Gas exchange

Gas exchange US Medical PG Question 1: A 33-year-old woman is brought to the emergency department 30 minutes after being rescued from a fire in her apartment. She reports nausea, headache, and dizziness. Physical examination shows black discoloration of her oral mucosa. Pulse oximetry shows an oxygen saturation of 99% on room air. The substance most likely causing symptoms in this patient primarily produces toxicity by which of the following mechanisms?

• A. Inhibition of mitochondrial complex V
• B. Degradation of 2,3-bisphosphoglycerate
• C. Oxidation of Fe2+
• D. Rise in serum pH
• E. Competitive binding to heme (Correct Answer)

Gas exchange Explanation: ***Competitive binding to heme*** - The patient's symptoms (nausea, headache, dizziness, black oral mucosa) and history of being rescued from a fire strongly suggest **carbon monoxide (CO) poisoning** [1]. - **Carbon monoxide** primarily exerts its toxicity by competitively binding to the **heme iron** in hemoglobin with an affinity 200-250 times greater than oxygen, forming **carboxyhemoglobin (COHb)** and displacing oxygen [2]. *Inhibition of mitochondrial complex V* - **Cyanide poisoning** inhibits **mitochondrial complex IV (cytochrome c oxidase)**, not complex V, leading to impaired cellular respiration. - While both cyanide and CO poisoning can occur in fires, CO is more common due to incomplete combustion, and the specific presentation points toward CO. *Degradation of 2,3-bisphosphoglycerate* - **2,3-BPG** is an important regulator of oxygen affinity for hemoglobin, promoting oxygen release to tissues [2]. Its degradation would increase hemoglobin's affinity for oxygen, thus reducing oxygen unloading, but this is not the primary mechanism of toxicity for CO or common fire-related toxins. - No common toxin directly causes widespread degradation of 2,3-BPG as its primary mechanism of acute toxicity or symptoms. *Oxidation of Fe2+* - The oxidation of **ferrous iron (Fe2+)** to **ferric iron (Fe3+)** in hemoglobin leads to the formation of **methemoglobin**, which cannot bind oxygen. This occurs in **methemoglobinemia** induced by certain drugs or toxins (e.g., nitrites, dapsone). - While **methemoglobinemia** impairs oxygen transport, it does not explain the black oral mucosa or the strong association with fire smoke toxicity in the context of CO. *Rise in serum pH* - A rise in serum pH (alkalosis) is not a direct or primary mechanism of toxicity for common fire-related toxins like carbon monoxide or cyanide. - Most severe forms of toxicity, including CO and cyanide poisoning, tend to cause **lactic acidosis** due to cellular hypoxia and anaerobic metabolism, leading to a **decrease** in serum pH.

Gas exchange US Medical PG Question 2: A 71-year-old man is admitted to the ICU with a history of severe pancreatitis and new onset difficulty breathing. His vital signs are a blood pressure of 100/60 mm Hg, heart rate of 100/min, respirations of 27/min, temperature of 36.7°C (98.1°F), and oxygen saturation of 85% on room air. Physical examination shows a cachectic male in severe respiratory distress. Rales are heard at the base of each lung. The patient is intubated and a Swan-Ganz catheter is inserted. Pulmonary capillary wedge pressure is 8 mm Hg. An arterial blood gas study reveals a PaO2: FiO2 ratio of 180. The patient is diagnosed with acute respiratory distress syndrome. In which of the following segments of the respiratory tract are the cells responsible for the symptoms observed in this patient found?

• A. Alveolar sacs (Correct Answer)
• B. Terminal bronchioles
• C. Bronchi
• D. Respiratory bronchioles
• E. Bronchioles

Gas exchange Explanation: ***Alveolar sacs*** - **Acute respiratory distress syndrome (ARDS)** is characterized by widespread inflammatory injury to the **alveolar-capillary membrane**, leading to increased permeability and fluid accumulation in the alveolar sacs. - The symptoms, including **severe hypoxemia** (PaO2:FiO2 ratio < 300), **non-cardiogenic pulmonary edema** (PCWP ≤ 18 mmHg), and **bilateral lung infiltrates**, directly result from damage to the **Type I and Type II pneumocytes** and endothelial cells within the alveolar units. *Terminal bronchioles* - These are the last airways that **do not contain alveoli**, primarily involved in air conduction rather than gas exchange. - While inflammation can extend to these structures in severe lung injury, the primary site of impaired gas exchange and fluid accumulation in ARDS occurs distal to them, in the respiratory zone. *Bronchi* - The bronchi are primarily involved in **air conduction** and consist of cartilage, smooth muscle, and ciliated epithelium, but they do not participate in gas exchange. - Injury to the bronchi would manifest as airway obstruction or mucus hypersecretion rather than the diffuse alveolar damage seen in ARDS. *Respiratory bronchioles* - These are the first airways that contain a **small number of alveoli** and participate in gas exchange, but their primary role is still more conductive than the alveolar sacs. - Although they can be affected in ARDS, the most critical damage and symptoms arise from the more extensive gas exchange surface of the alveolar sacs. *Bronchioles* - Bronchioles are small airways lacking cartilage, primarily responsible for **airflow regulation** and conduction. - While they can be affected by inflammation, the extensive impairment of gas exchange and the characteristic pathology of ARDS specifically involves the **alveolar units**, not primarily the bronchioles.

Gas exchange US Medical PG Question 3: A 32-year-old woman presents with progressive shortness of breath and a dry cough. She says that her symptoms onset recently after a 12-hour flight. Past medical history is unremarkable. Current medications are oral estrogen/progesterone containing contraceptive pills. Her vital signs include: blood pressure 110/60 mm Hg, pulse 101/min, respiratory rate 22/min, oxygen saturation 88% on room air, and temperature 37.9℃ (100.2℉). Her weight is 94 kg (207.2 lb) and height is 170 cm (5 ft 7 in). On physical examination, she is acrocyanotic. There are significant swelling and warmth over the right calf. There are widespread bilateral rales present. Cardiac auscultation reveals accentuation of the pulmonic component of the second heart sound (P2) and an S3 gallop. Which of the following ventilation/perfusion (V/Q) ratios most likely corresponds to this patient’s condition?

• A. 1.3 (Correct Answer)
• B. 1
• C. 0.8
• D. 0.5
• E. 0.3

Gas exchange Explanation: ***1.3*** - This value represents an increased V/Q ratio, or **dead space ventilation**, which is characteristic of a **pulmonary embolism (PE)**. In PE, a portion of the lung is ventilated but not perfused due to the embolism blocking blood flow, leading to wasted ventilation. - The patient's symptoms (sudden onset dyspnea after a long flight, use of oral contraceptives, calf swelling, hypoxia, and accentuated P2) are highly suggestive of a PE, which is the most likely cause of increased V/Q mismatch. *1* - A V/Q ratio of 1 indicates **perfect matching** of ventilation and perfusion, which is an ideal state not typically achieved throughout the entire lung, especially in disease. - This value would not explain the patient's severe **hypoxia** and overall clinical picture of respiratory distress. *0.8* - This is the **average normal V/Q ratio** for the lung as a whole, representing slightly more perfusion than ventilation. - While it's a normal physiological state, it does not account for the significant V/Q mismatch indicated by the patient's severe hypoxemia (SpO2 88%) and clinical symptoms. *0.5* - This value represents a **low V/Q ratio**, indicating relatively more perfusion than ventilation, often seen in conditions like **shunt physiology** (e.g., pneumonia, atelectasis, pulmonary edema). - While the patient has rales and an S3 gallop suggesting potential pulmonary edema or heart failure secondary to increased right heart strain, the primary pathophysiology in PE is increased V/Q due to unperfused but ventilated lung regions. *0.3* - This is a severely **low V/Q ratio**, approaching a **shunt**, where blood passes through the lungs without being adequately oxygenated. This is typical of conditions like **severe pneumonia, ARDS, or significant atelectasis**. - While PE can cause some degree of bronchoconstriction leading to areas of low V/Q, the predominant and most impactful V/Q mismatch in PE is the high V/Q ratio in areas of unperfused lung.

Gas exchange US Medical PG Question 4: Four days after undergoing an elective total hip replacement, a 65-year-old woman develops a DVT that embolizes to the lung. Along with tachypnea, tachycardia, and cough, the patient would most likely present with a PaO2 of what?

• A. 120 mmHg
• B. 100 mmHg
• C. 85 mmHg (Correct Answer)
• D. 110 mmHg
• E. 60 mmHg

Gas exchange Explanation: ***85 mmHg*** - A pulmonary embolism (PE) causes a **ventilation-perfusion (V/Q) mismatch**, leading to **hypoxemia** and a reduced PaO2. - While exact values vary, a PaO2 of 85 mmHg indicates **mild to moderate hypoxemia**, which is common in PE, especially with accompanying symptoms like tachypnea and tachycardia. *120 mmHg* - This value is significantly **higher than normal (75-100 mmHg)** and would indicate **hyperoxia**, which is inconsistent with acute pulmonary embolism causing respiratory distress. - A patient with PE would typically have **reduced oxygenation**, not supernormal levels, unless receiving high-flow supplemental oxygen. *100 mmHg* - A PaO2 of 100 mmHg is at the **upper end of the normal range** (75-100 mmHg) and would imply **no significant hypoxemia**. - Given the patient's symptoms of tachypnea, tachycardia, and cough following a DVT with embolization, a normal or high-normal PaO2 is unlikely without aggressive oxygen therapy (which is not stated). *110 mmHg* - This value is **above the normal range** and suggests **hyperoxia**, which is contrary to the pathophysiology of a pulmonary embolism. - A PE impairs gas exchange, leading to a decrease in PaO2, not an increase. *60 mmHg* - A PaO2 of 60 mmHg indicates **significant hypoxemia**, which might occur in a severe, large pulmonary embolism or in a patient with underlying lung disease. - While possible, 85 mmHg represents a more common, moderate hypoxemia seen in PE, especially given the prompt presentation of symptoms.

Gas exchange US Medical PG Question 5: A 35-year-old woman volunteers for a study on respiratory physiology. Pressure probes A and B are placed as follows: Probe A: between the parietal and visceral pleura Probe B: within the cavity of an alveolus The probes provide a pressure reading relative to atmospheric pressure. To obtain a baseline reading, she is asked to sit comfortably and breathe normally. Which of the following sets of values will most likely be seen at the end of inspiration?

• A. Probe A: -6 mm Hg; Probe B: 0 mm Hg (Correct Answer)
• B. Probe A: 0 mm Hg; Probe B: -1 mm Hg
• C. Probe A: -4 mm Hg; Probe B: 0 mm Hg
• D. Probe A: -4 mm Hg; Probe B: -1 mm Hg
• E. Probe A: -6 mm Hg; Probe B: -1 mm Hg

Gas exchange Explanation: ***Probe A: -6 mm Hg; Probe B: 0 mm Hg*** - At the **end of inspiration**, the **intrapleural pressure (Probe A)** is at its most negative, typically around -6 to -8 cm H2O (equivalent to -4 to -6 mmHg), reflecting the maximum expansion of the thoracic cavity. - At the **end of inspiration**, just before exhalation begins, there is **no airflow**, so the **intrapulmonary pressure (Probe B)** equalizes with atmospheric pressure, resulting in a 0 mm Hg reading. *Probe A: 0 mm Hg; Probe B: -1 mm Hg* - An **intrapleural pressure of 0 mm Hg** would indicate a **pneumothorax** since it should always be negative to prevent lung collapse. - An **intrapulmonary pressure of -1 mm Hg** would indicate that **inspiration is still ongoing**, as air would be flowing into the lungs. *Probe A: -4 mm Hg; Probe B: 0 mm Hg* - While an **intrapulmonary pressure of 0 mm Hg** is correct at the end of inspiration, an **intrapleural pressure of -4 mm Hg** is typical for the **end of expiration (Functional Residual Capacity)** during quiet breathing, not the end of inspiration. - The **intrapleural pressure becomes more negative** during inspiration due to increased thoracic volume, so -4 mm Hg would be insufficient. *Probe A: -4 mm Hg; Probe B: -1 mm Hg* - An **intrapleural pressure of -4 mm Hg** is the normal pressure at the **end of expiration**, not the end of inspiration, where it becomes more negative. - An **intrapulmonary pressure of -1 mm Hg** indicates that **inspiration is still in progress**, not at its end, as air would still be flowing into the lungs. *Probe A: -6 mm Hg; Probe B: -1 mm Hg* - While an **intrapleural pressure of -6 mm Hg** is consistent with the end of inspiration, an **intrapulmonary pressure of -1 mm Hg** means that **airflow is still occurring into the lungs**. - At the **very end of inspiration**, just before the start of exhalation, airflow momentarily ceases, and intrapulmonary pressure becomes zero relative to the atmosphere.

Gas exchange US Medical PG Question 6: In which of the following pathological states would the oxygen content of the trachea resemble the oxygen content in the affected alveoli?

• A. Emphysema
• B. Exercise
• C. Pulmonary embolism (Correct Answer)
• D. Pulmonary fibrosis
• E. Foreign body obstruction distal to the trachea

Gas exchange Explanation: ***Pulmonary embolism*** - A pulmonary embolism blocks **blood flow** to a portion of the lung, creating **dead space ventilation** (high V/Q ratio). - In the affected alveoli, **no blood perfusion** means no oxygen extraction occurs, so the alveolar oxygen content remains **high and similar to tracheal/inspired air**. - This is the classic physiological state where ventilation continues but perfusion is absent, preventing gas exchange. *Foreign body obstruction distal to the trachea* - A complete obstruction **prevents fresh air** from reaching the affected alveoli. - The trapped gas undergoes **resorption atelectasis**: oxygen is absorbed into capillary blood, CO2 diffuses in, and alveolar gas equilibrates with **venous blood** composition. - Alveolar oxygen content becomes **very low**, not similar to tracheal air. *Emphysema* - Emphysema involves destruction of **alveolar walls** and enlargement of airspaces with impaired gas exchange. - While V/Q mismatch occurs, oxygen is still extracted by perfusing blood. - Alveolar oxygen content is **lower than tracheal air** due to ongoing (though inefficient) gas exchange. *Exercise* - During exercise, **oxygen consumption increases** dramatically with enhanced cardiac output and oxygen extraction. - Alveolar oxygen content is **significantly lower** than tracheal air due to increased oxygen uptake by blood. *Pulmonary fibrosis* - Pulmonary fibrosis causes **thickening of the alveolar-capillary membrane**, impairing oxygen diffusion. - Despite diffusion limitation, blood still perfuses the alveoli and extracts oxygen. - Alveolar oxygen content is **lower than tracheal air**, though the A-a gradient is increased.

Gas exchange US Medical PG Question 7: A 19-year-old male soccer player undergoes an exercise tolerance test to measure his maximal oxygen uptake during exercise. Which of the following changes are most likely to occur during exercise?

• A. Increased apical ventilation-perfusion ratio
• B. Decreased physiologic dead space (Correct Answer)
• C. Decreased alveolar-arterial oxygen gradient
• D. Increased arterial partial pressure of oxygen
• E. Increased pulmonary vascular resistance

Gas exchange Explanation: **Decreased physiologic dead space** - During exercise, there is improved perfusion to previously underperfused areas of the lung, leading to a **more uniform ventilation-perfusion (V/Q) matching** and thus a decrease in physiologic dead space. - The increased cardiac output helps to perfuse more capillaries, reducing the amount of ventilated air that does not participate in gas exchange. *Increased apical ventilation-perfusion ratio* - At rest, the **apical V/Q ratio is already high** due to gravity-dependent differences in blood flow; exercise partially normalizes these differences. - While overall V/Q matching improves, the relative V/Q differences between apical and basal regions may become less pronounced, not necessarily a further increase in the apical ratio. *Decreased alveolar-arterial oxygen gradient* - During severe exercise, the **A-a gradient often increases slightly** due to increased oxygen diffusion limitations and V/Q mismatch. - Although overall gas exchange efficiency improves, the sheer volume of oxygen demand can reveal small imbalances, rather than fully eliminating the gradient. *Increased arterial partial pressure of oxygen* - Exercise typically leads to **stable or slightly decreased arterial PO2** in healthy individuals due to the increased metabolic demand and potential small V/Q mismatches. - The body maintains arterial PO2 remarkably well even at high exertion, but it does not usually significantly increase. *Increased pulmonary vascular resistance* - During exercise, **pulmonary vascular resistance (PVR) generally decreases** due to recruitment and distension of pulmonary capillaries. - This decrease in PVR helps to accommodate the increased cardiac output without a significant rise in pulmonary arterial pressure.

Gas exchange US Medical PG Question 8: During a clinical study examining the diffusion of gas between the alveolar compartment and the pulmonary capillary blood, men between the ages of 20 and 50 years are evaluated while they hold a sitting position. After inhaling a water-soluble gas that rapidly combines with hemoglobin, the concentration of the gas in the participant's exhaled air is measured and the diffusion capacity is calculated. Assuming that the concentration of the inhaled gas remains the same, which of the following is most likely to increase the flow of the gas across the alveolar membrane?

• A. Deep exhalation
• B. Entering a cold chamber
• C. Treadmill exercise (Correct Answer)
• D. Standing straight
• E. Assuming a hunched position

Gas exchange Explanation: ***Correct: Treadmill exercise*** - **Treadmill exercise** increases cardiac output and pulmonary blood flow, which in turn recruits and distends more **pulmonary capillaries**. This increases the **surface area** available for gas exchange and reduces the diffusion distance, thereby enhancing the flow of gas across the alveolar membrane. - Exercise also typically leads to deeper and more frequent breaths, increasing the **ventilation-perfusion matching** and overall efficiency of gas exchange. - According to Fick's law of diffusion (Vgas = A/T × D × ΔP), increasing the surface area (A) directly increases gas flow. *Incorrect: Deep exhalation* - **Deep exhalation** would empty the lungs more completely, potentially leading to alveolar collapse in some regions and thus **decreasing the alveolar surface area** available for gas exchange. - This would also reduce the **driving pressure** for gas diffusion by lowering the alveolar concentration of the inhaled gas. *Incorrect: Entering a cold chamber* - Exposure to a **cold chamber** can cause **bronchoconstriction** in some individuals, particularly those with reactive airways, which would increase airway resistance and potentially reduce alveolar ventilation. - While metabolic rate may slightly increase in the cold, the primary effect on the lungs is unlikely to promote increased gas diffusion in a healthy individual. *Incorrect: Standing straight* - **Standing straight** is a normal physiological posture and does not significantly alter the **pulmonary capillary recruitment** or the alveolar surface area in a way that would dramatically increase gas flow compared to a seated position. - There might be minor gravitational effects on blood flow distribution, but these are generally less impactful than dynamic changes like exercise. *Incorrect: Assuming a hunched position* - **Assuming a hunched position** can restrict chest wall expansion and diaphragm movement, leading to **reduced tidal volume** and overall alveolar ventilation. - This posture, by reducing lung volumes and potentially compressing the lungs, would likely **decrease the effective surface area** for gas exchange and therefore reduce gas flow.

Gas exchange US Medical PG Question 9: A 21-year-old man is admitted to the intensive care unit for respiratory failure requiring mechanical ventilation. His minute ventilation is calculated to be 7.0 L/min, and his alveolar ventilation is calculated to be 5.1 L/min. Which of the following is most likely to decrease the difference between minute ventilation and alveolar ventilation?

• A. Increasing the partial pressure of inhaled oxygen
• B. Decreasing the affinity of hemoglobin for oxygen
• C. Increasing the respiratory depth
• D. Decreasing the physiologic dead space (Correct Answer)
• E. Increasing the respiratory rate

Gas exchange Explanation: ***Decreasing the physiologic dead space*** - The difference between **minute ventilation (VE)** and **alveolar ventilation (VA)** is the **dead space ventilation (VD)**, calculated as: VE - VA = VD - In this case: 7.0 L/min - 5.1 L/min = 1.9 L/min of dead space ventilation - Decreasing the **physiologic dead space** directly reduces this difference by allowing a greater proportion of each breath to participate in gas exchange - This is the most direct way to narrow the gap between VE and VA *Increasing the partial pressure of inhaled oxygen* - This intervention primarily affects **oxygenation** by increasing the driving pressure for oxygen diffusion into the blood - It does not directly change the volume of air participating in alveolar ventilation or reduce dead space ventilation - The distribution of ventilation between alveolar and dead space remains unchanged *Decreasing the affinity of hemoglobin for oxygen* - A decrease in hemoglobin affinity for oxygen facilitates **oxygen unloading** to the tissues (rightward shift of the oxygen-hemoglobin dissociation curve) - This effect is related to **oxygen delivery** and does not alter the proportion of minute ventilation that reaches the alveoli for gas exchange - Dead space ventilation remains unchanged *Increasing the respiratory depth* - Increasing respiratory depth increases **tidal volume (VT)**, which improves the **ratio** of alveolar ventilation to minute ventilation (VA/VE efficiency) - However, the **absolute difference** (VE - VA) in L/min depends on the **total dead space volume**, which is not changed by increasing tidal volume alone - While this improves ventilation efficiency, it does not directly reduce the dead space ventilation measured in L/min unless physiologic dead space itself decreases *Increasing the respiratory rate* - While increasing respiratory rate increases **minute ventilation (VE)**, it also increases the frequency of ventilating the **dead space** with each breath - Since dead space ventilation (VD) = respiratory rate × dead space volume, increasing rate while keeping tidal volume constant will proportionally increase both VE and VD - This can actually widen the absolute gap between VE and VA, making it less efficient

Gas exchange US Medical PG Question 10: Two days after undergoing left hemicolectomy for a colonic mass, a 62-year-old man develops shortness of breath. His temperature is 38.1°C (100.6°F), pulse is 80/min, respirations are 22/min, and blood pressure is 120/78 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 88%. Cardiopulmonary examination shows decreased breath sounds and decreased fremitus at both lung bases. Arterial blood gas analysis on room air shows: pH 7.35 PaO2 70 mm Hg PCO2 40 mm Hg An x-ray of the chest shows a collapse of the bases of both lungs. Which of the following is the most likely underlying mechanism of this patient's hypoxemia?

• A. Increased anatomic dead space
• B. Decreased hemoglobin oxygen-binding capacity
• C. Decreased chest wall compliance
• D. Increased tidal volume
• E. Decreased ratio of ventilated alveoli (Correct Answer)

Gas exchange Explanation: ***Decreased ratio of ventilated alveoli*** - The patient's presentation with **shortness of breath**, **decreased breath sounds and fremitus at both lung bases**, and **collapsed lung bases on chest x-ray** points to **atelectasis**. - **Atelectasis** is a common cause of hypoxemia post-surgery. It occurs when alveoli collapse, leading to areas of the lung that are perfused but not ventilated, resulting in a **ventilation-perfusion (V/Q) mismatch** with a decreased ratio of ventilated alveoli. *Increased anatomic dead space* - **Anatomic dead space** refers to the conducting airways where gas exchange does not occur. This value is relatively constant and would not increase significantly to cause such profound hypoxemia in this context. - Conditions like chronic obstructive pulmonary disease (COPD) can increase dead space, but the patient's acute postoperative presentation and chest X-ray findings do not support this as the primary cause. *Decreased hemoglobin oxygen-binding capacity* - This would involve issues like **carbon monoxide poisoning** or specific hemoglobinopathies, which are not indicated by the clinical picture or ABG results (normal pH, PaO2 70 mmHg, PCO2 40 mmHg). - The PaO2 and SaO2 values indicate a problem with oxygen uptake, not oxygen transport by hemoglobin once bound. *Decreased chest wall compliance* - While surgery can cause **pain leading to splinting** and reduced chest wall expansion, which impacts compliance, the primary mechanism of hypoxemia in atelectasis is the **collapse of alveoli**, not solely reduced chest wall movement. - The **collapsed lung bases** on X-ray directly point to alveolar collapse rather than a general decrease in chest wall compliance as the primary problem. *Increased tidal volume* - **Increased tidal volume** would typically improve ventilation and oxygenation, not lead to hypoxemia. - The patient's **hypoxemia (SaO2 88%, PaO2 70 mmHg)** clearly indicates a problem with oxygen uptake, not an enhancement of respiratory function.

Gas exchange Flashcard 1 of 10

Question: In exercise, O2 exhibits _____-limited gas exchange

Answer: mixed

Gas exchange Flashcard 2 of 10

Question: N2O exhibits _____-limited gas exchange

Answer: perfusion

Gas exchange Flashcard 3 of 10

Question: CO2 exhibits _____-limited gas exchange

Answer: perfusion

Gas exchange Flashcard 4 of 10

Question: Why must fetal hemoglobin have a much higher O2 binding affinity than HbA? _____

Answer: Drives O2 diffusion across placenta from mother to fetus

Gas exchange Flashcard 5 of 10

Question: Carbon monoxide binds competitively to Hb and with 200-250x _____ affinity than O2

Answer: greater

Gas exchange Flashcard 6 of 10

Question: The alveolar gas equation states that the alveolar Po2 (PAo2) equals:_____

Answer:

Gas exchange Flashcard 7 of 10

Question: Increased ventilation (e.g. high altitude) causes _____ Paco2

Answer: decreased

Gas exchange Flashcard 8 of 10

Question: The lung diffusing capacity (DL) can be measured with _____ because it is exclusively diffusion-limited

Answer: carbon monoxide (CO)

Gas exchange Flashcard 9 of 10

Question: DLCO may be used to estimate the extent to which _____ passes from the air sacs of lungs into blood

Answer: oxygen

Gas exchange Flashcard 10 of 10

Question: What is the secondary regulator of cerebral perfusion?

Answer: PO2 - only takes effect during severe hypoxia