Respiratory System Practice Questions

Q: Which flow volume curve recording is shown below?

Variable extrathoracic obstruction. ***Variable extrathoracic obstruction*** - This flow-volume loop shows a **flattening** of the **inspiratory limb** (I), while the expiratory limb (E) remains relatively normal. - Variable extrathoracic obstructions, such as vocal cord dysfunction or laryngeal edema, predominantly affect airflow during inspiration because the extrathoracic airway pressure becomes more negative than atmospheric pressure during inspiration, leading to airway narrowing. *Parenchymal obstructive airway disease* - Characterized by a **diminished expiratory flow** and a **scooped-out appearance** of the expiratory limb on the flow-volume loop. - The inspiratory limb is usually well preserved, which is not seen here as the inspiratory limb is significantly affected. *Restrictive defect* - Presents as a **miniature version of a normal flow-volume loop**, indicating reduced lung volumes, but usually with preserved flow rates for the given lung volume. - Both inspiratory and expiratory flows would be proportionally reduced, unlike the isolated inspiratory flattening shown. *Variable intrathoracic obstruction* - This typically causes a **flattening or reduction in the expiratory limb** of the flow-volume loop, with a relatively normal inspiratory limb. - During forced expiration, the positive intrathoracic pressure compresses the compromised intrathoracic airway, leading to obstruction.

Q: Which of the following areas of nitrogen washout test indicate closing volume?

4. ***4*** - Area 4 represents the **closing volume**. This is the point where the **small airways in the dependent parts of the lungs close**, leading to a sharp increase in the nitrogen concentration in the exhaled gas. - This sharp increase occurs because air from the upper regions of the lungs, which are better ventilated, continues to empty, and this air has a higher concentration of nitrogen as the patient was initially breathing 100% oxygen. *1* - Area 1 is known as the **anatomical dead space**, representing the initial part of exhalation consisting entirely of gas from the conducting airways (which has a near-zero nitrogen concentration). - This phase reflects the emptying of gas that did not participate in gas exchange, thus showing very low nitrogen levels as it's primarily the 100% oxygen inhaled for the test. *2* - Area 2, or the **alveolar washout phase**, shows a rapid increase in nitrogen concentration as exhaled gas now includes a mixture of dead space air and alveolar air. - This phase reflects the emptying of alveoli from different regions of the lung, but not yet the effect of airway closure. *3* - Area 3 is the **alveolar plateau**, where the nitrogen concentration remains relatively stable, indicating uniform emptying from the remaining open alveoli. - This plateau phase shows the mixing of gases from various lung units, with a steady increase in nitrogen as the oxygen washes out.

Q: Which statement related to lung compliance shown in the image below is correct:

A = Emphysema, B = Fibrosis. ***A = Emphysema, B = Fibrosis*** - Curve A shows **higher lung volume for a given pressure, indicating increased compliance**, which is characteristic of **emphysema** due to destruction of elastic tissue in alveolar walls. - Curve B shows **lower lung volume for a given pressure, indicating decreased compliance**, which is characteristic of **fibrosis** due to increased stiffness and reduced distensibility of lung tissue. *A = Fibrosis, B = Emphysema* - This is incorrect because the curves are reversed. **Fibrosis causes decreased compliance** (curve would be positioned lower like B, not higher like A), while **emphysema causes increased compliance** (curve would be positioned higher like A, not lower like B). *A = Fibrosis, B = Alveolar Proteinosis* - This is incorrect because **alveolar proteinosis causes decreased lung compliance** similar to fibrosis. Both conditions would show curves in the lower position. Curve A clearly demonstrates **increased compliance**, which does not match either condition. *A = Alveolar Proteinosis, B = Fibrosis* - This is incorrect because **alveolar proteinosis results in decreased lung compliance** due to accumulation of surfactant-like material in alveoli. It would correspond to a lower compliance curve, not the increased compliance shown in curve A. While **fibrosis correctly matches decreased compliance** (curve B), alveolar proteinosis cannot be curve A.

Q: The baseline oxyhemoglobin dissociation curve is depicted in blue color. Shift of curve to which side indicates Bohr effect?

Red (shift to right). ***Red (shift to right)*** - The **Bohr effect** describes the rightward shift of the oxyhemoglobin dissociation curve caused by increased **CO2** and decreased **pH** (acidosis). - This rightward shift indicates **decreased oxygen affinity**, allowing hemoglobin to release oxygen more readily to metabolically active tissues that produce CO2 and acid. - This is represented by the **red curve** in the image. *Green (shift to left)* - A **left shift** indicates **increased oxygen affinity**, meaning hemoglobin holds onto oxygen more tightly and releases it less readily. - This occurs with **decreased CO2**, **increased pH** (alkalosis), **decreased temperature**, and **decreased 2,3-BPG**. - These are **opposite conditions** to the Bohr effect. *Blue (no shift)* - The **blue curve** represents the baseline oxyhemoglobin dissociation curve with no shift. - The Bohr effect specifically refers to a **curve shift** (rightward with increased CO2/decreased pH), not the baseline position. - Therefore, blue does not represent the Bohr effect. *None of these* - The **red curve** (rightward shift) accurately represents the Bohr effect, making this option incorrect. - The Bohr effect is a well-established concept with a **characteristic rightward shift** when CO2 increases or pH decreases.

Q: Which protein is responsible for the effect shown in RBC marked as $X$ ?

Band 3 protein. ***Band 3 protein*** - The image indicates that **X** facilitates the exchange of **bicarbonate (HCO₃⁻)** out of the red blood cell and **chloride (Cl⁻)** into the red blood cell, a process known as the **chloride shift** or **Hamburger phenomenon**. - This specific transporter is the **Band 3 anion exchanger 1 (AE1)**, also known as **Band 3 protein**, which is crucial for maintaining electrical neutrality during CO₂ transport. - **Band 3 protein** is the most abundant membrane protein in RBCs and accounts for approximately **25% of RBC membrane protein**. *Spectrin* - Spectrin is a **cytoskeletal protein** that forms a structural network on the inner surface of the RBC membrane. - It provides **mechanical stability and flexibility** to RBCs but does not participate in anion exchange. - Defects in spectrin cause hereditary spherocytosis and elliptocytosis. *Glycophorin* - Glycophorins are **surface glycoproteins** that carry many of the carbohydrate groups on the RBC surface. - They play roles in **membrane stability and blood group antigens** (MN blood group system). - They do not function as anion exchangers or transporters for bicarbonate/chloride. *Ankyrin* - Ankyrin is an **anchoring protein** that links the cytoskeletal protein spectrin to Band 3 protein. - It provides **structural support** and maintains membrane integrity but does not transport ions. - Ankyrin deficiency can cause hereditary spherocytosis.

Q: Which of the following dissociation curve mentioned is for myoglobin?

Green. ***Green*** - The **green curve** represents **myoglobin**, which has a much higher affinity for oxygen than hemoglobin. It binds oxygen at very low partial pressures and releases it only when oxygen levels are significantly depleted, as in active muscle tissue. - Myoglobin's dissociation curve is typically **hyperbolic** due to its single oxygen-binding site, reflecting its role in oxygen storage rather than transport. *Purple* - The **purple curve** represents normal **hemoglobin**, which exhibits a **sigmoidal** shape due to its **cooperative binding** of oxygen. This allows hemoglobin to efficiently load oxygen in the lungs and unload it in tissues. - Hemoglobin has a lower oxygen affinity than myoglobin and is designed for oxygen transport, adapting its binding based on oxygen partial pressure. *Red* - The **red curve** likely represents a **right-shifted hemoglobin dissociation curve**, indicating **decreased oxygen affinity**. This shift facilitates oxygen unloading to tissues. - Right shifts occur due to increased temperature, decreased pH (Bohr effect), increased 2,3-DPG, or increased CO₂. These physiological adaptations help deliver more oxygen to metabolically active tissues. *None* - This option is incorrect because the **green curve** clearly represents the characteristic oxygen dissociation curve for myoglobin.

Q: Calculate the FEV1/FVC ratio from the spirometry reading shown below.

80-89 %. ***80-89 %*** - **Normal FEV1/FVC ratio is >70% in adults, with healthy individuals typically showing 80-90%.** - From the spirometry graph, the total vital capacity (FVC) after full exhalation is approximately **4500 mL**. The volume exhaled in the first second (FEV1) is approximately **4000 mL**. - Therefore, FEV1/FVC = (4000 mL / 4500 mL) × 100% = **88.8%**. This falls within the 80-89% range, indicating **normal lung function**. *60-69 %* - This percentage indicates **severe airflow obstruction**, where the FEV1 is significantly reduced relative to the FVC, which is not supported by the graph's values of **FEV1 ~4000 mL** and **FVC ~4500 mL**. - A ratio of 60-69% is seen in **moderate to severe obstructive lung disease** (COPD, severe asthma). *70-79 %* - This range suggests **mild airflow obstruction**, corresponding to an **FEV1/FVC ratio** that is borderline or slightly reduced (below the normal 80% threshold but above the diagnostic cutoff for obstruction at 70%). - While less severe than 60-69%, it still implies some degree of airway limitation, which is not the case with the calculated ratio of 88.8%. *90-99 %* - This percentage implies an **FEV1/FVC ratio** of 0.9 or higher, meaning that nearly all of the vital capacity is exhaled in the first second. While **88.8%** is close to this range, it does not fall within it. - A ratio this high might be seen in individuals with **excellent lung function** or paradoxically in some cases of **restrictive lung disease** where both FEV1 and FVC are proportionally reduced, but the exact calculated value from the graph is 88.8%, which falls just below 90%.

Q: Which of the following pattern is reflected in the flow-volume curve?

Restrictive airway disease. ***Restrictive airway disease*** - The flow-volume loop for **restrictive lung disease** shows decreased volumes (both **TLC** and **RV** are reduced) while maintaining a relatively normal expiratory flow rate. - The loop appears 'narrower' along the volume axis compared to a normal loop, indicating a **reduction in lung capacity**. *Obstructive airway disease* - An **obstructive pattern** would exhibit a "scooped out" appearance on the expiratory limb of the curve, with reduced peak expiratory flow and **increased residual volume (RV)**. - The **total lung capacity (TLC)** might be normal or increased. *Mixed pattern airway disease* - A **mixed pattern** would show features of both obstruction and restriction, characterized by a decrease in absolute lung volumes (like restriction) and a reduction in expiratory flow rates (like obstruction). - This typically results in a small, narrowed loop with a **concave expiratory limb**. *Central hypoventilation syndrome* - **Central hypoventilation syndrome** primarily affects the **respiratory drive**, leading to underventilation, especially during sleep, and does not produce a characteristic shape on a flow-volume loop. - It would be diagnosed based on **blood gas abnormalities** (e.g., hypercapnia) and polysomnography, not specific flow-volume loop patterns.

Q: Which lung disease is shown in the image below marked as X?

Interstitial fibrosis. ***Interstitial fibrosis*** - The curve labeled 'X' shows a **lower lung volume for a given transpulmonary pressure** compared to the 'Normal' curve, indicating **decreased lung compliance**. - A decrease in lung compliance and **reduced total lung capacity (TLC)** are hallmarks of **restrictive lung diseases** like interstitial fibrosis, where the lungs become stiff and difficult to inflate. *Emphysema* - Emphysema is an **obstructive lung disease** characterized by **increased lung compliance** and **increased total lung capacity (TLC)** due to the destruction of elastic tissue. - Its curve would be shifted to the left and up compared to normal, indicating a larger volume for a given transpulmonary pressure, which is opposite to what is shown for 'X'. *Asthma* - Asthma is also an **obstructive lung disease** primarily affecting airflow due to **bronchoconstriction** and inflammation. - While lung compliance may be slightly altered, the hallmark features of the pressure-volume curve in asthma typically involve air trapping and often a **normal or increased TLC** during an exacerbation, not a significantly reduced TLC and decreased compliance as shown. *Normal* - The curve labeled 'Normal' represents typical lung compliance, where lung volume increases appropriately with transpulmonary pressure. - Curve 'X' clearly deviates from this normal pattern, showing a **reduced capacity** to expand for the same pressure.

Question 1

Which flow volume curve recording is shown below?

Accepted Answer

Variable extrathoracic obstruction

Answer

Parenchymal obstructive airway disease

Answer

Restrictive defect

Answer

Variable intrathoracic obstruction

Question 2

Which of the following areas of nitrogen washout test indicate closing volume?

Accepted Answer

4

Answer

1

Answer

2

Answer

3

Question 3

Which statement related to lung compliance shown in the image below is correct:

Accepted Answer

A = Emphysema, B = Fibrosis

Answer

A = Fibrosis, B = Emphysema

Answer

A = Fibrosis, B = Alveolar Proteinosis

Answer

A = Alveolar Proteinosis, B = Fibrosis

Question 4

The baseline oxyhemoglobin dissociation curve is depicted in blue color. Shift of curve to which side indicates Bohr effect?

Accepted Answer

Red (shift to right)

Answer

Green (shift to left)

Answer

Blue (no shift)

Answer

None of these

Question 5

Which protein is responsible for the effect shown in RBC marked as $X$ ?

Accepted Answer

Band 3 protein

Answer

Spectrin

Answer

Glycophorin

Answer

Ankyrin

Question 6

Which of the following dissociation curve mentioned is for myoglobin?

Accepted Answer

Green

Answer

Purple

Answer

Red

Answer

None

Question 7

Calculate the FEV1/FVC ratio from the spirometry reading shown below.

Accepted Answer

80-89 %

Answer

60-69 %

Answer

70-79 %

Answer

90-99 %

Question 8

Hysteresis is observed between the deflation and inflation curves in an isolated lung compliance diagram. What is the best description for the same?

Accepted Answer

Variation in surface tension forces at air- liquid interface

Answer

Stretching of elastic elements of lung parenchyma

Answer

Decrease in surface tension in air-water interface at higher lung volumes

Answer

Hering Breuer reflex is operational at higher lung volumes

Question 9

Which of the following pattern is reflected in the flow-volume curve?

Accepted Answer

Restrictive airway disease

Answer

Obstructive airway disease

Answer

Mixed pattern airway disease

Answer

Central hypoventilation syndrome

Question 10

Which lung disease is shown in the image below marked as X?

Accepted Answer

Interstitial fibrosis

Answer

Emphysema

Answer

Asthma

Answer

Normal

Respiratory System — MCQs

Respiratory System — MCQs

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