxygen delivery?
What is the purpose of haemoglobin (Hb) in oxygen delivery?
During internal respiration in the tissues, at a Po2 of 40 mmHg, approximately what percentage of oxygen saturation remains on hemoglobin (Hb)?
During internal respiration in the tissues, at a Po2 of 40 mmHg, approximately what percentage of oxygen saturation remains on hemoglobin (Hb)?
Which of the following accurately describes the role of central chemoreceptors in the control of ventilation?
Which of the following accurately describes the role of central chemoreceptors in the control of ventilation?
Where are the peripheral chemoreceptors located?
Where are the peripheral chemoreceptors located?
Which of the following is true about the relative importance of O2 and CO2 in ventilatory control at rest?
Which of the following is true about the relative importance of O2 and CO2 in ventilatory control at rest?
Where are the central chemoreceptors located?
Where are the central chemoreceptors located?
What do peripheral chemoreceptors sense?
What do peripheral chemoreceptors sense?
Which chemoreceptors are primarily responsible for detecting changes in carbon dioxide (CO2) levels?
Which chemoreceptors are primarily responsible for detecting changes in carbon dioxide (CO2) levels?
Which of the following statements about central chemoreceptors is true?
Which of the following statements about central chemoreceptors is true?
What is the role of peripheral chemoreceptors?
What is the role of peripheral chemoreceptors?
What happens to the pH of cerebrospinal fluid (CSF) during high CO2 level in blood?
What happens to the pH of cerebrospinal fluid (CSF) during high CO2 level in blood?
Where are the peripheral chemoreceptors located?
Where are the peripheral chemoreceptors located?
What activates the glomus cells in the peripheral chemoreceptors?
What activates the glomus cells in the peripheral chemoreceptors?
What happens to the ventilatory response to increased CO2 levels when the alveolar O2 level is constant?
What happens to the ventilatory response to increased CO2 levels when the alveolar O2 level is constant?
What happens to the ventilatory response when alveolar CO2 level is constant and there is a decrease in alveolar O2 level?
What happens to the ventilatory response when alveolar CO2 level is constant and there is a decrease in alveolar O2 level?
What happens to the ventilatory response when alveolar O2 level is low and there is a further increase in CO2 level?
What happens to the ventilatory response when alveolar O2 level is low and there is a further increase in CO2 level?
What happens to the ventilatory response curve in the presence of metabolic acidosis (high H+)?
What happens to the ventilatory response curve in the presence of metabolic acidosis (high H+)?
What happens to the ventilatory response in individuals using narcotic drugs, anesthetics, or COPD patients?
What happens to the ventilatory response in individuals using narcotic drugs, anesthetics, or COPD patients?
What response occurs when there is a combination of low pH with hypoxemia or hypercapnia?
What response occurs when there is a combination of low pH with hypoxemia or hypercapnia?
What is the reason that increasing alveolar oxygen (O2) is meaningless for hypoxemia caused by shunting?
What is the reason that increasing alveolar oxygen (O2) is meaningless for hypoxemia caused by shunting?
Which of the following conditions does oxygen therapy NOT work for?
Which of the following conditions does oxygen therapy NOT work for?
Select the correct statement on oxygen cascade and consumption:
Select the correct statement on oxygen cascade and consumption:
Select the correct statement on oxygen delivery:
Select the correct statement on oxygen delivery:
Select the best description on chemoreceptors:
Select the best description on chemoreceptors:
Select the correct statement on ventilatory responses:
Select the correct statement on ventilatory responses:
Select the correct statement on COPD management.
Select the correct statement on COPD management.
Why is oxygen therapy contraindicated in patients with severe COPD?
Why is oxygen therapy contraindicated in patients with severe COPD?
What is the recommended oxygen saturation range for patients receiving low O2 therapy?
What is the recommended oxygen saturation range for patients receiving low O2 therapy?
What is the potential risk of stopping oxygen therapy in patients with severe COPD?
What is the potential risk of stopping oxygen therapy in patients with severe COPD?
What should be monitored in patients receiving low O2 therapy?
What should be monitored in patients receiving low O2 therapy?
When may a shift to long-term oxygen therapy be necessary?
When may a shift to long-term oxygen therapy be necessary?
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Study Notes
Oxygen Cascade and Consumption
- The oxygen cascade refers to the process of oxygen delivery from the atmosphere to the body's tissues.
- A disruption to the oxygen cascade can lead to tissue hypoxia.
- At 100 mmHg, approximately 0.003 mL of O2 is dissolved in every 100 mL of blood.
- The approximate O2 consumption at rest is 250 mL/min.
- The heart requires 10-15% of the total O2 consumption, while the remaining 85-90% is consumed by the tissues.
Oxygen Delivery and Hemoglobin
- Hemoglobin (Hb) plays a crucial role in oxygen delivery by binding to oxygen in the lungs and releasing it to the tissues.
- During internal respiration in the tissues, at a Po2 of 40 mmHg, approximately 30% of oxygen saturation remains on hemoglobin (Hb).
Chemoreceptors and Ventilatory Control
- Central chemoreceptors are responsible for detecting changes in CO2 and H+ levels in the cerebrospinal fluid (CSF).
- Peripheral chemoreceptors are located in the carotid and aortic bodies and sense changes in O2 and CO2 levels.
- At rest, CO2 is the primary stimulus for ventilation, while O2 plays a minor role.
- Central chemoreceptors are primarily responsible for detecting changes in carbon dioxide (CO2) levels.
- Peripheral chemoreceptors are responsible for detecting changes in O2 levels.
Ventilatory Responses
- During high CO2 levels in the blood, the pH of cerebrospinal fluid (CSF) decreases.
- The glomus cells in the peripheral chemoreceptors are activated by hypoxia.
- When the alveolar O2 level is constant, an increase in CO2 levels stimulates ventilation.
- When the alveolar CO2 level is constant, a decrease in alveolar O2 level stimulates ventilation.
- When alveolar O2 level is low and there is a further increase in CO2 level, ventilation is strongly stimulated.
- In the presence of metabolic acidosis (high H+), the ventilatory response curve shifts to the left.
- In individuals using narcotic drugs, anesthetics, or COPD patients, the ventilatory response to CO2 is depressed.
- When there is a combination of low pH with hypoxemia or hypercapnia, ventilation is strongly stimulated.
Oxygen Therapy and COPD Management
- Increasing alveolar oxygen (O2) is meaningless for hypoxemia caused by shunting.
- Oxygen therapy does not work for shunting or ventilation-perfusion mismatch.
- Oxygen therapy is contraindicated in patients with severe COPD because it can lead to respiratory depression.
- The recommended oxygen saturation range for patients receiving low O2 therapy is 88-92%.
- The potential risk of stopping oxygen therapy in patients with severe COPD is respiratory failure.
- In patients receiving low O2 therapy, oxygen saturation and acid-base status should be monitored.
- A shift to long-term oxygen therapy may be necessary when oxygen saturation remains below 88% despite optimal medical therapy.
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